using OpenTK.Graphics.OpenGL;

namespace Dashboard.Drawing.OpenGL
{
    public static class ShaderUtil
    {
        public static int CompileShader(ShaderType type, string source)
        {
            int shader = GL.CreateShader(type);

            GL.ShaderSource(shader, source);
            GL.CompileShader(shader);

            int compileStatus = 0;
            GL.GetShaderi(shader, ShaderParameterName.CompileStatus, out compileStatus);

            if (compileStatus == 0)
            {
                GL.GetShaderInfoLog(shader, out string log);
                GL.DeleteShader(shader);
                throw new Exception($"{type} Shader compilation failed: " + log);
            }

            return shader;
        }

        public static int CompileShader(ShaderType type, Stream stream)
        {
            using StreamReader reader = new StreamReader(stream, leaveOpen: true);

            return CompileShader(type, reader.ReadToEnd());
        }

        public static int LinkProgram(int s1, int s2, IReadOnlyList<string>? attribLocations = null)
        {
            int program = GL.CreateProgram();

            GL.AttachShader(program, s1);
            GL.AttachShader(program, s2);

            for (int i = 0; i < attribLocations?.Count; i++)
            {
                GL.BindAttribLocation(program, (uint)i, attribLocations[i]);
            }

            GL.LinkProgram(program);

            int linkStatus = 0;
            GL.GetProgrami(program, ProgramProperty.LinkStatus, out linkStatus);
            if (linkStatus == 0)
            {
                GL.GetProgramInfoLog(program, out string log);
                GL.DeleteProgram(program);
                throw new Exception("Shader program linking failed: " + log);
            }

            return program;
        }
    }
}