Matrix: Setup bot, add PIN verification

PIN is verified but not used currently. Works a little different than
the others, you input your matrix user ID and then the PIN is sent to
you. The bot doesn't support E2EE, so the bot being the first one to
message ensures the chat is unencrypted.

matrix.go

@@ -0,0 +1,133 @@
+package main
+
+import (
+	"encoding/json"
+
+	"github.com/matrix-org/gomatrix"
+)
+
+type MatrixDaemon struct {
+	Stopped         bool
+	ShutdownChannel chan string
+	bot             *gomatrix.Client
+	userID          string
+	tokens          map[string]UnverifiedUser // Map of tokens to users
+	languages       map[string]string         // Map of roomIDs to language codes
+	app             *appContext
+}
+
+type UnverifiedUser struct {
+	Verified bool
+	User     *MatrixUser
+}
+
+type MatrixUser struct {
+	RoomID  string
+	UserID  string
+	Lang    string
+	Contact bool
+}
+
+var matrixFilter = gomatrix.Filter{
+	Room: gomatrix.RoomFilter{
+		Timeline: gomatrix.FilterPart{
+			Types: []string{
+				"m.room.message",
+				"m.room.member",
+			},
+		},
+	},
+	EventFields: []string{
+		"type",
+		"event_id",
+		"room_id",
+		"state_key",
+		"sender",
+		"content.body",
+		"content.membership",
+	},
+}
+
+func newMatrixDaemon(app *appContext) (d *MatrixDaemon, err error) {
+	matrix := app.config.Section("matrix")
+	homeserver := matrix.Key("homeserver").String()
+	token := matrix.Key("token").String()
+	d = &MatrixDaemon{
+		ShutdownChannel: make(chan string),
+		userID:          matrix.Key("user_id").String(),
+		tokens:          map[string]UnverifiedUser{},
+		languages:       map[string]string{},
+		app:             app,
+	}
+	d.bot, err = gomatrix.NewClient(homeserver, d.userID, token)
+	if err != nil {
+		return
+	}
+	filter, err := json.Marshal(matrixFilter)
+	if err != nil {
+		return
+	}
+	resp, err := d.bot.CreateFilter(filter)
+	d.bot.Store.SaveFilterID(d.userID, resp.FilterID)
+	for _, user := range app.storage.matrix {
+		if user.Lang != "" {
+			d.languages[user.RoomID] = user.Lang
+		}
+	}
+	return
+}
+
+func (d *MatrixDaemon) run() {
+	d.app.info.Println("Starting Matrix bot daemon")
+	syncer := d.bot.Syncer.(*gomatrix.DefaultSyncer)
+	syncer.OnEventType("m.room.message", d.handleMessage)
+	// syncer.OnEventType("m.room.member", d.handleMembership)
+	if err := d.bot.Sync(); err != nil {
+		d.app.err.Printf("Matrix sync failed: %v", err)
+	}
+}
+
+func (d *MatrixDaemon) Shutdown() {
+	d.bot.StopSync()
+	d.Stopped = true
+	close(d.ShutdownChannel)
+}
+
+func (d *MatrixDaemon) handleMessage(event *gomatrix.Event) { return }
+
+func (d *MatrixDaemon) SendStart(userID string) (ok bool) {
+	room, err := d.bot.CreateRoom(&gomatrix.ReqCreateRoom{
+		Visibility: "private",
+		Invite:     []string{userID},
+		Topic:      "jfa-go",
+	})
+	if err != nil {
+		d.app.err.Printf("Failed to create room for user \"%s\": %v", userID, err)
+		return
+	}
+	lang := "en-us"
+	pin := genAuthToken()
+	d.tokens[pin] = UnverifiedUser{
+		false,
+		&MatrixUser{
+			RoomID: room.RoomID,
+			UserID: userID,
+			Lang:   lang,
+		},
+	}
+	_, err = d.bot.SendText(
+		room.RoomID,
+		d.app.storage.lang.Telegram[lang].Strings.get("matrixStartMessage")+"\n\n"+pin+"\n\n"+
+			d.app.storage.lang.Telegram[lang].Strings.template("languageMessage", tmpl{"command": "!lang"}),
+	)
+	if err != nil {
+		d.app.err.Printf("Matrix: Failed to send welcome message to \"%s\": %v", userID, err)
+		return
+	}
+	ok = true
+	return
+}
+
+// User enters ID on sign-up, a PIN is sent to them. They enter it on sign-up.
+
+// Message the user first, to avoid E2EE by default