public class MusicPattern {
  	/* Pattern definition :
  	 *  0 : low  time
  	 *  1 : rise time
  	 *  2 : high time
  	 *  3 : fall time
  	 */
  	private int[] pattern; // in ms

  	private int totalLentgh;
  	private int[] patternTiming = new int[4]; // in ms
  	private long begin; // in ms
  	private long stop; // in ms

  	public MusicPattern(int[] pattern, int repeat, long begin) {

  		if(pattern.length != 4)
  			throw new InvalidPatternException();
  		this.pattern = pattern;

  		this.totalLentgh = pattern[0] + pattern[1] + pattern[2] + pattern[3];
  		this.patternTiming[0] = pattern[0];
  		for(int i=1; i<4; i++)
  			this.patternTiming[i] = this.patternTiming[i-1] + pattern[i];
  		this.begin = begin;
  		this.stop = repeat * totalLentgh;
  	}
  	
  	public double render(long tick) { // tick in ms
  		if(tick <= begin)
  			return 0;
  		if(tick >= stop)
  			return 0;
  		int tickMod = (int) (tick % totalLentgh);
  		if(tickMod < patternTiming[0])
  			return 0;
  		if(tickMod < patternTiming[1])
  			return (double) (tickMod - patternTiming[0]) / (double) (pattern[1]);
  		if(tickMod < patternTiming[2])
  			return 1;
  		return 1 - ((double) (tickMod - patternTiming[2]) / (double) (pattern[3]));

  	}
  }