//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="TimeSpanAwaitingToken.cs"
// Project: StgSharp
// AuthorGroup: Nitload Space
// Copyright (c) Nitload Space. All rights reserved.
//     
// 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.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using StgSharp.HighPerformance.Memory;

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace StgSharp.Timing
{
    public sealed class TimeSpanAwaitingToken : IDisposable
    {

        private static readonly ConcurrentStackBuffer<int> s_unusedID = new(1);

        private static int s_maxID;

        private EventHandler? _refreshHandler,_missHandler;
        private int _size, _id;

        private readonly object _participantObject = new();
        private SemaphoreSlim _awaitingSemaphore;

        private TimeSpanProvider _provider;

        internal TimeSpanAwaitingToken(TimeSpanProvider provider)
        {
            if (!s_unusedID.TryPop(out int id)) {
                id = Interlocked.Increment(ref s_maxID);
            }
            TokenID = id;
            _provider = provider;
            _size = 1;
            _awaitingSemaphore = new SemaphoreSlim(0, 1);
        }

        internal TimeSpanAwaitingToken(TimeSpanProvider provider, int count)
        {
            if (!s_unusedID.TryPop(out int id)) {
                id = Interlocked.Increment(ref s_maxID);
            }
            _provider = provider;
            _size = count;
            _awaitingSemaphore = new SemaphoreSlim(0, _size);
        }

        public event EventHandler MissTimeSpanRefreshed
        {
            add => _missHandler += value;
            remove => _missHandler -= value;
        }

        public event EventHandler TimeSpanRefreshed
        {
            add => _refreshHandler += value;
            remove => _refreshHandler -= value;
        }

        public int TokenID
        {
            get => _id;
            private set => _id = value;
        }

        internal SemaphoreSlim AwaitingSemaphoreSlim
        {
[MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _awaitingSemaphore;
        }

        public void Dispose()
        {
            _provider.QuitSpanAwaiting(this);
            s_unusedID.Push(TokenID);
            _awaitingSemaphore.Dispose();
            GC.SuppressFinalize(this);
        }

        public override int GetHashCode()
        {
            return _id;
        }

        public void Participant()
        {
            lock (_participantObject)
            {
                _size++;
                SemaphoreSlim newSemaphore = new(_awaitingSemaphore.CurrentCount, _size);
                Interlocked.Exchange(ref _awaitingSemaphore, newSemaphore).Dispose();
            }
        }

        public void WaitNextSpan()
        {
            _awaitingSemaphore.Wait();
        }

        internal void MissRefresh()
        {
            _missHandler?.Invoke(this, EventArgs.Empty);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal void Refresh()
        {
            _refreshHandler?.Invoke(this, EventArgs.Empty);
        }

        ~TimeSpanAwaitingToken()
        {
            Dispose();
        }

    }
}