/**
 * Copyright (c) 2018 Cornell University.
 *
 * Author: Ted Yin <tederminant@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to do
 * so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#ifndef _SALTICIDAE_EVENT_H
#define _SALTICIDAE_EVENT_H

#include <unistd.h>
#include <event2/event.h>
#include <sys/eventfd.h>
#ifdef SALTICIDAE_DEBUG_LOG
#include <thread>
#endif

#include "salticidae/queue.h"
#include "salticidae/util.h"
#include "salticidae/ref.h"

namespace salticidae {

struct _event_context_deleter {
    constexpr _event_context_deleter() = default;
    void operator()(struct event_base *ptr) {
        if (ptr != nullptr) event_base_free(ptr);
    }
};

using _event_context_ot = RcObj<struct event_base, _event_context_deleter>;

class EventContext: public _event_context_ot {
    public:
    EventContext(): _event_context_ot(event_base_new()) {}
    EventContext(struct event_base *eb): _event_context_ot(eb) {}
    EventContext(const EventContext &) = default;
    EventContext(EventContext &&) = default;
    EventContext &operator=(const EventContext &) = default;
    EventContext &operator=(EventContext &&) = default;
    void dispatch() { event_base_dispatch(get()); }
    void stop()  { event_base_loopbreak(get()); }
};

class Event {
    public:
    using callback_t = std::function<void(evutil_socket_t fd, short events)>;

    private:
    EventContext eb;
    evutil_socket_t fd;
    short events;
    struct event *ev;
    callback_t callback;
    static inline void _then(evutil_socket_t fd, short events, void *arg) {
        (static_cast<Event *>(arg))->callback(fd, events);
    }

    public:
    Event(): eb(nullptr), ev(nullptr) {}
    Event(const EventContext &eb,
        evutil_socket_t fd,
        short events,
        callback_t callback):
            eb(eb), fd(fd), events(events),
            ev(event_new(eb.get(), fd, events, Event::_then, this)),
            callback(callback) {}

    Event(const Event &) = delete;
    Event(Event &&other):
            eb(std::move(other.eb)), fd(other.fd), events(other.events),
            callback(std::move(other.callback)) {
        other.clear();
        ev = event_new(eb.get(), fd, events, Event::_then, this);
    }

    Event &operator=(Event &&other) {
        clear();
        other.clear();
        eb = std::move(other.eb);
        fd = other.fd;
        events = other.events;
        ev = event_new(eb.get(), fd, events, Event::_then, this);
        callback = std::move(other.callback);
        return *this;
    }

    ~Event() { clear(); }

    void clear() {
        if (ev != nullptr)
        {
            event_del(ev);
            event_free(ev);
            ev = nullptr;
        }
    }

    void add() { if (ev) event_add(ev, nullptr); }
    void del() { if (ev) event_del(ev); }
    void add_with_timeout(double timeout) {
        if (ev)
            event_add_with_timeout(ev, timeout);
    }

    operator bool() const { return ev != nullptr; }
};

template<typename T>
class MPSCQueueEventDriven: public MPMCQueue<T> {
    private:
    std::atomic<bool> wait_sig;
    int fd;
    Event ev;

    public:
    template<typename Func>
    MPSCQueueEventDriven(const EventContext &ec, Func &&func, size_t capacity = 65536):
        MPMCQueue<T>(capacity),
        wait_sig(true),
        fd(eventfd(0, EFD_NONBLOCK)),
        ev(Event(ec, fd, EV_READ | EV_PERSIST,
            [this, func=std::forward<Func>(func)](int, short) {
            uint64_t t;
            read(fd, &t, 8);
            SALTICIDAE_LOG_DEBUG("%x\n", std::this_thread::get_id());
            T elem;
            while (MPMCQueue<T>::try_dequeue(elem))
                func(std::move(elem));
            wait_sig.store(true, std::memory_order_relaxed);
        })) { ev.add(); }

    ~MPSCQueueEventDriven() { close(fd); }

    template<typename U>
    bool enqueue(U &&e) {
        static const uint64_t dummy = 1;
        bool ret = MPMCQueue<T>::enqueue(std::forward<U>(e));
        if (wait_sig.exchange(false, std::memory_order_relaxed))
        {
            SALTICIDAE_LOG_DEBUG("mpsc notify");
            write(fd, &dummy, 8);
        }
        return ret;
    }
};

template<typename T>
class MPMCQueueEventDriven: public MPMCQueue<T> {
    private:
    std::atomic<bool> wait_sig;
    std::vector<std::pair<BoxObj<Event>, int>> evs;

    public:
    MPMCQueueEventDriven(size_t capacity = 65536):
        MPMCQueue<T>(capacity),
        wait_sig(true) {}

    template<typename Func>
    void listen(const EventContext &ec, Func &&func) {
        int fd = eventfd(0, EFD_NONBLOCK);
        evs.emplace(evs.end(), std::make_pair(new Event(ec, fd, EV_READ | EV_PERSIST,
            [this, func=std::forward<Func>(func)](int fd, short) {
            uint64_t t;
            read(fd, &t, 8);
            SALTICIDAE_LOG_DEBUG("%x\n", std::this_thread::get_id());
            T elem;
            while (MPMCQueue<T>::try_dequeue(elem))
                func(std::move(elem));
            wait_sig.store(true, std::memory_order_relaxed);
        }), fd));
        evs.rbegin()->first->add();
    }

    ~MPMCQueueEventDriven() {
        for (const auto &p: evs)
            close(p.second);
    }

    template<typename U>
    bool enqueue(U &&e) {
        static const uint64_t dummy = 1;
        bool ret = MPMCQueue<T>::enqueue(std::forward<U>(e));
        if (wait_sig.exchange(false, std::memory_order_relaxed))
        {
            SALTICIDAE_LOG_DEBUG("mpmc notify");
            for (const auto &p: evs)
                write(p.second, &dummy, 8);
        }
        return ret;
    }
};

}

#endif