import java.io.*;
import javax.sound.midi.*;

/**
 * This will play files as songs.  Example usage:
 *
 *   java Java2Midi Java2Midi.class
 *
 */
public class Java2Midi {

  public static void main(String[] args) {
    new Java2Midi().realMain(args);
  }

  public void realMain(String[] args) {

    if (args.length == 0) {
      System.err.println("Usage: " + getClass().getSimpleName() + " <class-file>+");
      return;
    }

    for (String fileName : args) {
      try {
        play(fileName);
      } catch (IOException e) {
        e.printStackTrace();
      }
    }

  }

  private final static int[] SCALE = {
    1,   3,  5,  6,  8, 10, 12,
    13, 15, 17, 18, 20, 22, 24,
    25, 27, 29, 30, 32, 34, 36,
  };

  private void play(String fileName) throws IOException {
    if (!fileName.endsWith(".class")) {
      fileName += ".class";
    }


    Synthesizer	synth = null;
    try {
      synth = MidiSystem.getSynthesizer();
    } catch (MidiUnavailableException e) {
      e.printStackTrace();
      return;
		}
    try {
      synth.open();
    } catch (MidiUnavailableException e) {
      e.printStackTrace();
      return;
		}
    int channelNumber = 0;
    MidiChannel	channel = null;
    MidiChannel[]	channels = synth.getChannels();
    for (;;) {
      System.out.print("Please select a channel between 1 and " + channels.length + " > ");
      BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
      String channelNumberString = in.readLine();
      if (channelNumberString.trim().equals("")) {
        channelNumberString = "1";
      }
      in.close();
      int num = Integer.MIN_VALUE;
      try {
        num = Integer.parseInt(channelNumberString);
      } catch (NumberFormatException _) {}
      if (num == Integer.MIN_VALUE) {
        System.out.println("Invalid choice: " + channelNumberString);
      } else if (num < 1 || num > channels.length) {
        System.out.println(num + " must be >= 1 and <= " + channels.length);
      } else {
        System.out.println("\nUsing channel " + num + "...");
        channel = channels[num-1];
        break;
      }
    }

    BufferedInputStream in = new BufferedInputStream(new FileInputStream(fileName));
    int duration, note;
    for (;;) {
      if ((duration = in.read()) == -1) break;
      if ((note = in.read()) == -1) break;
      int scaledDuration = 100 + 4 * duration;
      int scaledNote = 50 + SCALE[note%SCALE.length];
      channel.noteOn(scaledNote,13);
      try {
        Thread.sleep(scaledDuration);
      } catch (InterruptedException _) {}
    }
    in.close();
  }

}