package de.gamezock.metacraft.ui;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.AbstractMap;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import javax.media.opengl.GL2;

public class ShaderLoader {
  private static Map<Entry<String, String>, Integer> programs = new HashMap<Entry<String, String>, Integer>();
  
  static private String readStream(InputStream stream) throws IOException {
    BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
    String ret = "", line;
    
    while ((line = reader.readLine()) != null) {
      ret += line + "\n";
    }
    
    return ret;
  }
  
  static boolean load(GL2 gl, String vsName, String fsName) {
    Integer savedProg = programs.get(new AbstractMap.SimpleEntry<String, String>(vsName, fsName));
    if(savedProg != null) {
      gl.glUseProgram(savedProg);
      return true;
    }
    
    int vs = gl.glCreateShader(GL2.GL_VERTEX_SHADER);
    int fs = gl.glCreateShader(GL2.GL_FRAGMENT_SHADER);
    
    InputStream vsStream = ShaderLoader.class.getResourceAsStream("/de/gamezock/metacraft/resources/shaders/" + vsName);
    String vsSource;
    try {
      vsSource = readStream(vsStream);
    } catch (IOException e) {
      return false;
    }
    
    gl.glShaderSource(vs, 1, new String[] {vsSource}, null);
    gl.glCompileShader(vs);

    InputStream fsStream = ShaderLoader.class.getResourceAsStream("/de/gamezock/metacraft/resources/shaders/" + fsName);
    String fsSource;
    try {
      fsSource = readStream(fsStream);
    } catch (IOException e) {
      return false;
    }
    
    gl.glShaderSource(fs, 1, new String[] {fsSource}, null);
    gl.glCompileShader(fs);

    int program = gl.glCreateProgram();
    gl.glAttachShader(program, vs);
    gl.glAttachShader(program, fs);
    gl.glLinkProgram(program);
    gl.glValidateProgram(program);

    gl.glUseProgram(program);
    
    programs.put(new AbstractMap.SimpleEntry<String, String>(vsName, fsName), program);
    
    return true;
  }
}