// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

#pragma once

#ifndef SPDLOG_HEADER_ONLY
    #include <spdlog/details/thread_pool.h>
#endif

#include <cassert>
#include <spdlog/common.h>

namespace spdlog {
namespace details {

SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items,
                                       size_t threads_n,
                                       std::function<void()> on_thread_start,
                                       std::function<void()> on_thread_stop)
    : q_(q_max_items) {
    if (threads_n == 0 || threads_n > 1000) {
        throw_spdlog_ex(
            "spdlog::thread_pool(): invalid threads_n param (valid "
            "range is 1-1000)");
    }
    for (size_t i = 0; i < threads_n; i++) {
        threads_.emplace_back([this, on_thread_start, on_thread_stop] {
            on_thread_start();
            this->thread_pool::worker_loop_();
            on_thread_stop();
        });
    }
}

SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items,
                                       size_t threads_n,
                                       std::function<void()> on_thread_start)
    : thread_pool(q_max_items, threads_n, on_thread_start, [] {}) {}

SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n)
    : thread_pool(
          q_max_items, threads_n, [] {}, [] {}) {}

// message all threads to terminate gracefully join them
SPDLOG_INLINE thread_pool::~thread_pool() {
    SPDLOG_TRY {
        for (size_t i = 0; i < threads_.size(); i++) {
            post_async_msg_(async_msg(async_msg_type::terminate), async_overflow_policy::block);
        }

        for (auto &t : threads_) {
            t.join();
        }
    }
    SPDLOG_CATCH_STD
}

void SPDLOG_INLINE thread_pool::post_log(async_logger_ptr &&worker_ptr,
                                         const details::log_msg &msg,
                                         async_overflow_policy overflow_policy) {
    async_msg async_m(std::move(worker_ptr), async_msg_type::log, msg);
    post_async_msg_(std::move(async_m), overflow_policy);
}

std::future<void> SPDLOG_INLINE thread_pool::post_flush(async_logger_ptr &&worker_ptr,
                                                        async_overflow_policy overflow_policy) {
    std::promise<void> promise;
    std::future<void> future = promise.get_future();
    post_async_msg_(async_msg(std::move(worker_ptr), async_msg_type::flush, std::move(promise)),
                    overflow_policy);
    return future;
}

size_t SPDLOG_INLINE thread_pool::overrun_counter() { return q_.overrun_counter(); }

void SPDLOG_INLINE thread_pool::reset_overrun_counter() { q_.reset_overrun_counter(); }

size_t SPDLOG_INLINE thread_pool::discard_counter() { return q_.discard_counter(); }

void SPDLOG_INLINE thread_pool::reset_discard_counter() { q_.reset_discard_counter(); }

size_t SPDLOG_INLINE thread_pool::queue_size() { return q_.size(); }

void SPDLOG_INLINE thread_pool::post_async_msg_(async_msg &&new_msg,
                                                async_overflow_policy overflow_policy) {
    switch(overflow_policy) {
    case async_overflow_policy::block:
        q_.enqueue(std::move(new_msg));
        break;
    case async_overflow_policy::overrun_oldest:
        q_.enqueue_nowait(std::move(new_msg));
        break;
    case async_overflow_policy::discard_new:
        // This check is essential to avoid deadlock on termination
        if (new_msg.msg_type != async_msg_type::terminate && new_msg.msg_type != async_msg_type::flush) {
            q_.enqueue_if_have_room(std::move(new_msg));
        } else {
            q_.enqueue(std::move(new_msg));
        }
        break;
    default:
        assert(false);
    }
}

void SPDLOG_INLINE thread_pool::worker_loop_() {
    while (process_next_msg_()) {
    }
}

// process next message in the queue
// return true if this thread should still be active (while no terminate msg
// was received)
bool SPDLOG_INLINE thread_pool::process_next_msg_() {
    async_msg incoming_async_msg;
    q_.dequeue(incoming_async_msg);

    switch (incoming_async_msg.msg_type) {
        case async_msg_type::log: {
            incoming_async_msg.worker_ptr->backend_sink_it_(incoming_async_msg);
            return true;
        }
        case async_msg_type::flush: {
            incoming_async_msg.worker_ptr->backend_flush_();
            incoming_async_msg.flush_promise.set_value();
            return true;
        }

        case async_msg_type::terminate: {
            return false;
        }

        default: {
            assert(false);
        }
    }

    return true;
}

}  // namespace details
}  // namespace spdlog
