/*
    PIP - Platform Independent Primitives

	Ivan Pelipenko, Stephan Fomenko

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

    This program 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "pithreadpoolworker.h"

#include "pisysteminfo.h"

//! \addtogroup Thread
//! \{
//! \class PIThreadPoolWorker pithreadpoolworker.h
//! \~\details
//! \~english
//! \PIThreadPoolWorker is a class that implements a fixed-size pool of worker threads for general-purpose task execution. It
//! allows starting threads, enqueuing tasks as functors or class member methods, and managing their execution. The class provides methods
//! to wait for all tasks or specific tasks by ID to complete, as well as to gracefully stop the pool with timeouts. The lifecycle of each
//! task can be monitored using the taskStarted and taskFinished events. It is a versatile tool for multithreaded asynchronous operations.
//! \~russian
//! PIThreadPoolWorker — это класс, реализующий фиксированный пул рабочих потоков для выполнения задач общего назначения. Он
//! позволяет запускать потоки, добавлять в очередь задачи в виде функторов или методов класса, а также управлять их выполнением. Класс
//! предоставляет методы для ожидания завершения всех задач или отдельных задач по их идентификатору, а также для корректной остановки пула
//! с таймаутами. С помощью событий taskStarted и taskFinished можно отслеживать жизненный цикл каждой задачи. Это универсальный инструмент
//! для многопоточного асинхронного выполнения операций.
//!
//! \}


PIThreadPoolWorker::PIThreadPoolWorker(int threads_count) {
	if (threads_count < 0) threads_count = PISystemInfo::instance()->processorsCount;
	assertm(threads_count > 0, "Invalid threads count!");
	for (int i = 0; i < threads_count; ++i) {
		Worker * w = new Worker();
		w->thread.setSlot([this, w]() { threadFunc(w); });
		workers << w;
	}
}


PIThreadPoolWorker::~PIThreadPoolWorker() {
	piDeleteAllAndClear(workers);
}


void PIThreadPoolWorker::start() {
	for (auto w: workers) {
		w->thread.start();
		w->notifier.notify();
	}
}


void PIThreadPoolWorker::stop() {
	for (auto w: workers) {
		w->thread.stop();
		w->notifier.notify();
	}
}


bool PIThreadPoolWorker::stopAndWait(PISystemTime timeout) {
	stop();
	return waitForFinish(timeout);
}


bool PIThreadPoolWorker::waitForStart(PISystemTime timeout) {
	PITimeMeasurer tm;
	for (auto w: workers) {
		if (timeout.isNull())
			w->thread.waitForStart();
		else {
			auto remains = timeout - tm.elapsed();
			if (remains.isNegative()) return false;
			if (!w->thread.waitForStart(remains)) return false;
		}
	}
	return true;
}


bool PIThreadPoolWorker::waitForFinish(PISystemTime timeout) {
	PITimeMeasurer tm;
	for (auto w: workers) {
		if (timeout.isNull())
			w->thread.waitForFinish();
		else {
			auto remains = timeout - tm.elapsed();
			if (remains.isNegative()) return false;
			if (!w->thread.waitForFinish(remains)) return false;
		}
	}
	return true;
}


bool PIThreadPoolWorker::isRunning() const {
	return workers.every([](Worker * w) { return w->thread.isRunning(); });
}


bool PIThreadPoolWorker::waitForTasks(PISystemTime timeout) {
	if (!isRunning()) return tasks_queue.getRef()->isEmpty();
	auto checkWorking = [this] {
		if (tasks_queue.getRef()->isNotEmpty()) return true;
		for (auto * w: workers)
			if (w->in_work > 0) return true;
		return false;
	};
	if (timeout.isNull()) {
		for (;;) {
			if (!checkWorking()) break;
			piMinSleep();
		}
		return true;
	}
	PITimeMeasurer tm;
	while (tm.elapsed() < timeout) {
		if (!checkWorking()) return true;
		piMinSleep();
	}
	return tm.elapsed() < timeout;
}


bool PIThreadPoolWorker::waitForTask(int64_t id, PISystemTime timeout) {
	if (!isRunning()) return tasks_queue.getRef()->every([id](const Task & t) { return t.id != id; });
	auto checkWorking = [this, id] {
		if (tasks_queue.getRef()->any([id](const Task & t) { return t.id == id; })) return true;
		for (auto * w: workers)
			if (w->in_work == id) return true;
		return false;
	};
	if (timeout.isNull()) {
		for (;;) {
			if (!checkWorking()) break;
			piMinSleep();
		}
		return true;
	}
	PITimeMeasurer tm;
	while (tm.elapsed() < timeout) {
		if (!checkWorking()) return true;
		piMinSleep();
	}
	return tm.elapsed() < timeout;
}


void PIThreadPoolWorker::exec() {
	start();
	waitForStart();
	waitForTasks();
	stopAndWait();
}


int64_t PIThreadPoolWorker::enqueueTask(std::function<void(int64_t)> func, PIObject * context) {
	if (context) {
		if (!contexts[context]) {
			contexts << context;
			CONNECTL(context, deleted, ([this, context](PIObject *) {
						 contexts.remove(context);
						 auto qref = tasks_queue.getRef();
						 // auto prev_size = qref->size();
						 // piCout << "deleted" << (void *)context << qref->map<void *>([](const Task & t) { return t.context; });
						 qref->removeWhere([context](const Task & t) { return t.context == context; });
						 // piCout << prev_size << qref->size() << qref->map<void *>([](const Task & t) { return t.context; });
					 }));
		}
	}
	int64_t id = ++next_task_id;
	Task task;
	task.id      = id;
	task.func    = std::move(func);
	task.context = context;
	tasks_queue.getRef()->enqueue(std::move(task));
	for (auto * w: workers)
		w->notifier.notify();
	return id;
}


bool PIThreadPoolWorker::removeTask(int64_t id) {
	auto qref      = tasks_queue.getRef();
	auto prev_size = qref->size();
	qref->removeWhere([id](const Task & t) { return t.id == id; });
	return prev_size != qref->size();
}


void PIThreadPoolWorker::clearTasks() {
	tasks_queue.getRef()->clear();
}


PIThreadPoolWorker::TaskStatus PIThreadPoolWorker::taskStatus(int64_t id) const {
	if (id <= 0) return TaskStatus::Unknown;
	auto qref = tasks_queue.getRef();
	for (auto w: workers)
		if (w->in_work == id) return TaskStatus::InProgress;
	for (const auto & t: *qref)
		if (t.id == id) return TaskStatus::Enqueued;
	return id <= next_task_id ? TaskStatus::DoneOrCancelled : TaskStatus::Unknown;
}


void PIThreadPoolWorker::threadFunc(Worker * w) {
	w->notifier.wait();
	if (w->thread.isStopping()) return;
	Task task;
	{
		auto ref = tasks_queue.getRef();
		if (ref->isEmpty()) return;
		task = ref->dequeue();
	}
	if (!task.isValid()) return;
	w->in_work = task.id;
	taskStarted(task.id);
	task.func(task.id);
	w->in_work = -1;
	taskFinished(task.id);
	w->notifier.notify();
}