/*
This file is part of Telegram Desktop,
the official desktop version of Telegram messaging app, see https://telegram.org

Telegram Desktop is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

It is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

In addition, as a special exception, the copyright holders give permission
to link the code of portions of this program with the OpenSSL library.

Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
Copyright (c) 2014-2016 John Preston, https://desktop.telegram.org
*/
#include "stdafx.h"
#include "core/observer.h"

namespace Notify {
namespace internal {
namespace {

struct StartCallbackData {
	void *that;
	StartCallback call;
};
struct FinishCallbackData {
	void *that;
	FinishCallback call;
};
struct UnregisterCallbackData {
	void *that;
	UnregisterCallback call;
};
using StartCallbacksList = QVector<StartCallbackData>;
using FinishCallbacksList = QVector<FinishCallbackData>;
NeverFreedPointer<StartCallbacksList> StartCallbacks;
NeverFreedPointer<FinishCallbacksList> FinishCallbacks;
UnregisterCallbackData UnregisterCallbacks[256]/* = { nullptr }*/;

ObservedEvent LastRegisteredEvent/* = 0*/;

} // namespace
} // namespace internal

void startObservers() {
	if (!internal::StartCallbacks) return;

	for (auto &callback : *internal::StartCallbacks) {
		callback.call(callback.that);
	}
}

void finishObservers() {
	if (!internal::FinishCallbacks) return;

	for (auto &callback : *internal::FinishCallbacks) {
		callback.call(callback.that);
	}
	internal::StartCallbacks.clear();
	internal::FinishCallbacks.clear();
}

namespace internal {

BaseObservedEventRegistrator::BaseObservedEventRegistrator(void *that
, StartCallback startCallback
, FinishCallback finishCallback
, UnregisterCallback unregisterCallback) {
	_event = LastRegisteredEvent++;

	StartCallbacks.makeIfNull();
	StartCallbacks->push_back({ that, startCallback });

	FinishCallbacks.makeIfNull();
	FinishCallbacks->push_back({ that, finishCallback });

	UnregisterCallbacks[_event] = { that, unregisterCallback };
}

} // namespace internal

// Observer base interface.
Observer::~Observer() {
	for_const (auto connection, _connections) {
		unregisterObserver(connection);
	}
}

void Observer::observerRegistered(ConnectionId connection) {
	_connections.push_back(connection);
}

void unregisterObserver(ConnectionId connection) {
	auto event = static_cast<internal::ObservedEvent>(connection >> 24);
	auto connectionIndex = int(connection & 0x00FFFFFFU) - 1;
	auto &callback = internal::UnregisterCallbacks[event];
	if (connectionIndex >= 0 && callback.call && callback.that) {
		callback.call(callback.that, connectionIndex);
	}
}

namespace internal {

void observerRegisteredDefault(Observer *observer, ConnectionId connection) {
	observer->observerRegistered(connection);
}

} // namespace internal
} // namespace Notify

namespace base {
namespace internal {
namespace {

bool CantUseObservables = false;

struct ObservableListWrap {
	~ObservableListWrap() {
		CantUseObservables = true;
	}
	OrderedSet<ObservableCallHandlers*> list;
};

ObservableListWrap &PendingObservables() {
	static ObservableListWrap result;
	return result;
}

ObservableListWrap &ActiveObservables() {
	static ObservableListWrap result;
	return result;
}

} // namespace

void RegisterPendingObservable(ObservableCallHandlers *handlers) {
	if (CantUseObservables) return;
	PendingObservables().list.insert(handlers);
	Global::RefHandleObservables().call();
}

void UnregisterActiveObservable(ObservableCallHandlers *handlers) {
	if (CantUseObservables) return;
	ActiveObservables().list.remove(handlers);
}

void UnregisterObservable(ObservableCallHandlers *handlers) {
	if (CantUseObservables) return;
	PendingObservables().list.remove(handlers);
	ActiveObservables().list.remove(handlers);
}

} // namespace internal

void HandleObservables() {
	if (internal::CantUseObservables) return;
	auto &active = internal::ActiveObservables().list;
	qSwap(active, internal::PendingObservables().list);
	while (!active.empty()) {
		auto first = *active.begin();
		(*first)();
		if (!active.empty() && *active.begin() == first) {
			active.erase(active.begin());
		}
	}
}

} // namespace base