using System;
using System.IO;
using System.Text;
using GL = OpenTK.Graphics.ES30.GL;
using ShaderType = OpenTK.Graphics.ES30.ShaderType;

namespace OpenTKTutorial {
    public class Shader : IDisposable {
        public int Handle;

        public Shader(string vertexPath, string fragmentPath) {
            string vertex, fragment;

            using (StreamReader reader = new StreamReader(vertexPath, Encoding.UTF8)) vertex = reader.ReadToEnd();
            using (StreamReader reader = new StreamReader(fragmentPath, Encoding.UTF8)) fragment = reader.ReadToEnd();

            int vertexShader = GL.CreateShader(ShaderType.VertexShader);
            GL.ShaderSource(vertexShader, vertex);

            int fragmentShader = GL.CreateShader(ShaderType.FragmentShader);
            GL.ShaderSource(fragmentShader, fragment);
            
            GL.CompileShader(vertexShader);

            string infoLogVert = GL.GetShaderInfoLog(vertexShader);
            if (infoLogVert != String.Empty)
                throw new Exception("Could not compile vertex shader: " + infoLogVert);

            GL.CompileShader(fragmentShader);

            string infoLogFrag = GL.GetShaderInfoLog(fragmentShader);
            if (infoLogFrag != String.Empty)
                throw new Exception("Could not compile fragment shader: " + infoLogFrag);
            
            Handle = GL.CreateProgram();
            GL.AttachShader(Handle, vertexShader);
            GL.AttachShader(Handle, fragmentShader);
            GL.LinkProgram(Handle);
            
            GL.DetachShader(Handle, vertexShader);
            GL.DetachShader(Handle, fragmentShader);
            GL.DeleteShader(fragmentShader);
            GL.DeleteShader(vertexShader);
        }
        
        public void Use()
        {
            GL.UseProgram(Handle);
        }
        
        private bool disposedValue = false;

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                GL.DeleteProgram(Handle);

                disposedValue = true;
            }
        }

        ~Shader()
        {
            GL.DeleteProgram(Handle);
        }


        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
    }
}