/*
    * Copyright (C) 2008 The Guava Authors
    *
    * 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.google.common.base;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.Beta;
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Arrays;
  
  import javax.annotation.CheckReturnValue;
  
  /**
   * Determines a true or false value for any Java {@code char} value, just as {@link Predicate} does
   * for any {@link Object}. Also offers basic text processing methods based on this function.
   * Implementations are strongly encouraged to be side-effect-free and immutable.
   *
   * <p>Throughout the documentation of this class, the phrase "matching character" is used to mean
   * "any character {@code c} for which {@code this.matches(c)} returns {@code true}".
   *
   * <p><b>Note:</b> This class deals only with {@code char} values; it does not understand
   * supplementary Unicode code points in the range {@code 0x10000} to {@code 0x10FFFF}. Such logical
   * characters are encoded into a {@code String} using surrogate pairs, and a {@code CharMatcher}
   * treats these just as two separate characters.
   *
   * <p>Example usages: <pre>
   *   String trimmed = {@link #WHITESPACE WHITESPACE}.{@link #trimFrom trimFrom}(userInput);
   *   if ({@link #ASCII ASCII}.{@link #matchesAllOf matchesAllOf}(s)) { ... }</pre>
   *
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/StringsExplained#CharMatcher">
   * {@code CharMatcher}</a>.
   *
   * @author Kevin Bourrillion
   * @since 1.0
   */
  @Beta // Possibly change from chars to code points; decide constants vs. methods
  @GwtCompatible(emulated = true)
  public abstract class CharMatcher implements Predicate<Character> {
  
    // Constants
    /**
     * Determines whether a character is a breaking whitespace (that is, a whitespace which can be
     * interpreted as a break between words for formatting purposes). See {@link #WHITESPACE} for a
     * discussion of that term.
     *
     * @since 2.0
     */
    public static final CharMatcher BREAKING_WHITESPACE = new CharMatcher() {
      @Override
      public boolean matches(char c) {
        switch (c) {
          case '\t':
          case '\n':
          case '\013':
          case '\f':
          case '\r':
          case ' ':
          case '\u0085':
          case '\u1680':
          case '\u2028':
          case '\u2029':
          case '\u205f':
          case '\u3000':
            return true;
          case '\u2007':
            return false;
          default:
            return c >= '\u2000' && c <= '\u200a';
        }
      }
  
      @Override
      public String toString() {
        return "CharMatcher.BREAKING_WHITESPACE";
      }
    };
  
    /**
     * Determines whether a character is ASCII, meaning that its code point is less than 128.
     */
    public static final CharMatcher ASCII = inRange('\0', '\u007f', "CharMatcher.ASCII");
  
   private static class RangesMatcher extends CharMatcher {
     private final char[] rangeStarts;
     private final char[] rangeEnds;
 
     RangesMatcher(String description, char[] rangeStarts, char[] rangeEnds) {
       super(description);
       this.rangeStarts = rangeStarts;
       this.rangeEnds = rangeEnds;
       checkArgument(rangeStarts.length == rangeEnds.length);
       for (int i = 0; i < rangeStarts.length; i++) {
         checkArgument(rangeStarts[i] <= rangeEnds[i]);
         if (i + 1 < rangeStarts.length) {
           checkArgument(rangeEnds[i] < rangeStarts[i + 1]);
         }
       }
     }
 
     @Override
     public boolean matches(char c) {
       int index = Arrays.binarySearch(rangeStarts, c);
       if (index >= 0) {
         return true;
       } else {
         index = ~index - 1;
         return index >= 0 && c <= rangeEnds[index];
       }
     }
   }
 
   // Must be in ascending order.
   private static final String ZEROES = "0\u0660\u06f0\u07c0\u0966\u09e6\u0a66\u0ae6\u0b66\u0be6"
       + "\u0c66\u0ce6\u0d66\u0e50\u0ed0\u0f20\u1040\u1090\u17e0\u1810\u1946\u19d0\u1b50\u1bb0"
       + "\u1c40\u1c50\ua620\ua8d0\ua900\uaa50\uff10";
 
   private static final String NINES;
   static {
     StringBuilder builder = new StringBuilder(ZEROES.length());
     for (int i = 0; i < ZEROES.length(); i++) {
       builder.append((char) (ZEROES.charAt(i) + 9));
     }
     NINES = builder.toString();
   }
 
   /**
    * Determines whether a character is a digit according to
    * <a href="http://unicode.org/cldr/utility/list-unicodeset.jsp?a=%5Cp%7Bdigit%7D">Unicode</a>.
    * If you only care to match ASCII digits, you can use {@code inRange('0', '9')}.
    */
   public static final CharMatcher DIGIT = new RangesMatcher(
       "CharMatcher.DIGIT", ZEROES.toCharArray(), NINES.toCharArray());
 
   /**
    * Determines whether a character is a digit according to {@linkplain Character#isDigit(char)
    * Java's definition}. If you only care to match ASCII digits, you can use {@code
    * inRange('0', '9')}.
    */
   public static final CharMatcher JAVA_DIGIT = new CharMatcher("CharMatcher.JAVA_DIGIT") {
     @Override public boolean matches(char c) {
       return Character.isDigit(c);
     }
   };
 
   /**
    * Determines whether a character is a letter according to {@linkplain Character#isLetter(char)
    * Java's definition}. If you only care to match letters of the Latin alphabet, you can use {@code
    * inRange('a', 'z').or(inRange('A', 'Z'))}.
    */
   public static final CharMatcher JAVA_LETTER = new CharMatcher("CharMatcher.JAVA_LETTER") {
     @Override public boolean matches(char c) {
       return Character.isLetter(c);
     }
   };
 
   /**
    * Determines whether a character is a letter or digit according to {@linkplain
    * Character#isLetterOrDigit(char) Java's definition}.
    */
   public static final CharMatcher JAVA_LETTER_OR_DIGIT =
       new CharMatcher("CharMatcher.JAVA_LETTER_OR_DIGIT") {
     @Override public boolean matches(char c) {
       return Character.isLetterOrDigit(c);
     }
   };
 
   /**
    * Determines whether a character is upper case according to {@linkplain
    * Character#isUpperCase(char) Java's definition}.
    */
   public static final CharMatcher JAVA_UPPER_CASE =
       new CharMatcher("CharMatcher.JAVA_UPPER_CASE") {
     @Override public boolean matches(char c) {
       return Character.isUpperCase(c);
     }
   };
 
   /**
    * Determines whether a character is lower case according to {@linkplain
    * Character#isLowerCase(char) Java's definition}.
    */
   public static final CharMatcher JAVA_LOWER_CASE =
       new CharMatcher("CharMatcher.JAVA_LOWER_CASE") {
     @Override public boolean matches(char c) {
       return Character.isLowerCase(c);
     }
   };
 
   /**
    * Determines whether a character is an ISO control character as specified by {@link
    * Character#isISOControl(char)}.
    */
   public static final CharMatcher JAVA_ISO_CONTROL =
       inRange('\u0000', '\u001f')
       .or(inRange('\u007f', '\u009f'))
       .withToString("CharMatcher.JAVA_ISO_CONTROL");
 
   /**
    * Determines whether a character is invisible; that is, if its Unicode category is any of
    * SPACE_SEPARATOR, LINE_SEPARATOR, PARAGRAPH_SEPARATOR, CONTROL, FORMAT, SURROGATE, and
    * PRIVATE_USE according to ICU4J.
    */
   public static final CharMatcher INVISIBLE = new RangesMatcher("CharMatcher.INVISIBLE", (
       "\u0000\u007f\u00ad\u0600\u061c\u06dd\u070f\u1680\u180e\u2000\u2028\u205f\u2066\u2067\u2068"
       + "\u2069\u206a\u3000\ud800\ufeff\ufff9\ufffa").toCharArray(), (
       "\u0020\u00a0\u00ad\u0604\u061c\u06dd\u070f\u1680\u180e\u200f\u202f\u2064\u2066\u2067\u2068"
       + "\u2069\u206f\u3000\uf8ff\ufeff\ufff9\ufffb").toCharArray());
 
   private static String showCharacter(char c) {
     String hex = "0123456789ABCDEF";
     char[] tmp = {'\\', 'u', '\0', '\0', '\0', '\0'};
     for (int i = 0; i < 4; i++) {
       tmp[5 - i] = hex.charAt(c & 0xF);
       c >>= 4;
     }
     return String.copyValueOf(tmp);
 
   }
 
   /**
    * Determines whether a character is single-width (not double-width). When in doubt, this matcher
    * errs on the side of returning {@code false} (that is, it tends to assume a character is
    * double-width).
    *
    * <p><b>Note:</b> as the reference file evolves, we will modify this constant to keep it up to
    * date.
    */
   public static final CharMatcher SINGLE_WIDTH = new RangesMatcher("CharMatcher.SINGLE_WIDTH",
       "\u0000\u05be\u05d0\u05f3\u0600\u0750\u0e00\u1e00\u2100\ufb50\ufe70\uff61".toCharArray(),
       "\u04f9\u05be\u05ea\u05f4\u06ff\u077f\u0e7f\u20af\u213a\ufdff\ufeff\uffdc".toCharArray());
 
   /** Matches any character. */
   public static final CharMatcher ANY =
       new FastMatcher("CharMatcher.ANY") {
         @Override public boolean matches(char c) {
           return true;
         }
 
         @Override public int indexIn(CharSequence sequence) {
           return (sequence.length() == 0) ? -1 : 0;
         }
 
         @Override public int indexIn(CharSequence sequence, int start) {
           int length = sequence.length();
           Preconditions.checkPositionIndex(start, length);
           return (start == length) ? -1 : start;
         }
 
         @Override public int lastIndexIn(CharSequence sequence) {
           return sequence.length() - 1;
         }
 
         @Override public boolean matchesAllOf(CharSequence sequence) {
           checkNotNull(sequence);
           return true;
         }
 
         @Override public boolean matchesNoneOf(CharSequence sequence) {
           return sequence.length() == 0;
         }
 
         @Override public String removeFrom(CharSequence sequence) {
           checkNotNull(sequence);
           return "";
         }
 
         @Override public String replaceFrom(CharSequence sequence, char replacement) {
           char[] array = new char[sequence.length()];
           Arrays.fill(array, replacement);
           return new String(array);
         }
 
         @Override public String replaceFrom(CharSequence sequence, CharSequence replacement) {
           StringBuilder retval = new StringBuilder(sequence.length() * replacement.length());
           for (int i = 0; i < sequence.length(); i++) {
             retval.append(replacement);
           }
           return retval.toString();
         }
 
         @Override public String collapseFrom(CharSequence sequence, char replacement) {
           return (sequence.length() == 0) ? "" : String.valueOf(replacement);
         }
 
         @Override public String trimFrom(CharSequence sequence) {
           checkNotNull(sequence);
           return "";
         }
 
         @Override public int countIn(CharSequence sequence) {
           return sequence.length();
         }
 
         @Override public CharMatcher and(CharMatcher other) {
           return checkNotNull(other);
         }
 
         @Override public CharMatcher or(CharMatcher other) {
           checkNotNull(other);
           return this;
         }
 
         @Override public CharMatcher negate() {
           return NONE;
         }
       };
 
   /** Matches no characters. */
   public static final CharMatcher NONE =
       new FastMatcher("CharMatcher.NONE") {
         @Override public boolean matches(char c) {
           return false;
         }
 
         @Override public int indexIn(CharSequence sequence) {
           checkNotNull(sequence);
           return -1;
         }
 
         @Override public int indexIn(CharSequence sequence, int start) {
           int length = sequence.length();
           Preconditions.checkPositionIndex(start, length);
           return -1;
         }
 
         @Override public int lastIndexIn(CharSequence sequence) {
           checkNotNull(sequence);
           return -1;
         }
 
         @Override public boolean matchesAllOf(CharSequence sequence) {
           return sequence.length() == 0;
         }
 
         @Override public boolean matchesNoneOf(CharSequence sequence) {
           checkNotNull(sequence);
           return true;
         }
 
         @Override public String removeFrom(CharSequence sequence) {
           return sequence.toString();
         }
 
         @Override public String replaceFrom(CharSequence sequence, char replacement) {
           return sequence.toString();
         }
 
         @Override public String replaceFrom(CharSequence sequence, CharSequence replacement) {
           checkNotNull(replacement);
           return sequence.toString();
         }
 
         @Override public String collapseFrom(CharSequence sequence, char replacement) {
           return sequence.toString();
         }
 
         @Override public String trimFrom(CharSequence sequence) {
           return sequence.toString();
         }
 
         @Override
         public String trimLeadingFrom(CharSequence sequence) {
           return sequence.toString();
         }
 
         @Override
         public String trimTrailingFrom(CharSequence sequence) {
           return sequence.toString();
         }
 
         @Override public int countIn(CharSequence sequence) {
           checkNotNull(sequence);
           return 0;
         }
 
         @Override public CharMatcher and(CharMatcher other) {
           checkNotNull(other);
           return this;
         }
 
         @Override public CharMatcher or(CharMatcher other) {
           return checkNotNull(other);
         }
 
         @Override public CharMatcher negate() {
           return ANY;
         }
       };
 
   // Static factories
 
   /**
    * Returns a {@code char} matcher that matches only one specified character.
    */
   public static CharMatcher is(final char match) {
     String description = "CharMatcher.is('" + showCharacter(match) + "')";
     return new FastMatcher(description) {
       @Override public boolean matches(char c) {
         return c == match;
       }
 
       @Override public String replaceFrom(CharSequence sequence, char replacement) {
         return sequence.toString().replace(match, replacement);
       }
 
       @Override public CharMatcher and(CharMatcher other) {
         return other.matches(match) ? this : NONE;
       }
 
       @Override public CharMatcher or(CharMatcher other) {
         return other.matches(match) ? other : super.or(other);
       }
 
       @Override public CharMatcher negate() {
         return isNot(match);
       }
     };
   }
 
   /**
    * Returns a {@code char} matcher that matches any character except the one specified.
    *
    * <p>To negate another {@code CharMatcher}, use {@link #negate()}.
    */
   public static CharMatcher isNot(final char match) {
     String description = "CharMatcher.isNot('" + showCharacter(match) + "')";
     return new FastMatcher(description) {
       @Override public boolean matches(char c) {
         return c != match;
       }
 
       @Override public CharMatcher and(CharMatcher other) {
         return other.matches(match) ? super.and(other) : other;
       }
 
       @Override public CharMatcher or(CharMatcher other) {
         return other.matches(match) ? ANY : this;
       }
 
       @Override public CharMatcher negate() {
         return is(match);
       }
     };
   }
 
   /**
    * Returns a {@code char} matcher that matches any character present in the given character
    * sequence.
    */
   public static CharMatcher anyOf(final CharSequence sequence) {
     switch (sequence.length()) {
       case 0:
         return NONE;
       case 1:
         return is(sequence.charAt(0));
       case 2:
         return isEither(sequence.charAt(0), sequence.charAt(1));
       default:
         // continue below to handle the general case
     }
     // TODO(user): is it potentially worth just going ahead and building a precomputed matcher?
     final char[] chars = sequence.toString().toCharArray();
     Arrays.sort(chars);
     StringBuilder description = new StringBuilder("CharMatcher.anyOf(\"");
     for (char c : chars) {
       description.append(showCharacter(c));
     }
     description.append("\")");
     return new CharMatcher(description.toString()) {
       @Override public boolean matches(char c) {
         return Arrays.binarySearch(chars, c) >= 0;
       }
     };
   }
 
   private static CharMatcher isEither(
       final char match1,
       final char match2) {
     String description = "CharMatcher.anyOf(\"" +
         showCharacter(match1) + showCharacter(match2) + "\")";
     return new FastMatcher(description) {
       @Override public boolean matches(char c) {
         return c == match1 || c == match2;
       }
     };
   }
 
   /**
    * Returns a {@code char} matcher that matches any character not present in the given character
    * sequence.
    */
   public static CharMatcher noneOf(CharSequence sequence) {
     return anyOf(sequence).negate();
   }
 
   /**
    * Returns a {@code char} matcher that matches any character in a given range (both endpoints are
    * inclusive). For example, to match any lowercase letter of the English alphabet, use {@code
    * CharMatcher.inRange('a', 'z')}.
    *
    * @throws IllegalArgumentException if {@code endInclusive < startInclusive}
    */
   public static CharMatcher inRange(final char startInclusive, final char endInclusive) {
     checkArgument(endInclusive >= startInclusive);
     String description = "CharMatcher.inRange('" +
         showCharacter(startInclusive) + "', '" +
         showCharacter(endInclusive) + "')";
     return inRange(startInclusive, endInclusive, description);
   }
 
   static CharMatcher inRange(final char startInclusive, final char endInclusive,
       String description) {
     return new FastMatcher(description) {
       @Override public boolean matches(char c) {
         return startInclusive <= c && c <= endInclusive;
       }
     };
   }
 
   /**
    * Returns a matcher with identical behavior to the given {@link Character}-based predicate, but
    * which operates on primitive {@code char} instances instead.
    */
   public static CharMatcher forPredicate(final Predicate<? super Character> predicate) {
     checkNotNull(predicate);
     if (predicate instanceof CharMatcher) {
       return (CharMatcher) predicate;
     }
     String description = "CharMatcher.forPredicate(" + predicate + ")";
     return new CharMatcher(description) {
       @Override public boolean matches(char c) {
         return predicate.apply(c);
       }
 
       @Override public boolean apply(Character character) {
         return predicate.apply(checkNotNull(character));
       }
     };
   }
 
   // State
   final String description;
 
   // Constructors
 
   /**
    * Sets the {@code toString()} from the given description.
    */
   CharMatcher(String description) {
     this.description = description;
   }
 
   /**
    * Constructor for use by subclasses. When subclassing, you may want to override
    * {@code toString()} to provide a useful description.
    */
   protected CharMatcher() {
     description = super.toString();
   }
 
   // Abstract methods
 
   /** Determines a true or false value for the given character. */
   public abstract boolean matches(char c);
 
   // Non-static factories
 
   /**
    * Returns a matcher that matches any character not matched by this matcher.
    */
   public CharMatcher negate() {
     return new NegatedMatcher(this);
   }
 
   private static class NegatedMatcher extends CharMatcher {
     final CharMatcher original;
 
     NegatedMatcher(String toString, CharMatcher original) {
       super(toString);
       this.original = original;
     }
 
     NegatedMatcher(CharMatcher original) {
       this(original + ".negate()", original);
     }
 
     @Override public boolean matches(char c) {
       return !original.matches(c);
     }
 
     @Override public boolean matchesAllOf(CharSequence sequence) {
       return original.matchesNoneOf(sequence);
     }
 
     @Override public boolean matchesNoneOf(CharSequence sequence) {
       return original.matchesAllOf(sequence);
     }
 
     @Override public int countIn(CharSequence sequence) {
       return sequence.length() - original.countIn(sequence);
     }
 
     @Override public CharMatcher negate() {
       return original;
     }
 
     @Override
     CharMatcher withToString(String description) {
       return new NegatedMatcher(description, original);
     }
   }
 
   /**
    * Returns a matcher that matches any character matched by both this matcher and {@code other}.
    */
   public CharMatcher and(CharMatcher other) {
     return new And(this, checkNotNull(other));
   }
 
   private static class And extends CharMatcher {
     final CharMatcher first;
     final CharMatcher second;
 
     And(CharMatcher a, CharMatcher b) {
       this(a, b, "CharMatcher.and(" + a + ", " + b + ")");
     }
 
     And(CharMatcher a, CharMatcher b, String description) {
       super(description);
       first = checkNotNull(a);
       second = checkNotNull(b);
     }
 
     @Override
     public boolean matches(char c) {
       return first.matches(c) && second.matches(c);
     }
 
     @Override
     CharMatcher withToString(String description) {
       return new And(first, second, description);
     }
   }
 
   /**
    * Returns a matcher that matches any character matched by either this matcher or {@code other}.
    */
   public CharMatcher or(CharMatcher other) {
     return new Or(this, checkNotNull(other));
   }
 
   private static class Or extends CharMatcher {
     final CharMatcher first;
     final CharMatcher second;
 
     Or(CharMatcher a, CharMatcher b, String description) {
       super(description);
       first = checkNotNull(a);
       second = checkNotNull(b);
     }
 
     Or(CharMatcher a, CharMatcher b) {
       this(a, b, "CharMatcher.or(" + a + ", " + b + ")");
     }
 
     @Override
     public boolean matches(char c) {
       return first.matches(c) || second.matches(c);
     }
 
     @Override
     CharMatcher withToString(String description) {
       return new Or(first, second, description);
     }
   }
 
   /**
    * Returns a {@code char} matcher functionally equivalent to this one, but which may be faster to
    * query than the original; your mileage may vary. Precomputation takes time and is likely to be
    * worthwhile only if the precomputed matcher is queried many thousands of times.
    *
    * <p>This method has no effect (returns {@code this}) when called in GWT: it's unclear whether a
    * precomputed matcher is faster, but it certainly consumes more memory, which doesn't seem like a
    * worthwhile tradeoff in a browser.
    */
   public CharMatcher precomputed() {
     return Platform.precomputeCharMatcher(this);
   }
 
   /**
    * Subclasses should provide a new CharMatcher with the same characteristics as {@code this},
    * but with their {@code toString} method overridden with the new description.
    *
    * <p>This is unsupported by default.
    */
   CharMatcher withToString(String description) {
     throw new UnsupportedOperationException();
   }
 
   private static final int DISTINCT_CHARS = Character.MAX_VALUE - Character.MIN_VALUE + 1;
 
   /**
    * A matcher for which precomputation will not yield any significant benefit.
    */
   abstract static class FastMatcher extends CharMatcher {
     FastMatcher() {
       super();
     }
 
     FastMatcher(String description) {
       super(description);
     }
 
     @Override
     public final CharMatcher precomputed() {
       return this;
     }
 
     @Override
     public CharMatcher negate() {
       return new NegatedFastMatcher(this);
     }
   }
 
   static final class NegatedFastMatcher extends NegatedMatcher {
     NegatedFastMatcher(CharMatcher original) {
       super(original);
     }
 
     NegatedFastMatcher(String toString, CharMatcher original) {
       super(toString, original);
     }
 
     @Override
     public final CharMatcher precomputed() {
       return this;
     }
 
     @Override
     CharMatcher withToString(String description) {
       return new NegatedFastMatcher(description, original);
     }
   }
 
   // Text processing routines
 
   /**
    * Returns {@code true} if a character sequence contains at least one matching character.
    * Equivalent to {@code !matchesNoneOf(sequence)}.
    *
    * <p>The default implementation iterates over the sequence, invoking {@link #matches} for each
    * character, until this returns {@code true} or the end is reached.
    *
    * @param sequence the character sequence to examine, possibly empty
    * @return {@code true} if this matcher matches at least one character in the sequence
    * @since 8.0
    */
   public boolean matchesAnyOf(CharSequence sequence) {
     return !matchesNoneOf(sequence);
   }
 
   /**
    * Returns {@code true} if a character sequence contains only matching characters.
    *
    * <p>The default implementation iterates over the sequence, invoking {@link #matches} for each
    * character, until this returns {@code false} or the end is reached.
    *
    * @param sequence the character sequence to examine, possibly empty
    * @return {@code true} if this matcher matches every character in the sequence, including when
    *         the sequence is empty
    */
   public boolean matchesAllOf(CharSequence sequence) {
     for (int i = sequence.length() - 1; i >= 0; i--) {
       if (!matches(sequence.charAt(i))) {
         return false;
       }
     }
     return true;
   }
 
   /**
    * Returns {@code true} if a character sequence contains no matching characters. Equivalent to
    * {@code !matchesAnyOf(sequence)}.
    *
    * <p>The default implementation iterates over the sequence, invoking {@link #matches} for each
    * character, until this returns {@code false} or the end is reached.
    *
    * @param sequence the character sequence to examine, possibly empty
    * @return {@code true} if this matcher matches every character in the sequence, including when
    *         the sequence is empty
    */
   public boolean matchesNoneOf(CharSequence sequence) {
     return indexIn(sequence) == -1;
   }
 
   /**
    * Returns the index of the first matching character in a character sequence, or {@code -1} if no
    * matching character is present.
    *
    * <p>The default implementation iterates over the sequence in forward order calling {@link
    * #matches} for each character.
    *
    * @param sequence the character sequence to examine from the beginning
    * @return an index, or {@code -1} if no character matches
    */
   public int indexIn(CharSequence sequence) {
     int length = sequence.length();
     for (int i = 0; i < length; i++) {
       if (matches(sequence.charAt(i))) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the index of the first matching character in a character sequence, starting from a
    * given position, or {@code -1} if no character matches after that position.
    *
    * <p>The default implementation iterates over the sequence in forward order, beginning at {@code
    * start}, calling {@link #matches} for each character.
    *
    * @param sequence the character sequence to examine
    * @param start the first index to examine; must be nonnegative and no greater than {@code
    *        sequence.length()}
    * @return the index of the first matching character, guaranteed to be no less than {@code start},
    *         or {@code -1} if no character matches
    * @throws IndexOutOfBoundsException if start is negative or greater than {@code
    *         sequence.length()}
    */
   public int indexIn(CharSequence sequence, int start) {
     int length = sequence.length();
     Preconditions.checkPositionIndex(start, length);
     for (int i = start; i < length; i++) {
       if (matches(sequence.charAt(i))) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the index of the last matching character in a character sequence, or {@code -1} if no
    * matching character is present.
    *
    * <p>The default implementation iterates over the sequence in reverse order calling {@link
    * #matches} for each character.
    *
    * @param sequence the character sequence to examine from the end
    * @return an index, or {@code -1} if no character matches
    */
   public int lastIndexIn(CharSequence sequence) {
     for (int i = sequence.length() - 1; i >= 0; i--) {
       if (matches(sequence.charAt(i))) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the number of matching characters found in a character sequence.
    */
   public int countIn(CharSequence sequence) {
     int count = 0;
     for (int i = 0; i < sequence.length(); i++) {
       if (matches(sequence.charAt(i))) {
         count++;
       }
     }
     return count;
   }
 
   /**
    * Returns a string containing all non-matching characters of a character sequence, in order. For
    * example: <pre>   {@code
    *
    *   CharMatcher.is('a').removeFrom("bazaar")}</pre>
    *
    * ... returns {@code "bzr"}.
    */
   @CheckReturnValue
   public String removeFrom(CharSequence sequence) {
     String string = sequence.toString();
     int pos = indexIn(string);
     if (pos == -1) {
       return string;
     }
 
     char[] chars = string.toCharArray();
     int spread = 1;
 
     // This unusual loop comes from extensive benchmarking
     OUT: while (true) {
       pos++;
       while (true) {
         if (pos == chars.length) {
           break OUT;
         }
         if (matches(chars[pos])) {
           break;
         }
         chars[pos - spread] = chars[pos];
         pos++;
       }
       spread++;
     }
     return new String(chars, 0, pos - spread);
   }
 
   /**
    * Returns a string containing all matching characters of a character sequence, in order. For
    * example: <pre>   {@code
    *
    *   CharMatcher.is('a').retainFrom("bazaar")}</pre>
    *
    * ... returns {@code "aaa"}.
    */
   @CheckReturnValue
   public String retainFrom(CharSequence sequence) {
     return negate().removeFrom(sequence);
   }
 
   /**
    * Returns a string copy of the input character sequence, with each character that matches this
    * matcher replaced by a given replacement character. For example: <pre>   {@code
    *
    *   CharMatcher.is('a').replaceFrom("radar", 'o')}</pre>
    *
    * ... returns {@code "rodor"}.
    *
    * <p>The default implementation uses {@link #indexIn(CharSequence)} to find the first matching
    * character, then iterates the remainder of the sequence calling {@link #matches(char)} for each
    * character.
    *
    * @param sequence the character sequence to replace matching characters in
    * @param replacement the character to append to the result string in place of each matching
    *        character in {@code sequence}
    * @return the new string
    */
   @CheckReturnValue
   public String replaceFrom(CharSequence sequence, char replacement) {
     String string = sequence.toString();
     int pos = indexIn(string);
     if (pos == -1) {
       return string;
     }
     char[] chars = string.toCharArray();
     chars[pos] = replacement;
     for (int i = pos + 1; i < chars.length; i++) {
       if (matches(chars[i])) {
         chars[i] = replacement;
       }
     }
     return new String(chars);
   }
 
   /**
    * Returns a string copy of the input character sequence, with each character that matches this
    * matcher replaced by a given replacement sequence. For example: <pre>   {@code
    *
    *   CharMatcher.is('a').replaceFrom("yaha", "oo")}</pre>
    *
    * ... returns {@code "yoohoo"}.
    *
    * <p><b>Note:</b> If the replacement is a fixed string with only one character, you are better
    * off calling {@link #replaceFrom(CharSequence, char)} directly.
    *
    * @param sequence the character sequence to replace matching characters in
    * @param replacement the characters to append to the result string in place of each matching
    *        character in {@code sequence}
    * @return the new string
    */
   @CheckReturnValue
   public String replaceFrom(CharSequence sequence, CharSequence replacement) {
     int replacementLen = replacement.length();
     if (replacementLen == 0) {
       return removeFrom(sequence);
     }
     if (replacementLen == 1) {
       return replaceFrom(sequence, replacement.charAt(0));
     }
 
     String string = sequence.toString();
     int pos = indexIn(string);
     if (pos == -1) {
       return string;
     }
 
     int len = string.length();
     StringBuilder buf = new StringBuilder((len * 3 / 2) + 16);
 
     int oldpos = 0;
     do {
       buf.append(string, oldpos, pos);
       buf.append(replacement);
       oldpos = pos + 1;
       pos = indexIn(string, oldpos);
     } while (pos != -1);
 
     buf.append(string, oldpos, len);
     return buf.toString();
   }
 
   /**
    * Returns a substring of the input character sequence that omits all characters this matcher
    * matches from the beginning and from the end of the string. For example: <pre>   {@code
    *
    *   CharMatcher.anyOf("ab").trimFrom("abacatbab")}</pre>
    *
    * ... returns {@code "cat"}.
    *
    * <p>Note that: <pre>   {@code
    *
    *   CharMatcher.inRange('\0', ' ').trimFrom(str)}</pre>
    *
    * ... is equivalent to {@link String#trim()}.
    */
   @CheckReturnValue
   public String trimFrom(CharSequence sequence) {
     int len = sequence.length();
     int first;
     int last;
 
     for (first = 0; first < len; first++) {
       if (!matches(sequence.charAt(first))) {
         break;
       }
     }
     for (last = len - 1; last > first; last--) {
       if (!matches(sequence.charAt(last))) {
         break;
       }
     }
 
     return sequence.subSequence(first, last + 1).toString();
   }
 
   /**
    * Returns a substring of the input character sequence that omits all characters this matcher
    * matches from the beginning of the string. For example: <pre> {@code
    *
    *   CharMatcher.anyOf("ab").trimLeadingFrom("abacatbab")}</pre>
    *
    * ... returns {@code "catbab"}.
    */
   @CheckReturnValue
   public String trimLeadingFrom(CharSequence sequence) {
     int len = sequence.length();
     for (int first = 0; first < len; first++) {
       if (!matches(sequence.charAt(first))) {
         return sequence.subSequence(first, len).toString();
       }
     }
     return "";
   }
 
   /**
    * Returns a substring of the input character sequence that omits all characters this matcher
    * matches from the end of the string. For example: <pre> {@code
    *
    *   CharMatcher.anyOf("ab").trimTrailingFrom("abacatbab")}</pre>
    *
    * ... returns {@code "abacat"}.
    */
   @CheckReturnValue
   public String trimTrailingFrom(CharSequence sequence) {
     int len = sequence.length();
     for (int last = len - 1; last >= 0; last--) {
       if (!matches(sequence.charAt(last))) {
         return sequence.subSequence(0, last + 1).toString();
       }
     }
     return "";
   }
 
   /**
    * Returns a string copy of the input character sequence, with each group of consecutive
    * characters that match this matcher replaced by a single replacement character. For example:
    * <pre>   {@code
    *
    *   CharMatcher.anyOf("eko").collapseFrom("bookkeeper", '-')}</pre>
    *
    * ... returns {@code "b-p-r"}.
    *
    * <p>The default implementation uses {@link #indexIn(CharSequence)} to find the first matching
    * character, then iterates the remainder of the sequence calling {@link #matches(char)} for each
    * character.
    *
    * @param sequence the character sequence to replace matching groups of characters in
    * @param replacement the character to append to the result string in place of each group of
    *        matching characters in {@code sequence}
    * @return the new string
    */
   @CheckReturnValue
   public String collapseFrom(CharSequence sequence, char replacement) {
     // This implementation avoids unnecessary allocation.
     int len = sequence.length();
     for (int i = 0; i < len; i++) {
       char c = sequence.charAt(i);
       if (matches(c)) {
         if (c == replacement
             && (i == len - 1 || !matches(sequence.charAt(i + 1)))) {
           // a no-op replacement
           i++;
         } else {
           StringBuilder builder = new StringBuilder(len)
               .append(sequence.subSequence(0, i))
               .append(replacement);
           return finishCollapseFrom(sequence, i + 1, len, replacement, builder, true);
         }
       }
     }
     // no replacement needed
     return sequence.toString();
   }
 
   /**
    * Collapses groups of matching characters exactly as {@link #collapseFrom} does, except that
    * groups of matching characters at the start or end of the sequence are removed without
    * replacement.
    */
   @CheckReturnValue
   public String trimAndCollapseFrom(CharSequence sequence, char replacement) {
     // This implementation avoids unnecessary allocation.
     int len = sequence.length();
     int first;
     int last;
 
     for (first = 0; first < len && matches(sequence.charAt(first)); first++) {}
     for (last = len - 1; last > first && matches(sequence.charAt(last)); last--) {}
 
     return (first == 0 && last == len - 1)
         ? collapseFrom(sequence, replacement)
         : finishCollapseFrom(
               sequence, first, last + 1, replacement,
               new StringBuilder(last + 1 - first),
               false);
   }
 
   private String finishCollapseFrom(
       CharSequence sequence, int start, int end, char replacement,
       StringBuilder builder, boolean inMatchingGroup) {
     for (int i = start; i < end; i++) {
       char c = sequence.charAt(i);
       if (matches(c)) {
         if (!inMatchingGroup) {
           builder.append(replacement);
           inMatchingGroup = true;
         }
       } else {
         builder.append(c);
         inMatchingGroup = false;
       }
     }
     return builder.toString();
   }
 
   /**
    * @deprecated Provided only to satisfy the {@link Predicate} interface; use {@link #matches}
    *     instead.
    */
   @Deprecated
   @Override
   public boolean apply(Character character) {
     return matches(character);
   }
 
   /**
    * Returns a string representation of this {@code CharMatcher}, such as
    * {@code CharMatcher.or(WHITESPACE, JAVA_DIGIT)}.
    */
   @Override
   public String toString() {
     return description;
   }
 
   static final String WHITESPACE_TABLE = ""
       + "\u2002\u3000\r\u0085\u200A\u2005\u2000\u3000"
       + "\u2029\u000B\u3000\u2008\u2003\u205F\u3000\u1680"
       + "\u0009\u0020\u2006\u2001\u202F\u00A0\u000C\u2009"
       + "\u3000\u2004\u3000\u3000\u2028\n\u2007\u3000";
   static final int WHITESPACE_MULTIPLIER = 1682554634;
   static final int WHITESPACE_SHIFT = Integer.numberOfLeadingZeros(WHITESPACE_TABLE.length() - 1);
 
   /**
    * Determines whether a character is whitespace according to the latest Unicode standard, as
    * illustrated
    * <a href="http://unicode.org/cldr/utility/list-unicodeset.jsp?a=%5Cp%7Bwhitespace%7D">here</a>.
    * This is not the same definition used by other Java APIs. (See a
    * <a href="http://spreadsheets.google.com/pub?key=pd8dAQyHbdewRsnE5x5GzKQ">comparison of several
    * definitions of "whitespace"</a>.)
    *
    * <p><b>Note:</b> as the Unicode definition evolves, we will modify this constant to keep it up
    * to date.
    */
   public static final CharMatcher WHITESPACE = new FastMatcher("WHITESPACE") {
     @Override
     public boolean matches(char c) {
       return WHITESPACE_TABLE.charAt((WHITESPACE_MULTIPLIER * c) >>> WHITESPACE_SHIFT) == c;
     }
   };
 }