using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Tango.ScreenCapture
{
    public class ScreenCaptureEngine : IDisposable
    {
        private bool _isDisposed;
        private Thread _captureThread;
        private Bitmap _previousBitmap;
        private ImageComparer _comparer;

        public event EventHandler<ScreenCaptureFrameReceivedEventArgs> ScreenFrameReceived;

        public IScreenCaptureMethod CaptureMethod { get; set; }
        public CaptureRegion CaptureRegion { get; set; }
        public bool IsStarted { get; set; }
        public TimeSpan Interval { get; set; }
        public bool CaptureCursor { get; set; }
        public bool EnableImageComparison { get; set; }

        public ScreenCaptureEngine()
        {
            Interval = TimeSpan.FromMilliseconds(100);
            CaptureMethod = new GdiScreenCapture();
            CaptureRegion = new CaptureRegion(System.Windows.Forms.Screen.PrimaryScreen.Bounds);
            _comparer = new ImageComparer();
            EnableImageComparison = true;
        }

        public void Start()
        {
            if (_isDisposed)
            {
                throw new ObjectDisposedException("Screen capture engine cannot be started after disposed.");
            }

            if (!IsStarted)
            {
                IsStarted = true;

                _captureThread = new Thread(CaptureThreadMethod);
                _captureThread.IsBackground = true;
                _captureThread.Name = "Screen Capture Thread";
                _captureThread.Start();
            }
        }

        public void Stop()
        {
            if (IsStarted)
            {
                IsStarted = false;
            }
        }

        private void CaptureThreadMethod()
        {
            while (IsStarted)
            {
                var bitmap = CaptureMethod.GetDesktopBitmap(CaptureRegion);

                if (CaptureCursor)
                {
                    using (Graphics g = Graphics.FromImage(bitmap))
                    {
                        CursorUtils.ApplyCursor(g, bitmap, CaptureRegion.Left, CaptureRegion.Top);
                    }
                }

                if (EnableImageComparison)
                {
                    if (_previousBitmap == null)
                    {
                        _previousBitmap = bitmap.Clone() as Bitmap;
                        OnScreenFrameReceived(new ScreenCaptureFrame(bitmap, null));
                    }
                    else
                    {
                        var diffBitmap = _comparer.CreateDifferenceBitmap(_previousBitmap, bitmap, Color.Transparent);
                        _previousBitmap.Dispose();
                        _previousBitmap = bitmap.Clone() as Bitmap;
                        OnScreenFrameReceived(new ScreenCaptureFrame(bitmap, diffBitmap));
                    }
                }
                else
                {
                    OnScreenFrameReceived(new ScreenCaptureFrame(bitmap, null));
                }

                Thread.Sleep(Interval);
            }
        }

        public void Dispose()
        {
            if (!_isDisposed)
            {
                _isDisposed = true;
                Stop();
                CaptureMethod?.Dispose();
            }
        }

        protected virtual void OnScreenFrameReceived(ScreenCaptureFrame frame)
        {
            ScreenFrameReceived?.Invoke(this, new ScreenCaptureFrameReceivedEventArgs()
            {
                Frame = frame,
            });
        }
    }
}