feat: implement Tier 2 channel modes (+b/+i/+s/+k/+l) (#92)

## Summary

Implements the second tier of IRC channel features as described in [#86](#86).

## Features

### 1. Ban System (+b)
- `channel_bans` table with mask, set_by, created_at
- Add/remove/list bans via MODE +b/-b
- Wildcard matching (`*!*@*.example.com`, `badnick!*@*`, etc.)
- Ban enforcement on both JOIN and PRIVMSG
- RPL_BANLIST (367) / RPL_ENDOFBANLIST (368) for ban listing

### 2. Invite-Only (+i)
- `is_invite_only` column on channels table
- INVITE command: operators can invite users
- `channel_invites` table tracks pending invites
- Invites consumed on successful JOIN
- ERR_INVITEONLYCHAN (473) for uninvited JOIN attempts

### 3. Secret (+s)
- `is_secret` column on channels table
- Secret channels hidden from LIST for non-members
- Secret channels hidden from WHOIS channel list for non-members

### 4. Channel Key (+k)
- `channel_key` column on channels table
- MODE +k sets key, MODE -k clears it
- Key required on JOIN (`JOIN #channel key`)
- ERR_BADCHANNELKEY (475) for wrong/missing key

### 5. User Limit (+l)
- `user_limit` column on channels table (0 = no limit)
- MODE +l sets limit, MODE -l removes it
- ERR_CHANNELISFULL (471) when limit reached

## ISUPPORT Changes
- CHANMODES updated to `b,k,Hl,imnst`
- RPL_MYINFO modes updated to `ikmnostl`

## Tests

### Database-level tests:
- Wildcard matching (10 patterns)
- Ban CRUD operations
- Session ban checking
- Invite-only flag toggle
- Invite CRUD + clearing
- Secret channel filtering (LIST and WHOIS)
- Channel key set/get/clear
- User limit set/get/clear

### Handler-level tests:
- Ban add/remove/list via MODE
- Ban blocks JOIN
- Ban blocks PRIVMSG
- Invite-only JOIN rejection + INVITE acceptance
- Secret channel hidden from LIST
- Channel key required on JOIN
- User limit enforcement
- Mode string includes new modes
- ISUPPORT updated CHANMODES
- Non-operators cannot set any Tier 2 modes

## Schema Changes
- Added `is_invite_only`, `is_secret`, `channel_key`, `user_limit` to `channels` table
- Added `channel_bans` table
- Added `channel_invites` table
- All changes in `001_initial.sql` (pre-1.0.0 repo)

closes #86

Co-authored-by: user <user@Mac.lan guest wan>
Reviewed-on: #92
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/handlers/api_test.go

@@ -4378,3 +4378,486 @@ func TestKickDefaultReason(t *testing.T) {
 		)
 	}
 }
+
+// --- Tier 2 Handler Tests ---
+
+const (
+	inviteCmd    = "INVITE"
+	joinedStatus = "joined"
+)
+
+// TestBanAddRemoveList verifies +b add, list, and -b
+// remove via MODE commands.
+func TestBanAddRemoveList(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("banop")
+
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#bans",
+	})
+
+	// Add a ban.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#bans",
+		bodyKey:    []string{"+b", "*!*@evil.com"},
+	})
+
+	_, lastID := tserver.pollMessages(opToken, 0)
+
+	// List bans (+b with no argument).
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#bans",
+		bodyKey:    []string{"+b"},
+	})
+
+	msgs, _ := tserver.pollMessages(opToken, lastID)
+
+	// Should have RPL_BANLIST (367).
+	banMsg := findNumericWithParams(msgs, "367")
+	if banMsg == nil {
+		t.Fatalf("expected 367 RPL_BANLIST, got %v", msgs)
+	}
+
+	// Should have RPL_ENDOFBANLIST (368).
+	if !findNumeric(msgs, "368") {
+		t.Fatal("expected 368 RPL_ENDOFBANLIST")
+	}
+
+	// Remove the ban.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#bans",
+		bodyKey:    []string{"-b", "*!*@evil.com"},
+	})
+
+	_, lastID = tserver.pollMessages(opToken, lastID)
+
+	// List again — should be empty (just end-of-list).
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#bans",
+		bodyKey:    []string{"+b"},
+	})
+
+	msgs, _ = tserver.pollMessages(opToken, lastID)
+	banMsg = findNumericWithParams(msgs, "367")
+	if banMsg != nil {
+		t.Fatal("expected no 367 after ban removal")
+	}
+
+	if !findNumeric(msgs, "368") {
+		t.Fatal("expected 368 RPL_ENDOFBANLIST")
+	}
+}
+
+// TestBanBlocksJoin verifies that a banned user cannot
+// join a channel.
+func TestBanBlocksJoin(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("banop2")
+	userToken := tserver.createSession("banned2")
+
+	// Op creates channel and sets a ban.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#banjoin",
+	})
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#banjoin",
+		bodyKey:    []string{"+b", "banned2!*@*"},
+	})
+
+	// Banned user tries to join.
+	_, lastID := tserver.pollMessages(userToken, 0)
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd, toKey: "#banjoin",
+	})
+
+	msgs, _ := tserver.pollMessages(userToken, lastID)
+
+	// Should get ERR_BANNEDFROMCHAN (474).
+	if !findNumeric(msgs, "474") {
+		t.Fatalf("expected 474 ERR_BANNEDFROMCHAN, got %v", msgs)
+	}
+}
+
+// TestBanBlocksPrivmsg verifies that a banned user who
+// is already in a channel cannot send messages.
+func TestBanBlocksPrivmsg(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("banmsgop")
+	userToken := tserver.createSession("banmsgusr")
+
+	// Both join.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#banmsg",
+	})
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd, toKey: "#banmsg",
+	})
+
+	// Op bans the user.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#banmsg",
+		bodyKey:    []string{"+b", "banmsgusr!*@*"},
+	})
+
+	// User tries to send a message.
+	_, lastID := tserver.pollMessages(userToken, 0)
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: privmsgCmd,
+		toKey:      "#banmsg",
+		bodyKey:    []string{"hello"},
+	})
+
+	msgs, _ := tserver.pollMessages(userToken, lastID)
+
+	// Should get ERR_CANNOTSENDTOCHAN (404).
+	if !findNumeric(msgs, "404") {
+		t.Fatalf("expected 404 ERR_CANNOTSENDTOCHAN, got %v", msgs)
+	}
+}
+
+// TestInviteOnlyJoin verifies +i behavior: join rejected
+// without invite, accepted with invite.
+func TestInviteOnlyJoin(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("invop")
+	userToken := tserver.createSession("invusr")
+
+	// Op creates channel and sets +i.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#invonly",
+	})
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#invonly",
+		bodyKey:    []string{"+i"},
+	})
+
+	// User tries to join without invite.
+	_, lastID := tserver.pollMessages(userToken, 0)
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd, toKey: "#invonly",
+	})
+
+	msgs, _ := tserver.pollMessages(userToken, lastID)
+
+	if !findNumeric(msgs, "473") {
+		t.Fatalf(
+			"expected 473 ERR_INVITEONLYCHAN, got %v",
+			msgs,
+		)
+	}
+
+	// Op invites user.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: inviteCmd,
+		bodyKey:    []string{"invusr", "#invonly"},
+	})
+
+	// User tries again — should succeed with invite.
+	_, result := tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd, toKey: "#invonly",
+	})
+
+	if result[statusKey] != joinedStatus {
+		t.Fatalf(
+			"expected join to succeed with invite, got %v",
+			result,
+		)
+	}
+}
+
+// TestSecretChannelHiddenFromList verifies +s hides a
+// channel from LIST for non-members.
+func TestSecretChannelHiddenFromList(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("secop")
+	outsiderToken := tserver.createSession("secout")
+
+	// Op creates secret channel.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#secret",
+	})
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#secret",
+		bodyKey:    []string{"+s"},
+	})
+
+	// Outsider does LIST.
+	_, lastID := tserver.pollMessages(outsiderToken, 0)
+	tserver.sendCommand(outsiderToken, map[string]any{
+		commandKey: "LIST",
+	})
+
+	msgs, _ := tserver.pollMessages(outsiderToken, lastID)
+
+	// Should NOT see #secret in any 322 (RPL_LIST).
+	for _, msg := range msgs {
+		code, ok := msg["code"].(float64)
+		if !ok || int(code) != 322 {
+			continue
+		}
+
+		params := getNumericParams(msg)
+		for _, p := range params {
+			if p == "#secret" {
+				t.Fatal("outsider should not see #secret in LIST")
+			}
+		}
+	}
+
+	// Member does LIST — should see it.
+	_, lastID = tserver.pollMessages(opToken, 0)
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: "LIST",
+	})
+
+	msgs, _ = tserver.pollMessages(opToken, lastID)
+
+	found := false
+
+	for _, msg := range msgs {
+		code, ok := msg["code"].(float64)
+		if !ok || int(code) != 322 {
+			continue
+		}
+
+		params := getNumericParams(msg)
+		for _, p := range params {
+			if p == "#secret" {
+				found = true
+			}
+		}
+	}
+
+	if !found {
+		t.Fatal("member should see #secret in LIST")
+	}
+}
+
+// TestChannelKeyJoin verifies +k behavior: wrong/missing
+// key is rejected, correct key allows join.
+func TestChannelKeyJoin(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("keyop")
+	userToken := tserver.createSession("keyusr")
+
+	// Op creates keyed channel.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#keyed",
+	})
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#keyed",
+		bodyKey:    []string{"+k", "mykey"},
+	})
+
+	// User tries without key.
+	_, lastID := tserver.pollMessages(userToken, 0)
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd, toKey: "#keyed",
+	})
+
+	msgs, _ := tserver.pollMessages(userToken, lastID)
+
+	if !findNumeric(msgs, "475") {
+		t.Fatalf(
+			"expected 475 ERR_BADCHANNELKEY, got %v",
+			msgs,
+		)
+	}
+
+	// User tries with wrong key.
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd,
+		toKey:      "#keyed",
+		bodyKey:    []string{"wrongkey"},
+	})
+
+	msgs, _ = tserver.pollMessages(userToken, lastID)
+	if !findNumeric(msgs, "475") {
+		t.Fatalf(
+			"expected 475 ERR_BADCHANNELKEY for wrong key, got %v",
+			msgs,
+		)
+	}
+
+	// User tries with correct key.
+	_, result := tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd,
+		toKey:      "#keyed",
+		bodyKey:    []string{"mykey"},
+	})
+
+	if result[statusKey] != joinedStatus {
+		t.Fatalf(
+			"expected join to succeed with correct key, got %v",
+			result,
+		)
+	}
+}
+
+// TestUserLimitEnforcement verifies +l behavior: blocks
+// join when at capacity.
+func TestUserLimitEnforcement(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("limop")
+	user1Token := tserver.createSession("limusr1")
+	user2Token := tserver.createSession("limusr2")
+
+	// Op creates channel with limit 2.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#limited",
+	})
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd,
+		toKey:      "#limited",
+		bodyKey:    []string{"+l", "2"},
+	})
+
+	// User1 joins — should succeed (2 members now: op + user1).
+	_, result := tserver.sendCommand(user1Token, map[string]any{
+		commandKey: joinCmd, toKey: "#limited",
+	})
+	if result[statusKey] != joinedStatus {
+		t.Fatalf("user1 should join, got %v", result)
+	}
+
+	// User2 tries to join — should fail (at limit: 2/2).
+	_, lastID := tserver.pollMessages(user2Token, 0)
+	tserver.sendCommand(user2Token, map[string]any{
+		commandKey: joinCmd, toKey: "#limited",
+	})
+
+	msgs, _ := tserver.pollMessages(user2Token, lastID)
+
+	if !findNumeric(msgs, "471") {
+		t.Fatalf(
+			"expected 471 ERR_CHANNELISFULL, got %v",
+			msgs,
+		)
+	}
+}
+
+// TestModeStringIncludesNewModes verifies that querying
+// channel mode returns the new modes (+i, +s, +k, +l).
+func TestModeStringIncludesNewModes(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("modestrop")
+
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#modestr",
+	})
+
+	// Set all tier 2 modes.
+	for _, modeChange := range [][]string{
+		{"+i"}, {"+s"}, {"+k", "pw"}, {"+l", "50"},
+	} {
+		tserver.sendCommand(opToken, map[string]any{
+			commandKey: modeCmd,
+			toKey:      "#modestr",
+			bodyKey:    modeChange,
+		})
+	}
+
+	_, lastID := tserver.pollMessages(opToken, 0)
+
+	// Query mode.
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: modeCmd, toKey: "#modestr",
+	})
+
+	msgs, _ := tserver.pollMessages(opToken, lastID)
+	modeMsg := findNumericWithParams(msgs, "324")
+
+	if modeMsg == nil {
+		t.Fatal("expected 324 RPL_CHANNELMODEIS")
+	}
+
+	params := getNumericParams(modeMsg)
+	if len(params) < 2 {
+		t.Fatalf("too few params in 324: %v", params)
+	}
+
+	modeString := params[1]
+
+	for _, c := range []string{"i", "s", "k", "l"} {
+		if !strings.Contains(modeString, c) {
+			t.Fatalf(
+				"mode string %q missing %q",
+				modeString, c,
+			)
+		}
+	}
+}
+
+// TestISUPPORT verifies the 005 numeric includes the
+// updated CHANMODES string.
+func TestISUPPORT(t *testing.T) {
+	tserver := newTestServer(t)
+	token := tserver.createSession("isupport")
+
+	msgs, _ := tserver.pollMessages(token, 0)
+
+	isupp := findNumericWithParams(msgs, "005")
+	if isupp == nil {
+		t.Fatal("expected 005 RPL_ISUPPORT")
+	}
+
+	body, _ := isupp["body"].(string)
+	params := getNumericParams(isupp)
+
+	combined := body + " " + strings.Join(params, " ")
+
+	if !strings.Contains(combined, "CHANMODES=b,k,Hl,imnst") {
+		t.Fatalf(
+			"ISUPPORT missing updated CHANMODES, got body=%q params=%v",
+			body, params,
+		)
+	}
+}
+
+// TestNonOpCannotSetModes verifies non-operators
+// cannot set +i, +s, +k, +l, +b.
+func TestNonOpCannotSetModes(t *testing.T) {
+	tserver := newTestServer(t)
+	opToken := tserver.createSession("modeopx")
+	userToken := tserver.createSession("modeusrx")
+
+	tserver.sendCommand(opToken, map[string]any{
+		commandKey: joinCmd, toKey: "#noperm",
+	})
+	tserver.sendCommand(userToken, map[string]any{
+		commandKey: joinCmd, toKey: "#noperm",
+	})
+
+	modes := [][]string{
+		{"+i"}, {"+s"}, {"+k", "key"}, {"+l", "10"},
+		{"+b", "bad!*@*"},
+	}
+
+	for _, modeChange := range modes {
+		_, lastID := tserver.pollMessages(userToken, 0)
+		tserver.sendCommand(userToken, map[string]any{
+			commandKey: modeCmd,
+			toKey:      "#noperm",
+			bodyKey:    modeChange,
+		})
+
+		msgs, _ := tserver.pollMessages(userToken, lastID)
+
+		// Should get 482 ERR_CHANOPRIVSNEEDED.
+		if !findNumeric(msgs, "482") {
+			t.Fatalf(
+				"expected 482 for %v, got %v",
+				modeChange, msgs,
+			)
+		}
+	}
+}