Add subscribed-to-premium toast.

Telegram/Resources/langs/lang.strings

@@ -1701,6 +1701,8 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 "lng_premium_summary_bottom_about" = "While the free version of Telegram already gives its users more than any other messaging application, **Telegram Premium** pushes its capabilities even further.\n\n**Telegram Premium** is a paid option, because most Premium Features require additional expenses from Telegram to third parties such as data center providers and server manufacturers. Contributions from **Telegram Premium** users allow us to cover such costs and also help Telegram stay free for everyone.";
 "lng_premium_summary_button" = "Subscribe for {cost} per month";
 
+"lng_premium_success" = "You've successfully subscribed to Telegram Premium!";
+
 "lng_accounts_limit_title" = "Limit Reached";
 "lng_accounts_limit1#one" = "You have reached the limit of **{count}** connected accounts.";
 "lng_accounts_limit1#other" = "You have reached the limit of **{count}** connected accounts.";

Telegram/SourceFiles/window/window_session_controller.cpp

@@ -40,6 +40,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_changes.h"
 #include "data/data_group_call.h"
 #include "data/data_chat_filters.h"
+#include "data/data_peer_values.h"
 #include "passport/passport_form_controller.h"
 #include "chat_helpers/tabbed_selector.h"
 #include "chat_helpers/emoji_interactions.h"
@@ -665,6 +666,7 @@ SessionController::SessionController(
 
 	crl::on_main(this, [=] {
 		activateFirstChatsFilter();
+		setupPremiumToast();
 	});
 }
 
@@ -817,6 +819,30 @@ void SessionController::closeFolder() {
 	_openedFolder = nullptr;
 }
 
+void SessionController::setupPremiumToast() {
+	rpl::combine(
+		Data::AmPremiumValue(&session()),
+		session().changes().peerUpdates(
+			Data::PeerUpdate::Flag::FullInfo
+		)
+	) | rpl::filter([=] {
+		return session().user()->isFullLoaded();
+	}) | rpl::map([=](bool premium, const auto&) {
+		return premium;
+	}) | rpl::distinct_until_changed() | rpl::skip(
+		1
+	) | rpl::filter([=](bool premium) {
+		return premium;
+	}) | rpl::start_with_next([=] {
+		Ui::Toast::Show(
+			Window::Show(this).toastParent(),
+			{
+				.text = tr::lng_premium_success(tr::now),
+				.st = &st::defaultToast,
+			});
+	}, _lifetime);
+}
+
 const rpl::variable<Data::Folder*> &SessionController::openedFolder() const {
 	return _openedFolder;
 }

Telegram/SourceFiles/window/window_session_controller.h

@@ -540,6 +540,7 @@ private:
 	void resetFakeUnreadWhileOpened();
 
 	void checkInvitePeek();
+	void setupPremiumToast();
 
 	void pushDefaultChatBackground();
 	void cacheChatTheme(
@@ -616,8 +617,10 @@ public:
 	[[nodiscard]] not_null<QWidget*> toastParent() const override;
 	[[nodiscard]] bool valid() const override;
 	operator bool() const override;
+
 private:
 	const base::weak_ptr<Controller> _window;
+
 };
 
 } // namespace Window