using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Drawing;

using System.Drawing.Imaging;

using System.Runtime.InteropServices;



namespace GammaJul.LgLcd {



	/// <summary>

	/// Represents a <see cref="LcdPage"/> that use GDI+ to do its drawing.

	/// </summary>

	public class LcdGdiPage : LcdPage {

		private readonly List<LcdGdiObject> _children = new List<LcdGdiObject>();

		private readonly Bitmap _bitmap;

		private readonly Rectangle _rectangle;

		private readonly byte[] _32BppPixels;

		private readonly byte[] _8BppPixels;

		private Graphics _graphics;



		/// <summary>

		/// Gets the <see cref="Bitmap"/> used to draw this page.

		/// </summary>

		public Bitmap Bitmap {

			get { return _bitmap; }

		}



		/// <summary>

		/// Gets a list of <see cref="LcdGdiObject"/>s that are the children of this page.

		/// </summary>

		public List<LcdGdiObject> Children {

			get { return _children; }

		}



		/// <summary>

		/// Occurs just after the page have been cleared of all contents, but before the children are drawn.

		/// This event provides a <see cref="Graphics"/> object to use for custom drawing.

		/// </summary>

		public event EventHandler<GdiDrawingEventArgs> GdiDrawing;



		/// <summary>

		/// Raises the <see cref="GdiDrawing"/> event.

		/// </summary>

		/// <param name="graphics"><see cref="Graphics"/> to use for custom drawing.</param>

		protected void OnGdiDrawing(Graphics graphics) {

			EventHandler<GdiDrawingEventArgs> handler = GdiDrawing;

			if (handler != null)

				handler(this, new GdiDrawingEventArgs(graphics));

		}





		/// <summary>

		/// Prepares a <see cref="Graphics"/> object for drawing.

		/// </summary>

		/// <param name="graphics"><see cref="Graphics"/> to prepare for drawing.</param>

		protected static void PrepareGraphics(Graphics graphics) {

			if (graphics == null)

				throw new ArgumentNullException("graphics");

			graphics.PageUnit = GraphicsUnit.Pixel;

			graphics.PageScale = 1.0f;

		}



		/// <summary>

		/// Prepares a <see cref="Graphics"/> object for drawing a specified <see cref="LcdGdiObject"/>,

		/// by setting the appropriate properties (clip, interpolation, etc) on the <see cref="Graphics"/>.

		/// </summary>

		/// <param name="graphics"><see cref="Graphics"/> to prepare for drawing <paramref name="child"/>.</param>

		/// <param name="child"><see cref="LcdGdiObject"/> that will be drawn on <paramref name="graphics"/>.</param>

		internal protected static void PrepareGraphicsForChild(Graphics graphics, LcdGdiObject child) {

			if (graphics == null)

				throw new ArgumentNullException("graphics");

			if (child == null)

				throw new ArgumentNullException("child");

			graphics.Transform = child.Transform;

			if (child.Clip != null)

				graphics.Clip = child.Clip;

			graphics.InterpolationMode = child.InterpolationMode;

			graphics.PixelOffsetMode = child.PixelOffsetMode;

			graphics.RenderingOrigin = child.RenderingOrigin;

			graphics.SmoothingMode = child.SmoothingMode;

		}



		/// <summary>

		/// Derived classes override this method in order to update the page content.

		/// </summary>

		/// <param name="elapsedTotalTime">Time elapsed since the device creation.</param>

		/// <param name="elapsedTimeSinceLastFrame">Time elapsed since last frame update.</param>

		/// <returns><c>true</c> if the update has done something and a redraw is required.</returns>

		protected override bool UpdateCore(TimeSpan elapsedTotalTime, TimeSpan elapsedTimeSinceLastFrame) {

			Graphics graphics = Graphics.FromImage(_bitmap);

			PrepareGraphics(graphics);

			bool hasChanged = false;

			foreach (LcdGdiObject child in _children) {

				if (child.HasChanged) {

					hasChanged = true;

					PrepareGraphicsForChild(graphics, child);

					child.Update(elapsedTotalTime, elapsedTimeSinceLastFrame, this, graphics);

					child.HasChanged = false;

					graphics.ResetClip();

				}

			}

			if (hasChanged)

				_graphics = graphics;

			else {

				graphics.Dispose();

				_graphics = null;

			}

			return hasChanged;

		}



		/// <summary>

		/// Derived classes override this method in order to draw the page content visually.

		/// </summary>

		/// <returns>Implementors must return a pixel array conforming to

		/// <see cref="LcdPage.Device"/>'s <see cref="LcdDevice.DeviceType"/>.</returns>

		protected override byte[] DrawCore() {

			if (_graphics == null)

				_graphics = Graphics.FromImage(_bitmap);

			using (Graphics graphics = _graphics) {

				PrepareGraphics(graphics);

				graphics.FillRectangle(Brushes.White, _rectangle);

				foreach (LcdGdiObject child in _children) {

					if (child.IsVisible) {

						PrepareGraphicsForChild(graphics, child);

						child.Draw(this, graphics);

						graphics.ResetClip();

					}

				}

				OnGdiDrawing(graphics);

			}

			_graphics = null;

			return PixelsFromBitmap();

		}



		/// <summary>

		/// Copies the pixels from <see cref="Bitmap"/> and returns them.

		/// </summary>

		/// <returns>A copy of the pixels from <see cref="Bitmap"/>.</returns>

		protected byte[] PixelsFromBitmap() {

			BitmapData bitmapData = _bitmap.LockBits(_rectangle, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

			try {

				Marshal.Copy(bitmapData.Scan0, _32BppPixels, 0, _32BppPixels.Length);



				// 32bpp, simply returns

				if (Device.BitsPerPixel == 32)

					return _32BppPixels;



				// 8bpp, take the mean of each of the 4 8bit color components

				for (int i = 0; i < _8BppPixels.Length; ++i)

					_8BppPixels[i] = (byte) (255 - (_32BppPixels[i * 4] + _32BppPixels[i * 4 + 1] + _32BppPixels[i * 4 + 2] + _32BppPixels[i * 4 + 3]) / 4);

				return _8BppPixels;



			}

			finally {

				_bitmap.UnlockBits(bitmapData);

			}

		}



		/// <summary>

		/// Creates a new <see cref="LcdGdiPage"/> on the given device.

		/// </summary>

		/// <param name="device">Device where this page will be shown.</param>

		public LcdGdiPage(LcdDevice device)

			: base(device) {

			if (device.BitsPerPixel != 8 && device.BitsPerPixel != 32)

				throw new NotSupportedException("Only 8bpp and 32bpp devices are supported.");

			_bitmap = new Bitmap(device.PixelWidth, device.PixelHeight, PixelFormat.Format32bppArgb);

			_rectangle = new Rectangle(0, 0, device.PixelWidth, device.PixelHeight);

			_32BppPixels = new byte[device.PixelWidth * device.PixelHeight * 4];

			if (device.BitsPerPixel == 8)

				_8BppPixels = new byte[device.PixelWidth * device.PixelHeight];

		}

	}



}