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/transport/protocol.go

@@ -0,0 +1,86 @@
+package transport
+
+import (
+	"net"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/proto/codec"
+)
+
+// Protocol is MTProto transport protocol.
+//
+// See https://core.telegram.org/mtproto/mtproto-transports
+type Protocol struct {
+	codec func() Codec
+}
+
+// NewProtocol creates new transport protocol using user Codec constructor.
+//
+// See https://core.telegram.org/mtproto/mtproto-transports
+func NewProtocol(getCodec func() Codec) Protocol {
+	return Protocol{
+		codec: getCodec,
+	}
+}
+
+// Telegram transport protocols.
+//
+// See https://core.telegram.org/mtproto/mtproto-transports
+var (
+	// Abridged is abridged transport protocol.
+	//
+	// See https://core.telegram.org/mtproto/mtproto-transports#abridged
+	Abridged = NewProtocol(func() Codec { return codec.Abridged{} })
+
+	// Intermediate is intermediate transport protocol.
+	//
+	// See https://core.telegram.org/mtproto/mtproto-transports#intermediate
+	Intermediate = NewProtocol(func() Codec { return codec.Intermediate{} })
+
+	// PaddedIntermediate is padded intermediate transport protocol.
+	//
+	// See https://core.telegram.org/mtproto/mtproto-transports#padded-intermediate
+	PaddedIntermediate = NewProtocol(func() Codec { return codec.PaddedIntermediate{} })
+
+	// Full is full transport protocol.
+	//
+	// See https://core.telegram.org/mtproto/mtproto-transports#full
+	Full = NewProtocol(func() Codec { return &codec.Full{} })
+)
+
+// Codec creates new codec using protocol settings.
+func (p Protocol) Codec() Codec {
+	return p.codec()
+}
+
+// CodecNoHeader is Codec without header.
+func (p Protocol) CodecNoHeader() Codec {
+	return codec.NoHeader{Codec: p.codec()}
+}
+
+// Handshake inits given net.Conn as MTProto connection.
+func (p Protocol) Handshake(conn net.Conn) (Conn, error) {
+	connCodec := p.codec()
+	if err := connCodec.WriteHeader(conn); err != nil {
+		return nil, errors.Wrap(err, "write header")
+	}
+
+	return &connection{
+		conn:  conn,
+		codec: connCodec,
+	}, nil
+}
+
+// Pipe creates an in-memory MTProto connection.
+func (p Protocol) Pipe() (a, b Conn) {
+	p1, p2 := net.Pipe()
+
+	return &connection{
+			conn:  p1,
+			codec: p.codec(),
+		}, &connection{
+			conn:  p2,
+			codec: p.codec(),
+		}
+}