using System;
using System.Collections.Generic;
using System.IO;
using ANX.Framework.Graphics;
using ANX.Framework.NonXNA;
using OpenTK.Graphics.OpenGL;
using System.Text;
using System.Security.Cryptography;

#region License

//
// This file is part of the ANX.Framework created by the "ANX.Framework developer group".
//
// This file is released under the Ms-PL license.
//
//
//
// Microsoft Public License (Ms-PL)
//
// This license governs use of the accompanying software. If you use the software, you accept this license. 
// If you do not accept the license, do not use the software.
//
// 1.Definitions
//   The terms "reproduce," "reproduction," "derivative works," and "distribution" have the same meaning 
//   here as under U.S. copyright law.
//   A "contribution" is the original software, or any additions or changes to the software.
//   A "contributor" is any person that distributes its contribution under this license.
//   "Licensed patents" are a contributor's patent claims that read directly on its contribution.
//
// 2.Grant of Rights
//   (A) Copyright Grant- Subject to the terms of this license, including the license conditions and limitations 
//       in section 3, each contributor grants you a non-exclusive, worldwide, royalty-free copyright license to 
//       reproduce its contribution, prepare derivative works of its contribution, and distribute its contribution
//       or any derivative works that you create.
//   (B) Patent Grant- Subject to the terms of this license, including the license conditions and limitations in 
//       section 3, each contributor grants you a non-exclusive, worldwide, royalty-free license under its licensed
//       patents to make, have made, use, sell, offer for sale, import, and/or otherwise dispose of its contribution 
//       in the software or derivative works of the contribution in the software.
//
// 3.Conditions and Limitations
//   (A) No Trademark License- This license does not grant you rights to use any contributors' name, logo, or trademarks.
//   (B) If you bring a patent claim against any contributor over patents that you claim are infringed by the software, your 
//       patent license from such contributor to the software ends automatically.
//   (C) If you distribute any portion of the software, you must retain all copyright, patent, trademark, and attribution 
//       notices that are present in the software.
//   (D) If you distribute any portion of the software in source code form, you may do so only under this license by including
//       a complete copy of this license with your distribution. If you distribute any portion of the software in compiled or 
//       object code form, you may only do so under a license that complies with this license.
//   (E) The software is licensed "as-is." You bear the risk of using it. The contributors give no express warranties, guarantees,
//       or conditions. You may have additional consumer rights under your local laws which this license cannot change. To the
//       extent permitted under your local laws, the contributors exclude the implied warranties of merchantability, fitness for a 
//       particular purpose and non-infringement.

#endregion // License

namespace ANX.Framework.Windows.GL3
{
	/// <summary>
	/// Native OpenGL Effect implementation.
	/// 
	/// http://wiki.delphigl.com/index.php/Tutorial_glsl
	/// </summary>
	public class EffectGL3 : INativeEffect
	{
		#region ShaderAttribute (Helper struct)
		public struct ShaderAttribute
		{
			public string Name;
			public uint Location;
			public int Size;
			public ActiveAttribType Type;
		}
		#endregion

		#region Constants
		private const string FragmentSeparator = "##!fragment!##";
		#endregion

		#region Private
		/// <summary>
		/// The native shader handle.
		/// </summary>
		internal int programHandle;

    private Effect managedEffect;

		internal Dictionary<string, ShaderAttribute> ActiveAttributes
		{
			get;
			private set;
		}
		#endregion

		#region Public
		#region Techniques (TODO)
		public IEnumerable<EffectTechnique> Techniques
		{
			get
			{
				List<EffectTechnique> techniques = new List<EffectTechnique>();

				// TODO: dummy, fill with actual data.
				techniques.Add(new EffectTechnique(this.managedEffect, new EffectTechniqueGL3()));

                return techniques;
			}
		}
		#endregion

		#region Parameters (TODO)
		public IEnumerable<EffectParameter> Parameters
		{
			get
			{
				List<EffectParameter> parameters = new List<EffectParameter>();

				int uniformCount;
				GL.GetProgram(programHandle, ProgramParameter.ActiveUniforms,
					out uniformCount);
				ErrorHelper.Check("GetProgram ActiveUniforms");

				List<string> names = new List<string>();
				for (int index = 0; index < uniformCount; index++)
				{
					string name = GL.GetActiveUniformName(programHandle, index);
					ErrorHelper.Check("GetActiveUniformName name=" + name);

					if (names.Contains(name) == false)
					{
						names.Add(name);
						int uniformIndex = GL.GetUniformLocation(programHandle, name);
						ErrorHelper.Check("GetUniformLocation name=" + name +
							" uniformIndex=" + uniformIndex);
						parameters.Add(new EffectParameter()
						{
							NativeParameter =
								new EffectParameterGL3(this, name, uniformIndex),
						});
					}
				}

				return parameters;
			}
		}
		#endregion
		#endregion

		#region Constructor
		/// <summary>
		/// Create a new effect instance of separate streams.
		/// </summary>
		/// <param name="vertexShaderByteCode">The vertex shader code.</param>
		/// <param name="pixelShaderByteCode">The fragment shader code.</param>
		public EffectGL3(Effect managedEffect, Stream vertexShaderByteCode, Stream pixelShaderByteCode)
		{
            this.managedEffect = managedEffect;
			CreateShader(LoadShaderCode(vertexShaderByteCode), LoadShaderCode(pixelShaderByteCode));
		}

		/// <summary>
		/// Create a new effect instance of one streams.
		/// </summary>
		/// <param name="byteCode">The byte code of the shader.</param>
		public EffectGL3(Effect managedEffect, Stream byteCode)
		{
            this.managedEffect = managedEffect;
			string source = LoadShaderCode(byteCode);
			string[] parts = source.Split(new string[] { FragmentSeparator },
				StringSplitOptions.RemoveEmptyEntries);

			CreateShader(parts[0], parts[1]);
		}
		#endregion

		#region CreateShader
		private void CreateShader(string vertexSource, string fragmentSource)
		{
			int vertexShader = GL.CreateShader(ShaderType.VertexShader);
			string vertexError = CompileShader(vertexShader, vertexSource);
			if (String.IsNullOrEmpty(vertexError) == false)
			{
				throw new InvalidDataException("Failed to compile the vertex " +
					"shader because of: " + vertexError);
			}

			int fragmentShader = GL.CreateShader(ShaderType.FragmentShader);
			string fragmentError = CompileShader(fragmentShader, fragmentSource);
			if (String.IsNullOrEmpty(fragmentError) == false)
			{
				throw new InvalidDataException("Failed to compile the fragment " +
					"shader because of: " + fragmentError);
			}

			programHandle = GL.CreateProgram();
			ErrorHelper.Check("CreateProgram");
			GL.AttachShader(programHandle, vertexShader);
			ErrorHelper.Check("AttachShader vertexShader");
			GL.AttachShader(programHandle, fragmentShader);
			ErrorHelper.Check("AttachShader fragmentShader");
			GL.LinkProgram(programHandle);

			int result;
			GL.GetProgram(programHandle, ProgramParameter.LinkStatus, out result);
			if (result == 0)
			{
				string programError;
				GL.GetProgramInfoLog(programHandle, out programError);
				throw new InvalidDataException("Failed to link the shader program " +
					"because of: " + programError);
			}

			GetAttributes();
		}
		#endregion

		#region CompileShader
		private string CompileShader(int shader, string source)
		{
			GL.ShaderSource(shader, source);
			GL.CompileShader(shader);

			int result;
			GL.GetShader(shader, ShaderParameter.CompileStatus, out result);
			if (result == 0)
			{
				string error = "";
				GL.GetShaderInfoLog(shader, out error);

				GL.DeleteShader(shader);

				return error;
			}

			return null;
		}
		#endregion

		#region CompileShader (for external)
		public static byte[] CompileShader(string effectCode)
		{
			#region Source Cleanup
			// We wanna clean up the shader a little bit, so we remove
			// empty lines, spaces and tabs at beginning and end and also
			// remove comments.
			List<string> lines = new List<string>(effectCode.Split('\n'));
			for (int index = lines.Count - 1; index >= 0; index--)
			{
				lines[index] = lines[index].Trim();
				if (String.IsNullOrEmpty(lines[index]) ||
					lines[index].StartsWith("//"))
				{
					lines.RemoveAt(index);
					continue;
				}

				// TODO: add /**/ comment checking and removing.
			}

			effectCode = "";
			foreach (string line in lines)
			{
				effectCode += line + "\n";
			}

			// Now to some additional cleanup
			string[] minimizables =
			{
				" * ", " = ", " + ", " / ", " - ", ", ",
			};

			foreach (string mizable in minimizables)
			{
				effectCode = effectCode.Replace(mizable, mizable.Trim());
			}

			effectCode = effectCode.Replace("\n{\n", "{\n");
			effectCode = effectCode.Replace("\n}\n", "}\n");
			#endregion

			MemoryStream stream = new MemoryStream();
			BinaryWriter writer = new BinaryWriter(stream);

			// First of all writer the shader code (which is already preceeded
			// by a length identifier, making it harder to manipulate the code)
			writer.Write(effectCode);

			// And now we additionally generate a sha hash so it nearly becomes
			// impossible to manipulate the shader.
			SHA512Managed sha = new SHA512Managed();
			byte[] data = stream.ToArray();
			byte[] hash = sha.ComputeHash(data);
			// The hash is added to the end of the stream.
			writer.Write(hash);
			writer.Flush();
			sha.Dispose();

			return stream.ToArray();
		}
		#endregion

		#region LoadShaderCode
		private static string LoadShaderCode(Stream stream)
		{
			BinaryReader reader = new BinaryReader(stream);
			// First load the source.
			string source = reader.ReadString();
			// And now check if it was manipulated.
			SHA512Managed sha = new SHA512Managed();
			int lengthRead = (int)stream.Position;
			stream.Position = 0;
			byte[] data = reader.ReadBytes(lengthRead);
			byte[] hash = sha.ComputeHash(data);
			sha.Dispose();
			byte[] loadedHash = reader.ReadBytes(64);
			for (int index = 0; index < hash.Length; index++)
			{
				if (hash[index] != loadedHash[index])
				{
					throw new InvalidDataException("Failed to load the shader " +
						"because the data got manipulated!");
				}
			}

			return source;
		}
		#endregion

		#region GetAttributes
		private void GetAttributes()
		{
			ActiveAttributes = new Dictionary<string, ShaderAttribute>();
			int attributeCount;
			GL.GetProgram(programHandle, ProgramParameter.ActiveAttributes,
				out attributeCount);
			for (int index = 0; index < attributeCount; index++)
			{
				int attributeSize;
				ActiveAttribType attributeType;
				string name = GL.GetActiveAttrib(programHandle, index,
					out attributeSize, out attributeType);
				uint attributeIndex = (uint)GL.GetAttribLocation(programHandle, name);
				ActiveAttributes.Add(name, new ShaderAttribute
				{
					Name = name,
					Location = attributeIndex,
					Size = attributeSize,
					Type = attributeType,
				});
			}
		}
		#endregion

		#region Apply (TODO)
		public void Apply(GraphicsDevice graphicsDevice)
		{
			if (GraphicsDeviceWindowsGL3.activeEffect != this)
			{
				GL.Enable(EnableCap.Blend);
				GL.UseProgram(programHandle);
				GraphicsDeviceWindowsGL3.activeEffect = this;
				ErrorHelper.Check("UseProgram");
			}
		}
		#endregion

		#region Dispose
		/// <summary>
		/// Dispose the native shader data.
		/// </summary>
		public void Dispose()
		{
			GL.DeleteProgram(programHandle);
			ErrorHelper.Check("DeleteProgram");

			int result;
			GL.GetProgram(programHandle, ProgramParameter.DeleteStatus, out result);
			if (result == 0)
			{
				string deleteError;
				GL.GetProgramInfoLog(programHandle, out deleteError);
				throw new Exception("Failed to delete the shader program because of: " +
					deleteError);
			}
		}
		#endregion
	}
}