feat: add subscription invite link methods

CreateChatSubscriptionInviteLink and EditChatSubscriptionInviteLink over
messages.exportChatInvite / editExportedChatInvite, with subscription
pricing surfaced on ChatInviteLink.

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

Author: ernado

chat_member.go

@@ -90,6 +90,12 @@ type ChatInviteLink struct {
 	ExpireDate              int    `json:"expire_date,omitempty"`
 	MemberLimit             int    `json:"member_limit,omitempty"`
 	PendingJoinRequestCount int    `json:"pending_join_request_count,omitempty"`
+	// SubscriptionPeriod is the number of seconds the subscription is active
+	// before the next payment, for subscription invite links.
+	SubscriptionPeriod int `json:"subscription_period,omitempty"`
+	// SubscriptionPrice is the amount of Telegram Stars a user must pay initially
+	// and after each subsequent subscription period to join via the link.
+	SubscriptionPrice int `json:"subscription_price,omitempty"`
 }
 
 // ChatMemberUpdated represents a change in the status of a chat member.

subscription_links.go

@@ -0,0 +1,116 @@
+package botapi
+
+import (
+	"context"
+
+	"github.com/gotd/td/telegram/peers"
+	"github.com/gotd/td/tg"
+)
+
+// errUnexpectedInvite is returned when an invite RPC answers with an unexpected
+// constructor.
+func errUnexpectedInvite() *Error {
+	return &Error{Code: 500, Description: "Internal Server Error: unexpected invite response"}
+}
+
+// inviteLinkName resolves the optional name from invite-link options, ignoring
+// the other fields that subscription links do not support.
+func inviteLinkName(opts []InviteLinkOption) string {
+	var o peers.ExportLinkOptions
+
+	for _, opt := range opts {
+		opt(&o)
+	}
+
+	return o.Title
+}
+
+// inviteLinkFromExported converts an MTProto exported invite into the Bot API
+// type. The bot is always the creator of the links it makes.
+func (b *Bot) inviteLinkFromExported(inv *tg.ChatInviteExported) *ChatInviteLink {
+	out := &ChatInviteLink{
+		InviteLink:              inv.Link,
+		Creator:                 userFromTgUser(b.self),
+		CreatesJoinRequest:      inv.RequestNeeded,
+		IsPrimary:               inv.Permanent,
+		IsRevoked:               inv.Revoked,
+		Name:                    inv.Title,
+		ExpireDate:              inv.ExpireDate,
+		MemberLimit:             inv.UsageLimit,
+		PendingJoinRequestCount: inv.Requested,
+	}
+
+	if pricing, ok := inv.GetSubscriptionPricing(); ok {
+		out.SubscriptionPeriod = pricing.Period
+		out.SubscriptionPrice = int(pricing.Amount)
+	}
+
+	return out
+}
+
+// CreateChatSubscriptionInviteLink creates a subscription invite link for a
+// channel chat. Users joining through the link pay subscriptionPrice Telegram
+// Stars every subscriptionPeriod seconds (currently only 2592000, 30 days, is
+// supported). The bot must have the can_invite_users administrator right.
+func (b *Bot) CreateChatSubscriptionInviteLink(
+	ctx context.Context, chat ChatID, subscriptionPeriod, subscriptionPrice int, opts ...InviteLinkOption,
+) (*ChatInviteLink, error) {
+	peer, err := b.resolveInputPeer(ctx, chat)
+	if err != nil {
+		return nil, err
+	}
+
+	req := &tg.MessagesExportChatInviteRequest{Peer: peer}
+	req.SetSubscriptionPricing(tg.StarsSubscriptionPricing{
+		Period: subscriptionPeriod,
+		Amount: int64(subscriptionPrice),
+	})
+
+	if name := inviteLinkName(opts); name != "" {
+		req.SetTitle(name)
+	}
+
+	res, err := b.raw.MessagesExportChatInvite(ctx, req)
+	if err != nil {
+		return nil, asAPIError(err)
+	}
+
+	exported, ok := res.(*tg.ChatInviteExported)
+	if !ok {
+		return nil, errUnexpectedInvite()
+	}
+
+	return b.inviteLinkFromExported(exported), nil
+}
+
+// EditChatSubscriptionInviteLink edits the name of a subscription invite link
+// created by the bot. The price and period of a subscription link cannot be
+// changed.
+func (b *Bot) EditChatSubscriptionInviteLink(
+	ctx context.Context, chat ChatID, inviteLink string, opts ...InviteLinkOption,
+) (*ChatInviteLink, error) {
+	peer, err := b.resolveInputPeer(ctx, chat)
+	if err != nil {
+		return nil, err
+	}
+
+	req := &tg.MessagesEditExportedChatInviteRequest{Peer: peer, Link: inviteLink}
+	req.SetTitle(inviteLinkName(opts))
+
+	res, err := b.raw.MessagesEditExportedChatInvite(ctx, req)
+	if err != nil {
+		return nil, asAPIError(err)
+	}
+
+	edited, ok := res.(*tg.MessagesExportedChatInvite)
+	if !ok {
+		return nil, errUnexpectedInvite()
+	}
+
+	exported, ok := edited.Invite.(*tg.ChatInviteExported)
+	if !ok {
+		return nil, errUnexpectedInvite()
+	}
+
+	return b.inviteLinkFromExported(exported), nil
+}

subscription_links_test.go

@@ -0,0 +1,74 @@
+package botapi
+
+import (
+	"context"
+	"testing"
+
+	"github.com/gotd/td/tg"
+)
+
+func TestCreateChatSubscriptionInviteLink(t *testing.T) {
+	inv := newMockInvoker()
+	inv.reply(tg.MessagesExportChatInviteRequestTypeID, &tg.ChatInviteExported{
+		Link:  "https://t.me/+sub",
+		Title: "Subs",
+		SubscriptionPricing: tg.StarsSubscriptionPricing{
+			Period: 2592000,
+			Amount: 100,
+		},
+	})
+
+	b := newMockBot(inv)
+
+	link, err := b.CreateChatSubscriptionInviteLink(
+		context.Background(), tdlibChannel(50), 2592000, 100, WithInviteLinkName("Subs"),
+	)
+	if err != nil {
+		t.Fatalf("CreateChatSubscriptionInviteLink: %v", err)
+	}
+
+	if link.SubscriptionPeriod != 2592000 || link.SubscriptionPrice != 100 || link.Name != "Subs" {
+		t.Fatalf("link = %#v", link)
+	}
+
+	var req tg.MessagesExportChatInviteRequest
+
+	inv.decode(t, tg.MessagesExportChatInviteRequestTypeID, &req)
+
+	pricing, ok := req.GetSubscriptionPricing()
+	if !ok || pricing.Period != 2592000 || pricing.Amount != 100 {
+		t.Fatalf("pricing = %#v, ok=%v", pricing, ok)
+	}
+
+	if title, ok := req.GetTitle(); !ok || title != "Subs" {
+		t.Fatalf("title = %q, ok=%v", title, ok)
+	}
+}
+
+func TestEditChatSubscriptionInviteLink(t *testing.T) {
+	inv := newMockInvoker()
+	inv.reply(tg.MessagesEditExportedChatInviteRequestTypeID, &tg.MessagesExportedChatInvite{
+		Invite: &tg.ChatInviteExported{Link: "https://t.me/+sub", Title: "Renamed"},
+	})
+
+	b := newMockBot(inv)
+
+	link, err := b.EditChatSubscriptionInviteLink(
+		context.Background(), tdlibChannel(50), "https://t.me/+sub", WithInviteLinkName("Renamed"),
+	)
+	if err != nil {
+		t.Fatalf("EditChatSubscriptionInviteLink: %v", err)
+	}
+
+	if link.Name != "Renamed" {
+		t.Fatalf("link = %#v", link)
+	}
+
+	var req tg.MessagesEditExportedChatInviteRequest
+
+	inv.decode(t, tg.MessagesEditExportedChatInviteRequestTypeID, &req)
+
+	if req.Link != "https://t.me/+sub" {
+		t.Fatalf("link = %q", req.Link)
+	}
+}