Show similar channels under join message.

Telegram/SourceFiles/api/api_chat_participants.cpp

@@ -211,6 +211,23 @@ void ApplyBotsList(
 		Data::PeerUpdate::Flag::FullInfo);
 }
 
+[[nodiscard]] std::vector<not_null<ChannelData*>> ParseSimilar(
+		not_null<ChannelData*> channel,
+		const MTPmessages_Chats &chats) {
+	auto result = std::vector<not_null<ChannelData*>>();
+	chats.match([&](const auto &data) {
+		const auto &list = data.vchats().v;
+		result.reserve(list.size());
+		for (const auto &chat : list) {
+			const auto peer = channel->owner().processChat(chat);
+			if (const auto channel = peer->asChannel()) {
+				result.push_back(channel);
+			}
+		}
+	});
+	return result;
+}
+
 } // namespace
 
 ChatParticipant::ChatParticipant(
@@ -559,6 +576,7 @@ void ChatParticipants::requestSelf(not_null<ChannelData*> channel) {
 			UserId inviter = -1,
 			TimeId inviteDate = 0,
 			bool inviteViaRequest = false) {
+		const auto dateChanged = (channel->inviteDate != inviteDate);
 		channel->inviter = inviter;
 		channel->inviteDate = inviteDate;
 		channel->inviteViaRequest = inviteViaRequest;
@@ -569,6 +587,9 @@ void ChatParticipants::requestSelf(not_null<ChannelData*> channel) {
 			} else {
 				history->owner().histories().requestDialogEntry(history);
 			}
+			if (dateChanged) {
+				loadSimilarChannels(channel);
+			}
 		}
 	};
 	_selfParticipantRequests.emplace(channel);
@@ -685,4 +706,35 @@ void ChatParticipants::unblock(
 	_kickRequests.emplace(kick, requestId);
 }
 
+void ChatParticipants::loadSimilarChannels(not_null<ChannelData*> channel) {
+	if (!channel->isBroadcast() || _similar.contains(channel)) {
+		return;
+	}
+	_similar[channel].requestId = _api.request(
+		MTPchannels_GetChannelRecommendations(channel->inputChannel)
+	).done([=](const MTPmessages_Chats &result) {
+		_similar[channel] = {
+			.list = ParseSimilar(channel, result),
+		};
+		_similarLoaded.fire_copy(channel);
+	}).send();
+}
+
+const std::vector<not_null<ChannelData*>> &ChatParticipants::similar(
+		not_null<ChannelData*> channel) {
+	const auto i = channel->isBroadcast()
+		? _similar.find(channel)
+		: end(_similar);
+	if (i != end(_similar)) {
+		return i->second.list;
+	}
+	static const auto empty = std::vector<not_null<ChannelData*>>();
+	return empty;
+}
+
+auto ChatParticipants::similarLoaded() const
+-> rpl::producer<not_null<ChannelData*>> {
+	return _similarLoaded.events();
+}
+
 } // namespace Api