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;
using Tango.Core;
using Tango.RemoteDesktop.Utils;

namespace Tango.RemoteDesktop
{
    /// <summary>
    /// Represents a generic screen capture engine.
    /// The <see cref="TFrame"/> type will be the type of difference object delivered by the engine.
    /// </summary>
    /// <typeparam name="TFrame">The type of the frame.</typeparam>
    /// <seealso cref="Tango.RemoteDesktop.IScreenCaptureEngine{TFrame}" />
    public class ScreenCaptureEngine<TFrame> : ExtendedObject, IScreenCaptureEngine<TFrame> where TFrame : class, IFrame
    {
        private Thread _captureThread;
        private Bitmap _previousBitmap;
        private bool _isDisposed;

        /// <summary>
        /// Occurs when a new screen frame is available.
        /// </summary>
        public event EventHandler<ScreenCaptureFrameReceivedEventArgs<TFrame>> FrameReceived;

        /// <summary>
        /// Gets or sets the screen capture method.
        /// </summary>
        public ICaptureMethod CaptureMethod { get; set; }

        /// <summary>
        /// Gets or sets the screen capture region.
        /// </summary>
        public CaptureRegion CaptureRegion { get; set; }

        /// <summary>
        /// Gets a value indicating whether this instance is currently capturing.
        /// </summary>
        public bool IsStarted { get; private set; }

        /// <summary>
        /// Gets or sets the frame rate per second.
        /// Default is 10.
        /// </summary>
        public int FrameRate { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether to include the cursor when capturing.
        /// </summary>
        public bool CaptureCursor { get; set; }

        /// <summary>
        /// Gets or sets the bitmap comparer.
        /// </summary>
        public IBitmapComparer<TFrame> Comparer { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether to enable image comparison.
        /// </summary>
        public bool EnableComparer { get; set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="ScreenCaptureEngine{TFrame}"/> class using the specified <see cref="IBitmapComparer{TFrame}"/>.
        /// </summary>
        /// <param name="comparer">The comparer.</param>
        public ScreenCaptureEngine(IBitmapComparer<TFrame> comparer)
        {
            FrameRate = 10;
            CaptureMethod = new CaptureMethods.GdiScreenCapture();
            CaptureRegion = new CaptureRegion(System.Windows.Forms.Screen.PrimaryScreen.Bounds);
            Comparer = comparer;
            CaptureCursor = true;

            if (Comparer != null)
            {
                EnableComparer = true;
            }
        }

        /// <summary>
        /// Start capturing.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Screen capture engine cannot be started after disposed.</exception>
        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();
            }
        }

        /// <summary>
        /// Stop capturing.
        /// </summary>
        public void Stop()
        {
            if (IsStarted)
            {
                IsStarted = false;
            }
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        public void Dispose()
        {
            if (!_isDisposed)
            {
                _isDisposed = true;
                Stop();
                CaptureMethod?.Dispose();
            }
        }

        private void CaptureThreadMethod()
        {
            Stopwatch watch = new Stopwatch();

            LogManager.Log($"Screen capture engine started with the following definitions:\nCapture Region: {CaptureRegion}\nCapture Method: {CaptureMethod.GetType().Name}\nFrame Rate: {FrameRate}\nComparer Enabled: {EnableComparer}");

            while (IsStarted)
            {
                watch.Restart();

                try
                {
                    var bitmap = CaptureMethod.GetDesktopBitmap(CaptureRegion);

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

                    if (EnableComparer && Comparer != null)
                    {
                        if (_previousBitmap == null)
                        {
                            _previousBitmap = bitmap.Clone() as Bitmap;
                            OnFrameReceived(bitmap, null, 0);
                        }
                        else
                        {
                            try
                            {
                                BitmapComparerResult<TFrame> result = Comparer.CreateDifference(_previousBitmap, bitmap);
                                _previousBitmap.Dispose();
                                _previousBitmap = bitmap.Clone() as Bitmap;
                                OnFrameReceived(bitmap, result.Frame, result.DifferenceCount);
                            }
                            catch (MaxDifferencesReachedException)
                            {
                                _previousBitmap.Dispose();
                                _previousBitmap = bitmap.Clone() as Bitmap;
                                OnFrameReceived(bitmap, null, (uint)(bitmap.Width * bitmap.Height));
                            }
                        }
                    }
                    else
                    {
                        OnFrameReceived(bitmap, null, 0);
                    }
                }
                catch (Exception ex)
                {
                    Debug.WriteLine($"Error in screen capture engine: {ex.Message}");
                    _previousBitmap = null;
                }

                int delay = Math.Max(5, (1000 / FrameRate) - (int)watch.ElapsedMilliseconds);
                Thread.Sleep(delay);
            }

            _previousBitmap = null;

            LogManager.Log("Screen capture engine stopped.");
        }

        private void OnFrameReceived(Bitmap currentBitmap, TFrame diffFrame, uint differenceCount)
        {
            if (!IsStarted) return;

            FrameReceived?.Invoke(this, new ScreenCaptureFrameReceivedEventArgs<TFrame>()
            {
                Frame = new ScreenCaptureFrame<TFrame>(currentBitmap, diffFrame)
                {
                    DifferenceCount = differenceCount
                }
            });
        }
    }
}