/*

 * Authored by Alex Hultman, 2018-2020.

 * Intellectual property of third-party.

 * 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.

 */

#ifndef UWS_LOOP_H

#define UWS_LOOP_H

/* The loop is lazily created per-thread and run with run() */

#include "LoopData.h"

#include <libusockets.h>

#include <iostream>

namespace uWS {

struct Loop {

private:

    static void wakeupCb(us_loop_t *loop) {

        LoopData *loopData = (LoopData *) us_loop_ext(loop);

        /* Swap current deferQueue */

        loopData->deferMutex.lock();

        int oldDeferQueue = loopData->currentDeferQueue;

        loopData->currentDeferQueue = (loopData->currentDeferQueue + 1) % 2;

        loopData->deferMutex.unlock();

        /* Drain the queue */

        for (auto &x : loopData->deferQueues[oldDeferQueue]) {

            x();

        }

        loopData->deferQueues[oldDeferQueue].clear();

    }

    static void preCb(us_loop_t *loop) {

        LoopData *loopData = (LoopData *) us_loop_ext(loop);

        for (auto &p : loopData->preHandlers) {

            p.second((Loop *) loop);

        }

    }

    static void postCb(us_loop_t *loop) {

        LoopData *loopData = (LoopData *) us_loop_ext(loop);

        for (auto &p : loopData->postHandlers) {

            p.second((Loop *) loop);

        }

        /* After every event loop iteration, we must not hold the cork buffer */

        if (loopData->corkedSocket) {

            std::cerr << "Error: Cork buffer must not be held across event loop iterations!" << std::endl;

            std::terminate();

        }

    }

    Loop() = delete;

    ~Loop() = default;

    Loop *init() {

        new (us_loop_ext((us_loop_t *) this)) LoopData;

        return this;

    }

    static Loop *create(void *hint) {

        Loop *loop = ((Loop *) us_create_loop(hint, wakeupCb, preCb, postCb, sizeof(LoopData)))->init();

        /* We also need some timers (should live off the one 4 second timer rather) */

        LoopData *loopData = (LoopData *) us_loop_ext((struct us_loop_t *) loop);

        loopData->dateTimer = us_create_timer((struct us_loop_t *) loop, 1, sizeof(LoopData *));

        memcpy(us_timer_ext(loopData->dateTimer), &loopData, sizeof(LoopData *));

        us_timer_set(loopData->dateTimer, [](struct us_timer_t *t) {

            LoopData *loopData;

            memcpy(&loopData, us_timer_ext(t), sizeof(LoopData *));

            loopData->updateDate();

        }, 1000, 1000);

        return loop;

    }

    /* What to do with loops created with existingNativeLoop? */

    struct LoopCleaner {

        ~LoopCleaner() {

            if(loop && cleanMe) {

                loop->free();

            }

        }

        Loop *loop = nullptr;

        bool cleanMe = false;

    };

    static LoopCleaner &getLazyLoop() {

        static thread_local LoopCleaner lazyLoop;

        return lazyLoop;

    }

public:

    /* Lazily initializes a per-thread loop and returns it.

     * Will automatically free all initialized loops at exit. */

    static Loop *get(void *existingNativeLoop = nullptr) {

        if (!getLazyLoop().loop) {

            /* If we are given a native loop pointer we pass that to uSockets and let it deal with it */

            if (existingNativeLoop) {

                /* Todo: here we want to pass the pointer, not a boolean */

                getLazyLoop().loop = create(existingNativeLoop);

                /* We cannot register automatic free here, must be manually done */

            } else {

                getLazyLoop().loop = create(nullptr);

                getLazyLoop().cleanMe = true;

            }

        }

        return getLazyLoop().loop;

    }

    /* Freeing the default loop should be done once */

    void free() {

        LoopData *loopData = (LoopData *) us_loop_ext((us_loop_t *) this);

        /* Stop and free dateTimer first */

        us_timer_close(loopData->dateTimer);

        loopData->~LoopData();

        /* uSockets will track whether this loop is owned by us or a borrowed alien loop */

        us_loop_free((us_loop_t *) this);

        /* Reset lazyLoop */

        getLazyLoop().loop = nullptr;

    }

    void addPostHandler(void *key, MoveOnlyFunction<void(Loop *)> &&handler) {

        LoopData *loopData = (LoopData *) us_loop_ext((us_loop_t *) this);

        loopData->postHandlers.emplace(key, std::move(handler));

    }

    /* Bug: what if you remove a handler while iterating them? */

    void removePostHandler(void *key) {

        LoopData *loopData = (LoopData *) us_loop_ext((us_loop_t *) this);

        loopData->postHandlers.erase(key);

    }

    void addPreHandler(void *key, MoveOnlyFunction<void(Loop *)> &&handler) {

        LoopData *loopData = (LoopData *) us_loop_ext((us_loop_t *) this);

        loopData->preHandlers.emplace(key, std::move(handler));

    }

    /* Bug: what if you remove a handler while iterating them? */

    void removePreHandler(void *key) {

        LoopData *loopData = (LoopData *) us_loop_ext((us_loop_t *) this);

        loopData->preHandlers.erase(key);

    }

    /* Defer this callback on Loop's thread of execution */

    void defer(MoveOnlyFunction<void()> &&cb) {

        LoopData *loopData = (LoopData *) us_loop_ext((us_loop_t *) this);

        //if (std::thread::get_id() == ) // todo: add fast path for same thread id

        loopData->deferMutex.lock();

        loopData->deferQueues[loopData->currentDeferQueue].emplace_back(std::move(cb));

        loopData->deferMutex.unlock();

        us_wakeup_loop((us_loop_t *) this);

    }

    /* Actively block and run this loop */

    void run() {

        us_loop_run((us_loop_t *) this);

    }

    /* Passively integrate with the underlying default loop */

    /* Used to seamlessly integrate with third parties such as Node.js */

    void integrate() {

        us_loop_integrate((us_loop_t *) this);

    }

    /* Dynamically change this */

    void setSilent(bool silent) {

        ((LoopData *) us_loop_ext((us_loop_t *) this))->noMark = silent;

    }

};

/* Can be called from any thread to run the thread local loop */

inline void run() {

    Loop::get()->run();

}

}

#endif // UWS_LOOP_H