/*
    * Copyright 2011 Király Attila
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.github.cage.token;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Random;
  
  import com.github.cage.IGenerator;
  import com.github.cage.IGeneratorFactory;
  
  /**
   * Factory that can generate {@link Character} generating {@link IGenerator}s.
   * 
   * @author akiraly
   */
  public class RandomCharacterGeneratorFactory implements
  		IGeneratorFactory<Character> {
  	/**
  	 * English lower cased vowel character array.
  	 */
  	public static final char[] ENGLISH_VOWELS = "aeiou".toCharArray();
  
  	/**
  	 * English lower cased consonant character array.
  	 */
  	public static final char[] ENGLISH_CONSONANTS = "bcdfghjklmnpqrstxyvz"
  			.toCharArray();
  
  	/**
  	 * Arabic numeral character array.
  	 */
  	public static final char[] ARABIC_NUMERALS = "0123456789".toCharArray();
  
  	/**
  	 * Default character set for the default case. It contains the English lower
  	 * cased letters.
  	 */
  	public static final char[] DEFAULT_DEFAULT_CHARACTER_SET = (new String(
  			ENGLISH_VOWELS) + new String(ENGLISH_CONSONANTS)).toCharArray();
  
  	/**
  	 * Special character sets for the default case.
  	 */
  	public static final Map<Character, char[]> DEFAULT_SPECIAL_CHARACTER_SETS = Collections
  			.unmodifiableMap(createDefaultSpecialCharacterSets());
  
  	private final char[] defaultCharacterSet;
  
  	private final Map<Character, char[]> specialCharacterSets;
  
  	private final Random rnd;
  
  	/**
  	 * Generates characters based on the settings of the factory. This is
  	 * <b>not</b> thread safe!
  	 */
  	public class RandomCharacterGenerator implements IGenerator<Character> {
  		private char[] currentCharacterSet = defaultCharacterSet;
  
  		public Character next() {
  			char next = currentCharacterSet[rnd
  					.nextInt(currentCharacterSet.length)];
  
  			if (specialCharacterSets != null) {
  				char[] nextCharacterSet = specialCharacterSets.get(next);
  				if (nextCharacterSet != null) {
  					if (nextCharacterSet.length < 1) {
  						throw new IllegalStateException(
  								"specialCharacterSets should not hold an empty char[] value");
  					}
  					currentCharacterSet = nextCharacterSet;
  				} else {
  					currentCharacterSet = defaultCharacterSet;
  				}
  			}
  
  			return next;
  		}
  	}
  
  	/**
  	 * Constructor.
  	 */
  	public RandomCharacterGeneratorFactory() {
 		this(null);
 	}
 
 	/**
 	 * Constructor.
 	 * 
 	 * @param rnd
 	 *            used to generate random numbers. Can be null.
 	 */
 	public RandomCharacterGeneratorFactory(Random rnd) {
 		this(null, DEFAULT_SPECIAL_CHARACTER_SETS, rnd);
 	}
 
 	/**
 	 * Constructor.
 	 * 
 	 * @param defaultCharacterSet
 	 *            used generally for character choosing, can be null.
 	 * @param specialCharacterSets
 	 *            map contains special cases. A (k, v) pair in this map means
 	 *            that character k can only be immediately followed by a
 	 *            character in v array. No value should be empty or null. The
 	 *            map parameter itself can be null.
 	 * @param rnd
 	 *            used to generate random numbers. Can be null.
 	 */
 	public RandomCharacterGeneratorFactory(char[] defaultCharacterSet,
 			Map<Character, char[]> specialCharacterSets, Random rnd) {
 		this.defaultCharacterSet = defaultCharacterSet != null
 				&& defaultCharacterSet.length > 0 ? defaultCharacterSet
 				: DEFAULT_DEFAULT_CHARACTER_SET;
 		this.specialCharacterSets = specialCharacterSets != null
 				&& !specialCharacterSets.isEmpty() ? specialCharacterSets
 				: null;
 		this.rnd = rnd != null ? rnd : new Random();
 	}
 
 	/**
 	 * Helper function to build {@link #DEFAULT_SPECIAL_CHARACTER_SETS}. It
 	 * contains some rules to avoid confusing character pairs. Also makes sure
 	 * that vowels and consonants follow each other in an alternating fashion.
 	 * 
 	 * @return populated map
 	 */
 	protected static Map<Character, char[]> createDefaultSpecialCharacterSets() {
 		Map<Character, char[]> m = new HashMap<Character, char[]>();
 
 		char[] con = ENGLISH_CONSONANTS;
 		String conS = new String(con);
 		char[] vow = ENGLISH_VOWELS;
 		String vowS = new String(vow);
 
 		m.put('a', con);
 		m.put('b', vow);
 		m.put('c', vowS.replaceAll("o", "").toCharArray());
 		m.put('d', vowS.replaceAll("o", "").toCharArray());
 		m.put('e', con);
 		m.put('f', vow);
 		m.put('g', vow);
 		m.put('h', vow);
 		m.put('i', conS.replaceAll("j|l", "").toCharArray());
 		m.put('j', vowS.replaceAll("i", "").toCharArray());
 		m.put('k', vow);
 		m.put('l', vowS.replaceAll("i|o", "").toCharArray());
 		m.put('m', vow);
 		m.put('n', vowS.replaceAll("u", "").toCharArray());
 		m.put('o', conS.replaceAll("b|l|p", "").toCharArray());
 		m.put('p', vow);
 		m.put('q', vowS.replaceAll("o", "").toCharArray());
 		m.put('r', vowS.replaceAll("u", "").toCharArray());
 		m.put('s', vow);
 		m.put('t', vow);
 		m.put('u', con);
 		m.put('v', vow);
 		m.put('w', vow);
 		m.put('x', vow);
 		m.put('y', vow);
 		m.put('z', vow);
 
 		return m;
 	}
 
 	public IGenerator<Character> next() {
 		return new RandomCharacterGenerator();
 	}
 
 	/**
 	 * @return default character set for character generation, not null
 	 */
 	public char[] getDefaultCharacterSet() {
 		return defaultCharacterSet;
 	}
 
 	/**
 	 * @return map holding the special rules for each character, can be null
 	 */
 	public Map<Character, char[]> getSpecialCharacterSets() {
 		return specialCharacterSets;
 	}
 }