/*************************************************************************
 * ModernUO                                                              *
 * Copyright (C) 2019-2021 - ModernUO Development Team                   *
 * Email: hi@modernuo.com                                                *
 * File: Timer.DelayCall.cs                                              *
 *                                                                       *
 * 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 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 *************************************************************************/

using System;
#if DEBUG_TIMERS
using System.Collections.Generic;
#endif
using System.Diagnostics;
using System.Runtime.CompilerServices;

namespace Server
{
    public partial class Timer
    {
        private static string FormatDelegate(Delegate callback) =>
            callback == null ? "null" : $"{callback.Method.DeclaringType?.FullName ?? ""}.{callback.Method.Name}";

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer DelayCall(Action callback) => DelayCall(TimeSpan.Zero, TimeSpan.Zero, 1, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer DelayCall(TimeSpan delay, Action callback) => DelayCall(delay, TimeSpan.Zero, 1, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer DelayCall(TimeSpan delay, TimeSpan interval, Action callback) =>
            DelayCall(delay, interval, 0, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer DelayCall(TimeSpan interval, int count, Action callback) =>
            DelayCall(TimeSpan.Zero, interval, count, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer DelayCall(TimeSpan delay, TimeSpan interval, int count, Action callback)
        {
            DelayCallTimer t = new DelayCallTimer(delay, interval, count, callback);
            t.Start();
#if DEBUG_TIMERS
            t._allowFinalization = true;
#endif

            return t;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(Action callback) => StartTimer(TimeSpan.Zero, TimeSpan.Zero, 1, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan delay, Action callback) => StartTimer(delay, TimeSpan.Zero, 1, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan delay, TimeSpan interval, Action callback) =>
            StartTimer(delay, interval, 0, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan interval, int count, Action callback) =>
            StartTimer(TimeSpan.Zero, interval, count, callback);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan delay, TimeSpan interval, int count, Action callback)
        {
            DelayCallTimer t = DelayCallTimer.GetTimer(delay, interval, count, callback);
            t._returnOnDetach = true;
            t.Start();

#if DEBUG_TIMERS
            DelayCallTimer._stackTraces[t.GetHashCode()] = new StackTrace().ToString();
#endif
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(Action callback, out TimerExecutionToken token) =>
            StartTimer(TimeSpan.Zero, TimeSpan.Zero, 1, callback, out token);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan delay, Action callback, out TimerExecutionToken token) =>
            StartTimer(delay, TimeSpan.Zero, 1, callback, out token);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan delay, TimeSpan interval, Action callback, out TimerExecutionToken token) =>
            StartTimer(delay, interval, 0, callback, out token);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan interval, int count, Action callback, out TimerExecutionToken token) =>
            StartTimer(TimeSpan.Zero, interval, count, callback, out token);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void StartTimer(TimeSpan delay, TimeSpan interval, int count, Action callback, out TimerExecutionToken token)
        {
            DelayCallTimer t = DelayCallTimer.GetTimer(delay, interval, count, callback);
            t.Start();

#if DEBUG_TIMERS
            DelayCallTimer._stackTraces[t.GetHashCode()] = new StackTrace().ToString();
#endif
            token = new TimerExecutionToken(t);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer Pause(TimeSpan ms) => new(ms);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static DelayCallTimer Pause(int ms) => Pause(TimeSpan.FromMilliseconds(ms));

        public sealed class DelayCallTimer : Timer, INotifyCompletion
        {
            internal bool _returnOnDetach;
#if DEBUG_TIMERS
            internal bool _allowFinalization;
#endif
            private Action _continuation;
            private bool _complete;

            internal DelayCallTimer(TimeSpan delay, TimeSpan interval, int count, Action callback) : base(
                delay,
                interval,
                count
            ) =>
                _continuation = callback;

            internal DelayCallTimer(TimeSpan delay) : base(delay)
            {
#if DEBUG_TIMERS
                _allowFinalization = true;
#endif
                Start();
            }

            protected override void OnTick()
            {
                _complete = true;
                _continuation?.Invoke();
            }

            internal override void OnDetach()
            {
                if (Running)
                {
                    logger.Error("Timer is returned while still running!\n{StackTrace}", new StackTrace());
                    return;
                }

                if (_returnOnDetach)
                {
                    // Increment the version so if this is called from OnTick() and another timer is started, we don't have a problem
                    // Version++;

#if DEBUG_TIMERS
                    _stackTraces.Remove(GetHashCode());
#endif

                    if (_poolCount >= _poolCapacity)
                    {
#if DEBUG_TIMERS
                        logger.Warning("DelayCallTimer pool reached maximum of {Capacity} timers", _poolCapacity);
                        _allowFinalization = true;
#endif
                        return;
                    }

                    _continuation = null;
                    _returnOnDetach = false;
                    ReturnToPool(1, this, this);
                }
            }

            public static DelayCallTimer GetTimer(TimeSpan delay, TimeSpan interval, int count, Action callback)
            {
                var timer = GetFromPool();
                if (timer != null)
                {
#if DEBUG_TIMERS
                    logger.Information("Getting from pool: ({Count} / {Capacity})", _poolCount, _poolCapacity);
#endif

                    timer.Init(delay, interval, count);
                    timer._continuation = callback;
                    timer._returnOnDetach = false;
#if DEBUG_TIMERS
                    timer._allowFinalization = false;
#endif

                    return timer;
                }

                _timerPoolDepletionAmount++;

#if DEBUG_TIMERS
                logger.Warning("Timer pool depleted and timer was allocated.\n{StackTrace}", new StackTrace());
#endif
                return new DelayCallTimer(delay, interval, count, callback);
            }

            public override string ToString() => $"DelayCallTimer[{FormatDelegate(_continuation)}]";

#if DEBUG_TIMERS
            internal static Dictionary<int, string> _stackTraces = new();

            ~DelayCallTimer()
            {
                if (!_allowFinalization)
                {
                    logger.Warning("Pooled timer was not returned to the pool.\n{StackTrace}", _stackTraces[GetHashCode()]);
                }
            }
#endif

            public DelayCallTimer GetAwaiter() => this;

            public bool IsCompleted => _complete;

            public void OnCompleted(Action continuation) => _continuation = continuation;

            public void GetResult()
            {
            }
        }
    }
}