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   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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 General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.util.regex;
  
  import com.android.icu.util.regex.MatcherNative;
  
  /**
   * An engine that performs match operations on a {@linkplain CharSequence
   * character sequence} by interpreting a {@link Pattern}.
   *
   * <p> A matcher is created from a pattern by invoking the pattern's {@link
   * Pattern#matcher matcher} method.  Once created, a matcher can be used to
   * perform three different kinds of match operations:
   *
   * <ul>
   *
   *   <li><p> The {@link #matches matches} method attempts to match the entire
   *   input sequence against the pattern.  </p></li>
   *
   *   <li><p> The {@link #lookingAt lookingAt} method attempts to match the
   *   input sequence, starting at the beginning, against the pattern.  </p></li>
   *
   *   <li><p> The {@link #find find} method scans the input sequence looking for
   *   the next subsequence that matches the pattern.  </p></li>
   *
   * </ul>
   *
   * <p> Each of these methods returns a boolean indicating success or failure.
   * More information about a successful match can be obtained by querying the
   * state of the matcher.
   *
   * <p> A matcher finds matches in a subset of its input called the
   * <i>region</i>. By default, the region contains all of the matcher's input.
   * The region can be modified via the{@link #region region} method and queried
   * via the {@link #regionStart regionStart} and {@link #regionEnd regionEnd}
   * methods. The way that the region boundaries interact with some pattern
   * constructs can be changed. See {@link #useAnchoringBounds
   * useAnchoringBounds} and {@link #useTransparentBounds useTransparentBounds}
   * for more details.
   *
   * <p> This class also defines methods for replacing matched subsequences with
   * new strings whose contents can, if desired, be computed from the match
   * result.  The {@link #appendReplacement appendReplacement} and {@link
   * #appendTail appendTail} methods can be used in tandem in order to collect
   * the result into an existing string buffer, or the more convenient {@link
   * #replaceAll replaceAll} method can be used to create a string in which every
   * matching subsequence in the input sequence is replaced.
   *
   * <p> The explicit state of a matcher includes the start and end indices of
   * the most recent successful match.  It also includes the start and end
   * indices of the input subsequence captured by each <a
   * href="Pattern.html#cg">capturing group</a> in the pattern as well as a total
   * count of such subsequences.  As a convenience, methods are also provided for
   * returning these captured subsequences in string form.
   *
   * <p> The explicit state of a matcher is initially undefined; attempting to
   * query any part of it before a successful match will cause an {@link
   * IllegalStateException} to be thrown.  The explicit state of a matcher is
   * recomputed by every match operation.
   *
   * <p> The implicit state of a matcher includes the input character sequence as
   * well as the <i>append position</i>, which is initially zero and is updated
   * by the {@link #appendReplacement appendReplacement} method.
   *
   * <p> A matcher may be reset explicitly by invoking its {@link #reset()}
   * method or, if a new input sequence is desired, its {@link
   * #reset(CharSequence) reset(CharSequence)} method.  Resetting a
   * matcher discards its explicit state information and sets the append position
   * to zero.
   *
   * <p> Instances of this class are not safe for use by multiple concurrent
   * threads. </p>
   *
   *
   * @author      Mike McCloskey
   * @author      Mark Reinhold
   * @author      JSR-51 Expert Group
   * @since       1.4
   * @spec        JSR-51
   */
  
  public final class Matcher implements MatchResult {
  
      /**
       * The Pattern object that created this Matcher.
       */
      private Pattern parentPattern;
  
      /**
       * Holds the offsets for the most recent match.
       */
      int[] groups;
  
      /**
       * The range within the sequence that is to be matched (between  0
       * and text.length()).
       */
      int from, to;
  
      /**
       * Holds the input text.
       */
      String text;
  
      /**
       * Reflects whether a match has been found during the most recent find
       * operation.
       */
      private boolean matchFound;
  
      private MatcherNative nativeMatcher;
  
      /**
       * The index of the last position appended in a substitution.
       */
      int appendPos = 0;
  
      /**
       * Holds the original CharSequence for use in {@link #reset}. {@link #text} is used during
       * matching. Note that CharSequence is mutable while String is not, so reset can cause the input
       * to match to change.
       */
      private CharSequence originalInput;
  
      /**
       * If transparentBounds is true then the boundaries of this
       * matcher's region are transparent to lookahead, lookbehind,
       * and boundary matching constructs that try to see beyond them.
       */
      boolean transparentBounds = false;
  
      /**
       * If anchoringBounds is true then the boundaries of this
       * matcher's region match anchors such as ^ and $.
       */
      boolean anchoringBounds = true;
  
      /**
       * All matchers have the state used by Pattern during a match.
       */
      Matcher(Pattern parent, CharSequence text) {
          usePattern(parent);
          reset(text);
      }
  
      /**
       * Returns the pattern that is interpreted by this matcher.
       *
       * @return  The pattern for which this matcher was created
       */
      public Pattern pattern() {
          return parentPattern;
      }
  
      /**
       * Returns the match state of this matcher as a {@link MatchResult}.
       * The result is unaffected by subsequent operations performed upon this
       * matcher.
       *
       * @return  a <code>MatchResult</code> with the state of this matcher
       * @since 1.5
       */
      public MatchResult toMatchResult() {
          ensureMatch();
          return new OffsetBasedMatchResult(text, groups);
      }
  
      /**
        * Changes the <tt>Pattern</tt> that this <tt>Matcher</tt> uses to
        * find matches with.
        *
        * <p> This method causes this matcher to lose information
        * about the groups of the last match that occurred. The
        * matcher's position in the input is maintained and its
        * last append position is unaffected.</p>
        *
        * @param  newPattern
        *         The new pattern used by this matcher
        * @return  This matcher
        * @throws  IllegalArgumentException
        *          If newPattern is <tt>null</tt>
        * @since 1.5
        */
      public Matcher usePattern(Pattern newPattern) {
          if (newPattern == null)
              throw new IllegalArgumentException("Pattern cannot be null");
  
          synchronized (this) {
              // may throw
              nativeMatcher = MatcherNative.create(newPattern.nativePattern);
          }
          parentPattern = newPattern;
  
          if (text != null) {
              resetForInput();
          }
  
          groups = new int[(groupCount() + 1) * 2];
          matchFound = false;
          return this;
      }
  
      /**
       * Resets this matcher.
       *
       * <p> Resetting a matcher discards all of its explicit state information
       * and sets its append position to zero. The matcher's region is set to the
       * default region, which is its entire character sequence. The anchoring
       * and transparency of this matcher's region boundaries are unaffected.
       *
       * @return  This matcher
       */
      public Matcher reset() {
          return reset(originalInput, 0, originalInput.length());
      }
  
      /**
       * Resets this matcher with a new input sequence.
       *
       * <p> Resetting a matcher discards all of its explicit state information
       * and sets its append position to zero.  The matcher's region is set to
       * the default region, which is its entire character sequence.  The
       * anchoring and transparency of this matcher's region boundaries are
       * unaffected.
       *
       * @param  input
       *         The new input character sequence
       *
       * @return  This matcher
       */
      public Matcher reset(CharSequence input) {
          return reset(input, 0, input.length());
      }
  
      /**
       * Returns the start index of the previous match.
       *
       * @return  The index of the first character matched
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       */
      public int start() {
          return start(0);
      }
  
      /**
       * Returns the start index of the subsequence captured by the given group
       * during the previous match operation.
       *
       * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
       * to right, starting at one.  Group zero denotes the entire pattern, so
       * the expression <i>m.</i><tt>start(0)</tt> is equivalent to
       * <i>m.</i><tt>start()</tt>.  </p>
       *
       * @param  group
       *         The index of a capturing group in this matcher's pattern
       *
       * @return  The index of the first character captured by the group,
       *          or <tt>-1</tt> if the match was successful but the group
       *          itself did not match anything
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IndexOutOfBoundsException
       *          If there is no capturing group in the pattern
       *          with the given index
       */
      public int start(int group) {
          ensureMatch();
          if (group < 0 || group > groupCount())
              throw new IndexOutOfBoundsException("No group " + group);
          return groups[group * 2];
      }
  
      /**
       * Returns the start index of the subsequence captured by the given
       * <a href="Pattern.html#groupname">named-capturing group</a> during the
       * previous match operation.
       *
       * @param  name
       *         The name of a named-capturing group in this matcher's pattern
       *
       * @return  The index of the first character captured by the group,
       *          or {@code -1} if the match was successful but the group
       *          itself did not match anything
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IllegalArgumentException
       *          If there is no capturing group in the pattern
       *          with the given name
       * @since 1.8
       */
      public int start(String name) {
          return groups[getMatchedGroupIndex(name) * 2];
      }
  
      /**
       * Returns the offset after the last character matched.
       *
       * @return  The offset after the last character matched
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       */
      public int end() {
          return end(0);
      }
  
      /**
       * Returns the offset after the last character of the subsequence
       * captured by the given group during the previous match operation.
       *
       * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
       * to right, starting at one.  Group zero denotes the entire pattern, so
       * the expression <i>m.</i><tt>end(0)</tt> is equivalent to
       * <i>m.</i><tt>end()</tt>.  </p>
       *
       * @param  group
       *         The index of a capturing group in this matcher's pattern
       *
       * @return  The offset after the last character captured by the group,
       *          or <tt>-1</tt> if the match was successful
       *          but the group itself did not match anything
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IndexOutOfBoundsException
       *          If there is no capturing group in the pattern
       *          with the given index
       */
      public int end(int group) {
          ensureMatch();
          if (group < 0 || group > groupCount())
              throw new IndexOutOfBoundsException("No group " + group);
          return groups[group * 2 + 1];
      }
  
      /**
       * Returns the offset after the last character of the subsequence
       * captured by the given <a href="Pattern.html#groupname">named-capturing
       * group</a> during the previous match operation.
       *
       * @param  name
       *         The name of a named-capturing group in this matcher's pattern
       *
       * @return  The offset after the last character captured by the group,
       *          or {@code -1} if the match was successful
       *          but the group itself did not match anything
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IllegalArgumentException
       *          If there is no capturing group in the pattern
       *          with the given name
       * @since 1.8
       */
      public int end(String name) {
          return groups[getMatchedGroupIndex(name) * 2 + 1];
      }
  
      /**
       * Returns the input subsequence matched by the previous match.
       *
       * <p> For a matcher <i>m</i> with input sequence <i>s</i>,
       * the expressions <i>m.</i><tt>group()</tt> and
       * <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(),</tt>&nbsp;<i>m.</i><tt>end())</tt>
       * are equivalent.  </p>
       *
       * <p> Note that some patterns, for example <tt>a*</tt>, match the empty
       * string.  This method will return the empty string when the pattern
       * successfully matches the empty string in the input.  </p>
       *
       * @return The (possibly empty) subsequence matched by the previous match,
       *         in string form
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       */
      public String group() {
          return group(0);
      }
  
      /**
       * Returns the input subsequence captured by the given group during the
       * previous match operation.
       *
       * <p> For a matcher <i>m</i>, input sequence <i>s</i>, and group index
       * <i>g</i>, the expressions <i>m.</i><tt>group(</tt><i>g</i><tt>)</tt> and
       * <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(</tt><i>g</i><tt>),</tt>&nbsp;<i>m.</i><tt>end(</tt><i>g</i><tt>))</tt>
       * are equivalent.  </p>
       *
       * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
       * to right, starting at one.  Group zero denotes the entire pattern, so
       * the expression <tt>m.group(0)</tt> is equivalent to <tt>m.group()</tt>.
       * </p>
       *
       * <p> If the match was successful but the group specified failed to match
       * any part of the input sequence, then <tt>null</tt> is returned. Note
       * that some groups, for example <tt>(a*)</tt>, match the empty string.
       * This method will return the empty string when such a group successfully
       * matches the empty string in the input.  </p>
       *
       * @param  group
       *         The index of a capturing group in this matcher's pattern
       *
       * @return  The (possibly empty) subsequence captured by the group
       *          during the previous match, or <tt>null</tt> if the group
       *          failed to match part of the input
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IndexOutOfBoundsException
       *          If there is no capturing group in the pattern
       *          with the given index
       */
      public String group(int group) {
          ensureMatch();
          if (group < 0 || group > groupCount())
              throw new IndexOutOfBoundsException("No group " + group);
          if ((groups[group*2] == -1) || (groups[group*2+1] == -1))
              return null;
          return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
      }
  
      /**
       * Returns the input subsequence captured by the given
       * <a href="Pattern.html#groupname">named-capturing group</a> during the previous
       * match operation.
       *
       * <p> If the match was successful but the group specified failed to match
       * any part of the input sequence, then <tt>null</tt> is returned. Note
       * that some groups, for example <tt>(a*)</tt>, match the empty string.
       * This method will return the empty string when such a group successfully
       * matches the empty string in the input.  </p>
       *
       * @param  name
       *         The name of a named-capturing group in this matcher's pattern
       *
       * @return  The (possibly empty) subsequence captured by the named group
       *          during the previous match, or <tt>null</tt> if the group
       *          failed to match part of the input
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IllegalArgumentException
       *          If there is no capturing group in the pattern
       *          with the given name
       * @since 1.7
       */
      public String group(String name) {
          int group = getMatchedGroupIndex(name);
          if ((groups[group*2] == -1) || (groups[group*2+1] == -1))
              return null;
          return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
      }
  
      /**
       * Returns the number of capturing groups in this matcher's pattern.
       *
       * <p> Group zero denotes the entire pattern by convention. It is not
       * included in this count.
       *
       * <p> Any non-negative integer smaller than or equal to the value
       * returned by this method is guaranteed to be a valid group index for
       * this matcher.  </p>
       *
       * @return The number of capturing groups in this matcher's pattern
       */
      public int groupCount() {
          synchronized (this) {
              return nativeMatcher.groupCount();
          }
      }
  
      /**
       * Attempts to match the entire region against the pattern.
       *
       * <p> If the match succeeds then more information can be obtained via the
       * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
       *
       * @return  <tt>true</tt> if, and only if, the entire region sequence
       *          matches this matcher's pattern
       */
      public boolean matches() {
          synchronized (this) {
              matchFound = nativeMatcher.matches(groups);
          }
          return matchFound;
      }
  
      /**
       * Attempts to find the next subsequence of the input sequence that matches
       * the pattern.
       *
       * <p> This method starts at the beginning of this matcher's region, or, if
       * a previous invocation of the method was successful and the matcher has
       * not since been reset, at the first character not matched by the previous
       * match.
       *
       * <p> If the match succeeds then more information can be obtained via the
       * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
       *
       * @return  <tt>true</tt> if, and only if, a subsequence of the input
       *          sequence matches this matcher's pattern
       */
      public boolean find() {
          synchronized (this) {
              matchFound = nativeMatcher.findNext(groups);
          }
          return matchFound;
      }
  
      /**
       * Resets this matcher and then attempts to find the next subsequence of
       * the input sequence that matches the pattern, starting at the specified
       * index.
       *
       * <p> If the match succeeds then more information can be obtained via the
       * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods, and subsequent
       * invocations of the {@link #find()} method will start at the first
       * character not matched by this match.  </p>
       *
       * @param start the index to start searching for a match
       * @throws  IndexOutOfBoundsException
       *          If start is less than zero or if start is greater than the
       *          length of the input sequence.
       *
       * @return  <tt>true</tt> if, and only if, a subsequence of the input
       *          sequence starting at the given index matches this matcher's
       *          pattern
       */
      public boolean find(int start) {
          int limit = getTextLength();
          if ((start < 0) || (start > limit))
              throw new IndexOutOfBoundsException("Illegal start index");
          reset();
          synchronized (this) {
              matchFound = nativeMatcher.find(start, groups);
          }
          return matchFound;
      }
  
      /**
       * Attempts to match the input sequence, starting at the beginning of the
       * region, against the pattern.
       *
       * <p> Like the {@link #matches matches} method, this method always starts
       * at the beginning of the region; unlike that method, it does not
       * require that the entire region be matched.
       *
       * <p> If the match succeeds then more information can be obtained via the
       * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
       *
       * @return  <tt>true</tt> if, and only if, a prefix of the input
       *          sequence matches this matcher's pattern
       */
      public boolean lookingAt() {
          synchronized (this) {
              matchFound = nativeMatcher.lookingAt(groups);
          }
          return matchFound;
      }
  
      /**
       * Returns a literal replacement <code>String</code> for the specified
       * <code>String</code>.
       *
       * This method produces a <code>String</code> that will work
       * as a literal replacement <code>s</code> in the
       * <code>appendReplacement</code> method of the {@link Matcher} class.
       * The <code>String</code> produced will match the sequence of characters
       * in <code>s</code> treated as a literal sequence. Slashes ('\') and
       * dollar signs ('$') will be given no special meaning.
       *
       * @param  s The string to be literalized
       * @return  A literal string replacement
       * @since 1.5
       */
      public static String quoteReplacement(String s) {
          if ((s.indexOf('\\') == -1) && (s.indexOf('$') == -1))
              return s;
          StringBuilder sb = new StringBuilder();
          for (int i=0; i<s.length(); i++) {
              char c = s.charAt(i);
              if (c == '\\' || c == '$') {
                  sb.append('\\');
              }
              sb.append(c);
          }
          return sb.toString();
      }
  
      /**
       * Implements a non-terminal append-and-replace step.
       *
       * <p> This method performs the following actions: </p>
       *
       * <ol>
       *
       *   <li><p> It reads characters from the input sequence, starting at the
       *   append position, and appends them to the given string buffer.  It
       *   stops after reading the last character preceding the previous match,
       *   that is, the character at index {@link
       *   #start()}&nbsp;<tt>-</tt>&nbsp;<tt>1</tt>.  </p></li>
       *
       *   <li><p> It appends the given replacement string to the string buffer.
       *   </p></li>
       *
       *   <li><p> It sets the append position of this matcher to the index of
       *   the last character matched, plus one, that is, to {@link #end()}.
       *   </p></li>
       *
       * </ol>
       *
       * <p> The replacement string may contain references to subsequences
       * captured during the previous match: Each occurrence of
       * <tt>${</tt><i>name</i><tt>}</tt> or <tt>$</tt><i>g</i>
       * will be replaced by the result of evaluating the corresponding
       * {@link #group(String) group(name)} or {@link #group(int) group(g)}
       * respectively. For  <tt>$</tt><i>g</i>,
       * the first number after the <tt>$</tt> is always treated as part of
       * the group reference. Subsequent numbers are incorporated into g if
       * they would form a legal group reference. Only the numerals '0'
       * through '9' are considered as potential components of the group
       * reference. If the second group matched the string <tt>"foo"</tt>, for
       * example, then passing the replacement string <tt>"$2bar"</tt> would
       * cause <tt>"foobar"</tt> to be appended to the string buffer. A dollar
       * sign (<tt>$</tt>) may be included as a literal in the replacement
       * string by preceding it with a backslash (<tt>\$</tt>).
       *
       * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
       * the replacement string may cause the results to be different than if it
       * were being treated as a literal replacement string. Dollar signs may be
       * treated as references to captured subsequences as described above, and
       * backslashes are used to escape literal characters in the replacement
       * string.
       *
       * <p> This method is intended to be used in a loop together with the
       * {@link #appendTail appendTail} and {@link #find find} methods.  The
       * following code, for example, writes <tt>one dog two dogs in the
       * yard</tt> to the standard-output stream: </p>
       *
       * <blockquote><pre>
       * Pattern p = Pattern.compile("cat");
       * Matcher m = p.matcher("one cat two cats in the yard");
       * StringBuffer sb = new StringBuffer();
       * while (m.find()) {
       *     m.appendReplacement(sb, "dog");
       * }
       * m.appendTail(sb);
       * System.out.println(sb.toString());</pre></blockquote>
       *
       * @param  sb
       *         The target string buffer
       *
       * @param  replacement
       *         The replacement string
       *
       * @return  This matcher
       *
       * @throws  IllegalStateException
       *          If no match has yet been attempted,
       *          or if the previous match operation failed
       *
       * @throws  IllegalArgumentException
       *          If the replacement string refers to a named-capturing
       *          group that does not exist in the pattern
       *
       * @throws  IndexOutOfBoundsException
       *          If the replacement string refers to a capturing group
       *          that does not exist in the pattern
       */
      public Matcher appendReplacement(StringBuffer sb, String replacement) {
  
          sb.append(text.substring(appendPos, start()));
          appendEvaluated(sb, replacement);
          appendPos = end();
  
          return this;
      }
  
      /**
       * Internal helper method to append a given string to a given string buffer.
       * If the string contains any references to groups, these are replaced by
       * the corresponding group's contents.
       *
       * @param buffer the string buffer.
       * @param s the string to append.
       */
      private void appendEvaluated(StringBuffer buffer, String s) {
          boolean escape = false;
          boolean dollar = false;
          boolean escapeNamedGroup = false;
          int escapeNamedGroupStart = -1;
  
          for (int i = 0; i < s.length(); i++) {
              char c = s.charAt(i);
              if (c == '\\' && !escape) {
                  escape = true;
              } else if (c == '$' && !escape) {
                  dollar = true;
              } else if (c >= '0' && c <= '9' && dollar && !escapeNamedGroup) {
                  String groupValue = group(c - '0');
                  if (groupValue != null) {
                      buffer.append(groupValue);
                  }
                  dollar = false;
              } else if (c == '{' && dollar) {
                  escapeNamedGroup = true;
                  escapeNamedGroupStart = i;
              } else if (c == '}' && dollar && escapeNamedGroup) {
                  String groupValue = group(s.substring(escapeNamedGroupStart + 1, i));
                  if (groupValue != null) {
                      buffer.append(groupValue);
                  }
                  dollar = false;
                  escapeNamedGroup = false;
              } else if (c != '}' && dollar && escapeNamedGroup) {
                  continue;
              } else {
                  buffer.append(c);
                  dollar = false;
                  escape = false;
                  escapeNamedGroup = false;
              }
          }
  
          if (escape) {
              throw new IllegalArgumentException("character to be escaped is missing");
          }
  
          if (dollar) {
              throw new IllegalArgumentException("Illegal group reference: group index is missing");
          }
  
          if (escapeNamedGroup) {
              throw new IllegalArgumentException("Missing ending brace '}' from replacement string");
          }
      }
  
      /**
       * Implements a terminal append-and-replace step.
       *
       * <p> This method reads characters from the input sequence, starting at
       * the append position, and appends them to the given string buffer.  It is
       * intended to be invoked after one or more invocations of the {@link
       * #appendReplacement appendReplacement} method in order to copy the
       * remainder of the input sequence.  </p>
       *
       * @param  sb
       *         The target string buffer
       *
       * @return  The target string buffer
       */
      public StringBuffer appendTail(StringBuffer sb) {
          if (appendPos < to) {
              sb.append(text.substring(appendPos, to));
          }
          return sb;
      }
  
      /**
       * Replaces every subsequence of the input sequence that matches the
       * pattern with the given replacement string.
       *
       * <p> This method first resets this matcher.  It then scans the input
       * sequence looking for matches of the pattern.  Characters that are not
       * part of any match are appended directly to the result string; each match
       * is replaced in the result by the replacement string.  The replacement
       * string may contain references to captured subsequences as in the {@link
       * #appendReplacement appendReplacement} method.
       *
       * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
       * the replacement string may cause the results to be different than if it
       * were being treated as a literal replacement string. Dollar signs may be
       * treated as references to captured subsequences as described above, and
       * backslashes are used to escape literal characters in the replacement
       * string.
       *
       * <p> Given the regular expression <tt>a*b</tt>, the input
       * <tt>"aabfooaabfooabfoob"</tt>, and the replacement string
       * <tt>"-"</tt>, an invocation of this method on a matcher for that
       * expression would yield the string <tt>"-foo-foo-foo-"</tt>.
       *
       * <p> Invoking this method changes this matcher's state.  If the matcher
       * is to be used in further matching operations then it should first be
       * reset.  </p>
       *
       * @param  replacement
       *         The replacement string
       *
       * @return  The string constructed by replacing each matching subsequence
       *          by the replacement string, substituting captured subsequences
       *          as needed
       */
      public String replaceAll(String replacement) {
          reset();
          boolean result = find();
          if (result) {
              StringBuffer sb = new StringBuffer();
              do {
                  appendReplacement(sb, replacement);
                  result = find();
              } while (result);
              appendTail(sb);
              return sb.toString();
          }
          return text.toString();
      }
  
      /**
       * Replaces the first subsequence of the input sequence that matches the
       * pattern with the given replacement string.
       *
       * <p> This method first resets this matcher.  It then scans the input
       * sequence looking for a match of the pattern.  Characters that are not
       * part of the match are appended directly to the result string; the match
       * is replaced in the result by the replacement string.  The replacement
       * string may contain references to captured subsequences as in the {@link
       * #appendReplacement appendReplacement} method.
       *
       * <p>Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
       * the replacement string may cause the results to be different than if it
       * were being treated as a literal replacement string. Dollar signs may be
       * treated as references to captured subsequences as described above, and
       * backslashes are used to escape literal characters in the replacement
       * string.
       *
       * <p> Given the regular expression <tt>dog</tt>, the input
       * <tt>"zzzdogzzzdogzzz"</tt>, and the replacement string
       * <tt>"cat"</tt>, an invocation of this method on a matcher for that
       * expression would yield the string <tt>"zzzcatzzzdogzzz"</tt>.  </p>
       *
       * <p> Invoking this method changes this matcher's state.  If the matcher
       * is to be used in further matching operations then it should first be
       * reset.  </p>
       *
       * @param  replacement
       *         The replacement string
       * @return  The string constructed by replacing the first matching
       *          subsequence by the replacement string, substituting captured
       *          subsequences as needed
       */
      public String replaceFirst(String replacement) {
          if (replacement == null)
              throw new NullPointerException("replacement");
          reset();
          if (!find())
              return text.toString();
          StringBuffer sb = new StringBuffer();
          appendReplacement(sb, replacement);
          appendTail(sb);
          return sb.toString();
      }
  
      /**
       * Sets the limits of this matcher's region. The region is the part of the
       * input sequence that will be searched to find a match. Invoking this
       * method resets the matcher, and then sets the region to start at the
       * index specified by the <code>start</code> parameter and end at the
       * index specified by the <code>end</code> parameter.
       *
       * <p>Depending on the transparency and anchoring being used (see
       * {@link #useTransparentBounds useTransparentBounds} and
       * {@link #useAnchoringBounds useAnchoringBounds}), certain constructs such
       * as anchors may behave differently at or around the boundaries of the
       * region.
       *
       * @param  start
       *         The index to start searching at (inclusive)
       * @param  end
       *         The index to end searching at (exclusive)
       * @throws  IndexOutOfBoundsException
       *          If start or end is less than zero, if
       *          start is greater than the length of the input sequence, if
       *          end is greater than the length of the input sequence, or if
       *          start is greater than end.
       * @return  this matcher
       * @since 1.5
       */
      public Matcher region(int start, int end) {
          return reset(originalInput, start, end);
      }
  
      /**
       * Reports the start index of this matcher's region. The
       * searches this matcher conducts are limited to finding matches
       * within {@link #regionStart regionStart} (inclusive) and
       * {@link #regionEnd regionEnd} (exclusive).
       *
       * @return  The starting point of this matcher's region
       * @since 1.5
       */
      public int regionStart() {
          return from;
      }
  
      /**
       * Reports the end index (exclusive) of this matcher's region.
       * The searches this matcher conducts are limited to finding matches
       * within {@link #regionStart regionStart} (inclusive) and
       * {@link #regionEnd regionEnd} (exclusive).
       *
       * @return  the ending point of this matcher's region
       * @since 1.5
       */
      public int regionEnd() {
          return to;
      }
  
      /**
       * Queries the transparency of region bounds for this matcher.
       *
       * <p> This method returns <tt>true</tt> if this matcher uses
       * <i>transparent</i> bounds, <tt>false</tt> if it uses <i>opaque</i>
       * bounds.
       *
       * <p> See {@link #useTransparentBounds useTransparentBounds} for a
       * description of transparent and opaque bounds.
       *
       * <p> By default, a matcher uses opaque region boundaries.
       *
       * @return <tt>true</tt> iff this matcher is using transparent bounds,
       *         <tt>false</tt> otherwise.
       * @see Matcher#useTransparentBounds(boolean)
       * @since 1.5
       */
      public boolean hasTransparentBounds() {
          return transparentBounds;
      }
  
      /**
       * Sets the transparency of region bounds for this matcher.
       *
       * <p> Invoking this method with an argument of <tt>true</tt> will set this
       * matcher to use <i>transparent</i> bounds. If the boolean
       * argument is <tt>false</tt>, then <i>opaque</i> bounds will be used.
       *
       * <p> Using transparent bounds, the boundaries of this
       * matcher's region are transparent to lookahead, lookbehind,
       * and boundary matching constructs. Those constructs can see beyond the
       * boundaries of the region to see if a match is appropriate.
       *
       * <p> Using opaque bounds, the boundaries of this matcher's
       * region are opaque to lookahead, lookbehind, and boundary matching
       * constructs that may try to see beyond them. Those constructs cannot
       * look past the boundaries so they will fail to match anything outside
       * of the region.
       *
       * <p> By default, a matcher uses opaque bounds.
       *
       * @param  b a boolean indicating whether to use opaque or transparent
       *         regions
       * @return this matcher
       * @see Matcher#hasTransparentBounds
       * @since 1.5
       */
      public Matcher useTransparentBounds(boolean b) {
          synchronized (this) {
              transparentBounds = b;
              nativeMatcher.useTransparentBounds(b);
          }
          return this;
      }
  
      /**
       * Queries the anchoring of region bounds for this matcher.
       *
       * <p> This method returns <tt>true</tt> if this matcher uses
       * <i>anchoring</i> bounds, <tt>false</tt> otherwise.
       *
       * <p> See {@link #useAnchoringBounds useAnchoringBounds} for a
       * description of anchoring bounds.
       *
       * <p> By default, a matcher uses anchoring region boundaries.
       *
       * @return <tt>true</tt> iff this matcher is using anchoring bounds,
       *         <tt>false</tt> otherwise.
       * @see Matcher#useAnchoringBounds(boolean)
       * @since 1.5
       */
      public boolean hasAnchoringBounds() {
          return anchoringBounds;
      }
  
      /**
       * Sets the anchoring of region bounds for this matcher.
       *
       * <p> Invoking this method with an argument of <tt>true</tt> will set this
       * matcher to use <i>anchoring</i> bounds. If the boolean
       * argument is <tt>false</tt>, then <i>non-anchoring</i> bounds will be
       * used.
       *
       * <p> Using anchoring bounds, the boundaries of this
       * matcher's region match anchors such as ^ and $.
       *
       * <p> Without anchoring bounds, the boundaries of this
       * matcher's region will not match anchors such as ^ and $.
       *
       * <p> By default, a matcher uses anchoring region boundaries.
       *
       * @param  b a boolean indicating whether or not to use anchoring bounds.
       * @return this matcher
       * @see Matcher#hasAnchoringBounds
       * @since 1.5
       */
      public Matcher useAnchoringBounds(boolean b) {
          synchronized (this) {
              anchoringBounds = b;
              nativeMatcher.useAnchoringBounds(b);
          }
          return this;
      }
  
      /**
       * <p>Returns the string representation of this matcher. The
       * string representation of a <code>Matcher</code> contains information
       * that may be useful for debugging. The exact format is unspecified.
       *
       * @return  The string representation of this matcher
       * @since 1.5
       */
      public String toString() {
          StringBuilder sb = new StringBuilder();
          sb.append("java.util.regex.Matcher");
          sb.append("[pattern=" + pattern());
          sb.append(" region=");
          sb.append(regionStart() + "," + regionEnd());
          sb.append(" lastmatch=");
          if (matchFound && (group() != null)) {
              sb.append(group());
          }
          sb.append("]");
          return sb.toString();
      }
  
      /**
       * <p>Returns true if the end of input was hit by the search engine in
       * the last match operation performed by this matcher.
       *
       * <p>When this method returns true, then it is possible that more input
       * would have changed the result of the last search.
       *
       * @return  true iff the end of input was hit in the last match; false
       *          otherwise
       * @since 1.5
       */
      public boolean hitEnd() {
          synchronized (this) {
              return nativeMatcher.hitEnd();
          }
      }
  
      /**
       * <p>Returns true if more input could change a positive match into a
       * negative one.
       *
       * <p>If this method returns true, and a match was found, then more
       * input could cause the match to be lost. If this method returns false
       * and a match was found, then more input might change the match but the
       * match won't be lost. If a match was not found, then requireEnd has no
       * meaning.
       *
       * @return  true iff more input could change a positive match into a
       *          negative one.
       * @since 1.5
       */
      public boolean requireEnd() {
          synchronized (this) {
              return nativeMatcher.requireEnd();
          }
      }
  
      /**
       * Returns the end index of the text.
       *
       * @return the index after the last character in the text
       */
      int getTextLength() {
          return text.length();
      }
  
      /**
       * Generates a String from this Matcher's input in the specified range.
       *
       * @param  beginIndex   the beginning index, inclusive
       * @param  endIndex     the ending index, exclusive
       * @return A String generated from this Matcher's input
       */
      CharSequence getSubSequence(int beginIndex, int endIndex) {
          return text.subSequence(beginIndex, endIndex);
      }
  
      /**
       * Resets the Matcher. A new input sequence and a new region can be
       * specified. Results of a previous find get lost. The next attempt to find
       * an occurrence of the Pattern in the string will start at the beginning of
       * the region. This is the internal version of reset() to which the several
       * public versions delegate.
       *
       * @param input
       *            the input sequence.
       * @param start
       *            the start of the region.
       * @param end
       *            the end of the region.
       *
       * @return the matcher itself.
       */
      private Matcher reset(CharSequence input, int start, int end) {
          if (input == null) {
              throw new IllegalArgumentException("input == null");
          }
  
          if (start < 0 || end < 0 || start > input.length() || end > input.length() || start > end) {
              throw new IndexOutOfBoundsException();
          }
  
          this.originalInput = input;
          this.text = input.toString();
          this.from = start;
          this.to = end;
          resetForInput();
  
          matchFound = false;
          appendPos = 0;
  
          return this;
      }
  
      private void resetForInput() {
          synchronized (this) {
              nativeMatcher.setInput(text, from, to);
              nativeMatcher.useAnchoringBounds(anchoringBounds);
              nativeMatcher.useTransparentBounds(transparentBounds);
          }
      }
  
      /**
       * Makes sure that a successful match has been made. Is invoked internally
       * from various places in the class.
       *
       * @throws IllegalStateException
       *             if no successful match has been made.
       */
      private void ensureMatch() {
          if (!matchFound) {
              throw new IllegalStateException("No successful match so far");
          }
      }
  
      private int getMatchedGroupIndex(String name) {
          ensureMatch();
          int result = nativeMatcher.getMatchedGroupIndex(name);
          if (result < 0) {
              throw new IllegalArgumentException("No capturing group in the pattern " +
                                                 "with the name " + name);
          }
          return result;
      }
  
      /**
       * A trivial match result implementation that's based on an array of integers
       * representing match offsets. The array is of the form
       * {@code { start1, end1, start2, end2 ....}) where each consecutive pair of elements represents
       * the start and end of a match respectively.
       */
      static final class OffsetBasedMatchResult implements MatchResult {
          private final String input;
          private final int[] offsets;
  
          OffsetBasedMatchResult(String input, int[] offsets) {
              this.input = input;
              this.offsets = offsets.clone();
          }
  
          @Override
          public int start() {
              return start(0);
          }
  
          @Override
          public int start(int group) {
              return offsets[2 * group];
          }
  
          @Override
          public int end() {
              return end(0);
          }
  
          @Override
          public int end(int group) {
              return offsets[2 * group + 1];
          }
  
          @Override
          public String group() {
              return group(0);
          }
  
          @Override
          public String group(int group) {
              final int start = start(group);
              final int end = end(group);
              if (start == -1 || end == -1) {
                  return null;
              }
  
              return input.substring(start, end);
          }
  
          @Override
          public int groupCount() {
              return (offsets.length / 2) - 1;
          }
      }
  }
  