Add convert to gigagroup button.

Telegram/Resources/langs/lang.strings

@@ -2014,6 +2014,17 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 "lng_slowmode_no_many" = "Slow mode is enabled. You can't send more than one message at a time.";
 "lng_slowmode_too_long" = "Sorry, this text is too long to send as one message.\n\nSlow mode is enabled. You can't send more than one message at a time.";
 
+"lng_rights_gigagroup_title" = "Broadcast group";
+"lng_rights_gigagroup_convert" = "Convert to Broadcast Group";
+"lng_rights_gigagroup_about" = "Broadcast groups can have over 200,000 members, but only admins can send messages in them.";
+"lng_gigagroup_convert_title" = "Broadcast Groups";
+"lng_gigagroup_convert_feature1" = "No limit on the number of members.";
+"lng_gigagroup_convert_feature2" = "Only admins can send messages.";
+"lng_gigagroup_convert_feature3" = "Can't be turned back into a regular group.";
+"lng_gigagroup_convert_sure" = "Convert";
+"lng_gigagroup_warning_title" = "Are you sure?";
+"lng_gigagroup_warning" = "Regular members of the group (non-admins) will **irrevocably** lose their right to post messages in the group.\n\nThis action **can't** be undone.";
+
 "lng_rights_channel_info" = "Change channel info";
 "lng_rights_channel_post" = "Post messages";
 "lng_rights_channel_edit" = "Edit messages of others";

Telegram/SourceFiles/boxes/peers/edit_peer_permissions_box.cpp

@@ -11,6 +11,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_channel.h"
 #include "data/data_chat.h"
 #include "ui/wrap/vertical_layout.h"
+#include "ui/layers/generic_box.h"
 #include "ui/widgets/labels.h"
 #include "ui/widgets/checkbox.h"
 #include "ui/widgets/buttons.h"
@@ -22,7 +23,9 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "boxes/peers/edit_participants_box.h"
 #include "boxes/peers/edit_peer_info_box.h"
 #include "window/window_session_controller.h"
+#include "main/main_session.h"
 #include "mainwindow.h"
+#include "apiwrap.h"
 #include "app.h"
 #include "styles/style_layers.h"
 #include "styles/style_boxes.h"
@@ -31,6 +34,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 namespace {
 
 constexpr auto kSlowmodeValues = 7;
+constexpr auto kSuggestGigagroupThreshold = 199000;
 
 int SlowmodeDelayByIndex(int index) {
 	Expects(index >= 0 && index < kSlowmodeValues);
@@ -369,6 +373,14 @@ void EditPeerPermissionsBox::prepare() {
 	inner->add(std::move(checkboxes));
 
 	const auto getSlowmodeSeconds = addSlowmodeSlider(inner);
+
+	if (const auto channel = _peer->asChannel()) {
+		if (channel->amCreator()
+			&& channel->membersCount() >= kSuggestGigagroupThreshold) {
+			addSuggestGigagroup(inner);
+		}
+	}
+
 	addBannedButtons(inner);
 
 	_value = [=, rights = getRestrictions]() -> Result {
@@ -520,6 +532,93 @@ void EditPeerPermissionsBox::addSlowmodeLabels(
 	}
 }
 
+void EditPeerPermissionsBox::addSuggestGigagroup(
+		not_null<Ui::VerticalLayout*> container) {
+	container->add(
+		object_ptr<Ui::FlatLabel>(
+			container,
+			tr::lng_rights_gigagroup_title(),
+			st::rightsHeaderLabel),
+		st::rightsHeaderMargin);
+	const auto channel = _peer->asChannel();
+	const auto converting = std::make_shared<bool>();
+	const auto convertSure = [=] {
+		if (*converting) {
+			return;
+		}
+		*converting = true;
+		channel->session().api().request(MTPchannels_ConvertToGigagroup(
+			channel->inputChannel
+		)).done([=](const MTPUpdates &result) {
+			channel->session().api().applyUpdates(result);
+			Ui::hideLayer();
+		}).fail([=](const RPCError &error) {
+			*converting = false;
+		}).send();
+	};
+	const auto convertWarn = [=] {
+		if (*converting) {
+			return;
+		}
+		getDelegate()->show(Box([=](not_null<Ui::GenericBox*> box) {
+			box->setTitle(tr::lng_gigagroup_warning_title());
+			box->addRow(
+				object_ptr<Ui::FlatLabel>(
+					box,
+					tr::lng_gigagroup_warning(),
+					st::defaultFlatLabel),
+				style::margins(
+					st::boxRowPadding.left(),
+					st::boxLittleSkip,
+					st::boxRowPadding.right(),
+					st::boxLittleSkip));
+			box->addButton(tr::lng_gigagroup_convert_sure(), convertSure);
+			box->addButton(tr::lng_cancel(), [=] { box->closeBox(); });
+		}));
+	};
+	const auto convert = [=] {
+		if (*converting) {
+			return;
+		}
+		getDelegate()->show(Box([=](not_null<Ui::GenericBox*> box) {
+			box->setTitle(tr::lng_gigagroup_convert_title());
+			const auto addFeature = [&](rpl::producer<QString> text) {
+				box->addRow(
+					object_ptr<Ui::FlatLabel>(
+						box,
+						std::move(text),
+						st::defaultFlatLabel),
+					style::margins(
+						st::boxRowPadding.left(),
+						st::boxLittleSkip,
+						st::boxRowPadding.right(),
+						st::boxLittleSkip));
+			};
+			addFeature(tr::lng_gigagroup_convert_feature1());
+			addFeature(tr::lng_gigagroup_convert_feature2());
+			addFeature(tr::lng_gigagroup_convert_feature3());
+			box->addButton(tr::lng_gigagroup_convert_sure(), convertWarn);
+			box->addButton(tr::lng_cancel(), [=] { box->closeBox(); });
+		}));
+	};
+	container->add(EditPeerInfoBox::CreateButton(
+		container,
+		tr::lng_rights_gigagroup_convert(),
+		rpl::single(QString()),
+		convert,
+		st::peerPermissionsButton));
+
+	container->add(
+		object_ptr<Ui::DividerLabel>(
+			container,
+			object_ptr<Ui::FlatLabel>(
+				container,
+				tr::lng_rights_gigagroup_about(),
+				st::boxDividerLabel),
+			st::proxyAboutPadding),
+		style::margins(0, st::infoProfileSkip, 0, st::infoProfileSkip));
+}
+
 void EditPeerPermissionsBox::addBannedButtons(
 		not_null<Ui::VerticalLayout*> container) {
 	if (const auto chat = _peer->asChat()) {

Telegram/SourceFiles/boxes/peers/edit_peer_permissions_box.h

@@ -39,6 +39,7 @@ protected:
 private:
 	Fn<int()> addSlowmodeSlider(not_null<Ui::VerticalLayout*> container);
 	void addSlowmodeLabels(not_null<Ui::VerticalLayout*> container);
+	void addSuggestGigagroup(not_null<Ui::VerticalLayout*> container);
 	void addBannedButtons(not_null<Ui::VerticalLayout*> container);
 
 	const not_null<Window::SessionNavigation*> _navigation;