using Silk.NET.Maths;
using Silk.NET.OpenGL;
using System.Numerics;

namespace Engine_silk.NET.Shaders;

public class Shader
{
    private readonly GL _glContext;
    private readonly uint _shaderProgramId;

    public Shader(GL openGLContext, string pathToVertexShader, string pathToFragmentShader)
    {
        _glContext = openGLContext;
        var vertexCode = File.ReadAllText(pathToVertexShader);
        var fragmentCode = File.ReadAllText(pathToFragmentShader);

        var vertexShader = CompileShader(vertexCode, ShaderType.VertexShader);
        var fragmentShader = CompileShader(fragmentCode, ShaderType.FragmentShader);

        _shaderProgramId = CreateProgram(vertexShader, fragmentShader);
    }

    public void Use() { _glContext.UseProgram(_shaderProgramId); }

    #region Set uniforms
    public void SetInt(string name, int value)
    {
        _glContext.Uniform1(_glContext.GetUniformLocation(_shaderProgramId, name), value);
    }

    public void SetFloat(string name, float value)
    {
        _glContext.Uniform1(_glContext.GetUniformLocation(_shaderProgramId, name), value);
    }

    public unsafe void SetMatrix(string name, Matrix4x4 matrix)
    {
        _glContext.UniformMatrix4(_glContext.GetUniformLocation(_shaderProgramId, name), 1, false, (float*) &matrix);
	}
    public unsafe void SetMatrix(string name, Matrix4X4<float> matrix)
    {
        _glContext.UniformMatrix4(_glContext.GetUniformLocation(_shaderProgramId, name), 1, false, (float*) &matrix);
	}
	#endregion


	/// <summary>
	/// Compiles the given shadercode.
	/// </summary>
	/// <param name="shaderCode">The shadercode</param>
	/// <param name="shaderType">The type of shader to compile</param>
	/// <returns>Returns the id of the compiled shader.</returns>
	/// <exception cref="ShaderCompileException"></exception>
	protected uint CompileShader(string shaderCode, ShaderType shaderType)
    {
        uint shader = _glContext.CreateShader(shaderType);
        _glContext.ShaderSource(shader, shaderCode);
        _glContext.CompileShader(shader);

        _glContext.GetShader(shader, ShaderParameterName.CompileStatus, out int status);

        if (status != (int)GLEnum.True)
            throw new ShaderCompileException(shaderType, $"Failed to compile shader with message: \n {_glContext.GetShaderInfoLog(shader)}");

        return shader;
    }

    /// <summary>
    /// Creates a shader program and links the vertex and fragment shader together.
    /// </summary>
    /// <returns>Returns the id of the created shader program</returns>
    /// <exception cref="ShaderLinkException"></exception>
    protected uint CreateProgram(uint vertexShader, uint fragmentShader)
    {
        uint program = _glContext.CreateProgram();
		_glContext.AttachShader(program, vertexShader);
		_glContext.AttachShader(program, fragmentShader);
		_glContext.LinkProgram(program);

		_glContext.GetProgram(program, ProgramPropertyARB.LinkStatus, out int lStatus);
		if (lStatus != (int)GLEnum.True)
			throw new ShaderLinkException("Error occured while trying to link a shader with message: \n" + _glContext.GetProgramInfoLog(program));

		// should be done right after compiling and linking
		_glContext.DetachShader(program, vertexShader);
		_glContext.DetachShader(program, fragmentShader);
		_glContext.DeleteShader(vertexShader);
		_glContext.DeleteShader(fragmentShader);

        return program;
	}

}