Make an IRC listener connection follow its session's nick (closes #184)

An IRC listener connection kept its own copy of its nick, so after the session's nick was changed from another client it went on sending under the old nick, which another user could then take. Now, whenever the relay passes on a NICK line and after the connection's own NICK is stored, the connection takes the nick its session holds in the database, read by session ID under the connection's lock. Taking the nick from the database rather than from the line means a connection can never follow another user's rename and send as them. Handlers read the nick under the same lock.

Untested: an HTTP API rename landing while the connection's own NICK is being stored; that order cannot be produced reliably.

Model: opus-5-5

README.md

@@ -180,7 +180,7 @@ For users who want to access the same session from multiple devices:
 - **Set password via IRC PASS command**: the authenticated client sends
   `POST /api/v1/messages` with `{"command":"PASS","body":["mypassword"]}`. The
   server hashes the password with bcrypt and stores it on the session. Password
-  must be at least 8 characters.
+  must be 8 to 72 bytes.
 - **Login from another client**: `POST /api/v1/login` with nick and password →
   server verifies the password, creates a new client for the existing session,
   and sets an auth cookie. Channel memberships are shared; the new client gets
@@ -268,10 +268,15 @@ rules). Case-sensitive comparison is unambiguous.
 A single user session can have multiple clients (phone, laptop, terminal).
 
 - Each client gets a **separate server-to-client (S2C) message queue**.
-- The server fans out messages and events from other users, and the user's own
-  DMs and the channel messages it sends over the HTTP API, to every client queue
-  for that user session. Replies to a command (numerics) go only to the client
-  that sent it.
+- The server fans out messages and events from other users to every client queue
+  for that user session.
+- When the user sends a `PRIVMSG`, `NOTICE`, `JOIN`, `PART`, `NICK`, `TOPIC`,
+  `MODE` or `KICK` from one of its clients, the resulting event goes to every
+  client queue of the user's own session, as well as to the other users it is
+  meant for. The one exception is an IRC listener connection that sent the
+  command, which gets nothing queued for it: it has already sent its user the
+  echo, or, for `PRIVMSG` and `NOTICE`, IRC sends none.
+- Replies to a command (numerics) go only to the client that sent it.
 - `GET /api/v1/messages` delivers from the calling client's specific queue,
   identified by the auth cookie.
 - Client queues have **independent expiry/pruning** — one client going offline
@@ -744,7 +749,7 @@ Leave a channel.
 {"command": "PART", "to": "#general", "body": ["goodbye"]}
 ```
 
-**S2C (broadcast to the other channel members):**
+**S2C (broadcast to all channel members, including the departing user):**
 
 ```json
 {
@@ -760,9 +765,8 @@ Leave a channel.
 
 **Behavior:**
 
-- The PART event goes to the other channel members, not to the departing user;
-  the HTTP response confirms the part. (The IRC listener echoes the PART to its
-  own connection.)
+- The PART event goes to every channel member, the departing user's own clients
+  included. (An IRC listener connection that sends a PART echoes it itself.)
 - If the channel is empty after the user leaves, the channel is **deleted**
   (ephemeral channels).
 - If the user is not in the channel, the server returns an error.
@@ -835,10 +839,11 @@ Set a password on the current session, enabling multi-client login via
 
 **Behavior:**
 
-- `body[0]` is the password. Must be at least 8 characters.
+- `body[0]` is the password. Must be 8 to 72 bytes; bcrypt cannot hash a longer
+  one.
 - On success, the server responds with `{"status": "ok"}`.
-- If the password is too short or missing, the server sends ERR_NEEDMOREPARAMS
-  (461) via the message queue.
+- If the password is too short, too long or missing, the server sends
+  ERR_NEEDMOREPARAMS (461) via the message queue.
 - Calling PASS again overwrites the previous password.
 - Once a password is set, `POST /api/v1/login` can be used with the nick and
   password to create additional clients on the same session.
@@ -1018,9 +1023,8 @@ On the IRC listener, `MODE #channel <modes> [values...]` takes several letters
 in one string, e.g. `MODE #general +mt-i` or `MODE #general +ov alice bob`. It
 accepts `i`, `m`, `n`, `s`, `t`, `o` and `v` (with a nick) and `H` (with bits
 from 1 to 40 when setting), but not `b`, `k` or `l`. A letter whose value is
-missing is skipped. The changes made are echoed to the operator's connection and
-also sent to every channel member, the operator included, as one `MODE` line,
-e.g. `+o-v alice bob`.
+missing is skipped. The changes made are sent to every channel member as one
+`MODE` line, e.g. `+o-v alice bob`; the operator gets that line once.
 
 **Channel errors:**
 
@@ -1404,7 +1408,8 @@ Include the hashcash stamp in the `meta` field:
 **Server validation:** The server checks that the stamp is well-formed, meets
 the required difficulty, is bound to the correct channel and message body, has a
 recent date, and has not been previously used. Spent stamps are cached for 1
-year to prevent replay attacks.
+year to prevent replay attacks. The stamp is checked after membership, bans and
+`+m`, so a message refused for one of those does not spend it.
 
 **Error responses:** If the channel requires hashcash and the stamp is missing,
 invalid, or replayed, the server returns `ERR_CANNOTSENDTOCHAN (404)` with a
@@ -2569,10 +2574,13 @@ issues) and simpler than UUIDs (integer comparison vs. string comparison).
 - **Sessions**: Both anonymous and password-protected sessions are deleted on
   `QUIT` or when the last client logs out (`POST /api/v1/logout` with no
   remaining clients triggers session cleanup). There is no distinction between
-  session types in the cleanup path — `handleQuit` and `cleanupUser` both call
-  `DeleteSession` unconditionally. Idle clients are automatically removed after
-  `SESSION_IDLE_TIMEOUT` (default 30 days) without an authenticated HTTP API
-  request or, on the IRC listener, a command — the server runs a background
+  session types in the cleanup path: the session is parted from its channels,
+  deleted, and its QUIT queued to its channel peers in one database transaction,
+  so when several QUITs or logouts end one session at once only the one that
+  deletes it broadcasts QUIT, and whatever a new holder of the nick sends
+  reaches those peers after the QUIT. Idle clients are automatically removed
+  after `SESSION_IDLE_TIMEOUT` (default 30 days) without an authenticated HTTP
+  API request or, on the IRC listener, a command — the server runs a background
   cleanup loop that, for a session left with no clients, parts the user from all
   channels, broadcasts QUIT, and releases the nick.
 - **Clients**: Individual client auth cookies are invalidated on
@@ -2674,9 +2682,11 @@ IRC_LISTEN_ADDR: ""
 
 - **Wire format**: CR-LF delimited lines, max 512 bytes per line
 - **Connection registration**: Clients must send `NICK` and `USER` to register.
-  An optional `PASS` before registration sets the session password (minimum 8
-  characters). Registering creates a session without a hashcash stamp; closing
-  the connection ends the session, as `QUIT` does.
+  An optional `PASS` before registration sets the session password (8 to 72
+  bytes); one outside that range is refused with a `NOTICE` once registration
+  completes, as `PASS` after registration is. Registering creates a session
+  without a hashcash stamp; closing the connection ends the session, as `QUIT`
+  does.
 - **PING**: a connection that sends nothing for 90 seconds is sent a `PING`, and
   is closed if it sends nothing in the 30 seconds after that; any line, such as
   the client's `PONG`, starts both waits again.
@@ -2713,7 +2723,9 @@ Each line of a multi-line `body` reaches an IRC listener user as its own
 is sent, so it cannot start a line of its own. A mode change made over the HTTP
 API reaches IRC listener members as an IRC `MODE` line with its value as a
 separate parameter, e.g. `MODE #general +k secretpass` or
-`MODE #general +o bob`.
+`MODE #general +o bob`. An `INVITE` from either transport reaches the invited
+IRC listener user as an IRC `INVITE` line from the inviter, e.g.
+`:alice!alice@* INVITE bob #general`.
 
 ### Docker Usage
 
@@ -3081,6 +3093,10 @@ limits that punish shared networks.
     - Stamp has not been used before (replay prevention; the spent stamps are
       kept in memory, so a restart forgets them)
 
+    The stamp is spent only when the session is created. A request refused with
+    400 or 409 leaves it unspent, and the client can send the same stamp again
+    with another nick or username.
+
 ### Stamp Format
 
 Standard hashcash format:
@@ -3153,12 +3169,13 @@ creating one session pays once and keeps their session.
 ### Why Hashcash and Not Rate Limits?
 
 - **Little state to track**: No IP tables, no token buckets, no sliding windows.
-  The server verifies a single hash and remembers the stamps already spent.
+  The server hashes the stamp and remembers the stamps already spent.
 - **Works through NATs and proxies**: Doesn't punish shared IPs (university
   campuses, corporate networks, Tor exits). Every client computes their own
   proof independently.
 - **Cost falls on the requester**: The server's verification cost is constant
-  (one SHA-256 hash) regardless of difficulty. Only the client does more work.
+  regardless of difficulty: at most two SHA-256 hashes of the stamp per session
+  request, one to check it and one to spend it. Only the client does more work.
 - **Fits the "no accounts" philosophy**: Proof-of-work is the cost of entry. No
   registration, no email, no phone number, no CAPTCHA. Just compute.
 - **Language-agnostic**: SHA-256 is available in every programming language. The

internal/cli/api/client.go

@@ -250,7 +250,7 @@ func (client *Client) ListChannels() (
 // GetMembers returns members of a channel.
 func (client *Client) GetMembers(
 	channel string,
-) ([]string, error) {
+) ([]Member, error) {
 	name := strings.TrimPrefix(channel, "#")
 
 	data, err := client.do(
@@ -263,7 +263,7 @@ func (client *Client) GetMembers(
 		return nil, err
 	}
 
-	var members []string
+	var members []Member
 
 	err = json.Unmarshal(data, &members)
 	if err != nil {

internal/cli/api/client_test.go

@@ -2,18 +2,28 @@ package neoircapi_test
 
 import (
 	"context"
+	"encoding/json"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"reflect"
+	"slices"
+	"strconv"
 	"strings"
 	"testing"
 
 	api "sneak.berlin/go/neoirc/internal/cli/api"
+	"sneak.berlin/go/neoirc/internal/hashcash"
 )
 
-const cookieValue = "opaque-value"
+const (
+	cookieValue = "opaque-value"
+	testNick    = "alice"
+	testChannel = "#general"
+)
 
 // newSessionServer starts a plain-HTTP server that, like
 // neoircd, sets a Secure auth cookie when a session is
@@ -24,10 +34,16 @@ func newSessionServer(t *testing.T) *httptest.Server {
 
 	mux := http.NewServeMux()
 
+	// Without hashcash the server sends no hashcash_bits.
 	mux.HandleFunc("GET /api/v1/server", func(
 		writer http.ResponseWriter, _ *http.Request,
 	) {
-		_, _ = io.WriteString(writer, `{}`)
+		_, _ = io.WriteString(writer, `{
+			"name": "My NeoIRC Server",
+			"version": "0.1.0",
+			"motd": "Welcome! Be nice.",
+			"users": 42
+		}`)
 	})
 
 	mux.HandleFunc("POST /api/v1/session", func(
@@ -56,9 +72,14 @@ func newSessionServer(t *testing.T) *httptest.Server {
 			return
 		}
 
-		_, _ = io.WriteString(
-			writer, `{"id":1,"nick":"alice","channels":[]}`,
-		)
+		_, _ = io.WriteString(writer, `{
+			"id": 1,
+			"nick": "alice",
+			"channels": [
+				{"id": 1, "name": "#general", "topic": "Welcome!"},
+				{"id": 2, "name": "#dev", "topic": ""}
+			]
+		}`)
 	})
 
 	server := httptest.NewServer(mux)
@@ -67,6 +88,344 @@ func newSessionServer(t *testing.T) *httptest.Server {
 	return server
 }
 
+// newClientForPath starts a server that answers GET path with
+// body, and returns a client for it.
+func newClientForPath(t *testing.T, path, body string) *api.Client {
+	t.Helper()
+
+	mux := http.NewServeMux()
+
+	mux.HandleFunc("GET "+path, func(
+		writer http.ResponseWriter, _ *http.Request,
+	) {
+		_, _ = io.WriteString(writer, body)
+	})
+
+	server := httptest.NewServer(mux)
+	t.Cleanup(server.Close)
+
+	return api.NewClient(server.URL)
+}
+
+func TestGetStateDecodesFields(t *testing.T) {
+	t.Parallel()
+
+	client := api.NewClient(newSessionServer(t).URL)
+
+	_, err := client.CreateSession(testNick)
+	if err != nil {
+		t.Fatalf("create session: %v", err)
+	}
+
+	state, err := client.GetState()
+	if err != nil {
+		t.Fatalf("state: %v", err)
+	}
+
+	want := api.StateResponse{
+		ID:   1,
+		Nick: testNick,
+		Channels: []api.Channel{
+			{Name: testChannel, Topic: "Welcome!"},
+			{Name: "#dev", Topic: ""},
+		},
+	}
+	if !reflect.DeepEqual(*state, want) {
+		t.Fatalf("state: got %+v, want %+v", *state, want)
+	}
+}
+
+func TestGetServerInfoDecodesFields(t *testing.T) {
+	t.Parallel()
+
+	client := newClientForPath(t, "/api/v1/server", `{
+		"name": "My NeoIRC Server",
+		"version": "0.1.0",
+		"motd": "Welcome! Be nice.",
+		"users": 42,
+		"hashcash_bits": 20
+	}`)
+
+	info, err := client.GetServerInfo()
+	if err != nil {
+		t.Fatalf("server info: %v", err)
+	}
+
+	want := api.ServerInfo{
+		Name:         "My NeoIRC Server",
+		MOTD:         "Welcome! Be nice.",
+		Version:      "0.1.0",
+		HashcashBits: 20,
+	}
+	if *info != want {
+		t.Fatalf("server info: got %+v, want %+v", *info, want)
+	}
+}
+
+// TestCreateSessionSendsNickAndStamp serves a server that, like
+// neoircd with hashcash on, advertises hashcash_bits and creates
+// the session only for a pow_token the server's validator in
+// internal/hashcash accepts.
+func TestCreateSessionSendsNickAndStamp(t *testing.T) {
+	t.Parallel()
+
+	const (
+		serverName = "My NeoIRC Server"
+		stampBits  = 8
+		sessionID  = 7
+	)
+
+	mux := http.NewServeMux()
+
+	mux.HandleFunc("GET /api/v1/server", func(
+		writer http.ResponseWriter, _ *http.Request,
+	) {
+		_, _ = fmt.Fprintf(writer, `{
+			"name": %q,
+			"version": "0.1.0",
+			"motd": "Welcome! Be nice.",
+			"users": 42,
+			"hashcash_bits": %d
+		}`, serverName, stampBits)
+	})
+
+	validator := hashcash.NewValidator(serverName)
+
+	mux.HandleFunc("POST /api/v1/session", func(
+		writer http.ResponseWriter, request *http.Request,
+	) {
+		// Decoded with the field names handleCreateSession uses.
+		var payload struct {
+			Nick     string `json:"nick"`
+			Hashcash string `json:"pow_token"` //nolint:tagliatelle
+		}
+
+		err := json.NewDecoder(request.Body).Decode(&payload)
+		if err != nil {
+			writer.WriteHeader(http.StatusBadRequest)
+
+			return
+		}
+
+		err = validator.Claim(payload.Hashcash, stampBits)
+		if err != nil {
+			writer.WriteHeader(http.StatusPaymentRequired)
+
+			return
+		}
+
+		writer.WriteHeader(http.StatusCreated)
+
+		_ = json.NewEncoder(writer).Encode(map[string]any{
+			"id":   sessionID,
+			"nick": payload.Nick,
+		})
+	})
+
+	server := httptest.NewServer(mux)
+	t.Cleanup(server.Close)
+
+	session, err := api.NewClient(server.URL).CreateSession(testNick)
+	if err != nil {
+		t.Fatalf("create session: %v", err)
+	}
+
+	want := api.SessionResponse{ID: sessionID, Nick: testNick}
+	if *session != want {
+		t.Fatalf("session: got %+v, want %+v", *session, want)
+	}
+}
+
+func TestListChannelsDecodesNamesAndTopics(t *testing.T) {
+	t.Parallel()
+
+	client := newClientForPath(t, "/api/v1/channels", `[
+		{"id": 1, "name": "#general", "topic": "Welcome!"},
+		{"id": 2, "name": "#dev", "topic": "Development discussion"}
+	]`)
+
+	channels, err := client.ListChannels()
+	if err != nil {
+		t.Fatalf("list channels: %v", err)
+	}
+
+	want := []api.Channel{
+		{Name: testChannel, Topic: "Welcome!"},
+		{Name: "#dev", Topic: "Development discussion"},
+	}
+	if !slices.Equal(channels, want) {
+		t.Fatalf("channels: got %+v, want %+v", channels, want)
+	}
+}
+
+func TestGetMembersDecodesMemberObjects(t *testing.T) {
+	t.Parallel()
+
+	client := newClientForPath(t, "/api/v1/channels/general/members", `[
+		{
+			"id": 1, "nick": "alice", "username": "alice",
+			"hostname": "host.example.com",
+			"isOperator": true, "isVoiced": false,
+			"lastSeen": "2026-02-10T20:00:00Z"
+		},
+		{
+			"id": 2, "nick": "bob", "username": "bob",
+			"hostname": "host.example.com",
+			"isOperator": false, "isVoiced": true,
+			"lastSeen": "2026-02-10T20:00:00Z"
+		},
+		{
+			"id": 3, "nick": "Carol", "username": "carol",
+			"hostname": "host.example.com",
+			"isOperator": false, "isVoiced": false,
+			"lastSeen": "2026-02-10T20:00:00Z"
+		}
+	]`)
+
+	members, err := client.GetMembers(testChannel)
+	if err != nil {
+		t.Fatalf("get members: %v", err)
+	}
+
+	want := []api.Member{
+		{Nick: testNick, IsOperator: true, IsVoiced: false},
+		{Nick: "bob", IsOperator: false, IsVoiced: true},
+		{Nick: "Carol", IsOperator: false, IsVoiced: false},
+	}
+	if !slices.Equal(members, want) {
+		t.Fatalf("members: got %+v, want %+v", members, want)
+	}
+}
+
+// TestPollMessagesAdvancesCursor serves the queue as the server
+// does: entries after the cursor, and last_id as the new cursor.
+func TestPollMessagesAdvancesCursor(t *testing.T) {
+	t.Parallel()
+
+	const lastQueueID = 42
+
+	mux := http.NewServeMux()
+
+	mux.HandleFunc("GET /api/v1/messages", func(
+		writer http.ResponseWriter, request *http.Request,
+	) {
+		after := request.URL.Query().Get("after")
+		if after == strconv.Itoa(lastQueueID) {
+			_, _ = io.WriteString(
+				writer, `{"messages": [], "last_id": 42}`,
+			)
+
+			return
+		}
+
+		_, _ = io.WriteString(writer, `{
+			"messages": [{
+				"id": "b7c8210f-849c-4b90-9ee8-d99c8889358e",
+				"command": "PRIVMSG",
+				"from": "alice",
+				"to": "#general",
+				"body": ["hello world"],
+				"ts": "2026-02-10T20:00:01.234567891Z",
+				"meta": {}
+			}],
+			"last_id": 42
+		}`)
+	})
+
+	server := httptest.NewServer(mux)
+	t.Cleanup(server.Close)
+
+	client := api.NewClient(server.URL)
+
+	first, err := client.PollMessages(0, 0)
+	if err != nil {
+		t.Fatalf("first poll: %v", err)
+	}
+
+	if first.LastID != lastQueueID || len(first.Messages) != 1 {
+		t.Fatalf(
+			"first poll: got last ID %d and %d messages, "+
+				"want %d and 1",
+			first.LastID, len(first.Messages), lastQueueID,
+		)
+	}
+
+	second, err := client.PollMessages(first.LastID, 0)
+	if err != nil {
+		t.Fatalf("second poll: %v", err)
+	}
+
+	if len(second.Messages) != 0 {
+		t.Fatalf(
+			"second poll: got %d messages again, want none",
+			len(second.Messages),
+		)
+	}
+}
+
+// TestPollMessagesDecodesMessageFields serves a relayed PRIVMSG
+// with the sender's meta and a numeric, as the server queues
+// them.
+func TestPollMessagesDecodesMessageFields(t *testing.T) {
+	t.Parallel()
+
+	client := newClientForPath(t, "/api/v1/messages", `{
+		"messages": [
+			{
+				"id": "b7c8210f-849c-4b90-9ee8-d99c8889358e",
+				"command": "PRIVMSG",
+				"from": "alice",
+				"to": "#general",
+				"body": ["signed message"],
+				"ts": "2026-02-10T20:00:01.234567891Z",
+				"meta": {"sig": "base64...", "alg": "ed25519"}
+			},
+			{
+				"id": "7f5a04f8-eab4-4d2e-be55-f5cfcfaf43c5",
+				"command": "RPL_LUSEROP",
+				"code": 252,
+				"from": "neoirc",
+				"to": "alice",
+				"params": ["0"],
+				"body": ["operator(s) online"],
+				"ts": "2026-02-10T20:00:02Z",
+				"meta": {}
+			}
+		],
+		"last_id": 42
+	}`)
+
+	result, err := client.PollMessages(0, 0)
+	if err != nil {
+		t.Fatalf("poll: %v", err)
+	}
+
+	want := []api.Message{
+		{
+			ID:      "b7c8210f-849c-4b90-9ee8-d99c8889358e",
+			Command: "PRIVMSG",
+			From:    testNick,
+			To:      testChannel,
+			Body:    []any{"signed message"},
+			TS:      "2026-02-10T20:00:01.234567891Z",
+			Meta:    map[string]any{"sig": "base64...", "alg": "ed25519"},
+		},
+		{
+			ID:      "7f5a04f8-eab4-4d2e-be55-f5cfcfaf43c5",
+			Command: "RPL_LUSEROP",
+			From:    "neoirc",
+			To:      testNick,
+			Params:  []string{"0"},
+			Body:    []any{"operator(s) online"},
+			TS:      "2026-02-10T20:00:02Z",
+			Meta:    map[string]any{},
+		},
+	}
+	if !reflect.DeepEqual(result.Messages, want) {
+		t.Fatalf("messages: got %+v, want %+v", result.Messages, want)
+	}
+}
+
 func TestClientKeepsSessionOverPlainHTTPOnLocalhost(t *testing.T) {
 	t.Parallel()
 
@@ -85,7 +444,7 @@ func TestClientKeepsSessionOverPlainHTTPOnLocalhost(t *testing.T) {
 				"http://" + net.JoinHostPort(host, serverURL.Port()),
 			)
 
-			_, err := client.CreateSession("alice")
+			_, err := client.CreateSession(testNick)
 			if err != nil {
 				t.Fatalf("create session: %v", err)
 			}
@@ -118,7 +477,7 @@ func TestClientWithholdsCookieOverPlainHTTPFromOtherHosts(t *testing.T) {
 		},
 	}
 
-	_, err := client.CreateSession("alice")
+	_, err := client.CreateSession(testNick)
 	if err != nil {
 		t.Fatalf("create session: %v", err)
 	}

internal/cli/api/types.go

@@ -16,9 +16,9 @@ type SessionResponse struct {
 
 // StateResponse is the response from GET /api/v1/state.
 type StateResponse struct {
-	ID       int64    `json:"id"`
-	Nick     string   `json:"nick"`
-	Channels []string `json:"channels"`
+	ID       int64     `json:"id"`
+	Nick     string    `json:"nick"`
+	Channels []Channel `json:"channels"`
 }
 
 // Message represents a neoirc message envelope.
@@ -53,12 +53,19 @@ func (m *Message) BodyLines() []string {
 	}
 }
 
-// Channel represents a channel in the list response.
+// Channel is a channel as GET /api/v1/channels and
+// GET /api/v1/state describe it.
 type Channel struct {
-	Name      string `json:"name"`
-	Topic     string `json:"topic"`
-	Members   int    `json:"members"`
-	CreatedAt string `json:"createdAt"`
+	Name  string `json:"name"`
+	Topic string `json:"topic"`
+}
+
+// Member is one entry of the response from
+// GET /api/v1/channels/{name}/members.
+type Member struct {
+	Nick       string `json:"nick"`
+	IsOperator bool   `json:"isOperator"`
+	IsVoiced   bool   `json:"isVoiced"`
 }
 
 // ServerInfo is the response from GET /api/v1/server.
@@ -72,7 +79,7 @@ type ServerInfo struct {
 // MessagesResponse wraps polling results.
 type MessagesResponse struct {
 	Messages []Message `json:"messages"`
-	LastID   int64     `json:"lastId"`
+	LastID   int64     `json:"last_id"` //nolint:tagliatelle
 }
 
 // PollResult wraps the poll response including the cursor.

internal/cli/app.go

@@ -434,16 +434,9 @@ func (a *App) cmdTopic(args string) {
 		return
 	}
 
+	// The HTTP API has no topic query: a TOPIC needs text.
 	if args == "" {
-		err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-			Command: irc.CmdTopic,
-			To:      target,
-		})
-		if err != nil {
-			a.ui.AddStatus(fmt.Sprintf(
-				"[red]Topic query failed: %v", err,
-			))
-		}
+		a.ui.AddStatus("[red]Usage: /topic <text>")
 
 		return
 	}
@@ -487,12 +480,32 @@ func (a *App) cmdNames() {
 		return
 	}
 
+	nicks := make([]string, 0, len(members))
+
+	for _, member := range members {
+		nicks = append(nicks, memberPrefix(member)+member.Nick)
+	}
+
 	a.ui.AddLine(target, fmt.Sprintf(
 		"[cyan]*** Members of %s: %s",
-		target, strings.Join(members, " "),
+		target, strings.Join(nicks, " "),
 	))
 }
 
+// memberPrefix returns "@" for an operator, "+" for a voiced
+// member, and "" for anyone else.
+func memberPrefix(member api.Member) string {
+	if member.IsOperator {
+		return "@"
+	}
+
+	if member.IsVoiced {
+		return "+"
+	}
+
+	return ""
+}
+
 func (a *App) cmdList() {
 	a.mu.Lock()
 	connected := a.connected
@@ -517,8 +530,7 @@ func (a *App) cmdList() {
 
 	for _, ch := range channels {
 		a.ui.AddStatus(fmt.Sprintf(
-			"  %s (%d members) %s",
-			ch.Name, ch.Members, ch.Topic,
+			"  %s %s", ch.Name, ch.Topic,
 		))
 	}
 
@@ -676,7 +688,7 @@ func (a *App) cmdHelp() {
 		"  /part [#chan]    — Leave channel",
 		"  /msg <nick> <text> — Send DM",
 		"  /query <nick>   — Open DM window",
-		"  /topic [text]   — View/set topic",
+		"  /topic <text>   — Set topic",
 		"  /names          — List channel members",
 		"  /list           — List channels",
 		"  /who [#channel] — List users in channel",
@@ -745,7 +757,7 @@ func (a *App) handleServerMessage(msg *api.Message) {
 	case irc.CmdJoin:
 		a.handleJoinEvent(msg, timestamp)
 	case irc.CmdPart:
-		a.handlePartEvent(msg, timestamp)
+		a.handlePartEvent(msg, timestamp, myNick)
 	case irc.CmdQuit:
 		a.handleQuitEvent(msg, timestamp)
 	case irc.CmdNick:
@@ -801,10 +813,14 @@ func (a *App) handleJoinEvent(
 	))
 }
 
+// handlePartEvent shows another user's part. The server
+// also sends the user's own part back to it, which cmdPart
+// has already shown; showing it again would add a second
+// line and mark the channel just left as unread.
 func (a *App) handlePartEvent(
-	msg *api.Message, timestamp string,
+	msg *api.Message, timestamp, myNick string,
 ) {
-	if msg.To == "" {
+	if msg.To == "" || msg.From == myNick {
 		return
 	}
 

internal/cli/app_internal_test.go

@@ -0,0 +1,116 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/gdamore/tcell/v2"
+	api "sneak.berlin/go/neoirc/internal/cli/api"
+	"sneak.berlin/go/neoirc/pkg/irc"
+)
+
+func TestMemberPrefix(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name   string
+		member api.Member
+		want   string
+	}{
+		{
+			name:   "operator",
+			member: api.Member{Nick: "alice", IsOperator: true},
+			want:   "@",
+		},
+		{
+			name:   "voiced member",
+			member: api.Member{Nick: "bob", IsVoiced: true},
+			want:   "+",
+		},
+		{
+			name: "voiced operator",
+			member: api.Member{
+				Nick: "Carol", IsOperator: true, IsVoiced: true,
+			},
+			want: "@",
+		},
+		{
+			name:   "plain member",
+			member: api.Member{Nick: "dave"},
+			want:   "",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := memberPrefix(test.member)
+			if got != test.want {
+				t.Fatalf("got %q, want %q", got, test.want)
+			}
+		})
+	}
+}
+
+// TestPartEvent checks that a PART event adds a line to the
+// channel's buffer and marks it unread, except for the
+// user's own part, which cmdPart has already shown.
+func TestPartEvent(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name       string
+		from       string
+		wantLines  int
+		wantUnread int
+	}{
+		{name: "own part", from: "erin", wantLines: 0, wantUnread: 0},
+		{name: "other member", from: "bob", wantLines: 1, wantUnread: 1},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			app := &App{ui: NewUI(), nick: "erin"}
+			runUI(t, app.ui)
+
+			app.handleServerMessage(&api.Message{
+				Command: irc.CmdPart, From: test.from, To: "#chan",
+			})
+
+			var lines, unread int
+
+			app.ui.app.QueueUpdate(func() {
+				buf := app.ui.getOrCreateBuffer("#chan")
+				lines = len(buf.Lines)
+				unread = buf.Unread
+			})
+
+			if lines != test.wantLines || unread != test.wantUnread {
+				t.Fatalf("got %d lines and %d unread, want %d and %d",
+					lines, unread, test.wantLines, test.wantUnread)
+			}
+		})
+	}
+}
+
+// runUI runs ui on a simulated screen until the test ends.
+func runUI(t *testing.T, ui *UI) {
+	t.Helper()
+
+	ui.app.SetScreen(tcell.NewSimulationScreen(""))
+
+	done := make(chan error)
+
+	go func() { done <- ui.Run() }()
+
+	t.Cleanup(func() {
+		ui.Stop()
+
+		err := <-done
+		if err != nil {
+			t.Errorf("run ui: %v", err)
+		}
+	})
+}

internal/db/queries.go

@@ -264,6 +264,25 @@ func (database *Database) GetSessionByNick(
 	return sessionID, nil
 }
 
+// GetSessionNick returns the nick a session holds.
+func (database *Database) GetSessionNick(
+	ctx context.Context,
+	sessionID int64,
+) (string, error) {
+	var nick string
+
+	err := database.conn.QueryRowContext(
+		ctx,
+		"SELECT nick FROM sessions WHERE id = ?",
+		sessionID,
+	).Scan(&nick)
+	if err != nil {
+		return "", fmt.Errorf("get session nick: %w", err)
+	}
+
+	return nick, nil
+}
+
 // SessionHostInfo holds the username, hostname, and IP
 // for a session.
 type SessionHostInfo struct {
@@ -854,42 +873,6 @@ func (database *Database) SetChannelTopicLocked(
 	return nil
 }
 
-// PartChannel removes a session from a channel.
-func (database *Database) PartChannel(
-	ctx context.Context,
-	channelID, sessionID int64,
-) error {
-	_, err := database.conn.ExecContext(ctx,
-		`DELETE FROM channel_members
-		 WHERE channel_id = ? AND session_id = ?`,
-		channelID, sessionID)
-	if err != nil {
-		return fmt.Errorf("part channel: %w", err)
-	}
-
-	return nil
-}
-
-// DeleteChannelIfEmpty removes a channel with no members.
-func (database *Database) DeleteChannelIfEmpty(
-	ctx context.Context,
-	channelID int64,
-) error {
-	_, err := database.conn.ExecContext(ctx,
-		`DELETE FROM channels WHERE id = ?
-		 AND NOT EXISTS
-		 (SELECT 1 FROM channel_members
-		  WHERE channel_id = ?)`,
-		channelID, channelID)
-	if err != nil {
-		return fmt.Errorf(
-			"delete channel if empty: %w", err,
-		)
-	}
-
-	return nil
-}
-
 // PartChannelAndDeleteIfEmpty removes a session from a
 // channel and deletes the channel if that left it with no
 // members, in one transaction, so that no JOIN lands
@@ -905,7 +888,29 @@ func (database *Database) PartChannelAndDeleteIfEmpty(
 
 	defer func() { _ = transaction.Rollback() }()
 
-	_, err = transaction.ExecContext(ctx,
+	err = partChannelAndDeleteIfEmptyInTx(
+		ctx, transaction, channelID, sessionID,
+	)
+	if err != nil {
+		return err
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return fmt.Errorf("commit part: %w", err)
+	}
+
+	return nil
+}
+
+// partChannelAndDeleteIfEmptyInTx is
+// PartChannelAndDeleteIfEmpty, writing through transaction.
+func partChannelAndDeleteIfEmptyInTx(
+	ctx context.Context,
+	transaction *sql.Tx,
+	channelID, sessionID int64,
+) error {
+	_, err := transaction.ExecContext(ctx,
 		`DELETE FROM channel_members
 		 WHERE channel_id = ? AND session_id = ?`,
 		channelID, sessionID)
@@ -925,11 +930,6 @@ func (database *Database) PartChannelAndDeleteIfEmpty(
 		)
 	}
 
-	err = transaction.Commit()
-	if err != nil {
-		return fmt.Errorf("commit part: %w", err)
-	}
-
 	return nil
 }
 
@@ -1156,6 +1156,40 @@ func (database *Database) InsertMessage(
 	params json.RawMessage,
 	body json.RawMessage,
 	meta json.RawMessage,
+) (int64, string, error) {
+	transaction, err := database.conn.BeginTx(ctx, nil)
+	if err != nil {
+		return 0, "", fmt.Errorf("begin insert message: %w", err)
+	}
+
+	defer func() { _ = transaction.Rollback() }()
+
+	dbID, msgUUID, err := insertMessageInTx(
+		ctx, transaction, command, from, target,
+		toSessionID, toChannelID, params, body, meta,
+	)
+	if err != nil {
+		return 0, "", err
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return 0, "", fmt.Errorf("commit insert message: %w", err)
+	}
+
+	return dbID, msgUUID, nil
+}
+
+// insertMessageInTx is InsertMessage, writing through
+// transaction.
+func insertMessageInTx(
+	ctx context.Context,
+	transaction *sql.Tx,
+	command, from, target string,
+	toSessionID, toChannelID int64,
+	params json.RawMessage,
+	body json.RawMessage,
+	meta json.RawMessage,
 ) (int64, string, error) {
 	msgUUID := uuid.New().String()
 	now := time.Now().UTC()
@@ -1172,7 +1206,7 @@ func (database *Database) InsertMessage(
 		meta = json.RawMessage("{}")
 	}
 
-	res, err := database.conn.ExecContext(ctx,
+	res, err := transaction.ExecContext(ctx,
 		`INSERT INTO messages
 		 (uuid, command, msg_from, msg_to,
 		  to_session_id, to_channel_id,
@@ -1193,19 +1227,49 @@ func (database *Database) InsertMessage(
 	return dbID, msgUUID, nil
 }
 
-// EnqueueToSession adds a message to all clients of a
-// session's queues.
+// EnqueueToSession adds a message to the queues of all
+// clients of a session except client skipClientID, or of all
+// of them when skipClientID is 0.
 func (database *Database) EnqueueToSession(
 	ctx context.Context,
-	sessionID, messageID int64,
+	sessionID, messageID, skipClientID int64,
 ) error {
-	_, err := database.conn.ExecContext(ctx,
+	transaction, err := database.conn.BeginTx(ctx, nil)
+	if err != nil {
+		return fmt.Errorf("begin enqueue: %w", err)
+	}
+
+	defer func() { _ = transaction.Rollback() }()
+
+	err = enqueueToSessionInTx(
+		ctx, transaction, sessionID, messageID, skipClientID,
+	)
+	if err != nil {
+		return err
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return fmt.Errorf("commit enqueue: %w", err)
+	}
+
+	return nil
+}
+
+// enqueueToSessionInTx is EnqueueToSession, writing through
+// transaction.
+func enqueueToSessionInTx(
+	ctx context.Context,
+	transaction *sql.Tx,
+	sessionID, messageID, skipClientID int64,
+) error {
+	_, err := transaction.ExecContext(ctx,
 		`INSERT OR IGNORE INTO client_queues
 		 (client_id, message_id, created_at)
 		 SELECT c.id, ?, ?
 		 FROM clients c
-		 WHERE c.session_id = ?`,
-		messageID, time.Now(), sessionID)
+		 WHERE c.session_id = ? AND c.id != ?`,
+		messageID, time.Now(), sessionID, skipClientID)
 	if err != nil {
 		return fmt.Errorf(
 			"enqueue to session: %w", err,
@@ -1470,38 +1534,175 @@ func (database *Database) SetTopic(
 	return nil
 }
 
-// DeleteSession removes a session and all its data.
-func (database *Database) DeleteSession(
+// QuitSession ends a session in one transaction: it parts
+// the session from its channels, deleting each channel this
+// leaves with no members, deletes the session with its
+// clients, and stores a QUIT from nick with body and queues
+// it to the other sessions that were on those channels. It
+// returns those sessions, for the caller to wake once the
+// QUIT is committed. Of several calls for one session at
+// once, only the first finds the session; the others change
+// nothing and return none.
+func (database *Database) QuitSession(
 	ctx context.Context,
 	sessionID int64,
-) error {
-	_, err := database.conn.ExecContext(
-		ctx,
-		"DELETE FROM sessions WHERE id = ?",
-		sessionID,
-	)
+	nick string,
+	body json.RawMessage,
+) ([]int64, error) {
+	transaction, err := database.conn.BeginTx(ctx, nil)
 	if err != nil {
-		return fmt.Errorf("delete session: %w", err)
+		return nil, fmt.Errorf("begin quit: %w", err)
 	}
 
-	return nil
+	defer func() { _ = transaction.Rollback() }()
+
+	peerIDs, err := quitSessionInTx(
+		ctx, transaction, sessionID, nick, body,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return nil, fmt.Errorf("commit quit: %w", err)
+	}
+
+	return peerIDs, nil
 }
 
-// DeleteClient removes a single client record by ID.
-func (database *Database) DeleteClient(
+// LogoutClient deletes a client of a session and, if that
+// leaves the session with no clients, does what QuitSession
+// does, in one transaction. It returns what QuitSession
+// returns, or none if the session keeps a client.
+func (database *Database) LogoutClient(
 	ctx context.Context,
-	clientID int64,
-) error {
-	_, err := database.conn.ExecContext(
-		ctx,
-		"DELETE FROM clients WHERE id = ?",
-		clientID,
-	)
+	sessionID, clientID int64,
+	nick string,
+	body json.RawMessage,
+) ([]int64, error) {
+	transaction, err := database.conn.BeginTx(ctx, nil)
 	if err != nil {
-		return fmt.Errorf("delete client: %w", err)
+		return nil, fmt.Errorf("begin logout: %w", err)
 	}
 
-	return nil
+	defer func() { _ = transaction.Rollback() }()
+
+	_, err = transaction.ExecContext(ctx,
+		"DELETE FROM clients WHERE id = ?", clientID)
+	if err != nil {
+		return nil, fmt.Errorf("delete client: %w", err)
+	}
+
+	var remaining int64
+
+	err = transaction.QueryRowContext(ctx,
+		"SELECT COUNT(*) FROM clients WHERE session_id = ?",
+		sessionID,
+	).Scan(&remaining)
+	if err != nil {
+		return nil, fmt.Errorf("count clients: %w", err)
+	}
+
+	var peerIDs []int64
+
+	if remaining == 0 {
+		peerIDs, err = quitSessionInTx(
+			ctx, transaction, sessionID, nick, body,
+		)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return nil, fmt.Errorf("commit logout: %w", err)
+	}
+
+	return peerIDs, nil
+}
+
+// quitSessionInTx is QuitSession, writing through
+// transaction.
+func quitSessionInTx(
+	ctx context.Context,
+	transaction *sql.Tx,
+	sessionID int64,
+	nick string,
+	body json.RawMessage,
+) ([]int64, error) {
+	rows, err := transaction.QueryContext(ctx,
+		`SELECT DISTINCT session_id FROM channel_members
+		 WHERE session_id != ? AND channel_id IN
+		 (SELECT channel_id FROM channel_members
+		  WHERE session_id = ?)`,
+		sessionID, sessionID)
+	if err != nil {
+		return nil, fmt.Errorf("get channel peers: %w", err)
+	}
+
+	peerIDs, err := scanInt64s(rows)
+	if err != nil {
+		return nil, err
+	}
+
+	rows, err = transaction.QueryContext(ctx,
+		`SELECT channel_id FROM channel_members
+		 WHERE session_id = ?`, sessionID)
+	if err != nil {
+		return nil, fmt.Errorf(
+			"get session channel ids: %w", err,
+		)
+	}
+
+	channelIDs, err := scanInt64s(rows)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, channelID := range channelIDs {
+		err = partChannelAndDeleteIfEmptyInTx(
+			ctx, transaction, channelID, sessionID,
+		)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	result, err := transaction.ExecContext(ctx,
+		"DELETE FROM sessions WHERE id = ?", sessionID)
+	if err != nil {
+		return nil, fmt.Errorf("delete session: %w", err)
+	}
+
+	deletedRows, err := result.RowsAffected()
+	if err != nil {
+		return nil, fmt.Errorf("delete session: %w", err)
+	}
+
+	if deletedRows == 0 || len(peerIDs) == 0 {
+		return nil, nil
+	}
+
+	messageID, _, err := insertMessageInTx(
+		ctx, transaction, irc.CmdQuit, nick, "", 0, 0,
+		nil, body, nil,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, peerID := range peerIDs {
+		err = enqueueToSessionInTx(
+			ctx, transaction, peerID, messageID, 0,
+		)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return peerIDs, nil
 }
 
 // GetUserCount returns the number of active users.
@@ -1543,29 +1744,6 @@ func (database *Database) GetOperCount(
 	return count, nil
 }
 
-// ClientCountForSession returns the number of clients
-// belonging to a session.
-func (database *Database) ClientCountForSession(
-	ctx context.Context,
-	sessionID int64,
-) (int64, error) {
-	var count int64
-
-	err := database.conn.QueryRowContext(
-		ctx,
-		`SELECT COUNT(*) FROM clients
-		 WHERE session_id = ?`,
-		sessionID,
-	).Scan(&count)
-	if err != nil {
-		return 0, fmt.Errorf(
-			"client count for session: %w", err,
-		)
-	}
-
-	return count, nil
-}
-
 // DeleteStaleUsers removes clients not seen since the
 // cutoff and cleans up orphaned users (sessions).
 func (database *Database) DeleteStaleUsers(

internal/db/queries_test.go

@@ -2,6 +2,7 @@ package db_test
 
 import (
 	"encoding/json"
+	"slices"
 	"testing"
 
 	"sneak.berlin/go/neoirc/internal/db"
@@ -411,7 +412,7 @@ func TestJoinAndPart(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = database.PartChannel(ctx, chID, sid)
+	err = database.PartChannelAndDeleteIfEmpty(ctx, chID, sid)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -422,7 +423,10 @@ func TestJoinAndPart(t *testing.T) {
 	}
 }
 
-func TestDeleteChannelIfEmpty(t *testing.T) {
+// TestPartChannelAndDeleteIfEmpty checks that a part keeps
+// a channel another session is still on and deletes the
+// channel when its last member parts.
+func TestPartChannelAndDeleteIfEmpty(t *testing.T) {
 	t.Parallel()
 
 	database := setupTestDB(t)
@@ -435,22 +439,34 @@ func TestDeleteChannelIfEmpty(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	sid, _, _, err := database.CreateSession(ctx, "temp", "", "", "")
+	nicks := []string{"temp1", "temp2"}
+	sids := make([]int64, 0, len(nicks))
+
+	for _, nick := range nicks {
+		sid, _, _, createErr := database.CreateSession(ctx, nick, "", "", "")
+		if createErr != nil {
+			t.Fatal(createErr)
+		}
+
+		err = database.JoinChannel(ctx, chID, sid)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		sids = append(sids, sid)
+	}
+
+	err = database.PartChannelAndDeleteIfEmpty(ctx, chID, sids[0])
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	err = database.JoinChannel(ctx, chID, sid)
+	_, err = database.GetChannelByName(ctx, "#empty")
 	if err != nil {
-		t.Fatal(err)
+		t.Fatalf("channel deleted while a member is on it: %v", err)
 	}
 
-	err = database.PartChannel(ctx, chID, sid)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = database.DeleteChannelIfEmpty(ctx, chID)
+	err = database.PartChannelAndDeleteIfEmpty(ctx, chID, sids[1])
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -659,7 +675,7 @@ func TestPollMessages(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = database.EnqueueToSession(ctx, sid, dbID)
+	err = database.EnqueueToSession(ctx, sid, dbID, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -777,6 +793,11 @@ func TestGetHistoryReusedNames(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	err = database.JoinChannel(ctx, oldChID, oldSID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	body := json.RawMessage(`["hi"]`)
 
 	_, _, err = database.InsertMessage(
@@ -799,12 +820,9 @@ func TestGetHistoryReusedNames(t *testing.T) {
 		t.Fatal("expected one DM and one channel message")
 	}
 
-	err = database.DeleteSession(ctx, oldSID)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = database.DeleteChannelIfEmpty(ctx, oldChID)
+	// The session is the channel's only member, so quitting
+	// deletes the channel too.
+	_, err = database.QuitSession(ctx, oldSID, "reused", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -826,34 +844,42 @@ func TestGetHistoryReusedNames(t *testing.T) {
 	}
 }
 
-func TestDeleteSession(t *testing.T) {
+// TestQuitSession checks that QuitSession deletes the
+// session, keeps a channel another session is still on,
+// deletes a channel it leaves with no members, and queues
+// one QUIT to the other session; and that a second call for
+// the same session changes nothing.
+func TestQuitSession(t *testing.T) {
 	t.Parallel()
 
 	database := setupTestDB(t)
 	ctx := t.Context()
 
-	sid, _, _, err := database.CreateSession(
-		ctx, "deleteme", "", "", "",
+	sid, sharedID, _ := createSessionWithChannels(
+		t, database, "deleteme", "#shared", "#alone",
+	)
+
+	peerSID, peerClientID, _, err := database.CreateSession(
+		ctx, "peer", "", "", "",
 	)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	chID, err := database.GetOrCreateChannel(
-		ctx, "#delchan",
-	)
+	err = database.JoinChannel(ctx, sharedID, peerSID)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	err = database.JoinChannel(ctx, chID, sid)
+	body := json.RawMessage(`["bye"]`)
+
+	peerIDs, err := database.QuitSession(ctx, sid, "deleteme", body)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	err = database.DeleteSession(ctx, sid)
-	if err != nil {
-		t.Fatal(err)
+	if !slices.Equal(peerIDs, []int64{peerSID}) {
+		t.Fatalf("got peers %v, want [%d]", peerIDs, peerSID)
 	}
 
 	_, err = database.GetSessionByNick(ctx, "deleteme")
@@ -861,9 +887,80 @@ func TestDeleteSession(t *testing.T) {
 		t.Fatal("session should be deleted")
 	}
 
-	ids, _ := database.GetChannelMemberIDs(ctx, chID)
-	if len(ids) != 0 {
-		t.Fatal("expected no members after deletion")
+	ids, _ := database.GetChannelMemberIDs(ctx, sharedID)
+	if !slices.Equal(ids, []int64{peerSID}) {
+		t.Fatalf("#shared members: got %v, want [%d]", ids, peerSID)
+	}
+
+	_, err = database.GetChannelByName(ctx, "#alone")
+	if err == nil {
+		t.Fatal("expected the emptied channel to be deleted")
+	}
+
+	checkOneQuitQueued(t, database, peerClientID, "deleteme")
+
+	peerIDs, err = database.QuitSession(ctx, sid, "deleteme", body)
+	if err != nil || len(peerIDs) != 0 {
+		t.Fatalf("second quit: got %v, %v; want none", peerIDs, err)
+	}
+
+	checkOneQuitQueued(t, database, peerClientID, "deleteme")
+}
+
+// checkOneQuitQueued fails the test unless the queue of the
+// client clientID holds one message, a QUIT from nick.
+func checkOneQuitQueued(
+	t *testing.T,
+	database *db.Database,
+	clientID int64,
+	nick string,
+) {
+	t.Helper()
+
+	msgs, _, err := database.PollMessages(t.Context(), clientID, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(msgs) != 1 || msgs[0].Command != "QUIT" || msgs[0].From != nick {
+		t.Fatalf("queue: got %v, want one QUIT from %s", msgs, nick)
+	}
+}
+
+// TestLogoutClientFailureKeepsClient checks that when the
+// session of a logout's last client cannot be deleted,
+// LogoutClient fails and the client stays logged in.
+func TestLogoutClientFailureKeepsClient(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+	ctx := t.Context()
+
+	sid, clientID, token, err := database.CreateSession(
+		ctx, "stuck", "", "", "",
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = database.GetDB().ExecContext(ctx,
+		`CREATE TRIGGER keep_sessions
+		 BEFORE DELETE ON sessions
+		 BEGIN
+		   SELECT RAISE(ABORT, 'sessions are kept');
+		 END`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = database.LogoutClient(ctx, sid, clientID, "stuck", nil)
+	if err == nil {
+		t.Fatal("logout succeeded although the session was kept")
+	}
+
+	_, _, nick, err := database.GetSessionByToken(ctx, token)
+	if err != nil || nick != "stuck" {
+		t.Fatalf("client gone after a failed logout: %q, %v", nick, err)
 	}
 }
 

internal/handlers/api.go

@@ -199,7 +199,7 @@ func (hdlr *Handlers) handleCreateSession(
 		return
 	}
 
-	if !hdlr.validateHashcash(
+	if !hdlr.checkHashcash(
 		writer, request, payload.Hashcash,
 	) {
 		return
@@ -232,14 +232,15 @@ func (hdlr *Handlers) handleCreateSession(
 	}
 
 	hdlr.executeCreateSession(
-		writer, request, payload.Nick, username,
+		writer, request,
+		payload.Nick, username, payload.Hashcash,
 	)
 }
 
 func (hdlr *Handlers) executeCreateSession(
 	writer http.ResponseWriter,
 	request *http.Request,
-	nick, username string,
+	nick, username, stamp string,
 ) {
 	remoteIP := clientIP(request)
 
@@ -247,12 +248,17 @@ func (hdlr *Handlers) executeCreateSession(
 		request.Context(), remoteIP,
 	)
 
+	if !hdlr.claimHashcash(writer, request, stamp) {
+		return
+	}
+
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.CreateSession(
 			request.Context(),
 			nick, username, hostname, remoteIP,
 		)
 	if err != nil {
+		hdlr.hashcashVal.Release(stamp)
 		hdlr.handleCreateSessionError(
 			writer, request, err,
 		)
@@ -273,10 +279,10 @@ func (hdlr *Handlers) executeCreateSession(
 	}, http.StatusCreated)
 }
 
-// validateHashcash validates a hashcash stamp if required.
-// Returns false if validation failed and a response was
-// already sent.
-func (hdlr *Handlers) validateHashcash(
+// checkHashcash checks a hashcash stamp if required,
+// without spending it. Returns false if the check failed
+// and a response was already sent.
+func (hdlr *Handlers) checkHashcash(
 	writer http.ResponseWriter,
 	request *http.Request,
 	stamp string,
@@ -295,7 +301,31 @@ func (hdlr *Handlers) validateHashcash(
 		return false
 	}
 
-	err := hdlr.hashcashVal.Validate(
+	err := hdlr.hashcashVal.Check(
+		stamp, hdlr.params.Config.HashcashBits,
+	)
+	if err != nil {
+		hdlr.respondError(
+			writer, request,
+			"invalid hashcash stamp: "+err.Error(),
+			http.StatusPaymentRequired,
+		)
+
+		return false
+	}
+
+	return true
+}
+
+// claimHashcash spends a stamp that checkHashcash accepted.
+// Returns false if Claim refused the stamp, normally because
+// it was already spent, and a response was already sent.
+func (hdlr *Handlers) claimHashcash(
+	writer http.ResponseWriter,
+	request *http.Request,
+	stamp string,
+) bool {
+	err := hdlr.hashcashVal.Claim(
 		stamp, hdlr.params.Config.HashcashBits,
 	)
 	if err != nil {
@@ -783,7 +813,14 @@ func (hdlr *Handlers) HandleGetMessages() http.HandlerFunc {
 			timeout = maxLongPollTimeout
 		}
 
-		msgs, lastQID, err := hdlr.params.Database.PollMessages(
+		// Register with the broker before reading the queue.
+		// Notify wakes only the channels registered at that
+		// moment, so a message queued after the read below
+		// must find this one there already.
+		waitCh := hdlr.broker.Wait(sessionID)
+		defer hdlr.broker.Remove(sessionID, waitCh)
+
+		msgs, lastQID, err := hdlr.pollMessages(
 			request.Context(), clientID,
 			afterID, pollMessageLimit,
 		)
@@ -811,19 +848,22 @@ func (hdlr *Handlers) HandleGetMessages() http.HandlerFunc {
 
 		hdlr.longPoll(
 			writer, request,
-			sessionID, clientID, afterID, timeout,
+			waitCh, clientID, afterID, timeout,
 		)
 	}
 }
 
+// longPoll waits up to timeout seconds for the broker to
+// signal waitCh, then answers with the messages queued for
+// clientID after afterID. It answers nothing if the client
+// goes away first.
 func (hdlr *Handlers) longPoll(
 	writer http.ResponseWriter,
 	request *http.Request,
-	sessionID, clientID, afterID int64,
+	waitCh <-chan struct{},
+	clientID, afterID int64,
 	timeout int,
 ) {
-	waitCh := hdlr.broker.Wait(sessionID)
-
 	timer := time.NewTimer(
 		time.Duration(timeout) * time.Second,
 	)
@@ -834,14 +874,10 @@ func (hdlr *Handlers) longPoll(
 	case <-waitCh:
 	case <-timer.C:
 	case <-request.Context().Done():
-		hdlr.broker.Remove(sessionID, waitCh)
-
 		return
 	}
 
-	hdlr.broker.Remove(sessionID, waitCh)
-
-	msgs, lastQID, err := hdlr.params.Database.PollMessages(
+	msgs, lastQID, err := hdlr.pollMessages(
 		request.Context(), clientID,
 		afterID, pollMessageLimit,
 	)
@@ -1221,9 +1257,11 @@ func (hdlr *Handlers) handleChannelMsg(
 ) {
 	ctx := request.Context()
 
-	// Delegate validation + fan-out to service layer.
-	dbID, uuid, err := hdlr.svc.SendChannelMessage(
-		ctx, sessionID, nick,
+	// Delegate validation + fan-out to service layer. The
+	// fan-out includes the sender's own session, so all
+	// their clients see the message in long-poll responses.
+	uuid, err := hdlr.svc.SendChannelMessage(
+		ctx, sessionID, 0, nick,
 		command, target, body, meta,
 	)
 	if hdlr.handleServiceError(
@@ -1233,13 +1271,6 @@ func (hdlr *Handlers) handleChannelMsg(
 		return
 	}
 
-	// HTTP echo: enqueue to sender so all their clients
-	// see the message in long-poll responses.
-	_ = hdlr.params.Database.EnqueueToSession(
-		ctx, sessionID, dbID,
-	)
-	hdlr.broker.Notify(sessionID)
-
 	hdlr.respondJSON(writer, request,
 		map[string]string{"id": uuid, statusKey: "sent"},
 		http.StatusOK)
@@ -1254,7 +1285,7 @@ func (hdlr *Handlers) handleDirectMsg(
 	meta json.RawMessage,
 ) {
 	result, err := hdlr.svc.SendDirectMessage(
-		request.Context(), sessionID, nick,
+		request.Context(), sessionID, 0, nick,
 		command, target, body, meta,
 	)
 	if hdlr.handleServiceError(
@@ -1325,7 +1356,7 @@ func (hdlr *Handlers) executeJoin(
 	nick, channel, suppliedKey string,
 ) {
 	result, err := hdlr.svc.JoinChannel(
-		request.Context(), sessionID, nick,
+		request.Context(), sessionID, 0, nick,
 		channel, suppliedKey,
 	)
 	if hdlr.handleServiceError(
@@ -1509,7 +1540,7 @@ func (hdlr *Handlers) handlePart(
 	}
 
 	err := hdlr.svc.PartChannel(
-		request.Context(), sessionID,
+		request.Context(), sessionID, 0,
 		nick, channel, reason,
 	)
 	if hdlr.handleServiceError(
@@ -1580,7 +1611,7 @@ func (hdlr *Handlers) executeNickChange(
 	nick, newNick string,
 ) {
 	err := hdlr.svc.ChangeNick(
-		request.Context(), sessionID, nick, newNick,
+		request.Context(), sessionID, 0, nick, newNick,
 	)
 	if hdlr.handleServiceError(
 		writer, request,
@@ -1635,7 +1666,7 @@ func (hdlr *Handlers) handleTopic(
 	topic := strings.Join(lines, " ")
 
 	err := hdlr.svc.SetTopic(
-		request.Context(), sessionID,
+		request.Context(), sessionID, 0,
 		nick, channel, topic,
 	)
 	if hdlr.handleServiceError(
@@ -2121,7 +2152,7 @@ func (hdlr *Handlers) applyUserMode(
 
 	modeText := modeArgs[0] + " " + targetNick
 	hdlr.svc.BroadcastMode(
-		request.Context(), nick, channel, chID,
+		request.Context(), 0, nick, channel, chID,
 		modeText,
 	)
 
@@ -2167,7 +2198,7 @@ func (hdlr *Handlers) setChannelFlag(
 	}
 
 	hdlr.svc.BroadcastMode(
-		request.Context(), nick, channel, chID,
+		request.Context(), 0, nick, channel, chID,
 		modeStr,
 	)
 
@@ -3395,15 +3426,11 @@ func (hdlr *Handlers) HandleLogout() http.HandlerFunc {
 			return
 		}
 
-		ctx := request.Context()
-
-		err := hdlr.params.Database.DeleteClient(
-			ctx, clientID,
+		err := hdlr.svc.Logout(
+			request.Context(), sessionID, clientID, nick,
 		)
 		if err != nil {
-			hdlr.log.Error(
-				"delete client failed", "error", err,
-			)
+			hdlr.log.Error("logout failed", "error", err)
 			hdlr.respondError(
 				writer, request,
 				"internal error",
@@ -3413,23 +3440,6 @@ func (hdlr *Handlers) HandleLogout() http.HandlerFunc {
 			return
 		}
 
-		// If no clients remain, clean up the user fully:
-		// part all channels (notifying members) and
-		// delete the session.
-		remaining, err := hdlr.params.Database.
-			ClientCountForSession(ctx, sessionID)
-		if err != nil {
-			hdlr.log.Error(
-				"client count check failed", "error", err,
-			)
-		}
-
-		if remaining == 0 {
-			hdlr.cleanupUser(
-				ctx, sessionID, nick,
-			)
-		}
-
 		hdlr.clearAuthCookie(writer)
 
 		hdlr.respondJSON(writer, request,
@@ -3635,7 +3645,7 @@ func (hdlr *Handlers) handleKick(
 	}
 
 	err := hdlr.svc.KickUser(
-		request.Context(), sessionID, nick,
+		request.Context(), sessionID, 0, nick,
 		channel, targetNick, reason,
 	)
 	if hdlr.handleServiceError(
@@ -3708,7 +3718,7 @@ func (hdlr *Handlers) fanOut(
 
 	for _, sid := range sessionIDs {
 		enqErr := hdlr.params.Database.EnqueueToSession(
-			request.Context(), sid, dbID,
+			request.Context(), sid, dbID, 0,
 		)
 		if enqErr != nil {
 			hdlr.log.Error("enqueue failed",

internal/handlers/auth.go

@@ -8,7 +8,12 @@ import (
 	"sneak.berlin/go/neoirc/pkg/irc"
 )
 
-const minPasswordLength = 8
+// A session password is 8 to 72 bytes; bcrypt cannot hash
+// a longer one.
+const (
+	minPasswordLength = 8
+	maxPasswordLength = 72
+)
 
 // HandleLogin authenticates a user with nick and password.
 func (hdlr *Handlers) HandleLogin() http.HandlerFunc {
@@ -149,12 +154,13 @@ func (hdlr *Handlers) handlePass(
 
 	password := lines[0]
 
-	if len(password) < minPasswordLength {
+	if len(password) < minPasswordLength ||
+		len(password) > maxPasswordLength {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
 			irc.ErrNeedMoreParams, nick,
 			[]string{irc.CmdPass},
-			"Password must be at least 8 characters",
+			"Password must be 8 to 72 bytes",
 		)
 
 		return

internal/handlers/export_test.go

@@ -0,0 +1,19 @@
+package handlers
+
+import (
+	"context"
+
+	"sneak.berlin/go/neoirc/internal/db"
+)
+
+// SetPollMessages makes HandleGetMessages read the client
+// output queue with poll in place of Database.PollMessages.
+func (hdlr *Handlers) SetPollMessages(
+	poll func(
+		ctx context.Context,
+		clientID, afterQueueID int64,
+		limit int,
+	) ([]db.IRCMessage, int64, error),
+) {
+	hdlr.pollMessages = poll
+}

internal/handlers/handlers.go

@@ -64,6 +64,16 @@ type Handlers struct {
 	loginLimiter  *ratelimit.Limiter
 	stats         *stats.Tracker
 	cancelCleanup context.CancelFunc
+
+	// pollMessages is Database.PollMessages, with which
+	// HandleGetMessages reads the client output queue. Tests
+	// replace it to act just after a read, or to make a read
+	// fail.
+	pollMessages func(
+		ctx context.Context,
+		clientID, afterQueueID int64,
+		limit int,
+	) ([]db.IRCMessage, int64, error)
 }
 
 // New creates a new Handlers instance.
@@ -95,6 +105,7 @@ func New(
 		hashcashVal:  hashcash.NewValidator(resource),
 		loginLimiter: ratelimit.New(loginRate, loginBurst),
 		stats:        params.Stats,
+		pollMessages: params.Database.PollMessages,
 	}
 
 	lifecycle.Append(fx.Hook{

internal/hashcash/hashcash.go

@@ -77,9 +77,13 @@ func NewValidator(resource string) *Validator {
 	return validator
 }
 
-// Validate checks a hashcash stamp. It returns nil if the
-// stamp is valid and has not been seen before.
-func (v *Validator) Validate(
+// Check returns nil if requiredBits is not positive, or if
+// the stamp is a well-formed, recently dated proof of work
+// for this resource with at least requiredBits. It does not
+// look at or change the set of spent stamps, so a request
+// can check its stamp first and Claim it after its other
+// checks.
+func (v *Validator) Check(
 	stamp string,
 	requiredBits int,
 ) error {
@@ -87,9 +91,49 @@ func (v *Validator) Validate(
 		return nil
 	}
 
+	_, err := v.check(stamp, requiredBits)
+
+	return err
+}
+
+// Claim checks the stamp as Check does and, when
+// requiredBits is positive, records it as spent until it
+// expires. It returns an error if the stamp is already
+// spent. Release gives a claimed stamp back.
+func (v *Validator) Claim(
+	stamp string,
+	requiredBits int,
+) error {
+	if requiredBits <= 0 {
+		return nil
+	}
+
+	stampTime, err := v.check(stamp, requiredBits)
+	if err != nil {
+		return err
+	}
+
+	return v.checkAndRecordStamp(stamp, stampTime)
+}
+
+// Release forgets a claimed stamp so that it can be claimed
+// again, for a request that failed after its Claim.
+// Releasing a stamp that is not claimed does nothing.
+func (v *Validator) Release(stamp string) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+
+	delete(v.spent, stamp)
+}
+
+// check returns the stamp's date if Check accepts it.
+func (v *Validator) check(
+	stamp string,
+	requiredBits int,
+) (time.Time, error) {
 	parts := strings.Split(stamp, ":")
 	if len(parts) != stampFields {
-		return fmt.Errorf(
+		return time.Time{}, fmt.Errorf(
 			"%w: expected %d, got %d",
 			errInvalidFields, stampFields, len(parts),
 		)
@@ -104,25 +148,25 @@ func (v *Validator) Validate(
 		version, bitsStr, resource, requiredBits,
 	)
 	if err != nil {
-		return err
+		return time.Time{}, err
 	}
 
 	stampTime, err := parseStampDate(dateStr)
 	if err != nil {
-		return err
+		return time.Time{}, err
 	}
 
 	err = validateTime(stampTime)
 	if err != nil {
-		return err
+		return time.Time{}, err
 	}
 
 	err = validateProof(stamp, requiredBits)
 	if err != nil {
-		return err
+		return time.Time{}, err
 	}
 
-	return v.checkAndRecordStamp(stamp, stampTime)
+	return stampTime, nil
 }
 
 func (v *Validator) validateHeader(

internal/hashcash/hashcash_test.go

@@ -85,7 +85,7 @@ func TestMintAndValidate(t *testing.T) {
 		t, testBits, "test-resource", todayDate(),
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err != nil {
 		t.Fatalf("valid stamp rejected: %v", err)
 	}
@@ -99,17 +99,74 @@ func TestReplayDetection(t *testing.T) {
 		t, testBits, "test-resource", todayDate(),
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err != nil {
 		t.Fatalf("first use failed: %v", err)
 	}
 
-	err = validator.Validate(stamp, testBits)
+	err = validator.Claim(stamp, testBits)
 	if err == nil {
 		t.Fatal("replay not detected")
 	}
 }
 
+// TestCheckDoesNotSpendStamp checks that a stamp Check
+// accepts can still be claimed, and only once, and that
+// Check still accepts it once it is spent.
+func TestCheckDoesNotSpendStamp(t *testing.T) {
+	t.Parallel()
+
+	validator := hashcash.NewValidator("test-resource")
+	stamp := mintStampWithDate(
+		t, testBits, "test-resource", todayDate(),
+	)
+
+	for range 2 {
+		err := validator.Check(stamp, testBits)
+		if err != nil {
+			t.Fatalf("valid stamp rejected: %v", err)
+		}
+	}
+
+	err := validator.Claim(stamp, testBits)
+	if err != nil {
+		t.Fatalf("claim after check failed: %v", err)
+	}
+
+	err = validator.Claim(stamp, testBits)
+	if err == nil {
+		t.Fatal("replay not detected")
+	}
+
+	err = validator.Check(stamp, testBits)
+	if err != nil {
+		t.Fatalf("spent stamp rejected by Check: %v", err)
+	}
+}
+
+// TestReleasedStampCanBeClaimedAgain checks that Release
+// gives a claimed stamp back.
+func TestReleasedStampCanBeClaimedAgain(t *testing.T) {
+	t.Parallel()
+
+	validator := hashcash.NewValidator("test-resource")
+	stamp := mintStampWithDate(
+		t, testBits, "test-resource", todayDate(),
+	)
+
+	err := validator.Claim(stamp, testBits)
+	if err != nil {
+		t.Fatalf("first claim failed: %v", err)
+	}
+
+	validator.Release(stamp)
+
+	err = validator.Claim(stamp, testBits)
+	if err != nil {
+		t.Fatalf("claim after release failed: %v", err)
+	}
+}
+
 func TestResourceMismatch(t *testing.T) {
 	t.Parallel()
 
@@ -118,7 +175,7 @@ func TestResourceMismatch(t *testing.T) {
 		t, testBits, "wrong-resource", todayDate(),
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err == nil {
 		t.Fatal("expected resource mismatch error")
 	}
@@ -129,7 +186,7 @@ func TestInvalidStampFormat(t *testing.T) {
 
 	validator := hashcash.NewValidator("test-resource")
 
-	err := validator.Validate(
+	err := validator.Claim(
 		"not:a:valid:stamp", testBits,
 	)
 	if err == nil {
@@ -146,7 +203,7 @@ func TestBadVersion(t *testing.T) {
 		testBits, todayDate(), "test-resource",
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err == nil {
 		t.Fatal("expected bad version error")
 	}
@@ -162,7 +219,7 @@ func TestInsufficientDifficulty(t *testing.T) {
 		todayDate(), "test-resource",
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err == nil {
 		t.Fatal("expected insufficient bits error")
 	}
@@ -178,7 +235,7 @@ func TestExpiredStamp(t *testing.T) {
 		t, testBits, "test-resource", oldDate,
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err == nil {
 		t.Fatal("expected expired stamp error")
 	}
@@ -189,9 +246,14 @@ func TestZeroBitsSkipsValidation(t *testing.T) {
 
 	validator := hashcash.NewValidator("test-resource")
 
-	err := validator.Validate("garbage", 0)
+	err := validator.Check("garbage", 0)
 	if err != nil {
-		t.Fatalf("zero bits should skip: %v", err)
+		t.Fatalf("zero bits should skip the check: %v", err)
+	}
+
+	err = validator.Claim("garbage", 0)
+	if err != nil {
+		t.Fatalf("zero bits should skip the claim: %v", err)
 	}
 }
 
@@ -204,7 +266,7 @@ func TestLongDateFormat(t *testing.T) {
 		t, testBits, "test-resource", longDate,
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err != nil {
 		t.Fatalf("long date stamp rejected: %v", err)
 	}
@@ -219,7 +281,7 @@ func TestBadDateFormat(t *testing.T) {
 		testBits, "test-resource",
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err == nil {
 		t.Fatal("expected bad date error")
 	}
@@ -235,7 +297,7 @@ func TestMultipleUniqueStamps(t *testing.T) {
 			t, testBits, "test-resource", todayDate(),
 		)
 
-		err := validator.Validate(stamp, testBits)
+		err := validator.Claim(stamp, testBits)
 		if err != nil {
 			t.Fatalf("unique stamp rejected: %v", err)
 		}
@@ -251,7 +313,7 @@ func TestHigherBitsStillValid(t *testing.T) {
 		t, 4, "test-resource", todayDate(),
 	)
 
-	err := validator.Validate(stamp, testBits)
+	err := validator.Claim(stamp, testBits)
 	if err != nil {
 		t.Fatalf(
 			"higher-difficulty stamp rejected: %v",

internal/ircserver/commands.go

@@ -81,10 +81,10 @@ func (c *Conn) handleNick(
 	}
 
 	oldMask := c.hostmask()
-	oldNick := c.nick
+	oldNick := c.currentNick()
 
 	err := c.svc.ChangeNick(
-		ctx, c.sessionID, oldNick, newNick,
+		ctx, c.sessionID, c.clientID, oldNick, newNick,
 	)
 	if err != nil {
 		c.sendIRCError(err)
@@ -92,9 +92,10 @@ func (c *Conn) handleNick(
 		return
 	}
 
-	c.mu.Lock()
-	c.nick = newNick
-	c.mu.Unlock()
+	// Take the nick the session holds, not newNick: another
+	// client of the session may have changed it again since
+	// ChangeNick stored newNick.
+	c.loadSessionNick(ctx)
 
 	// Echo NICK change to the client on wire.
 	c.send(FormatMessage(oldMask, "NICK", newNick))
@@ -128,8 +129,8 @@ func (c *Conn) handlePrivmsg(
 	body, _ := json.Marshal([]string{text}) //nolint:errchkjson
 
 	if strings.HasPrefix(target, "#") {
-		_, _, err := c.svc.SendChannelMessage(
-			ctx, c.sessionID, c.nick,
+		_, err := c.svc.SendChannelMessage(
+			ctx, c.sessionID, c.clientID, c.currentNick(),
 			msg.Command, target, body, nil,
 		)
 		if err != nil {
@@ -137,7 +138,7 @@ func (c *Conn) handlePrivmsg(
 		}
 	} else {
 		result, err := c.svc.SendDirectMessage(
-			ctx, c.sessionID, c.nick,
+			ctx, c.sessionID, c.clientID, c.currentNick(),
 			msg.Command, target, body, nil,
 		)
 		if err != nil {
@@ -199,7 +200,7 @@ func (c *Conn) joinChannel(
 	channel, key string,
 ) {
 	result, err := c.svc.JoinChannel(
-		ctx, c.sessionID, c.nick, channel, key,
+		ctx, c.sessionID, c.clientID, c.currentNick(), channel, key,
 	)
 	if err != nil {
 		c.sendIRCError(err)
@@ -337,7 +338,7 @@ func (c *Conn) partChannel(
 	channel, reason string,
 ) {
 	err := c.svc.PartChannel(
-		ctx, c.sessionID, c.nick, channel, reason,
+		ctx, c.sessionID, c.clientID, c.currentNick(), channel, reason,
 	)
 	if err != nil {
 		c.sendIRCError(err)
@@ -401,7 +402,7 @@ func (c *Conn) handleTopic(
 	newTopic := msg.Params[1]
 
 	err := c.svc.SetTopic(
-		ctx, c.sessionID, c.nick, channel, newTopic,
+		ctx, c.sessionID, c.clientID, c.currentNick(), channel, newTopic,
 	)
 	if err != nil {
 		c.sendIRCError(err)
@@ -708,7 +709,7 @@ func (c *Conn) applyChannelModes(
 		c.send(FormatMessage(c.hostmask(), "MODE", params...))
 
 		c.svc.BroadcastMode(
-			ctx, c.nick, channel, chID, modeReply,
+			ctx, c.clientID, c.currentNick(), channel, chID, modeReply,
 		)
 	}
 }
@@ -1185,7 +1186,7 @@ func (c *Conn) handleKick(
 	}
 
 	err := c.svc.KickUser(
-		ctx, c.sessionID, c.nick,
+		ctx, c.sessionID, c.clientID, c.currentNick(),
 		channel, targetNick, reason,
 	)
 	if err != nil {
@@ -1216,17 +1217,16 @@ func (c *Conn) handlePassPostReg(
 	}
 
 	password := msg.Params[0]
-	if len(password) < minPasswordLen {
-		c.sendFromServer("NOTICE", c.nick,
-			"Password must be at least 8 characters",
-		)
-
+	if !c.checkPasswordLength(password) {
 		return
 	}
 
-	c.setPassword(ctx, password)
+	err := c.setPassword(ctx, password)
+	if err != nil {
+		return
+	}
 
-	c.sendFromServer("NOTICE", c.nick,
+	c.sendFromServer("NOTICE", c.currentNick(),
 		"Password set. You can reconnect using "+
 			"PASS <password> with your nick.",
 	)
@@ -1250,7 +1250,7 @@ func (c *Conn) handleInvite(
 	channel := msg.Params[1]
 
 	targetID, err := c.svc.InviteUser(
-		ctx, c.sessionID, c.nick, targetNick, channel,
+		ctx, c.sessionID, c.currentNick(), targetNick, channel,
 	)
 	if err != nil {
 		c.sendIRCError(err)
@@ -1262,14 +1262,13 @@ func (c *Conn) handleInvite(
 		irc.RplInviting, targetNick, channel,
 	)
 
-	// Send INVITE notice to target via service fan-out.
-	body, _ := json.Marshal( //nolint:errchkjson
-		[]string{"You have been invited to " + channel},
-	)
+	// Queue the INVITE to the target with the body the HTTP
+	// API uses.
+	body, _ := json.Marshal([]string{channel}) //nolint:errchkjson
 
 	_, _, _ = c.svc.FanOut( //nolint:dogsled // fire-and-forget broadcast
-		ctx, "INVITE", c.nick, targetNick, targetID, 0,
-		nil, body, nil, []int64{targetID},
+		ctx, "INVITE", c.currentNick(), targetNick, targetID, 0,
+		nil, body, nil, []int64{targetID}, 0,
 	)
 }
 

internal/ircserver/conn.go

@@ -27,6 +27,7 @@ const (
 	pingInterval    = 90 * time.Second
 	pongDeadline    = 30 * time.Second
 	minPasswordLen  = 8
+	maxPasswordLen  = 72 // bcrypt cannot hash a longer one
 	maxHashcashBits = 40
 )
 
@@ -62,6 +63,7 @@ type Conn struct {
 	registered bool
 	gotNick    bool
 	gotUser    bool
+	gotPass    bool
 	passWord   string
 
 	lastQueueID int64
@@ -70,7 +72,6 @@ type Conn struct {
 }
 
 func newConn(
-	ctx context.Context,
 	tcpConn net.Conn,
 	log *slog.Logger,
 	database *db.Database,
@@ -94,7 +95,6 @@ func newConn(
 		svc:       svc,
 		serverSfx: srvName,
 		remoteIP:  host,
-		hostname:  resolveHost(ctx, host),
 	}
 
 	conn.commands = conn.buildCommandMap()
@@ -212,12 +212,15 @@ func resolveHost(ctx context.Context, addr string) string {
 }
 
 // serve is the main loop for a single IRC client connection.
+// It first sets the client's hostname to what resolve returns
+// for the client's address.
 // Cancelling ctx when it returns stops the relay goroutine.
 // When nothing has been read for interval the client is sent
 // a PING, and when nothing is read within deadline after that
 // the connection is closed.
 func (c *Conn) serve(
 	ctx context.Context,
+	resolve func(ctx context.Context, addr string) string,
 	interval, deadline time.Duration,
 ) {
 	ctx, cancel := context.WithCancel(ctx)
@@ -226,6 +229,11 @@ func (c *Conn) serve(
 	// still end the session then.
 	defer c.cleanup(context.WithoutCancel(ctx))
 
+	// The hostname is looked up here, on this connection's
+	// goroutine, and not when the connection is accepted, so
+	// that a slow lookup holds up only this client.
+	c.hostname = resolve(ctx, c.remoteIP)
+
 	ping := time.AfterFunc(interval, func() {
 		c.send("PING :" + c.serverSfx)
 	})
@@ -305,6 +313,22 @@ func (c *Conn) currentNick() string {
 	return c.nick
 }
 
+// loadSessionNick sets c.nick to the nick the connection's
+// session holds in the database, read by session ID. The
+// connection's own NICK and the relay passing on a NICK line
+// both call it, and it reads and sets the nick under c.mu, so
+// whichever runs last leaves the connection on its session's
+// nick. If the read fails, c.nick is left as it is.
+func (c *Conn) loadSessionNick(ctx context.Context) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	nick, err := c.database.GetSessionNick(ctx, c.sessionID)
+	if err == nil {
+		c.nick = nick
+	}
+}
+
 // send writes a formatted IRC line to the connection.
 func (c *Conn) send(line string) {
 	c.sendWithin(writeTimeout, line)
@@ -337,7 +361,7 @@ func (c *Conn) sendNumeric(
 	code irc.IRCMessageType,
 	params ...string,
 ) {
-	nick := c.nick
+	nick := c.currentNick()
 	if nick == "" {
 		nick = "*"
 	}
@@ -361,9 +385,11 @@ func (c *Conn) sendFromServer(
 // hostmask returns the client's full hostmask
 // (nick!user@host).
 func (c *Conn) hostmask() string {
+	nick := c.currentNick()
+
 	user := c.username
 	if user == "" {
-		user = c.nick
+		user = nick
 	}
 
 	host := c.hostname
@@ -371,7 +397,7 @@ func (c *Conn) hostmask() string {
 		host = c.remoteIP
 	}
 
-	return c.nick + "!" + user + "@" + host
+	return nick + "!" + user + "@" + host
 }
 
 // handleMessage dispatches a parsed IRC message using
@@ -430,6 +456,7 @@ func (c *Conn) handlePreRegistration(
 		}
 
 		c.passWord = msg.Params[0]
+		c.gotPass = true
 	case irc.CmdNick:
 		if len(msg.Params) < 1 {
 			c.sendNumeric(
@@ -544,17 +571,20 @@ func (c *Conn) completeRegistration(ctx context.Context) {
 	// So that KILL, from either transport, can close it.
 	c.svc.RegisterWireConn(sessionID, c)
 
-	// If PASS was provided before registration, set the
-	// session password.
-	if c.passWord != "" && len(c.passWord) >= minPasswordLen {
-		c.setPassword(ctx, c.passWord)
-	}
-
 	// Send welcome burst.
 	c.deliverWelcome()
 	c.deliverLusers(ctx)
 	c.deliverMOTD()
 
+	// If PASS was given before registration, store its
+	// password now, after the welcome burst, so that a
+	// NOTICE refusing it reaches a registered client. A
+	// failure to store it is only logged, as it is for PASS
+	// after registration.
+	if c.gotPass && c.checkPasswordLength(c.passWord) {
+		_ = c.setPassword(ctx, c.passWord)
+	}
+
 	// Start the message relay goroutine.
 	go c.relayMessages(ctx)
 }
@@ -637,13 +667,33 @@ func (c *Conn) deliverMOTD() {
 	)
 }
 
-// setPassword sets a bcrypt password on the session.
-func (c *Conn) setPassword(ctx context.Context, pw string) {
+// checkPasswordLength reports whether pw is 8 to 72 bytes
+// long, and sends the client a NOTICE saying so when it is
+// not.
+func (c *Conn) checkPasswordLength(pw string) bool {
+	if len(pw) >= minPasswordLen && len(pw) <= maxPasswordLen {
+		return true
+	}
+
+	c.sendFromServer("NOTICE", c.currentNick(),
+		"Password must be 8 to 72 bytes",
+	)
+
+	return false
+}
+
+// setPassword sets a bcrypt password on the session, and
+// logs and returns the error when it was not stored.
+func (c *Conn) setPassword(ctx context.Context, pw string) error {
 	// Use the database's auth module to hash and store.
 	err := c.database.SetPassword(ctx, c.sessionID, pw)
 	if err != nil {
 		c.log.Error(
 			"failed to set password", "error", err,
 		)
+
+		return err
 	}
+
+	return nil
 }

internal/ircserver/export_test.go

@@ -15,7 +15,8 @@ import (
 
 // NewTestServer creates a Server suitable for testing, whose
 // connections use interval and deadline in place of
-// pingInterval and pongDeadline.
+// pingInterval and pongDeadline, and resolve in place of
+// resolveHost.
 // The caller must call Stop() when finished.
 func NewTestServer(
 	log *slog.Logger,
@@ -23,6 +24,7 @@ func NewTestServer(
 	database *db.Database,
 	brk *broker.Broker,
 	interval, deadline time.Duration,
+	resolve func(ctx context.Context, addr string) string,
 ) *Server {
 	globs := &globals.Globals{
 		Appname:   "neoirc",
@@ -44,9 +46,16 @@ func NewTestServer(
 
 		pingInterval: interval,
 		pongDeadline: deadline,
+		resolveHost:  resolve,
 	}
 }
 
+// ResolveHost is the reverse DNS lookup that a server made by
+// New does for each client.
+func ResolveHost(ctx context.Context, addr string) string {
+	return resolveHost(ctx, addr)
+}
+
 // Start exposes the unexported start method for tests.
 func (s *Server) Start(addr string) error {
 	return s.start(context.Background(), addr)
@@ -62,6 +71,11 @@ func (s *Server) Listener() net.Listener {
 	return s.listener
 }
 
+// Service returns the service the server's connections use.
+func (s *Server) Service() *service.Service {
+	return s.svc
+}
+
 // PingTimes returns how long the server's connections wait
 // with nothing read before they are sent a PING, and after it
 // before they are closed.
@@ -97,10 +111,7 @@ func NewTestConn(
 	tcpConn net.Conn,
 	nick string,
 ) *Conn {
-	conn := newConn(
-		context.Background(), tcpConn, log,
-		nil, nil, cfg, nil,
-	)
+	conn := newConn(tcpConn, log, nil, nil, cfg, nil)
 	conn.nick = nick
 
 	return conn

internal/ircserver/integration_test.go

@@ -1373,6 +1373,42 @@ func TestIntegrationInviteUserOnChannel(t *testing.T) {
 	)
 }
 
+// TestIntegrationInviteLine checks that an IRC listener user
+// invited by an IRC listener user, and then over the HTTP
+// API, gets an INVITE line from the inviter for the channel
+// each time.
+func TestIntegrationInviteLine(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	alice := env.dial(t)
+	alice.register("alice")
+	alice.joinAndDrain("#inv")
+
+	bob := env.dial(t)
+	bob.register("bob")
+
+	alice.sendAndExpect("INVITE bob #inv", " 341 ")
+
+	got := bob.readLine()
+	want := ":alice!alice@* INVITE bob #inv"
+
+	if got != want {
+		t.Errorf("from the IRC listener: got %q, want %q", got, want)
+	}
+
+	// The HTTP API queues an INVITE with the channel as its body.
+	env.queueMessage(t, "bob", "INVITE", "carol", "bob", []string{"#inv"})
+
+	got = bob.readLine()
+	want = ":carol!carol@* INVITE bob #inv"
+
+	if got != want {
+		t.Errorf("over the HTTP API: got %q, want %q", got, want)
+	}
+}
+
 // TestIntegrationModeSecretList checks that LIST shows a +s
 // channel only to its members.
 func TestIntegrationModeSecretList(t *testing.T) {

internal/ircserver/relay.go

@@ -27,17 +27,22 @@ func (c *Conn) relayMessages(ctx context.Context) {
 		default:
 		}
 
+		// Register with the broker before draining, so that a
+		// message queued after the drain has read the queue
+		// still signals waitCh.
+		waitCh := c.brk.Wait(c.sessionID)
+
 		// Drain any available messages.
 		delivered := c.drainQueue(ctx)
 
 		if delivered {
+			c.brk.Remove(c.sessionID, waitCh)
+
 			// Tight loop while there are messages.
 			continue
 		}
 
 		// Wait for notification or timeout.
-		waitCh := c.brk.Wait(c.sessionID)
-
 		select {
 		case <-waitCh:
 			// New message notification — loop back.
@@ -87,7 +92,7 @@ func (c *Conn) drainQueue(ctx context.Context) bool {
 //
 //nolint:cyclop // dispatch table
 func (c *Conn) deliverIRCMessage(
-	_ context.Context,
+	ctx context.Context,
 	msg *db.IRCMessage,
 ) {
 	command := msg.Command
@@ -115,7 +120,7 @@ func (c *Conn) deliverIRCMessage(
 	case command == irc.CmdPart:
 		c.deliverPart(msg, text)
 	case command == irc.CmdNick:
-		c.deliverNickChange(msg, text)
+		c.deliverNickChange(ctx, msg, text)
 	case command == irc.CmdQuit:
 		c.deliverQuitMsg(msg, text)
 	case command == irc.CmdTopic:
@@ -193,15 +198,6 @@ func (c *Conn) deliverTextMessage(
 	from := msg.From
 	target := msg.To
 
-	c.mu.Lock()
-	nick := c.nick
-	c.mu.Unlock()
-
-	// Don't echo our own messages back.
-	if from == nick {
-		return
-	}
-
 	prefix := from
 	if !strings.Contains(prefix, "!") {
 		prefix = from + "!" + from + "@*"
@@ -214,16 +210,6 @@ func (c *Conn) deliverTextMessage(
 
 // deliverJoin sends a JOIN notification.
 func (c *Conn) deliverJoin(msg *db.IRCMessage) {
-	c.mu.Lock()
-	nick := c.nick
-	c.mu.Unlock()
-
-	// Don't echo our own JOINs (we already sent them
-	// during joinChannel).
-	if msg.From == nick {
-		return
-	}
-
 	prefix := msg.From + "!" + msg.From + "@*"
 	channel := msg.To
 
@@ -232,14 +218,6 @@ func (c *Conn) deliverJoin(msg *db.IRCMessage) {
 
 // deliverPart sends a PART notification.
 func (c *Conn) deliverPart(msg *db.IRCMessage, text string) {
-	c.mu.Lock()
-	nick := c.nick
-	c.mu.Unlock()
-
-	if msg.From == nick {
-		return
-	}
-
 	prefix := msg.From + "!" + msg.From + "@*"
 	channel := msg.To
 
@@ -252,18 +230,17 @@ func (c *Conn) deliverPart(msg *db.IRCMessage, text string) {
 	}
 }
 
-// deliverNickChange sends a NICK change notification.
+// deliverNickChange sends a NICK change notification. The
+// change may be its own session's, made from another client,
+// so the connection first takes the nick its session holds
+// now. It does not go by the line's old nick: the connection
+// may have taken that nick after another user gave it up.
 func (c *Conn) deliverNickChange(
+	ctx context.Context,
 	msg *db.IRCMessage,
 	newNick string,
 ) {
-	c.mu.Lock()
-	nick := c.nick
-	c.mu.Unlock()
-
-	if msg.From == nick {
-		return
-	}
+	c.loadSessionNick(ctx)
 
 	prefix := msg.From + "!" + msg.From + "@*"
 
@@ -275,14 +252,6 @@ func (c *Conn) deliverQuitMsg(
 	msg *db.IRCMessage,
 	text string,
 ) {
-	c.mu.Lock()
-	nick := c.nick
-	c.mu.Unlock()
-
-	if msg.From == nick {
-		return
-	}
-
 	prefix := msg.From + "!" + msg.From + "@*"
 
 	if text != "" {
@@ -335,16 +304,24 @@ func (c *Conn) deliverKickMsg(
 	}
 }
 
-// deliverInviteMsg sends an INVITE notification.
+// deliverInviteMsg sends an INVITE line from the inviter
+// for the channel named in text, or nothing when text names
+// no channel.
 func (c *Conn) deliverInviteMsg(
-	_ *db.IRCMessage,
+	msg *db.IRCMessage,
 	text string,
 ) {
+	if text == "" {
+		return
+	}
+
 	c.mu.Lock()
 	nick := c.nick
 	c.mu.Unlock()
 
-	c.sendFromServer("NOTICE", nick, text)
+	prefix := msg.From + "!" + msg.From + "@*"
+
+	c.send(FormatMessage(prefix, "INVITE", nick, text))
 }
 
 // deliverWallops sends a WALLOPS notification.

internal/ircserver/relay_test.go

@@ -1,6 +1,7 @@
 package ircserver_test
 
 import (
+	"context"
 	"encoding/json"
 	"slices"
 	"strings"
@@ -8,6 +9,7 @@ import (
 	"time"
 
 	"sneak.berlin/go/neoirc/internal/ircserver"
+	"sneak.berlin/go/neoirc/internal/service"
 )
 
 // queueMessage queues a message for the user with nick
@@ -39,7 +41,7 @@ func (env *testEnv) queueMessage(
 		t.Fatalf("get session of %s: %v", recipient, err)
 	}
 
-	err = env.database.EnqueueToSession(ctx, sessionID, msgID)
+	err = env.database.EnqueueToSession(ctx, sessionID, msgID, 0)
 	if err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
@@ -47,14 +49,13 @@ func (env *testEnv) queueMessage(
 	env.brk.Notify(sessionID)
 }
 
-// TestRelayKeepsOneWaitChannel checks that an idle IRC
-// listener connection holds at most one broker wait channel
-// across several relay ticks, and none once it closes.
+// TestRelayKeepsOneWaitChannel checks that an IRC listener
+// connection holds at most one broker wait channel across
+// several relay ticks, both while idle and after the relay
+// has delivered it a message, and none once it closes.
 func TestRelayKeepsOneWaitChannel(t *testing.T) {
 	t.Parallel()
 
-	const idleTicks = 5
-
 	env := newTestEnv(t)
 
 	client := env.dial(t)
@@ -65,15 +66,17 @@ func TestRelayKeepsOneWaitChannel(t *testing.T) {
 		t.Fatalf("get session of idle: %v", err)
 	}
 
-	for tick := range idleTicks {
-		time.Sleep(ircserver.PollInterval)
+	env.checkOneWaitChannel(t, sessionID)
 
-		got := env.brk.ListenerCount(sessionID)
-		if got > 1 {
-			t.Fatalf("tick %d: got %d wait channels, want at most 1",
-				tick+1, got)
-		}
-	}
+	env.queueMessage(
+		t, "idle", "PRIVMSG", "carol", "idle", []string{"hello"},
+	)
+
+	client.readUntil(func(l string) bool {
+		return strings.Contains(l, "hello")
+	})
+
+	env.checkOneWaitChannel(t, sessionID)
 
 	err = client.conn.Close()
 	if err != nil {
@@ -92,6 +95,28 @@ func TestRelayKeepsOneWaitChannel(t *testing.T) {
 	}
 }
 
+// checkOneWaitChannel fails the test if the session
+// sessionID holds more than one broker wait channel at any of
+// several relay ticks.
+func (env *testEnv) checkOneWaitChannel(
+	t *testing.T,
+	sessionID int64,
+) {
+	t.Helper()
+
+	const ticks = 5
+
+	for tick := range ticks {
+		time.Sleep(ircserver.PollInterval)
+
+		got := env.brk.ListenerCount(sessionID)
+		if got > 1 {
+			t.Fatalf("tick %d: got %d wait channels, want at most 1",
+				tick+1, got)
+		}
+	}
+}
+
 // TestRelayMultiLineBody checks that each line of a PRIVMSG
 // or NOTICE body sent over the HTTP API reaches an IRC
 // listener user as its own line.
@@ -188,6 +213,38 @@ func TestRelayModeParameters(t *testing.T) {
 	}
 }
 
+// TestRelayInviteWithoutChannel checks that an INVITE whose
+// body names no channel sends the invited IRC listener user
+// no INVITE line.
+func TestRelayInviteWithoutChannel(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	bob := env.dial(t)
+	bob.register("bob")
+
+	// A nil body is stored as JSON null, which is not an array.
+	for _, body := range [][]string{nil, {}, {""}} {
+		env.queueMessage(t, "bob", "INVITE", "carol", "bob", body)
+	}
+
+	// The relay sends a user's queue in order, so this arrives
+	// after anything sent for the INVITEs above.
+	env.queueMessage(t, "bob", "PRIVMSG", "carol", "bob",
+		[]string{"the end"})
+
+	lines := bob.readUntil(func(l string) bool {
+		return strings.HasSuffix(l, " :the end")
+	})
+
+	for _, line := range lines {
+		if strings.Contains(line, " INVITE ") {
+			t.Errorf("got %q, want no INVITE line", line)
+		}
+	}
+}
+
 // TestRelayLineBreaks checks that a CR, LF or NUL in a stored
 // body line, key or mask never reaches an IRC listener user
 // as a line break, so no extra line arrives, and that a body
@@ -269,3 +326,372 @@ func TestRelayNickDiffersOnlyInCase(t *testing.T) {
 		}
 	}
 }
+
+// TestRelayOwnChangeOnce checks that an IRC listener user who
+// sets a topic, changes a channel mode or kicks gets one TOPIC,
+// MODE or KICK line for it, and so does the other member.
+func TestRelayOwnChangeOnce(t *testing.T) {
+	t.Parallel()
+
+	for _, step := range []struct {
+		command, line string
+	}{
+		{"TOPIC", "TOPIC #dup :new topic"},
+		{"MODE", "MODE #dup +m"},
+		{"KICK", "KICK #dup carl :bye"},
+	} {
+		t.Run(step.command, func(t *testing.T) {
+			t.Parallel()
+
+			env := newTestEnv(t)
+
+			alice := env.dial(t)
+			alice.register("alice")
+			alice.joinAndDrain("#dup")
+
+			carl := env.dial(t)
+			carl.register("carl")
+			carl.joinAndDrain("#dup")
+
+			alice.send(step.line)
+
+			// The reply to alice's next command comes after her
+			// command has finished, so her own copy comes before it.
+			beforePong := alice.sendAndExpect("PING :done", "PONG")
+
+			// The relay sends a user's queue in order, so a message
+			// queued now arrives after any relayed copy.
+			for nick, client := range map[string]*testClient{
+				"alice": alice, "carl": carl,
+			} {
+				env.queueMessage(
+					t, nick, "PRIVMSG", "dave", nick,
+					[]string{"after the change"},
+				)
+
+				lines := client.readUntil(func(l string) bool {
+					return strings.HasSuffix(l, " :after the change")
+				})
+
+				if client == alice {
+					lines = slices.Concat(beforePong, lines)
+				}
+
+				var changes []string
+
+				for _, line := range lines {
+					if strings.Contains(line, " "+step.command+" #dup ") {
+						changes = append(changes, line)
+					}
+				}
+
+				if len(changes) != 1 {
+					t.Errorf("%s got %q, want one %s line",
+						nick, changes, step.command)
+				}
+			}
+		})
+	}
+}
+
+// TestRelayOwnSessionOnce checks that a command a user makes
+// from one client of their session reaches each of the
+// session's clients once: an IRC listener connection and an
+// HTTP API client. The connection that sent a command gets
+// only its own echo, and none for PRIVMSG and NOTICE, which
+// IRC does not echo.
+//
+//nolint:funlen // table-driven test
+func TestRelayOwnSessionOnce(t *testing.T) {
+	t.Parallel()
+
+	hello := json.RawMessage(`["hello"]`)
+
+	for _, step := range []struct {
+		// line is the command as alice sends it on the IRC
+		// listener.
+		line string
+		// api makes the same command for her session the way
+		// the HTTP API does.
+		api func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error
+		// echoes is how many copies alice's connection gets of
+		// line when it sends line itself.
+		echoes int
+	}{
+		{"PRIVMSG #chan :hello", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			_, err := svc.SendChannelMessage(
+				ctx, sessionID, 0, "alice", "PRIVMSG", "#chan", hello, nil,
+			)
+
+			return err
+		}, 0},
+		{"NOTICE bob :hello", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			_, err := svc.SendDirectMessage(
+				ctx, sessionID, 0, "alice", "NOTICE", "bob", hello, nil,
+			)
+
+			return err
+		}, 0},
+		{"JOIN #other", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			_, err := svc.JoinChannel(ctx, sessionID, 0, "alice", "#other", "")
+
+			return err
+		}, 1},
+		{"PART #chan :bye", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			return svc.PartChannel(ctx, sessionID, 0, "alice", "#chan", "bye")
+		}, 1},
+		{"NICK alice2", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			return svc.ChangeNick(ctx, sessionID, 0, "alice", "alice2")
+		}, 1},
+		{"TOPIC #chan :new topic", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			return svc.SetTopic(
+				ctx, sessionID, 0, "alice", "#chan", "new topic",
+			)
+		}, 1},
+		{"MODE #chan +m", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			chID, err := svc.ValidateChannelOp(ctx, sessionID, "#chan")
+			if err != nil {
+				return err
+			}
+
+			err = svc.SetChannelFlag(ctx, chID, 'm', true)
+			if err != nil {
+				return err
+			}
+
+			svc.BroadcastMode(ctx, 0, "alice", "#chan", chID, "+m")
+
+			return nil
+		}, 1},
+		{"KICK #chan bob :bye", func(
+			ctx context.Context, svc *service.Service, sessionID int64,
+		) error {
+			return svc.KickUser(
+				ctx, sessionID, 0, "alice", "#chan", "bob", "bye",
+			)
+		}, 1},
+	} {
+		command := strings.Fields(step.line)[0]
+
+		t.Run(command+" from IRC", func(t *testing.T) {
+			t.Parallel()
+
+			ircCopies, httpCopies := ownSessionCopies(t, step.line, nil)
+			if ircCopies != step.echoes || httpCopies != 1 {
+				t.Errorf("connection got %d, HTTP client got %d, want %d and 1",
+					ircCopies, httpCopies, step.echoes)
+			}
+		})
+
+		t.Run(command+" from the HTTP API", func(t *testing.T) {
+			t.Parallel()
+
+			ircCopies, httpCopies := ownSessionCopies(t, step.line, step.api)
+			if ircCopies != 1 || httpCopies != 1 {
+				t.Errorf("connection got %d, HTTP client got %d, want 1 and 1",
+					ircCopies, httpCopies)
+			}
+		})
+	}
+}
+
+// ownSessionCopies sets up alice with aliceWithHTTPClient. It
+// makes the command line from her connection, or with api from
+// the HTTP API client when api is not nil, and returns how many
+// copies of it her connection and her HTTP API client got.
+func ownSessionCopies(
+	t *testing.T,
+	line string,
+	api func(ctx context.Context, svc *service.Service, sessionID int64) error,
+) (int, int) {
+	t.Helper()
+
+	ctx := t.Context()
+	env := newTestEnv(t)
+	alice, _, sessionID, httpClientID := aliceWithHTTPClient(t, env)
+
+	var lines []string
+
+	if api == nil {
+		alice.send(line)
+
+		// Her echo comes before the reply to her next command.
+		lines = alice.sendAndExpect("PING :done", "PONG")
+	} else {
+		err := api(ctx, env.srv.Service(), sessionID)
+		if err != nil {
+			t.Fatalf("%s over the HTTP API: %v", line, err)
+		}
+	}
+
+	msgs, _, err := env.database.PollMessages(ctx, httpClientID, 0, 0)
+	if err != nil {
+		t.Fatalf("poll the HTTP API client: %v", err)
+	}
+
+	httpCopies := 0
+
+	for _, msg := range msgs {
+		if msg.Command == strings.Fields(line)[0] {
+			httpCopies++
+		}
+	}
+
+	// The relay sends a queue in order, so this arrives after any
+	// copy. It is queued by session, as NICK changes her nick.
+	endID, _, err := env.database.InsertMessage(
+		ctx, "PRIVMSG", "dave", "alice", 0, 0,
+		nil, json.RawMessage(`["the end"]`), nil,
+	)
+	if err != nil {
+		t.Fatalf("insert message: %v", err)
+	}
+
+	err = env.database.EnqueueToSession(ctx, sessionID, endID, 0)
+	if err != nil {
+		t.Fatalf("enqueue: %v", err)
+	}
+
+	env.brk.Notify(sessionID)
+
+	lines = append(lines, alice.readUntil(func(l string) bool {
+		return strings.HasSuffix(l, " :the end")
+	})...)
+
+	// A copy starts with the command and its first parameter.
+	start := " " + strings.Join(strings.Fields(line)[:2], " ")
+	ircCopies := strings.Count(strings.Join(lines, "\n"), start)
+
+	return ircCopies, httpCopies
+}
+
+// aliceWithHTTPClient connects alice to the IRC listener and
+// has her join #chan, which bob is on too, then adds an HTTP API
+// client to her session with the password her connection set,
+// as POST /api/v1/login does. It returns her connection, bob's
+// connection, her session and her HTTP API client.
+func aliceWithHTTPClient(
+	t *testing.T, env *testEnv,
+) (*testClient, *testClient, int64, int64) {
+	t.Helper()
+
+	const password = "alicepass"
+
+	alice := env.dial(t)
+	alice.send("PASS " + password)
+	alice.register("alice")
+	// Registration stores the password before the JOIN runs.
+	alice.joinAndDrain("#chan")
+
+	bob := env.dial(t)
+	bob.register("bob")
+	bob.joinAndDrain("#chan")
+
+	sessionID, httpClientID, _, err := env.database.LoginUser(
+		t.Context(), "alice", password, "127.0.0.1", "localhost",
+	)
+	if err != nil {
+		t.Fatalf("log in as alice: %v", err)
+	}
+
+	return alice, bob, sessionID, httpClientID
+}
+
+// TestRelayNickChangeFromHTTPAPI checks that once alice's nick
+// is changed from her HTTP API client, her IRC listener
+// connection uses the new nick: what she then sends from it
+// reaches bob under the new nick.
+func TestRelayNickChangeFromHTTPAPI(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+	alice, bob, sessionID, _ := aliceWithHTTPClient(t, env)
+
+	bob.joinAndDrain("#other")
+
+	// As the HTTP API does.
+	err := env.srv.Service().ChangeNick(
+		t.Context(), sessionID, 0, "alice", "alice2",
+	)
+	if err != nil {
+		t.Fatalf("change nick over the HTTP API: %v", err)
+	}
+
+	// Her connection has taken the new nick once it has sent her
+	// the change.
+	const change = ":alice!alice@* NICK alice2"
+
+	alice.readUntil(func(l string) bool { return l == change })
+	bob.readUntil(func(l string) bool { return l == change })
+
+	for _, step := range []struct {
+		line, want string
+	}{
+		{"PRIVMSG #chan :hi there", ":alice2!alice2@* PRIVMSG #chan :hi there"},
+		{"JOIN #other", ":alice2!alice2@* JOIN #other"},
+		{"NICK alice3", ":alice2!alice2@* NICK alice3"},
+	} {
+		alice.send(step.line)
+
+		got := bob.readLine()
+		if got != step.want {
+			t.Errorf("%s: got %q, want %q", step.line, got, step.want)
+		}
+	}
+}
+
+// TestRelayNickChangeKeepsTakenNick checks that an IRC
+// listener connection which takes a nick another user has
+// given up keeps it when that user's change reaches it
+// afterwards: what it then sends goes out under the nick its
+// session holds.
+func TestRelayNickChangeKeepsTakenNick(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	bob := env.dial(t)
+	bob.register("bob")
+	bob.sendAndExpect("NICK bob2", " NICK bob2")
+
+	alice := env.dial(t)
+	alice.register("alice")
+	alice.sendAndExpect("NICK bob", " NICK bob")
+	alice.joinAndDrain("#chan")
+
+	bob.joinAndDrain("#chan")
+
+	// Bob's change reaches alice only now, as it does when she
+	// takes his old nick before her connection has passed the
+	// change on. She holds bob now, so it is queued to bob.
+	env.queueMessage(t, "bob", "NICK", "bob", "", []string{"bob2"})
+
+	alice.readUntil(func(l string) bool {
+		return l == ":bob!bob@* NICK bob2"
+	})
+
+	alice.send("PRIVMSG #chan :hi there")
+
+	const want = ":bob!bob@* PRIVMSG #chan :hi there"
+
+	got := bob.readLine()
+	if got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+}

internal/ircserver/server.go

@@ -52,6 +52,10 @@ type Server struct {
 	// same names, except in tests, which shorten them.
 	pingInterval time.Duration
 	pongDeadline time.Duration
+
+	// resolveHost is the function of the same name, except in
+	// tests, which replace it with one that blocks.
+	resolveHost func(ctx context.Context, addr string) string
 }
 
 // New creates a new IRC Server and registers its lifecycle
@@ -75,6 +79,7 @@ func New(
 
 		pingInterval: pingInterval,
 		pongDeadline: pongDeadline,
+		resolveHost:  resolveHost,
 	}
 
 	listenAddr := params.Config.IRCListenAddr
@@ -175,7 +180,7 @@ func (s *Server) acceptLoop(ctx context.Context) {
 		}
 
 		client := newConn(
-			ctx, tcpConn, s.log,
+			tcpConn, s.log,
 			s.database, s.brk, s.cfg, s.svc,
 		)
 
@@ -204,7 +209,10 @@ func (s *Server) acceptLoop(ctx context.Context) {
 				s.mu.Unlock()
 			}()
 
-			client.serve(ctx, s.pingInterval, s.pongDeadline)
+			client.serve(
+				ctx, s.resolveHost,
+				s.pingInterval, s.pongDeadline,
+			)
 		}()
 	}
 }

internal/ircserver/server_test.go

@@ -2,6 +2,7 @@ package ircserver_test
 
 import (
 	"bufio"
+	"context"
 	"crypto/rand"
 	"database/sql"
 	"errors"
@@ -11,6 +12,7 @@ import (
 	"os"
 	"runtime"
 	"strings"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -90,6 +92,21 @@ func newTestEnvWithPingTimes(
 ) *testEnv {
 	t.Helper()
 
+	return newTestEnvWithResolver(
+		t, cfg, interval, deadline, ircserver.ResolveHost,
+	)
+}
+
+// newTestEnvWithResolver is newTestEnvWithPingTimes, except
+// that the server looks up a client's hostname with resolve.
+func newTestEnvWithResolver(
+	t *testing.T,
+	cfg *config.Config,
+	interval, deadline time.Duration,
+	resolve func(ctx context.Context, addr string) string,
+) *testEnv {
+	t.Helper()
+
 	// A random name, so that no other test environment, not
 	// even an earlier run of the same test, can share it.
 	dsn := fmt.Sprintf(
@@ -147,7 +164,7 @@ func newTestEnvWithPingTimes(
 	))
 
 	srv := ircserver.NewTestServer(
-		log, cfg, database, brk, interval, deadline,
+		log, cfg, database, brk, interval, deadline, resolve,
 	)
 
 	err = srv.Start(addr)
@@ -415,6 +432,49 @@ func TestRegistration(t *testing.T) {
 	assertContains(t, lines, " 001 ", "RPL_WELCOME")
 }
 
+// TestRegistrationWhileAnotherLookupIsPending checks that a
+// client is accepted and registered while the hostname lookup
+// of an earlier client has not returned, and that it
+// registers with the hostname its own lookup returned.
+func TestRegistrationWhileAnotherLookupIsPending(t *testing.T) {
+	t.Parallel()
+
+	const lookedUpHost = "client.example"
+
+	var lookups atomic.Int32
+
+	firstLookupStarted := make(chan struct{})
+
+	// The first lookup returns only when the server stops.
+	resolve := func(ctx context.Context, _ string) string {
+		if lookups.Add(1) == 1 {
+			close(firstLookupStarted)
+			<-ctx.Done()
+		}
+
+		return lookedUpHost
+	}
+
+	env := newTestEnvWithResolver(
+		t, &config.Config{ServerName: testServerName},
+		ircserver.PingInterval, ircserver.PongDeadline, resolve,
+	)
+
+	env.dial(t)
+
+	select {
+	case <-firstLookupStarted:
+	case <-time.After(testTimeout):
+		t.Fatal("the first client's lookup did not start")
+	}
+
+	lines := env.dial(t).register("second")
+	assertContains(
+		t, lines, "second!second@"+lookedUpHost,
+		"RPL_WELCOME with the looked-up hostname",
+	)
+}
+
 // TestEachTestEnvHasItsOwnDatabase checks that a test
 // environment starts on an empty database while another one
 // is still open.
@@ -585,8 +645,6 @@ func TestNewPingTimes(t *testing.T) {
 func TestIdleCleanupKeepsActiveUser(t *testing.T) {
 	t.Parallel()
 
-	const idleTimeout = 500 * time.Millisecond
-
 	env := newTestEnv(t)
 
 	active := env.dial(t)
@@ -595,13 +653,17 @@ func TestIdleCleanupKeepsActiveUser(t *testing.T) {
 	idle := env.dial(t)
 	idle.register("idle")
 
-	time.Sleep(idleTimeout)
+	// Both users were last seen before cutoff, and only active
+	// sends a command after it, so the result does not depend
+	// on how long the PONG takes to arrive.
+	cutoff := time.Now()
+
 	active.sendAndExpect("PING :still here", "PONG")
 
 	// The idle cleanup in internal/handlers removes exactly
 	// the users this returns.
 	stale, err := env.database.GetStaleOrphanSessions(
-		t.Context(), time.Now().Add(-idleTimeout),
+		t.Context(), cutoff,
 	)
 	if err != nil {
 		t.Fatalf("get stale sessions: %v", err)
@@ -1098,6 +1160,165 @@ func TestHandlePassPostRegistration(t *testing.T) {
 	)
 }
 
+// The shortest and longest password PASS accepts; bcrypt
+// cannot hash more than 72 bytes.
+const (
+	minPasswordBytes = 8
+	maxPasswordBytes = 72
+)
+
+// passwordLengthNotice is the NOTICE text for a password that
+// is too short or too long.
+const passwordLengthNotice = "Password must be 8 to 72 bytes"
+
+// passwordCase is a password a PASS test sends, and whether
+// the server should store it.
+type passwordCase struct {
+	name     string
+	password string
+	stored   bool
+}
+
+// passwordCases returns the passwords the PASS length tests
+// send: one of 8 to 72 bytes is stored and any other is
+// refused. The limit counts bytes: "é" is two bytes in UTF-8,
+// so 72 of them are refused.
+func passwordCases() []passwordCase {
+	return []passwordCase{
+		{"empty", "", false},
+		{"7 bytes", strings.Repeat("a", minPasswordBytes-1), false},
+		{"8 bytes", strings.Repeat("a", minPasswordBytes), true},
+		{"72 bytes", strings.Repeat("a", maxPasswordBytes), true},
+		{"73 bytes", strings.Repeat("a", maxPasswordBytes+1), false},
+		{"72 characters", strings.Repeat("é", maxPasswordBytes), false},
+	}
+}
+
+// assertStored fails the test unless nick can log in with
+// password exactly when stored is true.
+func assertStored(
+	t *testing.T, env *testEnv, nick, password string, stored bool,
+) {
+	t.Helper()
+
+	_, _, token, err := env.database.LoginUser(
+		t.Context(), nick, password, "127.0.0.1", "localhost",
+	)
+
+	loggedIn := err == nil && token != ""
+	if loggedIn != stored {
+		t.Errorf(
+			"log in as %s: logged in %v, want %v (error: %v)",
+			nick, loggedIn, stored, err,
+		)
+	}
+}
+
+// TestPassPostRegistrationLength checks that PASS after
+// registration stores and confirms a password of 8 to 72
+// bytes, and refuses any other with a NOTICE.
+func TestPassPostRegistrationLength(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	for i, tc := range passwordCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			nick := fmt.Sprintf("postpass%d", i)
+			client := env.dial(t)
+
+			client.register(nick)
+			client.send("PASS :" + tc.password)
+
+			// The server answers commands in order, so its
+			// reply to PASS comes before the PONG.
+			lines := client.sendAndExpect("PING :after", "PONG")
+
+			reply := passwordLengthNotice
+			if tc.stored {
+				reply = "Password set"
+			}
+
+			assertContains(t, lines, reply, "reply to PASS")
+			assertStored(t, env, nick, tc.password, tc.stored)
+		})
+	}
+}
+
+// TestPassPostRegistrationNotStored checks that PASS is not
+// confirmed when the password could not be stored.
+func TestPassPostRegistrationNotStored(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+	client := env.dial(t)
+
+	client.register("failpass")
+
+	_, err := env.database.GetDB().ExecContext(t.Context(),
+		`CREATE TRIGGER refuse_password
+		 BEFORE UPDATE OF password_hash ON sessions
+		 BEGIN SELECT RAISE(ABORT, 'refused'); END`,
+	)
+	if err != nil {
+		t.Fatalf("create trigger: %v", err)
+	}
+
+	client.send("PASS :mypassword123")
+
+	// The server answers commands in order, so anything it
+	// sent about PASS comes before the PONG.
+	lines := client.sendAndExpect("PING :after", "PONG")
+
+	assertNotContains(
+		t, lines, "Password set",
+		"confirmation of a password that was not stored",
+	)
+}
+
+// TestPassBeforeRegistrationLength checks that a PASS before
+// registration stores a password of 8 to 72 bytes, and that
+// any other is refused with a NOTICE once registration
+// completes.
+func TestPassBeforeRegistrationLength(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	for i, tc := range passwordCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			nick := fmt.Sprintf("prepass%d", i)
+			client := env.dial(t)
+
+			client.send("PASS :" + tc.password)
+			client.register(nick)
+
+			// The password is checked after the welcome
+			// burst, which register reads; the PONG comes
+			// after that.
+			lines := client.sendAndExpect("PING :after", "PONG")
+
+			if tc.stored {
+				assertNotContains(
+					t, lines, passwordLengthNotice,
+					"refusal of a valid password",
+				)
+			} else {
+				assertContains(
+					t, lines, passwordLengthNotice,
+					"refusal after registration",
+				)
+			}
+
+			assertStored(t, env, nick, tc.password, tc.stored)
+		})
+	}
+}
+
 func TestPreRegistrationNotRegistered(t *testing.T) {
 	t.Parallel()
 

internal/service/service.go

@@ -312,7 +312,7 @@ func (s *Service) SendWallops(
 
 	_, _, err = s.FanOut(
 		ctx, irc.CmdWallops, nick, "*", 0, 0,
-		nil, body, nil, recipients,
+		nil, body, nil, recipients, 0,
 	)
 	if err != nil {
 		return fmt.Errorf("wallops: %w", err)
@@ -347,12 +347,19 @@ type DirectMsgResult struct {
 // session IDs, notifying each via the broker. toSessionID
 // and toChannelID are the recipient InsertMessage records
 // for history, 0 when there is none.
+//
+// skipClientID is the client whose queue the message is
+// not added to: the IRC listener connection that sent the
+// command, which has already shown it to its user. The HTTP
+// API passes 0, as its clients see their own commands
+// through their queues.
 func (s *Service) FanOut(
 	ctx context.Context,
 	command, from, to string,
 	toSessionID, toChannelID int64,
 	params, body, meta json.RawMessage,
 	sessionIDs []int64,
+	skipClientID int64,
 ) (int64, string, error) {
 	dbID, msgUUID, err := s.db.InsertMessage(
 		ctx, command, from, to,
@@ -363,66 +370,40 @@ func (s *Service) FanOut(
 	}
 
 	for _, sid := range sessionIDs {
-		_ = s.db.EnqueueToSession(ctx, sid, dbID)
+		_ = s.db.EnqueueToSession(ctx, sid, dbID, skipClientID)
 		s.broker.Notify(sid)
 	}
 
 	return dbID, msgUUID, nil
 }
 
-// excludeSession returns a copy of ids without the given
-// session.
-func excludeSession(
-	ids []int64,
-	exclude int64,
-) []int64 {
-	out := make([]int64, 0, len(ids))
-
-	for _, id := range ids {
-		if id != exclude {
-			out = append(out, id)
-		}
-	}
-
-	return out
-}
-
-// SendChannelMessage validates the hashcash stamp of a
-// PRIVMSG to a +H channel, membership and moderation, then
-// fans out a message to all channel members except the
-// sender. Returns the database row ID, message UUID, and
-// any error. The dbID lets callers enqueue the same
-// message to the sender when echo is needed (HTTP
-// transport).
+// SendChannelMessage checks membership, bans and
+// moderation, then the hashcash stamp of a PRIVMSG to a +H
+// channel, then fans out a message to all channel members,
+// the sender's session included, skipping client
+// skipClientID as FanOut does. The stamp is checked after
+// the other checks so that a message they refuse does not
+// spend it. Returns the message UUID and any error.
 func (s *Service) SendChannelMessage(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	nick, command, channel string,
 	body, meta json.RawMessage,
-) (int64, string, error) {
+) (string, error) {
 	noSuchChannel := &IRCError{
 		irc.ErrNoSuchChannel, []string{channel}, msgNoSuchChannel,
 	}
 
 	chID, err := s.db.GetChannelByName(ctx, channel)
 	if err != nil {
-		return 0, "", noSuchChannel
-	}
-
-	if command == irc.CmdPrivmsg {
-		err = s.checkChannelHashcash(
-			ctx, chID, channel, body, meta,
-		)
-		if err != nil {
-			return 0, "", err
-		}
+		return "", noSuchChannel
 	}
 
 	isMember, _ := s.db.IsChannelMember(
 		ctx, chID, sessionID,
 	)
 	if !isMember {
-		return 0, "", &IRCError{
+		return "", &IRCError{
 			irc.ErrCannotSendToChan,
 			[]string{channel},
 			"Cannot send to channel",
@@ -434,7 +415,7 @@ func (s *Service) SendChannelMessage(
 		ctx, chID, sessionID,
 	)
 	if banErr == nil && isBanned {
-		return 0, "", &IRCError{
+		return "", &IRCError{
 			irc.ErrCannotSendToChan,
 			[]string{channel},
 			"Cannot send to channel (+b)",
@@ -451,7 +432,7 @@ func (s *Service) SendChannelMessage(
 		)
 
 		if !isOp && !isVoiced {
-			return 0, "", &IRCError{
+			return "", &IRCError{
 				irc.ErrCannotSendToChan,
 				[]string{channel},
 				"Cannot send to channel (+m)",
@@ -459,31 +440,40 @@ func (s *Service) SendChannelMessage(
 		}
 	}
 
-	memberIDs, _ := s.db.GetChannelMemberIDs(ctx, chID)
-	recipients := excludeSession(memberIDs, sessionID)
+	if command == irc.CmdPrivmsg {
+		err = s.checkChannelHashcash(
+			ctx, chID, channel, body, meta,
+		)
+		if err != nil {
+			return "", err
+		}
+	}
 
-	dbID, uuid, fanErr := s.FanOut(
+	memberIDs, _ := s.db.GetChannelMemberIDs(ctx, chID)
+
+	_, uuid, fanErr := s.FanOut(
 		ctx, command, nick, channel, 0, chID,
-		nil, body, meta, recipients,
+		nil, body, meta, memberIDs, skipClientID,
 	)
 	// The channel was deleted after the lookup above.
 	if db.IsForeignKeyConstraintError(fanErr) {
-		return 0, "", noSuchChannel
+		return "", noSuchChannel
 	}
 
 	if fanErr != nil {
-		return 0, "", fanErr
+		return "", fanErr
 	}
 
-	return dbID, uuid, nil
+	return uuid, nil
 }
 
 // SendDirectMessage validates the target and sends a
-// direct message, returning the message UUID and any away
-// message set on the target.
+// direct message to the target and the sender's session,
+// skipping client skipClientID as FanOut does, and returns
+// the message UUID and any away message set on the target.
 func (s *Service) SendDirectMessage(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	nick, command, target string,
 	body, meta json.RawMessage,
 ) (*DirectMsgResult, error) {
@@ -505,7 +495,7 @@ func (s *Service) SendDirectMessage(
 
 	_, uuid, fanErr := s.FanOut(
 		ctx, command, nick, target, targetSID, 0,
-		nil, body, meta, recipients,
+		nil, body, meta, recipients, skipClientID,
 	)
 	// The target's session was deleted after the lookup above.
 	if db.IsForeignKeyConstraintError(fanErr) {
@@ -521,11 +511,12 @@ func (s *Service) SendDirectMessage(
 
 // JoinChannel creates or joins a channel, making the
 // first joiner the operator. Fans out the JOIN to all
-// channel members. A channel name that validChannelRe
-// does not match gets ERR_NOSUCHCHANNEL.
+// channel members, skipping client skipClientID as FanOut
+// does. A channel name that validChannelRe does not match
+// gets ERR_NOSUCHCHANNEL.
 func (s *Service) JoinChannel(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	nick, channel, suppliedKey string,
 ) (*JoinResult, error) {
 	if !validChannelRe.MatchString(channel) {
@@ -548,7 +539,7 @@ func (s *Service) JoinChannel(
 
 	_, _, _ = s.FanOut( //nolint:dogsled // fire-and-forget broadcast
 		ctx, irc.CmdJoin, nick, channel, 0, chID,
-		nil, body, nil, memberIDs,
+		nil, body, nil, memberIDs, skipClientID,
 	)
 
 	return &JoinResult{
@@ -557,12 +548,12 @@ func (s *Service) JoinChannel(
 	}, nil
 }
 
-// PartChannel validates membership, broadcasts PART to
-// remaining members, removes the user, and cleans up empty
-// channels.
+// PartChannel validates membership, broadcasts PART to all
+// channel members, skipping client skipClientID as FanOut
+// does, removes the user, and cleans up empty channels.
 func (s *Service) PartChannel(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	nick, channel, reason string,
 ) error {
 	chID, err := s.db.GetChannelByName(ctx, channel)
@@ -586,12 +577,11 @@ func (s *Service) PartChannel(
 	}
 
 	memberIDs, _ := s.db.GetChannelMemberIDs(ctx, chID)
-	recipients := excludeSession(memberIDs, sessionID)
 	body, _ := json.Marshal([]string{reason}) //nolint:errchkjson
 
 	_, _, _ = s.FanOut( //nolint:dogsled // fire-and-forget broadcast
 		ctx, irc.CmdPart, nick, channel, 0, chID,
-		nil, body, nil, recipients,
+		nil, body, nil, memberIDs, skipClientID,
 	)
 
 	s.db.PartChannelAndDeleteIfEmpty(ctx, chID, sessionID) //nolint:errcheck,gosec
@@ -600,10 +590,11 @@ func (s *Service) PartChannel(
 }
 
 // SetTopic validates membership and topic-lock, sets the
-// topic, and broadcasts the change.
+// topic, and broadcasts the change to all channel members,
+// skipping client skipClientID as FanOut does.
 func (s *Service) SetTopic(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	nick, channel, topic string,
 ) error {
 	chID, err := s.db.GetChannelByName(ctx, channel)
@@ -652,18 +643,19 @@ func (s *Service) SetTopic(
 
 	_, _, _ = s.FanOut( //nolint:dogsled // fire-and-forget broadcast
 		ctx, irc.CmdTopic, nick, channel, 0, chID,
-		nil, body, nil, memberIDs,
+		nil, body, nil, memberIDs, skipClientID,
 	)
 
 	return nil
 }
 
 // KickUser validates operator status and target
-// membership, broadcasts the KICK, removes the target,
-// and cleans up empty channels.
+// membership, broadcasts the KICK to all channel members,
+// skipping client skipClientID as FanOut does, removes the
+// target, and cleans up empty channels.
 func (s *Service) KickUser(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	nick, channel, targetNick, reason string,
 ) error {
 	chID, err := s.db.GetChannelByName(ctx, channel)
@@ -716,7 +708,7 @@ func (s *Service) KickUser(
 
 	_, _, _ = s.FanOut( //nolint:dogsled // fire-and-forget broadcast
 		ctx, irc.CmdKick, nick, channel, 0, chID,
-		params, body, nil, memberIDs,
+		params, body, nil, memberIDs, skipClientID,
 	)
 
 	s.db.PartChannelAndDeleteIfEmpty(ctx, chID, targetSID) //nolint:errcheck,gosec
@@ -797,10 +789,11 @@ func (s *Service) InviteUser(
 }
 
 // ChangeNick changes a user's nickname and broadcasts the
-// change to all users sharing channels.
+// change to the user's own session and all users sharing
+// channels, skipping client skipClientID as FanOut does.
 func (s *Service) ChangeNick(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	oldNick, newNick string,
 ) error {
 	err := s.db.ChangeNick(ctx, sessionID, newNick)
@@ -821,66 +814,62 @@ func (s *Service) ChangeNick(
 		}
 	}
 
-	s.broadcastNickChange(ctx, sessionID, oldNick, newNick)
+	s.broadcastNickChange(
+		ctx, sessionID, skipClientID, oldNick, newNick,
+	)
 
 	return nil
 }
 
-// BroadcastQuit broadcasts a QUIT to all channel peers,
-// parts all channels, and deletes the session. Uses the
-// FanOut pattern: one message row fanned out to all unique
-// peer sessions.
+// BroadcastQuit parts the session from all its channels,
+// deletes it, and queues a QUIT to the users who shared a
+// channel with it, in one transaction, so that the QUIT is
+// queued before anyone else can take the nick, and then
+// wakes those users' long polls. Of several calls for one
+// session at once, only the one that deletes it sends the
+// QUIT.
 func (s *Service) BroadcastQuit(
 	ctx context.Context,
 	sessionID int64,
 	nick, reason string,
 ) {
-	channels, err := s.db.GetSessionChannels(
-		ctx, sessionID,
-	)
+	body, _ := json.Marshal([]string{reason}) //nolint:errchkjson
+
+	peerIDs, err := s.db.QuitSession(ctx, sessionID, nick, body)
 	if err != nil {
+		s.log.Error("quit failed", "error", err)
+
 		return
 	}
 
-	notified := make(map[int64]bool)
+	for _, peerID := range peerIDs {
+		s.broker.Notify(peerID)
+	}
+}
 
-	for _, ch := range channels {
-		memberIDs, memErr := s.db.GetChannelMemberIDs(
-			ctx, ch.ID,
-		)
-		if memErr != nil {
-			continue
-		}
+// Logout deletes a client of the session and, if that was
+// the session's last client, does what BroadcastQuit does.
+// If that fails, nothing changes and Logout returns the
+// error.
+func (s *Service) Logout(
+	ctx context.Context,
+	sessionID, clientID int64,
+	nick string,
+) error {
+	body, _ := json.Marshal([]string{"Connection closed"}) //nolint:errchkjson
 
-		for _, mid := range memberIDs {
-			if mid == sessionID || notified[mid] {
-				continue
-			}
-
-			notified[mid] = true
-		}
+	peerIDs, err := s.db.LogoutClient(
+		ctx, sessionID, clientID, nick, body,
+	)
+	if err != nil {
+		return fmt.Errorf("logout: %w", err)
 	}
 
-	if len(notified) > 0 {
-		recipients := make([]int64, 0, len(notified))
-		for sid := range notified {
-			recipients = append(recipients, sid)
-		}
-
-		body, _ := json.Marshal([]string{reason}) //nolint:errchkjson
-
-		_, _, _ = s.FanOut(
-			ctx, irc.CmdQuit, nick, "", 0, 0,
-			nil, body, nil, recipients,
-		)
+	for _, peerID := range peerIDs {
+		s.broker.Notify(peerID)
 	}
 
-	for _, ch := range channels {
-		s.db.PartChannel(ctx, ch.ID, sessionID) //nolint:errcheck,gosec
-		s.db.DeleteChannelIfEmpty(ctx, ch.ID)   //nolint:errcheck,gosec
-	}
-
-	s.db.DeleteSession(ctx, sessionID) //nolint:errcheck,gosec
+	return nil
 }
 
 // SetAway sets or clears the away message. Returns true
@@ -1047,9 +1036,10 @@ func (s *Service) SetChannelFlag(
 }
 
 // BroadcastMode fans out a MODE change to all channel
-// members.
+// members, skipping client skipClientID as FanOut does.
 func (s *Service) BroadcastMode(
 	ctx context.Context,
+	skipClientID int64,
 	nick, channel string,
 	chID int64,
 	modeText string,
@@ -1059,7 +1049,7 @@ func (s *Service) BroadcastMode(
 
 	_, _, _ = s.FanOut( //nolint:dogsled // fire-and-forget broadcast
 		ctx, irc.CmdMode, nick, channel, 0, chID,
-		nil, body, nil, memberIDs,
+		nil, body, nil, memberIDs, skipClientID,
 	)
 }
 
@@ -1311,11 +1301,12 @@ func (s *Service) checkChannelHashcash(
 	return nil
 }
 
-// broadcastNickChange notifies channel peers of a nick
+// broadcastNickChange notifies the user's own session,
+// except client skipClientID, and channel peers of a nick
 // change.
 func (s *Service) broadcastNickChange(
 	ctx context.Context,
-	sessionID int64,
+	sessionID, skipClientID int64,
 	oldNick, newNick string,
 ) {
 	channels, err := s.db.GetSessionChannels(
@@ -1337,7 +1328,7 @@ func (s *Service) broadcastNickChange(
 	}
 
 	// Notify the user themselves (for multi-client sync).
-	_ = s.db.EnqueueToSession(ctx, sessionID, dbID)
+	_ = s.db.EnqueueToSession(ctx, sessionID, dbID, skipClientID)
 	s.broker.Notify(sessionID)
 	notified[sessionID] = true
 
@@ -1356,7 +1347,7 @@ func (s *Service) broadcastNickChange(
 
 			notified[mid] = true
 
-			_ = s.db.EnqueueToSession(ctx, mid, dbID)
+			_ = s.db.EnqueueToSession(ctx, mid, dbID, 0)
 			s.broker.Notify(mid)
 		}
 	}

internal/service/service_test.go

@@ -24,6 +24,7 @@ import (
 	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/db"
 	"sneak.berlin/go/neoirc/internal/globals"
+	"sneak.berlin/go/neoirc/internal/hashcash"
 	"sneak.berlin/go/neoirc/internal/logger"
 	"sneak.berlin/go/neoirc/internal/service"
 	"sneak.berlin/go/neoirc/pkg/irc"
@@ -167,7 +168,7 @@ func TestFanOut(t *testing.T) {
 	dbID, uuid, err := env.svc.FanOut(
 		ctx, irc.CmdPrivmsg, "alice", "#test", 0, 0,
 		nil, body, nil,
-		[]int64{sid1, sid2},
+		[]int64{sid1, sid2}, 0,
 	)
 	if err != nil {
 		t.Fatalf("FanOut: %v", err)
@@ -189,7 +190,7 @@ func TestJoinChannel(t *testing.T) {
 	sid := createSession(ctx, t, env.db, "alice")
 
 	result, err := env.svc.JoinChannel(
-		ctx, sid, "alice", "#general", "",
+		ctx, sid, 0, "alice", "#general", "",
 	)
 	if err != nil {
 		t.Fatalf("JoinChannel: %v", err)
@@ -207,7 +208,7 @@ func TestJoinChannel(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	result2, err := env.svc.JoinChannel(
-		ctx, sid2, "bob", "#general", "",
+		ctx, sid2, 0, "bob", "#general", "",
 	)
 	if err != nil {
 		t.Fatalf("JoinChannel bob: %v", err)
@@ -229,14 +230,14 @@ func TestPartChannel(t *testing.T) {
 	sid := createSession(ctx, t, env.db, "alice")
 
 	_, err := env.svc.JoinChannel(
-		ctx, sid, "alice", "#general", "",
+		ctx, sid, 0, "alice", "#general", "",
 	)
 	if err != nil {
 		t.Fatalf("JoinChannel: %v", err)
 	}
 
 	err = env.svc.PartChannel(
-		ctx, sid, "alice", "#general", "bye",
+		ctx, sid, 0, "alice", "#general", "bye",
 	)
 	if err != nil {
 		t.Fatalf("PartChannel: %v", err)
@@ -244,7 +245,7 @@ func TestPartChannel(t *testing.T) {
 
 	// Parting a non-existent channel returns error.
 	err = env.svc.PartChannel(
-		ctx, sid, "alice", "#nonexistent", "",
+		ctx, sid, 0, "alice", "#nonexistent", "",
 	)
 	if err == nil {
 		t.Error("expected error for non-existent channel")
@@ -308,7 +309,7 @@ func joinConcurrently(
 
 		joins[i] = func() error {
 			result, err := env.svc.JoinChannel(
-				ctx, sessionID, nick, channel, "",
+				ctx, sessionID, 0, nick, channel, "",
 			)
 			results[i] = result
 
@@ -334,7 +335,7 @@ func TestConcurrentJoinsRespectUserLimit(t *testing.T) {
 		opSID := createSession(ctx, t, env.db, opNick)
 
 		created, err := env.svc.JoinChannel(
-			ctx, opSID, opNick, channel, "",
+			ctx, opSID, 0, opNick, channel, "",
 		)
 		if err != nil {
 			t.Fatalf("join %s: %v", opNick, err)
@@ -447,7 +448,7 @@ func TestJoinConcurrentWithLastPart(t *testing.T) {
 		joinerSID := createSession(ctx, t, env.db, joinerNick)
 
 		_, err := env.svc.JoinChannel(
-			ctx, leaverSID, leaverNick, channel, "",
+			ctx, leaverSID, 0, leaverNick, channel, "",
 		)
 		if err != nil {
 			t.Fatalf("join %s: %v", leaverNick, err)
@@ -456,12 +457,12 @@ func TestJoinConcurrentWithLastPart(t *testing.T) {
 		errs := runConcurrently(
 			func() error {
 				return env.svc.PartChannel(
-					ctx, leaverSID, leaverNick, channel, "",
+					ctx, leaverSID, 0, leaverNick, channel, "",
 				)
 			},
 			func() error {
 				_, joinErr := env.svc.JoinChannel(
-					ctx, joinerSID, joinerNick, channel, "",
+					ctx, joinerSID, 0, joinerNick, channel, "",
 				)
 
 				return joinErr
@@ -495,6 +496,208 @@ func TestJoinConcurrentWithLastPart(t *testing.T) {
 	}
 }
 
+// TestJoinConcurrentWithLastQuit checks that a user who
+// sends JOIN without the key to a +k channel, again after
+// each ERR_BADCHANNELKEY, while the channel's only member
+// quits, gets in only once the channel is deleted, into a
+// new channel of that name with no key.
+func TestJoinConcurrentWithLastQuit(t *testing.T) {
+	env := newTestEnv(t)
+	ctx := t.Context()
+
+	for trial := range concurrentJoinTrials {
+		channel := fmt.Sprintf("#keyed%d", trial)
+		leaverNick := fmt.Sprintf("leaver%d", trial)
+		leaverSID := createSession(ctx, t, env.db, leaverNick)
+		joinerNick := fmt.Sprintf("joiner%d", trial)
+		joinerSID := createSession(ctx, t, env.db, joinerNick)
+
+		created, err := env.svc.JoinChannel(
+			ctx, leaverSID, 0, leaverNick, channel, "",
+		)
+		if err != nil {
+			t.Fatalf("join %s: %v", leaverNick, err)
+		}
+
+		err = env.db.SetChannelKey(ctx, created.ChannelID, "secret")
+		if err != nil {
+			t.Fatalf("set +k: %v", err)
+		}
+
+		var joined *service.JoinResult
+
+		errs := runConcurrently(
+			func() error {
+				env.svc.BroadcastQuit(ctx, leaverSID, leaverNick, "")
+
+				return nil
+			},
+			// The database has one connection, so retried
+			// JOINs take turns with the QUIT's statements
+			// and land between any two that are not in one
+			// transaction. A JOIN after the QUIT gets in, so
+			// the loop ends.
+			func() error {
+				for {
+					var (
+						joinErr error
+						ircErr  *service.IRCError
+					)
+
+					joined, joinErr = env.svc.JoinChannel(
+						ctx, joinerSID, 0, joinerNick, channel, "",
+					)
+					if !errors.As(joinErr, &ircErr) ||
+						ircErr.Code != irc.ErrBadChannelKey {
+						return joinErr
+					}
+				}
+			},
+		)
+		if errs[1] != nil {
+			t.Fatalf("trial %d: JOIN: %v", trial, errs[1])
+		}
+
+		key, _ := env.db.GetChannelKey(ctx, joined.ChannelID)
+		if key != "" {
+			t.Errorf(
+				"trial %d: %s got into +k %s without the key",
+				trial, joinerNick, channel,
+			)
+		}
+	}
+}
+
+// quitCrowdSize is how many sessions share a second channel
+// with the quitting session in
+// TestQuitQueuedAheadOfNewNickHoldersJoin.
+const quitCrowdSize = 10
+
+// TestQuitQueuedAheadOfNewNickHoldersJoin checks that when
+// a new session takes a quitting session's nick and joins a
+// channel the quitting session shared with a watcher, while
+// the QUIT is going out, the watcher has the QUIT queued
+// ahead of that JOIN. The quitting session is also on a
+// channel with quitCrowdSize other sessions, made before the
+// watcher's channel, so that its QUIT reaches the watcher
+// last.
+func TestQuitQueuedAheadOfNewNickHoldersJoin(t *testing.T) {
+	env := newTestEnv(t)
+	ctx := t.Context()
+
+	for trial := range concurrentJoinTrials {
+		nick := fmt.Sprintf("reused%d", trial)
+		crowd := fmt.Sprintf("#crowd%d", trial)
+		shared := fmt.Sprintf("#shared%d", trial)
+		quitterSID := createSession(ctx, t, env.db, nick)
+
+		for _, channel := range []string{crowd, shared} {
+			_, err := env.svc.JoinChannel(ctx, quitterSID, 0, nick, channel, "")
+			if err != nil {
+				t.Fatalf("join %s: %v", channel, err)
+			}
+		}
+
+		for member := range quitCrowdSize {
+			memberNick := fmt.Sprintf("crowd%dx%d", trial, member)
+			memberSID := createSession(ctx, t, env.db, memberNick)
+
+			_, err := env.svc.JoinChannel(ctx, memberSID, 0, memberNick, crowd, "")
+			if err != nil {
+				t.Fatalf("join %s: %v", memberNick, err)
+			}
+		}
+
+		watcherNick := fmt.Sprintf("watcher%d", trial)
+
+		watcherSID, watcherClientID, _, err := env.db.CreateSession(
+			ctx, watcherNick, watcherNick, "localhost", "127.0.0.1",
+		)
+		if err != nil {
+			t.Fatalf("create session %s: %v", watcherNick, err)
+		}
+
+		_, err = env.svc.JoinChannel(ctx, watcherSID, 0, watcherNick, shared, "")
+		if err != nil {
+			t.Fatalf("join %s: %v", watcherNick, err)
+		}
+
+		_, lastQueueID, err := env.db.PollMessages(ctx, watcherClientID, 0, 0)
+		if err != nil {
+			t.Fatalf("poll: %v", err)
+		}
+
+		errs := runConcurrently(
+			func() error {
+				env.svc.BroadcastQuit(ctx, quitterSID, nick, "")
+
+				return nil
+			},
+			func() error {
+				return takeNickAndJoin(ctx, env, nick, shared)
+			},
+		)
+		if errs[1] != nil {
+			t.Fatalf("trial %d: new session: %v", trial, errs[1])
+		}
+
+		msgs, _, err := env.db.PollMessages(
+			ctx, watcherClientID, lastQueueID, 0,
+		)
+		if err != nil {
+			t.Fatalf("poll: %v", err)
+		}
+
+		commands := commandsFrom(msgs, nick)
+		if !slices.Equal(commands, []string{irc.CmdQuit, irc.CmdJoin}) {
+			t.Errorf(
+				"trial %d: watcher got %v from %s, want QUIT then JOIN",
+				trial, commands, nick,
+			)
+		}
+	}
+}
+
+// takeNickAndJoin creates a session with nick, trying again
+// while another session holds the nick, and joins it to
+// channel.
+func takeNickAndJoin(
+	ctx context.Context,
+	env *testEnv,
+	nick, channel string,
+) error {
+	for {
+		sessionID, _, _, err := env.db.CreateSession(
+			ctx, nick, nick, "localhost", "127.0.0.1",
+		)
+		if db.IsUniqueConstraintError(err) {
+			continue
+		}
+
+		if err != nil {
+			return err
+		}
+
+		_, err = env.svc.JoinChannel(ctx, sessionID, 0, nick, channel, "")
+
+		return err
+	}
+}
+
+// commandsFrom returns the commands of the messages in msgs
+// that nick sent, in order.
+func commandsFrom(msgs []db.IRCMessage, nick string) []string {
+	commands := make([]string, 0, len(msgs))
+
+	for _, msg := range msgs {
+		if msg.From == nick {
+			commands = append(commands, msg.Command)
+		}
+	}
+
+	return commands
+}
+
 // TestJoinUsesUpInvite checks that the JOIN an invite let
 // into a +i channel uses the invite up, so that a JOIN
 // after leaving gets ERR_INVITEONLYCHAN.
@@ -507,7 +710,7 @@ func TestJoinUsesUpInvite(t *testing.T) {
 	opSID := createSession(ctx, t, env.db, "op")
 	guestSID := createSession(ctx, t, env.db, "guest")
 
-	created, err := env.svc.JoinChannel(ctx, opSID, "op", channel, "")
+	created, err := env.svc.JoinChannel(ctx, opSID, 0, "op", channel, "")
 	if err != nil {
 		t.Fatalf("join op: %v", err)
 	}
@@ -522,17 +725,17 @@ func TestJoinUsesUpInvite(t *testing.T) {
 		t.Fatalf("invite guest: %v", err)
 	}
 
-	_, err = env.svc.JoinChannel(ctx, guestSID, "guest", channel, "")
+	_, err = env.svc.JoinChannel(ctx, guestSID, 0, "guest", channel, "")
 	if err != nil {
 		t.Fatalf("invited join: %v", err)
 	}
 
-	err = env.svc.PartChannel(ctx, guestSID, "guest", channel, "")
+	err = env.svc.PartChannel(ctx, guestSID, 0, "guest", channel, "")
 	if err != nil {
 		t.Fatalf("part guest: %v", err)
 	}
 
-	_, err = env.svc.JoinChannel(ctx, guestSID, "guest", channel, "")
+	_, err = env.svc.JoinChannel(ctx, guestSID, 0, "guest", channel, "")
 
 	var ircErr *service.IRCError
 	if !errors.As(err, &ircErr) || ircErr.Code != irc.ErrInviteOnlyChan {
@@ -551,7 +754,7 @@ func TestJoinRefusedByHostmaskBan(t *testing.T) {
 
 	opSID := createSession(ctx, t, env.db, "op")
 
-	created, err := env.svc.JoinChannel(ctx, opSID, "op", channel, "")
+	created, err := env.svc.JoinChannel(ctx, opSID, 0, "op", channel, "")
 	if err != nil {
 		t.Fatalf("join op: %v", err)
 	}
@@ -570,7 +773,7 @@ func TestJoinRefusedByHostmaskBan(t *testing.T) {
 		t.Fatalf("create session guest: %v", err)
 	}
 
-	_, err = env.svc.JoinChannel(ctx, guestSID, "guest", channel, "")
+	_, err = env.svc.JoinChannel(ctx, guestSID, 0, "guest", channel, "")
 
 	var ircErr *service.IRCError
 	if !errors.As(err, &ircErr) || ircErr.Code != irc.ErrBannedFromChan {
@@ -590,17 +793,17 @@ func TestPartDeletesChannelOnlyWhenEmpty(t *testing.T) {
 	aliceSID := createSession(ctx, t, env.db, "alice")
 	bobSID := createSession(ctx, t, env.db, "bob")
 
-	_, err := env.svc.JoinChannel(ctx, aliceSID, "alice", channel, "")
+	_, err := env.svc.JoinChannel(ctx, aliceSID, 0, "alice", channel, "")
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
-	_, err = env.svc.JoinChannel(ctx, bobSID, "bob", channel, "")
+	_, err = env.svc.JoinChannel(ctx, bobSID, 0, "bob", channel, "")
 	if err != nil {
 		t.Fatalf("join bob: %v", err)
 	}
 
-	err = env.svc.PartChannel(ctx, aliceSID, "alice", channel, "")
+	err = env.svc.PartChannel(ctx, aliceSID, 0, "alice", channel, "")
 	if err != nil {
 		t.Fatalf("part alice: %v", err)
 	}
@@ -615,7 +818,7 @@ func TestPartDeletesChannelOnlyWhenEmpty(t *testing.T) {
 		t.Fatal("bob is not on the channel after alice parted")
 	}
 
-	err = env.svc.PartChannel(ctx, bobSID, "bob", channel, "")
+	err = env.svc.PartChannel(ctx, bobSID, 0, "bob", channel, "")
 	if err != nil {
 		t.Fatalf("part bob: %v", err)
 	}
@@ -636,12 +839,12 @@ func TestKickOfLastMemberDeletesChannel(t *testing.T) {
 
 	sid := createSession(ctx, t, env.db, "alice")
 
-	_, err := env.svc.JoinChannel(ctx, sid, "alice", channel, "")
+	_, err := env.svc.JoinChannel(ctx, sid, 0, "alice", channel, "")
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
-	err = env.svc.KickUser(ctx, sid, "alice", channel, "alice", "")
+	err = env.svc.KickUser(ctx, sid, 0, "alice", channel, "alice", "")
 	if err != nil {
 		t.Fatalf("kick alice: %v", err)
 	}
@@ -660,14 +863,14 @@ func TestSendChannelMessage(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	_, err := env.svc.JoinChannel(
-		ctx, sid1, "alice", "#chat", "",
+		ctx, sid1, 0, "alice", "#chat", "",
 	)
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
 	_, err = env.svc.JoinChannel(
-		ctx, sid2, "bob", "#chat", "",
+		ctx, sid2, 0, "bob", "#chat", "",
 	)
 	if err != nil {
 		t.Fatalf("join bob: %v", err)
@@ -675,18 +878,14 @@ func TestSendChannelMessage(t *testing.T) {
 
 	body, _ := json.Marshal([]string{"hello world"}) //nolint:errchkjson
 
-	dbID, uuid, err := env.svc.SendChannelMessage(
-		ctx, sid1, "alice",
+	uuid, err := env.svc.SendChannelMessage(
+		ctx, sid1, 0, "alice",
 		irc.CmdPrivmsg, "#chat", body, nil,
 	)
 	if err != nil {
 		t.Fatalf("SendChannelMessage: %v", err)
 	}
 
-	if dbID == 0 {
-		t.Error("expected non-zero dbID")
-	}
-
 	if uuid == "" {
 		t.Error("expected non-empty UUID")
 	}
@@ -694,8 +893,8 @@ func TestSendChannelMessage(t *testing.T) {
 	// Non-member cannot send.
 	sid3 := createSession(ctx, t, env.db, "charlie")
 
-	_, _, err = env.svc.SendChannelMessage(
-		ctx, sid3, "charlie",
+	_, err = env.svc.SendChannelMessage(
+		ctx, sid3, 0, "charlie",
 		irc.CmdPrivmsg, "#chat", body, nil,
 	)
 	if err == nil {
@@ -711,14 +910,14 @@ func TestBroadcastQuit(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	_, err := env.svc.JoinChannel(
-		ctx, sid1, "alice", "#room", "",
+		ctx, sid1, 0, "alice", "#room", "",
 	)
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
 	_, err = env.svc.JoinChannel(
-		ctx, sid2, "bob", "#room", "",
+		ctx, sid2, 0, "bob", "#room", "",
 	)
 	if err != nil {
 		t.Fatalf("join bob: %v", err)
@@ -760,7 +959,7 @@ func TestSendDirectMessageTargetQuits(t *testing.T) {
 	body, _ := json.Marshal([]string{"hi"}) //nolint:errchkjson
 
 	_, err = env.svc.SendDirectMessage(
-		ctx, sid, "alice", irc.CmdPrivmsg, "bob", body, nil,
+		ctx, sid, 0, "alice", irc.CmdPrivmsg, "bob", body, nil,
 	)
 
 	var ircErr *service.IRCError
@@ -780,7 +979,7 @@ func TestSendChannelMessageChannelDeleted(t *testing.T) {
 
 	sid := createSession(ctx, t, env.db, "alice")
 
-	_, err := env.svc.JoinChannel(ctx, sid, "alice", "#gone", "")
+	_, err := env.svc.JoinChannel(ctx, sid, 0, "alice", "#gone", "")
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
@@ -797,8 +996,8 @@ func TestSendChannelMessageChannelDeleted(t *testing.T) {
 
 	body, _ := json.Marshal([]string{"hi"}) //nolint:errchkjson
 
-	_, _, err = env.svc.SendChannelMessage(
-		ctx, sid, "alice", irc.CmdPrivmsg, "#gone", body, nil,
+	_, err = env.svc.SendChannelMessage(
+		ctx, sid, 0, "alice", irc.CmdPrivmsg, "#gone", body, nil,
 	)
 
 	var ircErr *service.IRCError
@@ -816,14 +1015,14 @@ func TestSendChannelMessage_Moderated(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	result, err := env.svc.JoinChannel(
-		ctx, sid1, "alice", "#modchat", "",
+		ctx, sid1, 0, "alice", "#modchat", "",
 	)
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
 	_, err = env.svc.JoinChannel(
-		ctx, sid2, "bob", "#modchat", "",
+		ctx, sid2, 0, "bob", "#modchat", "",
 	)
 	if err != nil {
 		t.Fatalf("join bob: %v", err)
@@ -836,8 +1035,8 @@ func TestSendChannelMessage_Moderated(t *testing.T) {
 	body, _ := json.Marshal([]string{"test"}) //nolint:errchkjson
 
 	// Bob (non-op, non-voiced) should fail to send.
-	_, _, err = env.svc.SendChannelMessage(
-		ctx, sid2, "bob",
+	_, err = env.svc.SendChannelMessage(
+		ctx, sid2, 0, "bob",
 		irc.CmdPrivmsg, "#modchat", body, nil,
 	)
 	if err == nil {
@@ -845,8 +1044,8 @@ func TestSendChannelMessage_Moderated(t *testing.T) {
 	}
 
 	// Alice (operator) should succeed.
-	_, _, err = env.svc.SendChannelMessage(
-		ctx, sid1, "alice",
+	_, err = env.svc.SendChannelMessage(
+		ctx, sid1, 0, "alice",
 		irc.CmdPrivmsg, "#modchat", body, nil,
 	)
 	if err != nil {
@@ -854,6 +1053,88 @@ func TestSendChannelMessage_Moderated(t *testing.T) {
 	}
 }
 
+// TestRefusedChannelMessageLeavesStampUnspent checks that a
+// PRIVMSG to a +H channel refused because the sender is not
+// a member, is banned, or has no voice on a +m channel does
+// not spend its hashcash stamp: the operator can then send
+// the same message with it.
+func TestRefusedChannelMessageLeavesStampUnspent(t *testing.T) {
+	const (
+		channel = "#paid"
+		bits    = 2
+	)
+
+	refusals := []struct {
+		name string
+		// refuse stops bob from sending to the channel.
+		refuse func(ctx context.Context, env *testEnv, chID, bobSID int64) error
+	}{
+		{"not a member", func(ctx context.Context, env *testEnv, _, bobSID int64) error {
+			return env.svc.PartChannel(ctx, bobSID, 0, "bob", channel, "")
+		}},
+		{"banned", func(ctx context.Context, env *testEnv, chID, _ int64) error {
+			return env.db.AddChannelBan(ctx, chID, "bob!*@*", "alice")
+		}},
+		{"moderated", func(ctx context.Context, env *testEnv, chID, _ int64) error {
+			return env.svc.SetChannelFlag(ctx, chID, 'm', true)
+		}},
+	}
+
+	body, _ := json.Marshal([]string{"hello"}) //nolint:errchkjson
+
+	for _, refusal := range refusals {
+		t.Run(refusal.name, func(t *testing.T) {
+			env := newTestEnv(t)
+			ctx := t.Context()
+
+			aliceSID := createSession(ctx, t, env.db, "alice")
+			bobSID := createSession(ctx, t, env.db, "bob")
+
+			joined, err := env.svc.JoinChannel(ctx, aliceSID, 0, "alice", channel, "")
+			if err != nil {
+				t.Fatalf("join alice: %v", err)
+			}
+
+			_, err = env.svc.JoinChannel(ctx, bobSID, 0, "bob", channel, "")
+			if err != nil {
+				t.Fatalf("join bob: %v", err)
+			}
+
+			err = env.db.SetChannelHashcashBits(ctx, joined.ChannelID, bits)
+			if err != nil {
+				t.Fatalf("set +H: %v", err)
+			}
+
+			err = refusal.refuse(ctx, env, joined.ChannelID, bobSID)
+			if err != nil {
+				t.Fatalf("refuse bob: %v", err)
+			}
+
+			stamp := hashcash.MintChannelStamp(
+				bits, channel, hashcash.BodyHash(body),
+			)
+			meta, _ := json.Marshal(map[string]string{"hashcash": stamp})
+
+			_, err = env.svc.SendChannelMessage(
+				ctx, bobSID, 0, "bob", irc.CmdPrivmsg, channel, body, meta,
+			)
+
+			var ircErr *service.IRCError
+			if !errors.As(err, &ircErr) ||
+				ircErr.Code != irc.ErrCannotSendToChan {
+				t.Fatalf("bob: want ERR_CANNOTSENDTOCHAN, got %v", err)
+			}
+
+			_, err = env.svc.SendChannelMessage(
+				ctx, aliceSID, 0, "alice", irc.CmdPrivmsg, channel, body, meta,
+			)
+			if err != nil {
+				t.Fatalf("alice with the same stamp: %v", err)
+			}
+		})
+	}
+}
+
 func TestQueryUserMode(t *testing.T) {
 	env := newTestEnv(t)
 	ctx := t.Context()

web/src/app.jsx

@@ -58,13 +58,13 @@ async function mintHashcash(bits, resource) {
   }
 }
 
+// Requests are authenticated by the auth cookie, which the browser
+// sends on its own.
 function api(path, opts = {}) {
-  const token = localStorage.getItem("neoirc_token");
   const headers = {
     "Content-Type": "application/json",
     ...(opts.headers || {}),
   };
-  if (token) headers["Authorization"] = `Bearer ${token}`;
   const { signal, ...rest } = opts;
 
   return fetch(API + path, { ...rest, headers, signal }).then(async (r) => {
@@ -122,12 +122,11 @@ function LoginScreen({ onLogin }) {
         if (s.name) hashcashResourceRef.current = s.name;
       })
       .catch(() => {});
-    const saved = localStorage.getItem("neoirc_token");
-    if (saved) {
-      api("/state?initChannelState=1")
-        .then((u) => onLogin(u.nick, true))
-        .catch(() => localStorage.removeItem("neoirc_token"));
-    }
+    // Resume the session if the browser still holds a valid auth
+    // cookie; a 401 leaves the login form up.
+    api("/state?initChannelState=1")
+      .then((u) => onLogin(u.nick, true))
+      .catch(() => {});
     inputRef.current?.focus();
   }, []);
 
@@ -152,7 +151,6 @@ function LoginScreen({ onLogin }) {
         method: "POST",
         body: JSON.stringify(reqBody),
       });
-      localStorage.setItem("neoirc_token", res.token);
       onLogin(res.nick);
     } catch (err) {
       setError(err.data?.error || "Connection failed");
@@ -227,10 +225,9 @@ function UserList({ members, onNickClick }) {
   const regular = [];
 
   for (const m of members) {
-    const mode = m.mode || "";
-    if (mode === "o") {
+    if (m.isOperator) {
       ops.push(m);
-    } else if (mode === "v") {
+    } else if (m.isVoiced) {
       voiced.push(m);
     } else {
       regular.push(m);
@@ -303,11 +300,14 @@ function App() {
     nickRef.current = nick;
   }, [nick]);
 
-  // Persist joined channels.
+  // Persist joined channels, once logged in: before then only the
+  // Server tab exists, and writing would erase the saved channels
+  // that onLogin rejoins.
   useEffect(() => {
+    if (!loggedIn) return;
     const channels = tabs.filter((t) => t.type === "channel").map((t) => t.name);
     localStorage.setItem("neoirc_channels", JSON.stringify(channels));
-  }, [tabs]);
+  }, [loggedIn, tabs]);
 
   // Clear unread on tab switch.
   useEffect(() => {
@@ -366,7 +366,9 @@ function App() {
         command: msg.command,
       };
 
-      switch (msg.command) {
+      // A numeric reply carries its number in `code` and its name in
+      // `command`; other messages have no `code`.
+      switch (msg.code || msg.command) {
         case "PRIVMSG":
         case "NOTICE": {
           let text = body;
@@ -464,8 +466,18 @@ function App() {
 
           break;
         }
-        case "353": {
-          // RPL_NAMREPLY — parse mode prefixes from names list.
+        case "MODE": {
+          // The body is the change, with its value where it has one:
+          // ["+o bob"], ["+m"], ["+k", "secretpass"].
+          const modes = Array.isArray(msg.body) ? msg.body.join(" ") : "";
+          const text = `${msg.from} sets mode ${modes} on ${msg.to}`;
+          if (msg.to) addMessage(msg.to, { ...base, text, system: true });
+
+          break;
+        }
+        case 353: {
+          // RPL_NAMREPLY — each name is a hostmask (nick!user@host),
+          // prefixed with @ for an operator or + for a voiced member.
           if (
             Array.isArray(msg.params) &&
             msg.params.length >= 2 &&
@@ -477,21 +489,18 @@ function App() {
               : String(msg.body);
             const names = namesStr.split(/\s+/).filter(Boolean);
             const parsed = names.map((n) => {
-              if (n.startsWith("@")) {
-                return { nick: n.slice(1), mode: "o" };
-              }
-              if (n.startsWith("+")) {
-                return { nick: n.slice(1), mode: "v" };
-              }
+              const isOperator = n.startsWith("@");
+              const isVoiced = n.startsWith("+");
+              const hostmask = isOperator || isVoiced ? n.slice(1) : n;
 
-              return { nick: n, mode: "" };
+              return { nick: hostmask.split("!")[0], isOperator, isVoiced };
             });
             setMembers((prev) => ({ ...prev, [channel]: parsed }));
           }
 
           break;
         }
-        case "332": {
+        case 332: {
           // RPL_TOPIC — set topic from server.
           if (Array.isArray(msg.params) && msg.params.length >= 1) {
             const channel = msg.params[0];
@@ -503,7 +512,7 @@ function App() {
 
           break;
         }
-        case "322": {
+        case 322: {
           // RPL_LIST — channel, member count, topic.
           if (Array.isArray(msg.params) && msg.params.length >= 2) {
             const chName = msg.params[0];
@@ -518,7 +527,7 @@ function App() {
 
           break;
         }
-        case "323":
+        case 323:
           addMessage("Server", {
             ...base,
             text: body || "End of channel list",
@@ -526,7 +535,7 @@ function App() {
           });
 
           break;
-        case "352": {
+        case 352: {
           // RPL_WHOREPLY — channel, user, host, server, nick, flags.
           if (Array.isArray(msg.params) && msg.params.length >= 5) {
             const whoCh = msg.params[0];
@@ -541,7 +550,7 @@ function App() {
 
           break;
         }
-        case "315":
+        case 315:
           addMessage("Server", {
             ...base,
             text: body || "End of /WHO list",
@@ -549,20 +558,20 @@ function App() {
           });
 
           break;
-        case "311": {
-          // RPL_WHOISUSER — nick, user, host, *, realname.
-          if (Array.isArray(msg.params) && msg.params.length >= 1) {
-            const wiNick = msg.params[0];
+        case 311: {
+          // RPL_WHOISUSER — params nick, user, host, *; body realname.
+          if (Array.isArray(msg.params) && msg.params.length >= 3) {
+            const [wiNick, wiUser, wiHost] = msg.params;
             addMessage("Server", {
               ...base,
-              text: `${wiNick} (${body})`,
+              text: `${wiNick} is ${wiUser}@${wiHost} (${body})`,
               system: true,
             });
           }
 
           break;
         }
-        case "312": {
+        case 312: {
           // RPL_WHOISSERVER — nick, server, server info.
           if (Array.isArray(msg.params) && msg.params.length >= 2) {
             const wiNick = msg.params[0];
@@ -576,7 +585,33 @@ function App() {
 
           break;
         }
-        case "319": {
+        case 313: {
+          // RPL_WHOISOPERATOR — nick; body "is an IRC operator".
+          if (Array.isArray(msg.params) && msg.params.length >= 1) {
+            addMessage("Server", {
+              ...base,
+              text: `${msg.params[0]} ${body}`,
+              system: true,
+            });
+          }
+
+          break;
+        }
+        case 317: {
+          // RPL_WHOISIDLE — nick, idle seconds, signon time (Unix).
+          if (Array.isArray(msg.params) && msg.params.length >= 3) {
+            const [wiNick, idle, signon] = msg.params;
+            const signedOn = new Date(Number(signon) * 1000).toLocaleString();
+            addMessage("Server", {
+              ...base,
+              text: `${wiNick} has been idle ${idle}s, signed on ${signedOn}`,
+              system: true,
+            });
+          }
+
+          break;
+        }
+        case 319: {
           // RPL_WHOISCHANNELS — nick, channels.
           if (Array.isArray(msg.params) && msg.params.length >= 1) {
             const wiNick = msg.params[0];
@@ -589,7 +624,7 @@ function App() {
 
           break;
         }
-        case "318":
+        case 318:
           addMessage("Server", {
             ...base,
             text: body || "End of /WHOIS list",
@@ -597,9 +632,21 @@ function App() {
           });
 
           break;
-        case "375":
-        case "372":
-        case "376":
+        case 324: {
+          // RPL_CHANNELMODEIS — channel, mode string.
+          if (Array.isArray(msg.params) && msg.params.length >= 2) {
+            addMessage("Server", {
+              ...base,
+              text: `${msg.params[0]} modes: ${msg.params[1]}`,
+              system: true,
+            });
+          }
+
+          break;
+        }
+        case 375:
+        case 372:
+        case 376:
           addMessage("Server", { ...base, text: body, system: true });
 
           break;
@@ -637,6 +684,14 @@ function App() {
         } catch (err) {
           if (!alive) break;
           if (err.name === "AbortError") continue;
+          // 401: the session is gone (QUIT from another client, or
+          // expiry). Reloading drops this page's state and brings
+          // back the login screen.
+          if (err.status === 401) {
+            window.location.reload();
+
+            return;
+          }
           setConnected(false);
           await new Promise((r) => setTimeout(r, RECONNECT_DELAY));
         }
@@ -716,6 +771,11 @@ function App() {
 
   const onLogin = useCallback(
     async (userNick, isResumed) => {
+      // Read before setLoggedIn(true): from then on the effect under
+      // "Persist joined channels" writes the open channel tabs over it.
+      const saved = JSON.parse(
+        localStorage.getItem("neoirc_channels") || "[]",
+      );
       setNick(userNick);
       setLoggedIn(true);
       addSystemMessage("Server", `Connected as ${userNick}`);
@@ -740,9 +800,6 @@ function App() {
       }
 
       // Fresh session — join any previously saved channels.
-      const saved = JSON.parse(
-        localStorage.getItem("neoirc_channels") || "[]",
-      );
       for (const ch of saved) {
         try {
           await api("/messages", {
@@ -972,27 +1029,22 @@ function App() {
 
           break;
         }
+        // With no arguments MODE is a query. A change is one sign and
+        // letter, then its value where it takes one: +m, +o nick.
         const modeArgs = parts.slice(1);
-        if (modeArgs.length > 0) {
-          try {
-            await api("/messages", {
-              method: "POST",
-              body: JSON.stringify({
-                command: "MODE",
-                to: tab.name,
-                params: modeArgs,
-              }),
-            });
-          } catch (err) {
-            addSystemMessage(
-              "Server",
-              `Mode change failed: ${err.data?.error || "error"}`,
-            );
-          }
-        } else {
+        const body =
+          modeArgs.length > 0
+            ? { command: "MODE", to: tab.name, body: modeArgs }
+            : { command: "MODE", to: tab.name };
+        try {
+          await api("/messages", {
+            method: "POST",
+            body: JSON.stringify(body),
+          });
+        } catch (err) {
           addSystemMessage(
             "Server",
-            "Usage: /mode <+/-mode> [params]",
+            `MODE failed: ${err.data?.error || "error"}`,
           );
         }
 
@@ -1009,7 +1061,6 @@ function App() {
         } catch (e) {
           // Ignore.
         }
-        localStorage.removeItem("neoirc_token");
         localStorage.removeItem("neoirc_channels");
         window.location.reload();
 
@@ -1128,7 +1179,7 @@ function App() {
           "  /me action            — Send an action",
           "  /nick newnick         — Change your nickname",
           "  /topic [text]         — View or set channel topic",
-          "  /mode +/-flags        — Set channel modes",
+          "  /mode [+/-flag [arg]] — View or set channel modes",
           "  /motd                 — Display the message of the day",
           "  /list                 — List all channels",
           "  /who [#channel]       — List users in a channel",