package de.gamezock.metacraft.ui;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.IntBuffer;
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 void printInfoLog(GL2 gl, int object) {
    IntBuffer lengthBuffer = IntBuffer.allocate(1);

    gl.glGetObjectParameterivARB(object, GL2.GL_OBJECT_INFO_LOG_LENGTH_ARB, lengthBuffer);
    
    int length = lengthBuffer.get(0);
    
    if(length > 0) {
      ByteBuffer log = ByteBuffer.allocate(length);
      
      IntBuffer foo = IntBuffer.allocate(1);
      gl.glGetInfoLogARB(object, length, foo, log);
      System.err.println(new String(log.array()));
    }

  }
  
  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 private int loadShader(GL2 gl, String name, int type) {
    int shader = gl.glCreateShaderObjectARB(type);
    
    try {
      InputStream stream = ShaderLoader.class.getResourceAsStream("/de/gamezock/metacraft/resources/shaders/" + name);
      
      String source = readStream(stream);
      
      gl.glShaderSourceARB(shader, 1, new String[] {source}, null);
      gl.glCompileShaderARB(shader);
      
      printInfoLog(gl, shader);
      
      return shader;
    } catch (IOException e) {
    }
    
    if(shader != 0)
      gl.glDeleteObjectARB(shader);
    
    return 0;
  }
  
  static public 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 = loadShader(gl, vsName, GL2.GL_VERTEX_SHADER);
    int fs = loadShader(gl, fsName, GL2.GL_FRAGMENT_SHADER);
    
    if(vs != 0 && fs != 0) {
      int program = gl.glCreateProgramObjectARB();
      gl.glAttachObjectARB(program, vs);
      gl.glAttachObjectARB(program, fs);
      gl.glLinkProgramARB(program);
      
      printInfoLog(gl, program);
      
      gl.glUseProgramObjectARB(program);

      programs.put(new AbstractMap.SimpleEntry<String, String>(vsName, fsName), program);

      return true;
    }

    return false;
  }
}