package passage.games;

import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL20.*;
import static org.lwjgl.util.glu.GLU.*;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;

public class Shader {
    public int programID;

    public int vertexShaderID;
    public int fragmentShaderID;

    public Shader()
    {
        programID = glCreateProgram();
    }

    public void attachVertexShader(String name)
    {
        String vertexShaderSource = sourceFromFile(name);

        vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertexShaderID, vertexShaderSource);

        glCompileShader(vertexShaderID);

        if (glGetShaderi(vertexShaderID, GL_COMPILE_STATUS) == GL_FALSE)
        {
            //The maxLength includes the NULL character

            System.out.println("Error in vertex shader: " + glGetShaderInfoLog(vertexShaderID, 256));
        }

        glAttachShader(programID, vertexShaderID);
    }

    public void attachFragmentShader(String name)
    {
        String fragmentShaderSource = sourceFromFile(name);

        fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragmentShaderID, fragmentShaderSource);

        glCompileShader(fragmentShaderID);

        if (glGetShaderi(fragmentShaderID, GL_COMPILE_STATUS) == GL_FALSE)
        {
            System.out.println("Error in fragment shader: " + glGetShaderInfoLog(fragmentShaderID, 256));
        }

        glAttachShader(programID, fragmentShaderID);
    }

    public void link()
    {
        glLinkProgram(programID);

        if (glGetProgrami(programID, GL_LINK_STATUS) == GL_FALSE)
        {
        }
    }

    public void bind()
    {
        glUseProgram(programID);
    }

    public void unbind()
    {
        glUseProgram(0);
    }

    public void dispose()
    {
        unbind();

        glDetachShader(programID, vertexShaderID);
        glDetachShader(programID, fragmentShaderID);

        glDeleteShader(vertexShaderID);
        glDeleteShader(fragmentShaderID);

        glDeleteProgram(programID);
    }

	public static String sourceFromFile(String name)
    {
        StringBuilder source = new StringBuilder();
        try
        {
            BufferedReader reader = new BufferedReader(new FileReader(new File(name)));

            String line;
            while ((line = reader.readLine()) != null)
            {
                source.append(line).append("\n");
            }

            reader.close();
        }
        catch (Exception e)
        {
            System.err.println("Error loading source code: " + name);
            e.printStackTrace();
        }

        return source.toString();
    }
}