// -----------------------------------------------------------------------------
// file="ShaderGenerator"
// Project: StgSharp
// Copyright (c) Nitload.
// SPDX-License-Identifier: MIT
// -----------------------------------------------------------------------------

using StgSharp.Graphics;
using StgSharp.Graphics.OpenGL;
using StgSharp.Mathematics;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.Text;
using System.Threading.Tasks;

namespace StgSharp.Graphics.ShaderEdit
{
    public class ShaderGenerator
    {

        private Dictionary<int, ShaderParameter> uniformDefine;
        private List<string> codeList;
        private List<ShaderFunction> usedShaderFunctions;

        public Uniform<T> DefineUniform<T>(
                          string name,
                          int index
        ) where T : unmanaged
        {
            ShaderParameter p = new ShaderParameter(name, ShaderParameter.TypeMarshal<T>());
            uniformDefine.Add(index, p);

            // return new Uniform<TView>();
            throw new NotImplementedException();
        }

    }

    public class ShaderFunction
    {

        private List<string> codeList;
        private List<ShaderParameter> inputList;
        private ShaderParameter outPut;
        private string name;

        public int ParameterCount => inputList.Count;

        public void EmitCall(
                    ShaderFunction function,
                    ShaderParameter outPut,
                    params ShaderParameter[] inputParams
        )
        {
            if (inputParams.Length != function.ParameterCount)
            {
                // Param list length not equal
                throw new ArgumentException(
                    "Provided parameters does not match function's parameter list.");
            }
            if (!ShaderParameter.IsSameType(outPut, function.outPut))
            {
                // Type of returning value not equal
                throw new ArgumentException(
                    "Provided parameters does not match function's parameter list.");
            }
            for (int i = 0; i < inputParams.Length; i++)
            {
                if (!ShaderParameter.IsSameType(function.inputList[i], inputParams[i]))
                {
                    // Input type not match
                    throw new InvalidCastException(
                        "Provided parameters does not match function's parameter list.");
                }
            }
            string codeLine = string.Empty;    // adding a line like " outvalue = Func(input1, input2,...); "
            if (outPut != ShaderParameter.Void) {
                codeLine += $"{outPut.name} = ";
            }
            codeLine += $"{function.name}(";
            foreach (ShaderParameter inputParam in inputParams) {
                codeLine += inputParam.name;
            }
            codeLine += ");\n";
            codeList.Add(codeLine);
        }

    }

    public class ShaderParameter
    {

        public static readonly ShaderParameter Void = new ShaderParameter(
            string.Empty, InternalShaderType.Void);
        internal readonly bool isReadOnly;
        internal readonly InternalShaderType type;
        internal readonly string name;

        public ShaderParameter(
               string name,
               InternalShaderType type
        )
        {
            this.name = name;
            this.type = type;
            isReadOnly = false;
        }

        public static bool IsSameType(
                           ShaderParameter param1,
                           ShaderParameter param2
        )
        {
            if (param1.type != InternalShaderType.Struct)
            {
                return param1.type == param2.type;
            } else
            {
                throw new Exception("Struct is currently not supported.");
            }
        }

        public static InternalShaderType TypeMarshal<T>() where T : unmanaged
        {
            switch (Type.GetTypeCode(typeof(T)))
            {
                case TypeCode.Single:
                    return InternalShaderType.Float;
                case TypeCode.Double:
                    return InternalShaderType.Double;
                case TypeCode.Int32:
                    return InternalShaderType.Int;
                case TypeCode.UInt32:
                    return InternalShaderType.UInt;
                default:
                    break;
            }
            switch (typeof(T).Name)
            {
                case "vec4d":
                    return InternalShaderType.Vector4;
                case "Matrix2x2":
                    return InternalShaderType.Matrix2x2;
                case "Matrix2x3":
                    return InternalShaderType.Matrix2x3;
                case "Matrix2x4":
                    return InternalShaderType.Matrix2x4;
                case "Matrix3x2":
                    return InternalShaderType.Matrix3x2;
                case "Matrix3x3":
                    return InternalShaderType.Matrix3x3;
                case "Matrix3x4":
                    return InternalShaderType.Matrix3x4;
                case "Matrix4x2":
                    return InternalShaderType.Matrix4x2;
                case "Matrix4x3":
                    return InternalShaderType.Matrix4x3;
                case "Matrix4x4":
                    return InternalShaderType.Matrix4x4;
                default:
                    throw new ArgumentException("Not supported shader data type.");
            }
        }

    }

    public enum InternalShaderType
    {
#pragma warning disable CS1591
        Struct,
        Void,
        Int,
        UInt,
        Float,
        Double,
        Vector2,
        Vector3,
        Vector4,
        VectorD2,
        VectorD3,
        VectorD4,
        Matrix2x2,
        Matrix2x3,
        Matrix2x4,
        Matrix3x2,
        Matrix3x3,
        Matrix3x4,
        Matrix4x2,
        Matrix4x3,
        Matrix4x4,
#pragma warning restore CS1591
    }
}