Added initial ability to request rate of credits from Credits component.

Telegram/SourceFiles/data/components/credits.cpp

@@ -29,6 +29,30 @@ void Credits::apply(const MTPDupdateStarsBalance &data) {
 	apply(data.vbalance().v);
 }
 
+rpl::producer<float64> Credits::rateValue(
+		not_null<PeerData*> ownedBotOrChannel) {
+	// Should be replaced in the future.
+	if (_rate > 0) {
+		return rpl::single(_rate);
+	}
+	return [=](auto consumer) {
+		auto lifetime = rpl::lifetime();
+
+		const auto api = lifetime.make_state<Api::CreditsEarnStatistics>(
+			ownedBotOrChannel);
+		api->request(
+		) | rpl::start_with_done([=] {
+			_rate = api->data().usdRate;
+			if (_rate > 0) {
+				consumer.put_next_copy(_rate);
+				consumer.put_done();
+			}
+		}, lifetime);
+
+		return lifetime;
+	};
+}
+
 void Credits::load(bool force) {
 	if (_loader
 		|| (!force

Telegram/SourceFiles/data/components/credits.h

@@ -30,6 +30,8 @@ public:
 
 	[[nodiscard]] uint64 balance() const;
 	[[nodiscard]] rpl::producer<uint64> balanceValue() const;
+	[[nodiscard]] rpl::producer<float64> rateValue(
+		not_null<PeerData*> ownedBotOrChannel);
 
 	void lock(int count);
 	void unlock(int count);
@@ -47,6 +49,7 @@ private:
 	rpl::variable<uint64> _locked;
 	rpl::event_stream<> _loadedChanges;
 	crl::time _lastLoaded = 0;
+	float64 _rate = 0.;
 
 	SingleQueuedInvokation _reload;