code: /*
   * Copyright (c) 2018, The Regents of the University of California
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   * 1. Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package edu.berkeley.cs.jqf.examples.chess;
  
  import com.pholser.junit.quickcheck.generator.GenerationStatus;
  import com.pholser.junit.quickcheck.generator.Generator;
  import com.pholser.junit.quickcheck.random.SourceOfRandomness;
  
  /**
   * @author Rohan Padhye
   */
  public class FENGenerator extends Generator<String> {
  
      public FENGenerator() {
          super(String.class);
      }
  
      @Override
      public String generate(SourceOfRandomness r, GenerationStatus g) {
          return String.join(" ", generateBoard(r), generateColor(r), generateCastles(r),
                  generateEnPassant(r), generateHalfMoveClock(r), generateFullMoveClock(r));
      }
  
      private char[] pieces = { 'K', 'Q', 'R', 'B', 'N', 'P', 'k', 'q', 'r', 'b', 'n', 'p'};
  
      private String generateBoard(SourceOfRandomness r) {
          String[] rows = new String[8];
          for (int i = 0; i < 8; i++) {
              String row = "";
              for (int j = 0; j < 8; j++) {
                  if (r.nextBoolean()) {
                      // empty square
                      int skip = r.nextInt(0, 8-j);
                      j += skip;
                      row += String.valueOf(skip+1); // Upper bound is exclusive
                  } else {
                      // piece
                      row += pieces[r.nextInt(pieces.length)];
                  }
              }
              rows[i] = row;
          }
          return String.join("/", rows);
      }
  
      private String generateColor(SourceOfRandomness r) {
          return r.nextBoolean() ? "w" : "b";
      }
  
      private String generateCastles(SourceOfRandomness r) {
          if (r.nextBoolean()) {
              return "-";
          }
          String castle = "";
          if (r.nextBoolean()) {
              castle += "K";
          }
          if (r.nextBoolean()) {
              castle += "Q";
          }
          if (r.nextBoolean()) {
              castle += "k";
          }
          if (r.nextBoolean()) {
              castle += "q";
          }
          if (castle.isEmpty()) {
              castle = "-";
          }
          return castle;
      }
  
      private String generateEnPassant(SourceOfRandomness r) {
          if (r.nextBoolean()) {
              return "-";
          }
          char x = r.nextChar('a', 'i'); // Upper-bound is exclusive
          int y =  r.nextInt(1, 9);      // Upper-bound is exclusive
          return String.valueOf(x) + String.valueOf(y);
      }
  
      private String generateHalfMoveClock(SourceOfRandomness r) {
          return Integer.toString(r.nextInt(0, 50));
      }
  
      private String generateFullMoveClock(SourceOfRandomness r) {
          return Integer.toString(r.nextInt(1, 100));
      }
  }
  