HTTP API: server, credential and the list of chats (closes #4)

The bot now serves an HTTP API on PORT (default 8080) beside the chat
client. Every request needs the credential read at startup from the
file named by API_TOKEN_FILE, sent as a bearer token; without one,
every request is refused. Responses carry the security headers, bodies
are capped at 64 KiB and each request's work at 10 seconds.

GET /api/v1/chats lists the bot's contacts from the chat client's
/_contacts command, ordered by id, and marks the contacts who deleted
their chat with the bot, which the chat client keeps listing. bot.Run
starts the API after set-up and stops it within 5 seconds; a listener
failure ends the bot as a chat client failure does.

Model: opus-5-5

internal/simplex/client.go

@@ -168,6 +168,18 @@ func (c *Client) SetAddressSettings(
 	return c.command(ctx, cmd, TypeUserContactLinkUpdated, nil)
 }
 
+// Contacts returns the user's contacts: everyone it has a direct chat
+// with.
+func (c *Client) Contacts(ctx context.Context, userID int64) ([]Contact, error) {
+	var r struct {
+		Contacts []Contact `json:"contacts"`
+	}
+
+	err := c.command(ctx, cmdListContacts(userID), TypeContactsList, &r)
+
+	return r.Contacts, err
+}
+
 // SendText sends a text message to a contact, as a reply to the message
 // quotedItemID (0 for none). It does not wait for the chat client to
 // accept it; a failure is logged when the client's answer arrives.

internal/simplex/client_test.go

@@ -7,6 +7,7 @@ import (
 	"log/slog"
 	"net/http"
 	"net/http/httptest"
+	"slices"
 	"strings"
 	"sync"
 	"testing"
@@ -43,6 +44,19 @@ const (
 
 	contactConnected = `{"type":"contactConnected","user":{"userId":1},
 		"contact":{"contactId":3,"localDisplayName":"alice"}}`
+
+	// Two contacts with the same display name, which the chat client
+	// tells apart by the local name it gives the second. The second has
+	// deleted its chat with the bot, and is still listed.
+	contactsList = `{"type":"contactsList","user":{"userId":1},"contacts":[
+		{"contactId":3,"localDisplayName":"tester","profile":{"profileId":3,
+		"displayName":"tester","fullName":"","localAlias":""},
+		"activeConn":{"connId":2,"connStatus":{"type":"ready"}},
+		"contactUsed":true,"contactStatus":"active","chatDeleted":false},
+		{"contactId":4,"localDisplayName":"tester_1","profile":{"profileId":4,
+		"displayName":"tester","fullName":"","localAlias":""},
+		"activeConn":{"connId":3,"connStatus":{"type":"deleted"}},
+		"contactUsed":true,"contactStatus":"deleted","chatDeleted":false}]}`
 )
 
 // fakeChat stands in for the chat client's API. It answers each command
@@ -220,6 +234,38 @@ func TestAddressSetup(t *testing.T) {
 	}
 }
 
+// TestContacts: the contacts of the given user come back with their
+// ids, display names and whether they are deleted.
+func TestContacts(t *testing.T) {
+	t.Parallel()
+
+	f, url := newFakeChat(t, map[string]string{"/_contacts": contactsList})
+	c, ctx := dial(t, url, nil)
+
+	contacts, err := c.Contacts(ctx, 1)
+	if err != nil {
+		t.Fatalf("Contacts: %v", err)
+	}
+
+	if got := f.next(t); got != "/_contacts 1" {
+		t.Errorf("command = %s, want /_contacts 1", got)
+	}
+
+	tester := simplex.Profile{DisplayName: "tester"}
+
+	want := []simplex.Contact{
+		{ContactID: 3, Profile: tester, Status: "active"},
+		{ContactID: 4, Profile: tester, Status: "deleted"},
+	}
+	if !slices.Equal(contacts, want) {
+		t.Fatalf("Contacts = %+v\nwant       %+v", contacts, want)
+	}
+
+	if contacts[0].Deleted() || !contacts[1].Deleted() {
+		t.Error("Deleted must be false for contact 3 and true for contact 4")
+	}
+}
+
 // TestRefusedCommand: a command the chat client refuses is an error
 // that names the reason.
 func TestRefusedCommand(t *testing.T) {

internal/simplex/protocol.go

@@ -14,6 +14,7 @@ const (
 	TypeUserContactLink        = "userContactLink"
 	TypeUserContactLinkCreated = "userContactLinkCreated"
 	TypeUserContactLinkUpdated = "userContactLinkUpdated"
+	TypeContactsList           = "contactsList"
 	TypeNewChatItems           = "newChatItems"
 	TypeContactConnected       = "contactConnected"
 	TypeChatCmdError           = "chatCmdError"
@@ -46,10 +47,14 @@ func (e Event) Decode(v any) error {
 type (
 	// User is the chat client's local user profile: the bot itself.
 	User struct {
-		UserID  int64 `json:"userId"`
-		Profile struct {
-			DisplayName string `json:"displayName"`
-		} `json:"profile"`
+		UserID  int64   `json:"userId"`
+		Profile Profile `json:"profile"`
+	}
+
+	// Profile is how the bot or a contact presents itself. Nothing
+	// makes a display name unique.
+	Profile struct {
+		DisplayName string `json:"displayName"`
 	}
 
 	// ConnLink is a SimpleX link. The short form is what people share;
@@ -61,7 +66,9 @@ type (
 
 	// Contact is a person connected to the bot.
 	Contact struct {
-		ContactID int64 `json:"contactId"`
+		ContactID int64   `json:"contactId"`
+		Profile   Profile `json:"profile"`
+		Status    string  `json:"contactStatus"`
 	}
 
 	// NewChatItems is the record of a newChatItems event: messages
@@ -142,6 +149,13 @@ type (
 	}
 )
 
+// Deleted reports whether the contact is gone, as it is once the person
+// deletes their chat with the bot. The chat client still lists such a
+// contact, with its chat, but nothing more reaches them.
+func (c Contact) Deleted() bool {
+	return c.Status != "active"
+}
+
 // Message is a text message a contact sent to the bot.
 type Message struct {
 	ContactID int64
@@ -190,6 +204,10 @@ func cmdSetAddressSettings(userID int64, s AddressSettings) (string, error) {
 	return "/_address_settings " + strconv.FormatInt(userID, 10) + " " + string(b), nil
 }
 
+func cmdListContacts(userID int64) string {
+	return "/_contacts " + strconv.FormatInt(userID, 10)
+}
+
 func cmdSendText(contactID, quotedItemID int64, text string) (string, error) {
 	b, err := json.Marshal([]composedMessage{{
 		QuotedItemID: quotedItemID,