/**
 * src/util/thread_pool_executor.cc
 *
 * Copyright (c) 2021-2022 Bartek Kryza <bkryza@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "thread_pool_executor.h"

namespace clanguml::util {
thread_pool_executor::thread_pool_executor()
    : thread_pool_executor{0}
{
}

thread_pool_executor::thread_pool_executor(unsigned int pool_size)
    : done_{false}
{
    if (pool_size == 0U)
        pool_size = std::thread::hardware_concurrency();

    for (auto i = 0U; i < pool_size; i++) {
        threads_.push_back(std::thread{&thread_pool_executor::worker, this});
    }
}

thread_pool_executor::~thread_pool_executor() { stop(); }

std::future<void> thread_pool_executor::add(std::function<void()> &&task)
{
    std::unique_lock<std::mutex> l(tasks_mutex_);

    std::packaged_task<void()> ptask{std::move(task)};
    auto res = ptask.get_future();

    tasks_.emplace_back(std::move(ptask));

    l.unlock();
    tasks_cond_.notify_one();

    return res;
}

void thread_pool_executor::stop()
{
    done_ = true;
    for (auto &thread : threads_) {
        if (thread.joinable())
            thread.join();
    }
}

void thread_pool_executor::worker()
{
    try {
        while (!done_) {
            auto task = get();

            task();
        }
    }
    catch (std::runtime_error &e) {
    }
}

std::packaged_task<void()> thread_pool_executor::get()
{
    std::unique_lock<std::mutex> l(tasks_mutex_);

    while (tasks_.empty()) {
        if (done_)
            throw std::runtime_error("Thread pool closing...");

        tasks_cond_.wait_for(l, std::chrono::seconds(1));
    }

    auto res = std::move(tasks_.front());
    tasks_.pop_front();
    return res;
}

}