code: /*
   * Computoser is a music-composition algorithm and a website to present the results
   * Copyright (C) 2012-2014  Bozhidar Bozhanov
   *
   * Computoser is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Affero General Public License as
   * published by the Free Software Foundation, either version 3 of the
   * License, or (at your option) any later version.
   *
   * Computoser is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU Affero General Public License for more details.
   *
   * You should have received a copy of the GNU Affero General Public License
   * along with Computoser.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package com.music;
  
  import java.util.Random;
  
  import com.music.model.prefs.Tempo;
  import com.music.model.prefs.UserPreferences;
  import com.music.util.music.Chance;
  
  import jm.JMC;
  import jm.music.data.Score;
  
  public class MetreConfigurer implements ScoreManipulator {
      private Random random = new Random();
  
      @Override
      public void handleScore(Score score, ScoreContext ctx, UserPreferences prefs) {
          int[] metre = getRandomMetre(random);
  
          if (prefs != null && prefs.getTempo() != null) {
              score.setTempo(prefs.getTempo().getFrom() 
                      + random.nextInt(prefs.getTempo().getTo() - prefs.getTempo().getFrom()));
          } else {
              score.setTempo(Tempo.ANY.getFrom() + random.nextInt(Tempo.ANY.getTo() - Tempo.ANY.getFrom()));
          }
  
          ctx.setMetre(metre);
          score.setNumerator(metre[0]);
          score.setDenominator(metre[1]);
  
          double normalizedMeasureSize = getNormalizedMeasureSize(ctx.getMetre());
          ctx.setNormalizedMeasureSize(normalizedMeasureSize);
          if (prefs != null && prefs.getMeasures() != 0) {
              ctx.setMeasures(prefs.getMeasures());
          } else {
              ctx.setMeasures((int) ((10 + random.nextInt(10)) * score.getTempo() / 40));
          }
  
          if (Chance.test(20) && metre[1] < 16) {
              ctx.setUpBeatLength(normalizedMeasureSize - Math.max(1, metre[0] - random.nextInt(3) - 1) * JMC.EIGHTH_NOTE);
          }
  
          // possibly have longer notes for faster tempo?
          ctx.setNoteLengthCoefficient(1);
      }
  
      public static double getNormalizedMeasureSize(int[] metre) {
          // jMusic's whole note = 4, so 4 is the dividend.
          double normalizedMeasureSize = 1d * metre[0] * 4 / metre[1];
          return normalizedMeasureSize;
      }
  
      public static int[] getRandomMetre(Random random) {
          int[] metre = new int[2];
          metre[1] = (int) Math.pow(2, 2 + random.nextInt(3));
          int metreSpec = random.nextInt(3);
          if (metreSpec == 0) {
              metre[0] = 2 + random.nextInt(metre[1]);
          } else if (metreSpec == 1){
              metre[0] = metre[1] / 2;
          } else if (metreSpec == 2) {
              metre[0] = metre[1];
          }
          return metre;
      }
  }
  