//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
//     file="Shader.cs"
//     Project: StgSharp
//     AuthorGroup: Nitload Space
//     Copyright (c) Nitload Space. All rights reserved.
//     
//     Permission is hereby granted, free of charge, to any person 
//     obtaining a copy of this software and associated documentation 
//     files (the “Software”), to deal in the Software without restriction, 
//     including without limitation the rights to use, copy, modify, merge,
//     publish, distribute, sublicense, and/or sell copies of the Software, 
//     and to permit persons to whom the Software is furnished to do so, 
//     subject to the following conditions:
//     
//     The above copyright notice and 
//     this permission notice shall be included in all copies 
//     or substantial portions of the Software.
//     
//     THE SOFTWARE IS PROVIDED “AS IS”, 
//     WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
//     INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
//     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
//     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
//     DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
//     ARISING FROM, OUT OF OR IN CONNECTION WITH 
//     THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//     
//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
using StgSharp;
using StgSharp.Internal;

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
using System.Xml.Linq;

namespace StgSharp.Graphics.OpenGL
{
    public abstract partial class glRender : RenderStream
    {

        /// <summary>
        ///   Create an instance of <see cref="Shader" /> program
        /// </summary>
        /// <returns>
        ///   New instance of <see cref="Shader" /> instance.
        /// </returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        protected override sealed ShaderProgram CreateShaderProgram()
        {
            return new ShaderProgram(this);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        protected override sealed Shader CreateShaderSegment(ShaderType type, int count)
        {
            return new Shader(GL.CreateShaderSet(count, type), type, this);
        }

    }

    public class Shader : ISSDSerializable
    {

        private readonly OpenGLFunction GL;
        internal readonly GlHandle[] handle;
        public readonly ShaderType type;

        internal unsafe Shader(GlHandle[] handle, ShaderType usage, glRender stream)
        {
            this.handle = handle;
            GL = stream.GL;
            type = usage;
        }

        public SerializableTypeCode SSDTypeCode => SerializableTypeCode.Shader;

        /// <summary>
        ///   Attach one shader code to a shader program.
        /// </summary>
        /// <param _label="target">
        ///   Shader program to attach
        /// </param>
        /// <param _label="index">
        ///   Index of shader code in current shader code set.
        /// </param>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void AttachTo(int index, [NotNull]ShaderProgram target)
        {
            GL.AttachShader(target.handle, handle[index]);
        }

        public void CheckStatus(int index, ShaderStatus status)
        {
            string log = GL.GetShaderStatus(this, index, (int)status);
            if (!string.IsNullOrEmpty(log)) {
                throw new InvalidOperationException($"{$"Shader Error \t{status}\n"}{log}");
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public unsafe void Compile(int index, ReadOnlySpan<byte> codeU8Stream)
        {
            GL.LoadShaderSource(handle[index], codeU8Stream);
            GL.CompileShader(handle[index]);
            CheckStatus(index, ShaderStatus.CompileStatus);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public unsafe void Compile(int index, byte[] codeStream)
        {
            ArgumentNullException.ThrowIfNull(codeStream);
            GL.LoadShaderSource(handle[index], codeStream);
            GL.CompileShader(handle[index]);
            CheckStatus(index, ShaderStatus.CompileStatus);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public unsafe void Compile(int index, string codeStream)
        {
            ArgumentNullException.ThrowIfNull(codeStream);
            GL.LoadShaderSource(handle[index], codeStream.AsSpan());
            GL.CompileShader(handle[index]);
            CheckStatus(index, ShaderStatus.CompileStatus);
        }

        public void FromBytes(byte[] stream)
        {
            throw new NotImplementedException();
        }

        public static byte[] FromCodeFile(string fileRoute)
        {
            string str = File.ReadAllText(fileRoute);
            if (string.IsNullOrEmpty(str)) {
                throw new InvalidOperationException($"Cannot load and GLSL code from {fileRoute}");
            }
            return Encoding.UTF8.GetBytes(str);
        }

        public byte[] GetBytes()
        {
            return Array.Empty<byte>();
        }

        public byte[] GetBytes(out int length)
        {
            throw new NotImplementedException();
        }

        public override string ToString()
        {
            return $"This is a {type} shader, its shader handles are {handle.ToString()}.";
        }

    }

    public enum ShaderStatus : int
    {

        CompileStatus = glConst.COMPILE_STATUS,

    }

    public class ShaderProgram
    {

        private readonly OpenGLFunction GL;
        internal readonly GlHandle handle;

        /// <summary>
        ///   CustomizeInit a program with no shader attached.
        /// </summary>
        internal unsafe ShaderProgram(glRender binding)
        {
            GL = binding.GL;
            handle = GL.CreateProgram();
        }

        /// <summary>
        ///   Get a uniform form current shader, the value type of the uniform should be provided.
        /// </summary>
        /// <param _label="name">
        ///   ContextName of the Uniform in shader code
        /// </param>
        /// <returns>
        ///
        /// </returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public unsafe Uniform<T> GetUniform<T>(string name) where T: unmanaged
        {
            return new Uniform<T>(GL.GetUniformLocation(this.handle, name));
        }

        /// <summary>
        ///   Get a uniform form current shader, the value type of the uniform should be provided.
        /// </summary>
        /// <param _label="name">
        ///   ContextName of the Uniform in shader code
        /// </param>
        /// <returns>
        ///
        /// </returns>
        public unsafe Uniform<T, U> GetUniform<T, U>(string name) where T: unmanaged where U: struct
        {
            return new Uniform<T, U>(GL.GetUniformLocation(this.handle, name));
        }

        /// <summary>
        ///   Get a uniform form current shader, the value type of the uniform should be provided.
        /// </summary>
        /// <param _label="name">
        ///   ContextName of the Uniform in shader code
        /// </param>
        /// <returns>
        ///
        /// </returns>
        public unsafe Uniform<T, U, V> GetUniform<T, U, V>(string name) where T: unmanaged
            where U: struct
            where V: struct
        {
            return new Uniform<T, U, V>(GL.GetUniformLocation(this.handle, name));
        }

        /// <summary>
        ///   Get a uniform form current shader, the value type of the uniform should be provided.
        /// </summary>
        /// <param _label="name">
        ///   ContextName of the Uniform in shader code
        /// </param>
        /// <returns>
        ///
        /// </returns>
        public unsafe Uniform<T, U, V, W> GetUniform<T, U, V, W>(string name) where T: unmanaged
            where U: struct
            where V: struct
            where W: struct
        {
            return new Uniform<T, U, V, W>(GL.GetUniformLocation(this.handle, name));
        }

        /// <summary>
        ///   Link the shader to current viewPortDisplay.
        /// </summary>
        public unsafe void Link()
        {
            if (InternalIO.InternalLinkShaderProgram(
                (OpenglContext*)this.GL.ContextHandle, handle.Value) ==
                0)
            {
                IntPtr logPtr = InternalIO.InternalReadSSCLog();
                try
                {
                    byte[] logByte = new byte[512];
                    Marshal.Copy(logPtr, logByte, 0, 512);
                    string log = Encoding.UTF8.GetString(logByte);
                    log = log.Replace("\0", string.Empty);
                    InternalIO.InternalWriteLog(log, LogType.Error);
                }
                catch (Exception ex)
                {
                    InternalIO.InternalWriteLog(ex.Message, LogType.Error);
                }
            }
        }

        /// <summary>
        ///   Let the current viewPortDisplay use this shader.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public unsafe void Use()
        {
            GL.UseProgram(handle);
        }

        ~ShaderProgram()
        {
            //handle.Dispose();
        }

    }
}