/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.lang3;
  
  import java.io.Serializable;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.stream.Stream;
  
  /**
   * A set of characters.
   *
   * <p>Instances are immutable, but instances of subclasses may not be.</p>
   *
   * <p>#ThreadSafe#</p>
   * @since 1.0
   */
  public class CharSet implements Serializable {
  
      /**
       * Required for serialization support. Lang version 2.0.
       *
       * @see java.io.Serializable
       */
      private static final long serialVersionUID = 5947847346149275958L;
  
      /**
       * A CharSet defining no characters.
       * @since 2.0
       */
      public static final CharSet EMPTY = new CharSet((String) null);
  
      /**
       * A CharSet defining ASCII alphabetic characters "a-zA-Z".
       * @since 2.0
       */
      public static final CharSet ASCII_ALPHA = new CharSet("a-zA-Z");
  
      /**
       * A CharSet defining ASCII alphabetic characters "a-z".
       * @since 2.0
       */
      public static final CharSet ASCII_ALPHA_LOWER = new CharSet("a-z");
  
      /**
       * A CharSet defining ASCII alphabetic characters "A-Z".
       * @since 2.0
       */
      public static final CharSet ASCII_ALPHA_UPPER = new CharSet("A-Z");
  
      /**
       * A CharSet defining ASCII alphabetic characters "0-9".
       * @since 2.0
       */
      public static final CharSet ASCII_NUMERIC = new CharSet("0-9");
  
      /**
       * A Map of the common cases used in the factory.
       * Subclasses can add more common patterns if desired
       * @since 2.0
       */
      protected static final Map<String, CharSet> COMMON = Collections.synchronizedMap(new HashMap<>());
  
      static {
          COMMON.put(null, EMPTY);
          COMMON.put(StringUtils.EMPTY, EMPTY);
          COMMON.put("a-zA-Z", ASCII_ALPHA);
          COMMON.put("A-Za-z", ASCII_ALPHA);
          COMMON.put("a-z", ASCII_ALPHA_LOWER);
          COMMON.put("A-Z", ASCII_ALPHA_UPPER);
          COMMON.put("0-9", ASCII_NUMERIC);
      }
  
      /**
       * Factory method to create a new CharSet using a special syntax.
       *
       * <ul>
       *  <li>{@code null} or empty string ("")
       * - set containing no characters</li>
       *  <li>Single character, such as "a"
       *  - set containing just that character</li>
       *  <li>Multi character, such as "a-e"
      *  - set containing characters from one character to the other</li>
      *  <li>Negated, such as "^a" or "^a-e"
      *  - set containing all characters except those defined</li>
      *  <li>Combinations, such as "abe-g"
      *  - set containing all the characters from the individual sets</li>
      * </ul>
      *
      * <p>The matching order is:</p>
      * <ol>
      *  <li>Negated multi character range, such as "^a-e"
      *  <li>Ordinary multi character range, such as "a-e"
      *  <li>Negated single character, such as "^a"
      *  <li>Ordinary single character, such as "a"
      * </ol>
      *
      * <p>Matching works left to right. Once a match is found the
      * search starts again from the next character.</p>
      *
      * <p>If the same range is defined twice using the same syntax, only
      * one range will be kept.
      * Thus, "a-ca-c" creates only one range of "a-c".</p>
      *
      * <p>If the start and end of a range are in the wrong order,
      * they are reversed. Thus "a-e" is the same as "e-a".
      * As a result, "a-ee-a" would create only one range,
      * as the "a-e" and "e-a" are the same.</p>
      *
      * <p>The set of characters represented is the union of the specified ranges.</p>
      *
      * <p>There are two ways to add a literal negation character ({@code ^}):</p>
      * <ul>
      *     <li>As the last character in a string, e.g. {@code CharSet.getInstance("a-z^")}</li>
      *     <li>As a separate element, e.g. {@code CharSet.getInstance("^", "a-z")}</li>
      * </ul>
      *
      * <p>Examples using the negation character:</p>
      * <pre>
      *     CharSet.getInstance("^a-c").contains('a') = false
      *     CharSet.getInstance("^a-c").contains('d') = true
      *     CharSet.getInstance("^^a-c").contains('a') = true // (only '^' is negated)
      *     CharSet.getInstance("^^a-c").contains('^') = false
      *     CharSet.getInstance("^a-cd-f").contains('d') = true
      *     CharSet.getInstance("a-c^").contains('^') = true
      *     CharSet.getInstance("^", "a-c").contains('^') = true
      * </pre>
      *
      * <p>All CharSet objects returned by this method will be immutable.</p>
      *
      * @param setStrs  Strings to merge into the set, may be null
      * @return a CharSet instance
      * @since 2.4
      */
     public static CharSet getInstance(final String... setStrs) {
         if (setStrs == null) {
             return null;
         }
         if (setStrs.length == 1) {
             final CharSet common = COMMON.get(setStrs[0]);
             if (common != null) {
                 return common;
             }
         }
         return new CharSet(setStrs);
     }
 
     /** The set of CharRange objects. */
     private final Set<CharRange> set = Collections.synchronizedSet(new HashSet<>());
 
     /**
      * Constructs a new CharSet using the set syntax.
      * Each string is merged in with the set.
      *
      * @param set  Strings to merge into the initial set
      * @throws NullPointerException if set is {@code null}
      */
     protected CharSet(final String... set) {
         Stream.of(set).forEach(this::add);
     }
 
     /**
      * Add a set definition string to the {@link CharSet}.
      *
      * @param str  set definition string
      */
     protected void add(final String str) {
         if (str == null) {
             return;
         }
 
         final int len = str.length();
         int pos = 0;
         while (pos < len) {
             final int remainder = len - pos;
             if (remainder >= 4 && str.charAt(pos) == '^' && str.charAt(pos + 2) == '-') {
                 // negated range
                 set.add(CharRange.isNotIn(str.charAt(pos + 1), str.charAt(pos + 3)));
                 pos += 4;
             } else if (remainder >= 3 && str.charAt(pos + 1) == '-') {
                 // range
                 set.add(CharRange.isIn(str.charAt(pos), str.charAt(pos + 2)));
                 pos += 3;
             } else if (remainder >= 2 && str.charAt(pos) == '^') {
                 // negated char
                 set.add(CharRange.isNot(str.charAt(pos + 1)));
                 pos += 2;
             } else {
                 // char
                 set.add(CharRange.is(str.charAt(pos)));
                 pos += 1;
             }
         }
     }
 
     /**
      * Does the {@link CharSet} contain the specified
      * character {@code ch}.
      *
      * @param ch  the character to check for
      * @return {@code true} if the set contains the characters
      */
     public boolean contains(final char ch) {
         synchronized (set) {
             return set.stream().anyMatch(range -> range.contains(ch));
         }
     }
 
     // Basics
     /**
      * Compares two {@link CharSet} objects, returning true if they represent
      * exactly the same set of characters defined in the same way.
      *
      * <p>The two sets {@code abc} and {@code a-c} are <i>not</i>
      * equal according to this method.</p>
      *
      * @param obj  the object to compare to
      * @return true if equal
      * @since 2.0
      */
     @Override
     public boolean equals(final Object obj) {
         if (obj == this) {
             return true;
         }
         if (!(obj instanceof CharSet)) {
             return false;
         }
         final CharSet other = (CharSet) obj;
         return set.equals(other.set);
     }
 
     /**
      * Gets the internal set as an array of CharRange objects.
      *
      * @return an array of immutable CharRange objects
      * @since 2.0
      */
 // NOTE: This is no longer public as CharRange is no longer a public class.
 //       It may be replaced when CharSet moves to Range.
     /*public*/ CharRange[] getCharRanges() {
         return set.toArray(CharRange.EMPTY_ARRAY);
     }
 
     /**
      * Gets a hash code compatible with the equals method.
      *
      * @return a suitable hash code
      * @since 2.0
      */
     @Override
     public int hashCode() {
         return 89 + set.hashCode();
     }
 
     /**
      * Gets a string representation of the set.
      *
      * @return string representation of the set
      */
     @Override
     public String toString() {
         return set.toString();
     }
 
 }