move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/mtproto/handle_message_fuzz.go

@@ -0,0 +1,84 @@
+//go:build fuzz
+// +build fuzz
+
+package mtproto
+
+import (
+	"time"
+
+	"github.com/go-faster/errors"
+	"go.uber.org/zap"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mt"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/proto"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/rpc"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/testutil"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tmap"
+)
+
+type fuzzHandler struct {
+	types *tmap.Constructor
+}
+
+func (h fuzzHandler) OnMessage(b *bin.Buffer) error {
+	id, err := b.PeekID()
+	if err != nil {
+		return err
+	}
+	v := h.types.New(id)
+	if v == nil {
+		return errors.New("not found")
+	}
+	if err := v.Decode(b); err != nil {
+		return errors.Wrap(err, "decode")
+	}
+
+	// Performing decode cycle.
+	var newBuff bin.Buffer
+	newV := h.types.New(id)
+	if err := v.Encode(&newBuff); err != nil {
+		panic(err)
+	}
+	if err := newV.Decode(&newBuff); err != nil {
+		panic(err)
+	}
+
+	return nil
+}
+
+func (fuzzHandler) OnSession(session Session) error { return nil }
+
+var (
+	conn *Conn
+	buf  *bin.Buffer
+)
+
+func init() {
+	handler := fuzzHandler{
+		// Handler will try to dynamically decode any incoming message.
+		types: tmap.NewConstructor(
+			tg.TypesConstructorMap(),
+			mt.TypesConstructorMap(),
+		),
+	}
+	c := &Conn{
+		rand:      testutil.ZeroRand{},
+		rpc:       rpc.New(rpc.NopSend, rpc.Options{}),
+		log:       zap.NewNop(),
+		messageID: proto.NewMessageIDGen(time.Now),
+		handler:   handler,
+	}
+
+	conn = c
+	buf = &bin.Buffer{}
+}
+
+func FuzzHandleMessage(data []byte) int {
+	buf.ResetTo(data)
+	if err := conn.handleMessage(buf); err != nil {
+		return 0
+	}
+	return 1
+}