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

namespace AcDream.App.Rendering;

public sealed class Shader : IDisposable
{
    private readonly GL _gl;
    private readonly Dictionary<string, int> _uniformLocations = new(StringComparer.Ordinal);
    public uint Program { get; private set; }

    public Shader(GL gl, string vertexPath, string fragmentPath)
    {
        _gl = gl;
        string vertexSource = File.ReadAllText(vertexPath);
        string fragmentSource = File.ReadAllText(fragmentPath);
        Program = ShaderProgramConstruction.Build(
            new GlShaderProgramBuildApi(gl),
            vertexSource,
            fragmentSource);
    }

    public void Use() => _gl.UseProgram(Program);

    public unsafe void SetMatrix4(string name, Matrix4x4 m)
    {
        int loc = GetUniformLocation(name);
        _gl.UniformMatrix4(loc, 1, false, (float*)&m);
    }

    public void SetInt(string name, int value)
    {
        int loc = GetUniformLocation(name);
        _gl.Uniform1(loc, value);
    }

    public void SetFloat(string name, float value)
    {
        int loc = GetUniformLocation(name);
        _gl.Uniform1(loc, value);
    }

    public void SetVec3(string name, Vector3 v)
    {
        int loc = GetUniformLocation(name);
        _gl.Uniform3(loc, v.X, v.Y, v.Z);
    }

    public void SetVec2(string name, Vector2 v)
    {
        int loc = GetUniformLocation(name);
        _gl.Uniform2(loc, v.X, v.Y);
    }

    public void SetVec4(string name, Vector4 v)
    {
        int loc = GetUniformLocation(name);
        _gl.Uniform4(loc, v.X, v.Y, v.Z, v.W);
    }

    private int GetUniformLocation(string name)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(name);
        if (_uniformLocations.TryGetValue(name, out int location))
            return location;

        location = _gl.GetUniformLocation(Program, name);
        _uniformLocations.Add(name, location);
        return location;
    }

    public void Dispose()
    {
        uint program = Program;
        if (program == 0)
            return;

        _uniformLocations.Clear();
        GlResourceCommand.DeleteProgram(_gl, program, $"delete Shader program {program}");
        Program = 0;
    }
}