/*
 * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 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 General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef __EVENTPROCESSOR_H
#define __EVENTPROCESSOR_H

#include "Define.h"
#include "Duration.h"
#include "Random.h"
#include <map>
#include <type_traits>

class EventProcessor;

// Note. All times are in milliseconds here.

class TC_COMMON_API BasicEvent
{
        friend class EventProcessor;

        enum class AbortState : uint8
        {
            STATE_RUNNING,
            STATE_ABORT_SCHEDULED,
            STATE_ABORTED
        };

    public:
        BasicEvent()
          : m_abortState(AbortState::STATE_RUNNING), m_addTime(0), m_execTime(0) { }

        virtual ~BasicEvent() { }                           // override destructor to perform some actions on event removal

        // this method executes when the event is triggered
        // return false if event does not want to be deleted
        // e_time is execution time, p_time is update interval
        virtual bool Execute(uint64 /*e_time*/, uint32 /*p_time*/) { return true; }

        virtual bool IsDeletable() const { return true; }   // this event can be safely deleted

        virtual void Abort(uint64 /*e_time*/) { }           // this method executes when the event is aborted

        // Aborts the event at the next update tick
        void ScheduleAbort();

    private:
        void SetAborted();
        bool IsRunning() const { return (m_abortState == AbortState::STATE_RUNNING); }
        bool IsAbortScheduled() const { return (m_abortState == AbortState::STATE_ABORT_SCHEDULED); }
        bool IsAborted() const { return (m_abortState == AbortState::STATE_ABORTED); }

        AbortState m_abortState;                            // set by externals when the event is aborted, aborted events don't execute

        // these can be used for time offset control
        uint64 m_addTime;                                   // time when the event was added to queue, filled by event handler
        uint64 m_execTime;                                  // planned time of next execution, filled by event handler
};

template<typename T>
class LambdaBasicEvent : public BasicEvent
{
public:
    LambdaBasicEvent(T&& callback) : BasicEvent(), _callback(std::move(callback)) { }

    bool Execute(uint64, uint32) override
    {
        _callback();
        return true;
    }

private:

    T _callback;
};

template<typename T>
using is_lambda_event = std::enable_if_t<!std::is_base_of_v<BasicEvent, std::remove_pointer_t<std::remove_cvref_t<T>>>>;

class TC_COMMON_API EventProcessor
{
    public:
        EventProcessor() : m_time(0) { }
        ~EventProcessor();

        void Update(uint32 p_time);
        void KillAllEvents(bool force);

        void AddEvent(BasicEvent* event, Milliseconds e_time, bool set_addtime = true);
        template<typename T>
        is_lambda_event<T> AddEvent(T&& event, Milliseconds e_time, bool set_addtime = true) { AddEvent(new LambdaBasicEvent<T>(std::move(event)), e_time, set_addtime); }
        void AddEventAtOffset(BasicEvent* event, Milliseconds offset) { AddEvent(event, CalculateTime(offset)); }
        void AddEventAtOffset(BasicEvent* event, Milliseconds offset, Milliseconds offset2) { AddEvent(event, CalculateTime(randtime(offset, offset2))); }
        template<typename T>
        is_lambda_event<T> AddEventAtOffset(T&& event, Milliseconds offset) { AddEventAtOffset(new LambdaBasicEvent<T>(std::move(event)), offset); }
        template<typename T>
        is_lambda_event<T> AddEventAtOffset(T&& event, Milliseconds offset, Milliseconds offset2) { AddEventAtOffset(new LambdaBasicEvent<T>(std::move(event)), offset, offset2); }
        void ModifyEventTime(BasicEvent* event, Milliseconds newTime);
        Milliseconds CalculateTime(Milliseconds t_offset) const { return Milliseconds(m_time) + t_offset; }
        std::multimap<uint64, BasicEvent*> const& GetEvents() const { return m_events; }

    protected:
        uint64 m_time;
        std::multimap<uint64, BasicEvent*> m_events;
};

#endif