package engine.utils;

import engine.utils.FileUtils;

import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL20.*;

public class ShaderUtils {

    private ShaderUtils(){

    }

    public static int load(String vertPath, String fragPath){
        String vert = FileUtils.loadAsString(vertPath);
        String frag = FileUtils.loadAsString(fragPath);
        return create(vert, frag);
    }

    public static int create(String vert, String frag){
        // On crée et compile le vertex et le fragment shader
        int vertID = glCreateShader(GL_VERTEX_SHADER);
        int fragID = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(vertID, vert);
        glShaderSource(fragID, frag);

        glCompileShader(vertID);
        if (glGetShaderi(vertID, GL_COMPILE_STATUS) == GL_FALSE){
            System.err.println("Failed to compile vertex shader");
            System.err.println(glGetShaderInfoLog(vertID));
            return -1;
        }

        glCompileShader(fragID);
        if (glGetShaderi(fragID, GL_COMPILE_STATUS) == GL_FALSE){
            System.err.println("Failed to compile fragment shader");
            System.err.println(glGetShaderInfoLog(fragID));
            return -1;
        }
        //on lie les shaders au programme
        int program = glCreateProgram();
        glAttachShader(program, vertID);
        glAttachShader(program, fragID);
        glLinkProgram(program);

        if(glGetProgrami(program, GL_LINK_STATUS) == GL_FALSE) {
            System.err.println("Failed to link vertex and fragment shader");
            System.err.println(glGetShaderInfoLog(program));
            return -1;
        }

        glValidateProgram(program);

        glDeleteShader(vertID);
        glDeleteShader(fragID);

        return program;
    }

}