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/migrate_to_dc.go

@@ -0,0 +1,78 @@
+package telegram
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+)
+
+func (c *Client) ensureRestart(ctx context.Context) error {
+	c.log.Debug("Triggering restart")
+	c.resetReady()
+
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case c.restart <- struct{}{}:
+		c.log.Debug("Restart initialized")
+	}
+
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-c.ready.Ready():
+		c.log.Info("Restart ensured")
+		return nil
+	}
+}
+
+func (c *Client) invokeMigrate(ctx context.Context, dcID int, input bin.Encoder, output bin.Decoder) error {
+	// Acquire or cancel.
+	select {
+	case c.migration <- struct{}{}:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+	// Release.
+	defer func() {
+		<-c.migration
+	}()
+
+	// Check if someone already migrated.
+	s := c.session.Load()
+	if s.DC == dcID {
+		return c.invokeConn(ctx, input, output)
+	}
+
+	mctx, cancel := context.WithTimeout(ctx, c.migrationTimeout)
+	defer cancel()
+	if err := c.migrateToDc(mctx, dcID); err != nil {
+		return errors.Wrap(err, "migrate to dc")
+	}
+
+	// Re-trying request on another connection.
+	return c.invokeConn(ctx, input, output)
+}
+
+func (c *Client) migrateToDc(ctx context.Context, dcID int) error {
+	c.session.Migrate(dcID)
+	return c.ensureRestart(ctx)
+}
+
+// MigrateTo forces client to migrate to another DC.
+func (c *Client) MigrateTo(ctx context.Context, dcID int) error {
+	// Acquire or cancel.
+	select {
+	case c.migration <- struct{}{}:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+	// Release.
+	defer func() {
+		<-c.migration
+	}()
+
+	return c.migrateToDc(ctx, dcID)
+}