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/telegram/message/peer/constraint.go

@@ -0,0 +1,113 @@
+package peer
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// PromiseDecorator is a decorator of peer promise.
+type PromiseDecorator = func(Promise) Promise
+
+// ConstraintError is a peer resolve constraint error.
+type ConstraintError struct {
+	Expected string
+	Got      tg.InputPeerClass
+}
+
+// Error implements error.
+func (c *ConstraintError) Error() string {
+	return fmt.Sprintf("expected %q, got %T", c.Expected, c.Got)
+}
+
+func tryUnpackConstraint(p tg.InputPeerClass, resolveErr error) (tg.InputPeerClass, error) {
+	var constraintErr *ConstraintError
+	if errors.As(resolveErr, &constraintErr) {
+		return constraintErr.Got, nil
+	}
+	return p, resolveErr
+}
+
+// OnlyChannel returns Promise which returns error if resolved peer is not a channel.
+func OnlyChannel(p Promise) Promise {
+	return func(ctx context.Context) (tg.InputPeerClass, error) {
+		resolved, err := tryUnpackConstraint(p(ctx))
+		if err != nil {
+			return nil, err
+		}
+
+		switch resolved.(type) {
+		case *tg.InputPeerChannel, *tg.InputPeerChannelFromMessage:
+			return resolved, nil
+		default:
+			return nil, &ConstraintError{
+				Expected: "channel",
+				Got:      resolved,
+			}
+		}
+	}
+}
+
+// OnlyChat returns Promise which returns error if resolved peer is not a chat.
+func OnlyChat(p Promise) Promise {
+	return func(ctx context.Context) (tg.InputPeerClass, error) {
+		resolved, err := tryUnpackConstraint(p(ctx))
+		if err != nil {
+			return nil, err
+		}
+
+		switch resolved.(type) {
+		case *tg.InputPeerChat:
+			return resolved, nil
+		default:
+			return nil, &ConstraintError{
+				Expected: "chat",
+				Got:      resolved,
+			}
+		}
+	}
+}
+
+// OnlyUser returns Promise which returns error if resolved peer is not a user.
+func OnlyUser(p Promise) Promise {
+	return func(ctx context.Context) (tg.InputPeerClass, error) {
+		resolved, err := tryUnpackConstraint(p(ctx))
+		if err != nil {
+			return nil, err
+		}
+
+		switch resolved.(type) {
+		case *tg.InputPeerUser, *tg.InputPeerUserFromMessage, *tg.InputPeerSelf:
+			return resolved, nil
+		default:
+			return nil, &ConstraintError{
+				Expected: "user",
+				Got:      resolved,
+			}
+		}
+	}
+}
+
+// OnlyUserID returns Promise which returns error if resolved peer is not a user object with ID.
+// Unlike OnlyUser, it returns error if resolved peer is tg.InputPeerSelf.
+func OnlyUserID(p Promise) Promise {
+	return func(ctx context.Context) (tg.InputPeerClass, error) {
+		resolved, err := tryUnpackConstraint(p(ctx))
+		if err != nil {
+			return nil, err
+		}
+
+		switch resolved.(type) {
+		case *tg.InputPeerUser, *tg.InputPeerUserFromMessage:
+			return resolved, nil
+		default:
+			return nil, &ConstraintError{
+				Expected: "userID",
+				Got:      resolved,
+			}
+		}
+	}
+}