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/gen/_template/handlers.tmpl

@@ -0,0 +1,93 @@
+{{ define "handlers" }}
+{{ $pkg := $.Package }}
+{{ template "header" $ }}
+
+type handler = func(context.Context, Entities, UpdateClass) error
+
+type UpdateDispatcher struct {
+    handlers map[uint32]handler
+}
+
+func NewUpdateDispatcher() UpdateDispatcher {
+    return UpdateDispatcher{
+        handlers: map[uint32]handler{},
+    }
+}
+
+type Entities struct {
+	Short    bool
+	Users    map[int64]*User
+	Chats    map[int64]*Chat
+	Channels map[int64]*Channel
+}
+
+func (u *Entities) short() {
+	u.Short = true
+	u.Users = make(map[int64]*User, 0)
+	u.Chats = make(map[int64]*Chat, 0)
+	u.Channels = make(map[int64]*Channel, 0)
+}
+
+// Handle implements UpdateDispatcher.
+func (u UpdateDispatcher) Handle(ctx context.Context, updates UpdatesClass) error {
+	var (
+		e Entities
+		upds []UpdateClass
+	)
+	switch u := updates.(type) {
+	case *Updates:
+		upds = u.Updates
+		e.Users = u.MapUsers().NotEmptyToMap()
+		chats := u.MapChats()
+		e.Chats = chats.ChatToMap()
+		e.Channels = chats.ChannelToMap()
+	case *UpdatesCombined:
+		upds = u.Updates
+		e.Users = u.MapUsers().NotEmptyToMap()
+		chats := u.MapChats()
+		e.Chats = chats.ChatToMap()
+		e.Channels = chats.ChannelToMap()
+	case *UpdateShort:
+		upds = []UpdateClass{u.Update}
+		e.short()
+	default:
+		// *UpdateShortMessage
+		// *UpdateShortChatMessage
+		// *UpdateShortSentMessage
+		// *UpdatesTooLong
+		return nil
+	}
+
+	var err error
+	for _, update := range upds {
+		multierr.AppendInto(&err, u.dispatch(ctx, e, update))
+	}
+	return err
+}
+
+func (u UpdateDispatcher) dispatch(ctx context.Context, e Entities, update UpdateClass) error {
+    if update == nil {
+        return nil
+    }
+    typeID := update.TypeID()
+    handler, ok := u.handlers[typeID]
+    if !ok {
+        return nil
+    }
+    return handler(ctx, e, update)
+}
+
+{{- range $s := $.Structs }}{{ if eq $s.Interface "UpdateClass" }}
+{{ $eventName := trimPrefix $s.Name "Update"}}
+// {{ $eventName }}Handler is a {{ $eventName }} event handler.
+type {{ $eventName }}Handler func(ctx context.Context, e Entities, update *{{ $s.Name }}) error
+
+// On{{ $eventName }} sets {{ $eventName }} handler.
+func (u UpdateDispatcher) On{{ $eventName }}(handler {{ $eventName }}Handler) {
+    u.handlers[{{ $s.Name }}TypeID] = func(ctx context.Context, e Entities, update UpdateClass) error {
+        return handler(ctx, e, update.(*{{ $s.Name }}))
+    }
+}
+{{- end }}{{ end }}
+
+{{ end }}