using System;
using System.Threading;
using System.Collections.Concurrent;

namespace RageCoop.Core
{
    /// <summary>
    /// A worker that constantly execute jobs in a background thread.
    /// </summary>
    public class Worker:IDisposable
    {
        private SemaphoreSlim _semaphoreSlim;
        private Thread _workerThread;
        private bool _stopping=false;
        /// <summary>
        /// Name of the worker
        /// </summary>
        public string Name { get; set; }
        /// <summary>
        /// Whether this worker is busy executing job(s).
        /// </summary>
        public bool IsBusy { get;private set; }
        internal Worker(string name,Logger logger,int maxJobs = Int32.MaxValue)
        {
            Name = name;
            _semaphoreSlim = new SemaphoreSlim(0,maxJobs);
            _workerThread=new Thread(() =>
            {
                while (!_stopping)
                {
                    IsBusy=false;
                    _semaphoreSlim.Wait();
                    if(Jobs.TryDequeue(out var job))
                    {
                        IsBusy=true;
                        try
                        {
                            job.Invoke();
                        }
                        catch (Exception ex)
                        {
                            logger.Error("Error occurred when executing queued job:");
                            logger.Error(ex);
                        }
                    }
                    else
                    {
                        throw new InvalidOperationException("Hmm... that's unexpected.");
                    }
                }
                IsBusy=false;
            });
            _workerThread.Start();
        }
        /// <summary>
        /// Queue a job to be executed
        /// </summary>
        /// <param name="work"></param>
        public void QueueJob(Action work)
        {
            Jobs.Enqueue(work);
            _semaphoreSlim.Release();
        }
        /// <summary>
        /// Finish current job and stop the worker.
        /// </summary>
        public void Stop()
        {
            _stopping=true;
            QueueJob(() => { });
            if (_workerThread.IsAlive)
            {
                _workerThread.Join();
            }
        }
        /// <summary>
        /// Finish current job and stop the worker.
        /// </summary>
        public void Dispose()
        {
            Stop();
            _semaphoreSlim.Dispose();
        }
        private ConcurrentQueue<Action> Jobs=new ConcurrentQueue<Action>();
    }
}