using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;

namespace VoxelEngine.Rendering;

public sealed class Shader : IDisposable
{
    private readonly int _handle;
    private readonly Dictionary<string, int> _uniforms = new();

    public Shader(string vertexPath, string fragmentPath)
    {
        int vertex = CompileFromFile(ShaderType.VertexShader, vertexPath);
        int fragment = CompileFromFile(ShaderType.FragmentShader, fragmentPath);

        _handle = GL.CreateProgram();
        GL.AttachShader(_handle, vertex);
        GL.AttachShader(_handle, fragment);
        GL.LinkProgram(_handle);

        GL.GetProgram(_handle, GetProgramParameterName.LinkStatus, out int linked);
        if (linked == 0)
            throw new InvalidOperationException($"Program link failed: {GL.GetProgramInfoLog(_handle)}");

        GL.DetachShader(_handle, vertex);
        GL.DetachShader(_handle, fragment);
        GL.DeleteShader(vertex);
        GL.DeleteShader(fragment);
    }

    public void Use() => GL.UseProgram(_handle);

    public void SetMatrix4(string name, Matrix4 value) =>
        GL.UniformMatrix4(Location(name), true, ref value);

    public void SetInt(string name, int value) =>
        GL.Uniform1(Location(name), value);

    private int Location(string name)
    {
        if (!_uniforms.TryGetValue(name, out int location))
        {
            location = GL.GetUniformLocation(_handle, name);
            _uniforms[name] = location;
        }
        return location;
    }

    private static int CompileFromFile(ShaderType type, string path)
    {
        string source = File.ReadAllText(path);
        int shader = GL.CreateShader(type);
        GL.ShaderSource(shader, source);
        GL.CompileShader(shader);

        GL.GetShader(shader, ShaderParameter.CompileStatus, out int compiled);
        if (compiled == 0)
            throw new InvalidOperationException($"{type} compile failed ({path}): {GL.GetShaderInfoLog(shader)}");

        return shader;
    }

    public void Dispose() => GL.DeleteProgram(_handle);
}