using Microsoft.Extensions.Logging;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EVCB_OCPP.WSServer.Helper;

public class GroupSingleHandler<T>
{
    public GroupSingleHandler(Func<IEnumerable<T>, Task> handleFunc, ILogger logger, int workerCnt = 1)
    {
        this.handleFunc = handleFunc;
        this.logger = logger;

        //singleWorkLock = new (_WorkerCnt);
        //singleHandleTask = StartHandleTask();

        _handleTasks = new Task[workerCnt];
        for (int cnt = 0; cnt < workerCnt; cnt++)
        {
            _handleTasks[cnt] = StartHandleTask();
        }
    }

    //private int _WorkerCnt = 1;
    //public int WorkerCnt
    //{
    //    get => _WorkerCnt;
    //    set
    //    {
    //        if (IsStarted)
    //        {
    //            throw new Exception($"{nameof(WorkerCnt)} must not be changed afted {nameof(HandleAsync)} is called");
    //        }

    //        _WorkerCnt = value;
    //        singleWorkLock = new (_WorkerCnt);
    //    }
    //}

    private readonly Func<IEnumerable<T>, Task> handleFunc;
    private readonly ILogger logger;
    private readonly BlockingCollection<(T param, SemaphoreSlim waitLock)> blockQueue = new();
    //private SemaphoreSlim singleWorkLock;// = new SemaphoreSlim(1);
    private bool IsStarted = false;
    private Task singleHandleTask;
    private Task[] _handleTasks;

    public Task HandleAsync(T param)
    {
        IsStarted = true;

        SemaphoreSlim reqLock = new(0);
        blockQueue.Add((param, reqLock));
        //TryStartHandler();
        return reqLock.WaitAsync();
    }

    //private void TryStartHandler()
    //{
    //    if (!singleWorkLock.Wait(0))
    //    {
    //        return;
    //    }

    //    if (waitList.Count == 0)
    //    {
    //        singleWorkLock.Release();
    //        return;
    //    }

    //    singleHandleTask = StartHandleTask();
    //}

    private Task StartHandleTask()
    {
        return Task.Run(async () => {
            while (true)
            {
                var handleList = new List<(T param, SemaphoreSlim waitLock)>();
                try
                {
                    var startData = blockQueue.Take();
                    handleList.Add(startData);
                }
                catch (InvalidOperationException e)
                {
                    logger.LogError(e, "blockQueue.Take Error");
                    break;
                }

                var watch = Stopwatch.StartNew();
                long t0, t1, t2, t3;

                while (blockQueue.TryTake(out var data))
                {
                    handleList.Add(data);
                }
                t0 = watch.ElapsedMilliseconds;
                var task = handleFunc(handleList.Select(x => x.param).ToList());
                t1 = watch.ElapsedMilliseconds;
                await task.ConfigureAwait(false);
                t2 = watch.ElapsedMilliseconds;

                foreach (var handled in handleList)
                {
                    handled.waitLock.Release();
                }
                watch.Stop();
                t3 = watch.ElapsedMilliseconds;
                if (t3 > 1000)
                {
                    logger.LogWarning("StartHandleTask {0}/{1}/{2}/{3}", t0, t1, t2, t3);
                }
            }
        });
    }

    //private async Task StartHandleTask()
    //{
    //    var handleList = new List<(T param, SemaphoreSlim waitLock)>();

    //    while (waitList.TryDequeue(out var handle))
    //    {
    //        handleList.Add(handle);
    //    }

    //    int cnt = 0;
    //    do
    //    {
    //        cnt++;
    //        try
    //        {
    //            var task = handleFunc(handleList.Select(x => x.param));
    //            await task;
    //            break;
    //        }
    //        catch (Exception e)
    //        {
    //            logger.LogError(e, "Trying Cnt {0}", cnt);
    //        }
    //    }
    //    while (true);

    //    foreach (var handled in handleList)
    //    {
    //        handled.waitLock.Release();
    //    }
    //    singleWorkLock.Release();
    //    TryStartHandler();
    //}
}