feat: send media on behalf of a business account

Route the media send paths (sendResolvedMedia, sendMedia, SendMediaGroup)
through senderFor(cfg) so WithBusinessConnection wraps the send RPC. File
uploads already run on b.raw (the bot session) inside the media builders, so
they stay unwrapped; only messages.sendMedia (and, for albums, uploadMedia +
sendMultiMedia) are wrapped in invokeWithBusinessConnection. Adds
BusinessContext.SendPhoto/SendDocument and broadens the WithBusinessConnection
doc.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ernado

business_context.go

@@ -78,3 +78,18 @@ func (c *BusinessContext) DeleteMessages(ctx context.Context, messageIDs []int)
 func (c *BusinessContext) SendMessage(ctx context.Context, chat ChatID, text string, opts ...SendOption) (*Message, error) {
 	return c.bot.SendMessage(ctx, chat, text, append(opts, WithBusinessConnection(c.connectionID))...)
 }
+
+// SendPhoto sends a photo to a chat on behalf of the connected business account.
+func (c *BusinessContext) SendPhoto(
+	ctx context.Context, chat ChatID, photo InputFile, caption string, opts ...SendOption,
+) (*Message, error) {
+	return c.bot.SendPhoto(ctx, chat, photo, caption, append(opts, WithBusinessConnection(c.connectionID))...)
+}
+
+// SendDocument sends a general file to a chat on behalf of the connected business
+// account.
+func (c *BusinessContext) SendDocument(
+	ctx context.Context, chat ChatID, document InputFile, caption string, opts ...SendOption,
+) (*Message, error) {
+	return c.bot.SendDocument(ctx, chat, document, caption, append(opts, WithBusinessConnection(c.connectionID))...)
+}

business_media_test.go

@@ -0,0 +1,177 @@
+package botapi
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/gotd/td/bin"
+	"github.com/gotd/td/tg"
+)
+
+// businessAlbumHandler answers the wrapped RPCs an album send issues on behalf of
+// a business account: uploadMedia per item (returning a usable photo) and the
+// final sendMultiMedia.
+func businessAlbumHandler(t *testing.T, connSeen *string) func(*bin.Buffer) (bin.Encoder, error) {
+	t.Helper()
+
+	return func(buf *bin.Buffer) (bin.Encoder, error) {
+		if err := buf.ConsumeID(tg.InvokeWithBusinessConnectionRequestTypeID); err != nil {
+			return nil, err
+		}
+
+		id, err := buf.String()
+		if err != nil {
+			return nil, err
+		}
+
+		*connSeen = id
+
+		inner, err := buf.PeekID()
+		if err != nil {
+			return nil, err
+		}
+
+		switch inner {
+		case tg.MessagesUploadMediaRequestTypeID:
+			m := &tg.MessageMediaPhoto{}
+			m.SetPhoto(&tg.Photo{
+				ID: 1, AccessHash: 2, FileReference: []byte{0}, DCID: 2,
+				Sizes: []tg.PhotoSizeClass{&tg.PhotoSize{Type: "x", W: 1, H: 1, Size: 1}},
+			})
+
+			return m, nil
+		case tg.MessagesSendMultiMediaRequestTypeID:
+			return multiMessageUpdates(11, 12), nil
+		default:
+			return nil, fmt.Errorf("unexpected inner request %#x", inner)
+		}
+	}
+}
+
+func TestSendPhotoWithBusinessConnection(t *testing.T) {
+	inv := newMockInvoker()
+	inv.reply(tg.InvokeWithBusinessConnectionRequestTypeID, sendMediaOK())
+
+	b := newMockBot(inv)
+
+	photo := &InputFileUpload{Name: "p.jpg", Bytes: []byte("img")}
+	if _, err := b.SendPhoto(context.Background(), userRef(10, 20), photo, "hi", WithBusinessConnection("bc1")); err != nil {
+		t.Fatalf("SendPhoto: %v", err)
+	}
+
+	// The file upload must stay in the bot session, unwrapped.
+	if !inv.called(tg.UploadSaveFilePartRequestTypeID) {
+		t.Fatal("expected a direct file upload")
+	}
+
+	wrapper := tg.InvokeWithBusinessConnectionRequest{Query: &tg.MessagesSendMediaRequest{}}
+
+	inv.decode(t, tg.InvokeWithBusinessConnectionRequestTypeID, &wrapper)
+
+	if wrapper.ConnectionID != "bc1" {
+		t.Fatalf("connection id = %q", wrapper.ConnectionID)
+	}
+
+	send, ok := wrapper.Query.(*tg.MessagesSendMediaRequest)
+	if !ok {
+		t.Fatalf("query = %#v", wrapper.Query)
+	}
+
+	if _, ok := send.Media.(*tg.InputMediaUploadedPhoto); !ok {
+		t.Fatalf("media = %#v, want uploaded photo", send.Media)
+	}
+}
+
+func TestSendDocumentWithBusinessConnection(t *testing.T) {
+	inv := newMockInvoker()
+	inv.reply(tg.InvokeWithBusinessConnectionRequestTypeID, sendMediaOK())
+
+	b := newMockBot(inv)
+
+	doc := &InputFileUpload{Name: "f.bin", Bytes: []byte("data")}
+	if _, err := b.SendDocument(context.Background(), userRef(10, 20), doc, "", WithBusinessConnection("bc2")); err != nil {
+		t.Fatalf("SendDocument: %v", err)
+	}
+
+	wrapper := tg.InvokeWithBusinessConnectionRequest{Query: &tg.MessagesSendMediaRequest{}}
+
+	inv.decode(t, tg.InvokeWithBusinessConnectionRequestTypeID, &wrapper)
+
+	if wrapper.ConnectionID != "bc2" {
+		t.Fatalf("connection id = %q", wrapper.ConnectionID)
+	}
+
+	send, ok := wrapper.Query.(*tg.MessagesSendMediaRequest)
+	if !ok {
+		t.Fatalf("query = %#v", wrapper.Query)
+	}
+
+	if _, ok := send.Media.(*tg.InputMediaUploadedDocument); !ok {
+		t.Fatalf("media = %#v, want uploaded document", send.Media)
+	}
+}
+
+func TestSendPhotoByFileIDWithBusinessConnection(t *testing.T) {
+	fid := documentFileID(t, 0x91)
+
+	inv := newMockInvoker()
+	inv.reply(tg.InvokeWithBusinessConnectionRequestTypeID, sendMediaOK())
+
+	b := newMockBot(inv)
+
+	// A file_id send performs no upload; only the send is wrapped.
+	if _, err := b.SendPhoto(context.Background(), userRef(10, 20), FileID(fid), "", WithBusinessConnection("bc3")); err != nil {
+		t.Fatalf("SendPhoto: %v", err)
+	}
+
+	if inv.called(tg.UploadSaveFilePartRequestTypeID) {
+		t.Fatal("a file_id send must not upload")
+	}
+
+	if !inv.called(tg.InvokeWithBusinessConnectionRequestTypeID) {
+		t.Fatal("expected a wrapped send")
+	}
+}
+
+func TestSendMediaGroupWithBusinessConnection(t *testing.T) {
+	inv := newMockInvoker()
+
+	var connSeen string
+
+	inv.handle(tg.InvokeWithBusinessConnectionRequestTypeID, businessAlbumHandler(t, &connSeen))
+
+	b := newMockBot(inv)
+
+	media := []InputMedia{
+		&InputMediaPhoto{Media: &InputFileUpload{Name: "a.jpg", Bytes: []byte("a")}},
+		&InputMediaPhoto{Media: &InputFileUpload{Name: "b.jpg", Bytes: []byte("b")}},
+	}
+
+	msgs, err := b.SendMediaGroup(context.Background(), userRef(10, 20), media, WithBusinessConnection("bc7"))
+	if err != nil {
+		t.Fatalf("SendMediaGroup: %v", err)
+	}
+
+	if len(msgs) != 2 {
+		t.Fatalf("got %d messages", len(msgs))
+	}
+
+	if connSeen != "bc7" {
+		t.Fatalf("connection id = %q", connSeen)
+	}
+
+	// Uploads happen in the bot session, unwrapped.
+	if !inv.called(tg.UploadSaveFilePartRequestTypeID) {
+		t.Fatal("expected direct file uploads")
+	}
+
+	// The final wrapped call is the multi-media send.
+	wrapper := tg.InvokeWithBusinessConnectionRequest{Query: &tg.MessagesSendMultiMediaRequest{}}
+
+	inv.decode(t, tg.InvokeWithBusinessConnectionRequestTypeID, &wrapper)
+
+	if _, ok := wrapper.Query.(*tg.MessagesSendMultiMediaRequest); !ok {
+		t.Fatalf("final query = %#v, want sendMultiMedia", wrapper.Query)
+	}
+}

media.go

@@ -134,7 +134,7 @@ func (b *Bot) sendResolvedMedia(
 		return nil, err
 	}
 
-	builder := &b.sender.To(peer).Builder
+	builder := &b.senderFor(cfg).To(peer).Builder
 
 	builder, err = b.applySendConfig(builder, cfg)
 	if err != nil {

media_group.go

@@ -180,7 +180,7 @@ func (b *Bot) SendMediaGroup(ctx context.Context, chat ChatID, media []InputMedi
 		return nil, err
 	}
 
-	builder := &b.sender.To(peer).Builder
+	builder := &b.senderFor(cfg).To(peer).Builder
 
 	builder, err = b.applySendConfig(builder, cfg)
 	if err != nil {

send.go

@@ -47,8 +47,10 @@ func WithParseMode(m ParseMode) SendOption { return func(c *sendConfig) { c.pars
 // WithBusinessConnection sends the message on behalf of the business account
 // identified by the given connection id, instead of as the bot itself.
 //
-// It currently applies to SendMessage (text). Sending media on behalf of a
-// business account is not yet supported.
+// It applies to the text and media send methods (SendMessage, SendPhoto,
+// SendDocument, SendVideo, SendAudio, SendMediaGroup, …). Files are uploaded in
+// the bot's own session; only the resulting send is performed on behalf of the
+// account.
 func WithBusinessConnection(connectionID string) SendOption {
 	return func(c *sendConfig) { c.businessConn = connectionID }
 }

send_other.go

@@ -20,7 +20,7 @@ func (b *Bot) sendMedia(ctx context.Context, chat ChatID, media message.MediaOpt
 		return nil, err
 	}
 
-	builder := &b.sender.To(peer).Builder
+	builder := &b.senderFor(cfg).To(peer).Builder
 
 	builder, err = b.applySendConfig(builder, cfg)
 	if err != nil {