using System;
using System.Collections.Generic;
using System.Text;
using OpenRa.FileFormats;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;

namespace OpenRa.Game
{
	static class Util
	{
		static float2 EncodeVertexAttributes(TextureChannel channel, int paletteLine)
		{
			Converter<TextureChannel, float> channelEncoder = delegate(TextureChannel c)
			{
				switch (c)
				{
					case TextureChannel.Red: return 0.75f;
					case TextureChannel.Green: return 0.25f;
					case TextureChannel.Blue: return -0.25f;
					case TextureChannel.Alpha: return -0.75f;
					default:
						throw new ArgumentException();
				}
			};

			return new float2(paletteLine / 16.0f, channelEncoder(channel));
		}

		public static Vertex MakeVertex(float2 o, float2 uv, Sprite r, int palette)
		{
			return new Vertex(
				float2.Lerp( o, o + new float2(r.bounds.Size), uv ),
				r.MapTextureCoords(uv), 
				EncodeVertexAttributes(r.channel, palette));
		}

		static float Lerp(float a, float b, float t)
		{
			return (1 - t) * a + t * b;
		}

		public static string[] ReadAllLines(Stream s)
		{
			List<string> result = new List<string>();
			using (StreamReader reader = new StreamReader(s))
				while (!reader.EndOfStream)
					result.Add(reader.ReadLine());

			return result.ToArray();
		}

		public static T[] MakeArray<T>(int count, Converter<int, T> f)
		{
			T[] result = new T[count];
			for (int i = 0; i < count; i++)
				result[i] = f(i);

			return result;
		}

		static float2[] uv = 
		{ 
			new float2( 0,0 ),
			new float2( 1,0 ),
			new float2( 0,1 ),
			new float2( 1,1 ),
		};

		public static void CreateQuad(List<Vertex> vertices, List<ushort> indices, float2 o, Sprite r, int palette)
		{
			ushort offset = (ushort)vertices.Count;

			foreach( float2 p in uv )
				vertices.Add(Util.MakeVertex(o, p, r, palette));

			indices.Add(offset);
			indices.Add((ushort)(offset + 1));
			indices.Add((ushort)(offset + 2));

			indices.Add((ushort)(offset + 1));
			indices.Add((ushort)(offset + 3));
			indices.Add((ushort)(offset + 2));
		}

		public static void FastCopyIntoChannel(Sprite dest, byte[] src)
		{
			var bitmap = dest.sheet.Bitmap;
			BitmapData bits = null;
			uint[] channelMasks = { 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000 };
			uint mask = channelMasks[(int)dest.channel];

			try
			{
				bits = bitmap.LockBits(dest.bounds, ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);

				int width = dest.bounds.Width;
				int height = dest.bounds.Height;

				for (int j = 0; j < height; j++)
				{
					unsafe
					{
						uint* p = (uint*)(bits.Scan0.ToInt32() + j * bits.Stride);
						for (int i = 0; i < width; i++, p++)
							*p = ReplaceChannel(*p, mask, src[i + width * j]);
					}
				}
			}
			finally
			{
				bitmap.UnlockBits(bits);
			}
		}

		static uint ReplaceChannel(uint o, uint mask, byte p)
		{
			uint pp = (uint)p;

			pp |= pp << 8;	// copy into all channels
			pp |= pp << 16;

			o &= ~mask;
			o |= (mask & pp);

			return o;
		}
	}
}