content: /*
   * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
   * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
   */
  
  package cn.edu.nju.moon.redos.regex;
  
  import java.util.Objects;
  import java.util.regex.MatchResult;
  
  import cn.edu.nju.moon.redos.Trace;
  
  // We modify some function for instrumentation
  public final class ReScueMatcher implements MatchResult {
  
      /**
       * The Pattern object that created this Matcher.
       */
      ReScuePattern parentPattern;
  
      /**
       * The storage used by groups. They may contain invalid values if
       * a group was skipped during the matching.
       */
      int[] groups;
  
      /**
       * The range within the sequence that is to be matched. Anchors
       * will match at these "hard" boundaries. Changing the region
       * changes these values.
       */
      int from, to;
  
      /**
       * Lookbehind uses this value to ensure that the subexpression
       * match ends at the point where the lookbehind was encountered.
       */
      int lookbehindTo;
  
      /**
       * The original string being matched.
       */
      CharSequence text;
  
      /**
       * Matcher state used by the last node. NOANCHOR is used when a
       * match does not have to consume all of the input. ENDANCHOR is
       * the mode used for matching all the input.
       */
      static final int ENDANCHOR = 1;
      static final int NOANCHOR = 0;
      int acceptMode = NOANCHOR;
  
      /**
       * The range of string that last matched the pattern. If the last
       * match failed then first is -1; last initially holds 0 then it
       * holds the index of the end of the last match (which is where the
       * next search starts).
       */
      int first = -1, last = 0;
  
      /**
       * The end index of what matched in the last match operation.
       */
      int oldLast = -1;
  
      /**
       * The index of the last position appended in a substitution.
       */
      int lastAppendPosition = 0;
  
      /**
       * Storage used by nodes to tell what repetition they are on in
       * a pattern, and where groups begin. The nodes themselves are stateless,
       * so they rely on this field to hold state during a match.
       */
      int[] locals;
  
      /**
       * Boolean indicating whether or not more input could change
       * the results of the last match.
       *
       * If hitEnd is true, and a match was found, then more input
       * might cause a different match to be found.
       * If hitEnd is true and a match was not found, then more
       * input could cause a match to be found.
       * If hitEnd is false and a match was found, then more input
       * will not change the match.
       * If hitEnd is false and a match was not found, then more
       * input will not cause a match to be found.
       */
      boolean hitEnd;
  
      /**
       * Boolean indicating whether or not more input could change
       * a positive match into a negative one.
       *
       * If requireEnd is true, and a match was found, then more
       * input could cause the match to be lost.
       * If requireEnd is 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.
       */
      boolean requireEnd;
  
      /**
       * 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;
  
      // @pGREAT The Trace should be record here.
      private Trace trace;
      
      /**
       * No default constructor.
       */
      ReScueMatcher() {
      }
  
      /**
       * All matchers have the state used by Pattern during a match.
       */
      ReScueMatcher(ReScuePattern parent, CharSequence text, Trace trace) {
          this.parentPattern = parent;
          this.text = text;
  
          // Allocate state storage
          int parentGroupCount = Math.max(parent.capturingGroupCount, 10);
          groups = new int[parentGroupCount * 2];
          locals = new int[parent.localCount];
  
          // Put fields into initial states
          reset();
          
          // @pGREAT Initiate trace here
          this.trace = trace;
          this.trace.setStr(text.toString());
  //        System.out.print(text.toString());
  //        trace = new Trace(text.toString());
      }
  
      /**
       * Returns the pattern that is interpreted by this matcher.
       *
       * @return  The pattern for which this matcher was created
       */
      public ReScuePattern 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() {
          ReScueMatcher result = new ReScueMatcher(this.parentPattern, text.toString(), this.trace);
          result.first = this.first;
          result.last = this.last;
          result.groups = this.groups.clone();
          return result;
      }
  
      /**
        * 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 ReScueMatcher usePattern(ReScuePattern newPattern) {
          if (newPattern == null)
              throw new IllegalArgumentException("Pattern cannot be null");
          parentPattern = newPattern;
  
          // Reallocate state storage
          int parentGroupCount = Math.max(newPattern.capturingGroupCount, 10);
          groups = new int[parentGroupCount * 2];
          locals = new int[newPattern.localCount];
          for (int i = 0; i < groups.length; i++)
              groups[i] = -1;
          for (int i = 0; i < locals.length; i++)
              locals[i] = -1;
          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 ReScueMatcher reset() {
          first = -1;
          last = 0;
          oldLast = -1;
          for(int i=0; i<groups.length; i++)
              groups[i] = -1;
          for(int i=0; i<locals.length; i++)
              locals[i] = -1;
          lastAppendPosition = 0;
          from = 0;
          to = getTextLength();
          return this;
      }
  
      /**
       * 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 ReScueMatcher reset(CharSequence input) {
          text = input;
          return reset();
      }
  
      /**
       * 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() {
          if (first < 0)
              throw new IllegalStateException("No match available");
          return first;
      }
  
      /**
       * 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) {
          if (first < 0)
              throw new IllegalStateException("No match available");
          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() {
          if (first < 0)
              throw new IllegalStateException("No match available");
          return last;
      }
  
      /**
       * 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) {
          if (first < 0)
              throw new IllegalStateException("No match available");
          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) {
          if (first < 0)
              throw new IllegalStateException("No match found");
          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() {
          return parentPattern.capturingGroupCount - 1;
      }
  
      /**
       * 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
       * @throws CatastrophicBacktrackingException 
       */
      public boolean matches(){
          return match(from, ENDANCHOR);
      }
  
      /**
       * 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
       * @throws CatastrophicBacktrackingException 
       */
      public Trace find(){    	
          int nextSearchIndex = last;
          if (nextSearchIndex == first)
              nextSearchIndex++;
  
          // If next search starts before region, start it at region
          if (nextSearchIndex < from)
              nextSearchIndex = from;
          
          boolean trace_result = false;
          // If next search starts beyond region then it fails
          if (nextSearchIndex > to) {
              for (int i = 0; i < groups.length; i++)
                  groups[i] = -1;
              trace_result = false;
          } else {
          	ReScuePattern.trace = this.trace;
          	trace_result = search(nextSearchIndex);
          	this.trace = ReScuePattern.trace;
          }
          
          trace.setEffectiveStr(text.toString());
          trace.matchSuccess = trace_result;
          // @pGREAT this trace contain enough info
          return trace;
      }
  
      /**
       * 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
       * @throws CatastrophicBacktrackingException 
       */
      public boolean find(int start){
          int limit = getTextLength();
          if ((start < 0) || (start > limit))
              throw new IndexOutOfBoundsException("Illegal start index");
          reset();
          return search(start);
      }
  
      /**
       * 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
       * @throws CatastrophicBacktrackingException 
       */
      public boolean lookingAt(){
          return match(from, NOANCHOR);
      }
  
      /**
       * 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 ReScueMatcher} 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 ReScueMatcher appendReplacement(StringBuffer sb, String replacement) {
  
          // If no match, return error
          if (first < 0)
              throw new IllegalStateException("No match available");
  
          // Process substitution string to replace group references with groups
          int cursor = 0;
          StringBuilder result = new StringBuilder();
  
          while (cursor < replacement.length()) {
              char nextChar = replacement.charAt(cursor);
              if (nextChar == '\\') {
                  cursor++;
                  if (cursor == replacement.length())
                      throw new IllegalArgumentException(
                          "character to be escaped is missing");
                  nextChar = replacement.charAt(cursor);
                  result.append(nextChar);
                  cursor++;
              } else if (nextChar == '$') {
                  // Skip past $
                  cursor++;
                  // Throw IAE if this "$" is the last character in replacement
                  if (cursor == replacement.length())
                     throw new IllegalArgumentException(
                          "Illegal group reference: group index is missing");
                  nextChar = replacement.charAt(cursor);
                  int refNum = -1;
                  if (nextChar == '{') {
                      cursor++;
                      StringBuilder gsb = new StringBuilder();
                      while (cursor < replacement.length()) {
                          nextChar = replacement.charAt(cursor);
                          if (ASCII.isLower(nextChar) ||
                              ASCII.isUpper(nextChar) ||
                              ASCII.isDigit(nextChar)) {
                              gsb.append(nextChar);
                              cursor++;
                          } else {
                              break;
                          }
                      }
                      if (gsb.length() == 0)
                          throw new IllegalArgumentException(
                              "named capturing group has 0 length name");
                      if (nextChar != '}')
                          throw new IllegalArgumentException(
                              "named capturing group is missing trailing '}'");
                      String gname = gsb.toString();
                      if (ASCII.isDigit(gname.charAt(0)))
                          throw new IllegalArgumentException(
                              "capturing group name {" + gname +
                              "} starts with digit character");
                      if (!parentPattern.namedGroups().containsKey(gname))
                          throw new IllegalArgumentException(
                              "No group with name {" + gname + "}");
                      refNum = parentPattern.namedGroups().get(gname);
                      cursor++;
                  } else {
                      // The first number is always a group
                      refNum = (int)nextChar - '0';
                      if ((refNum < 0)||(refNum > 9))
                          throw new IllegalArgumentException(
                              "Illegal group reference");
                      cursor++;
                      // Capture the largest legal group string
                      boolean done = false;
                      while (!done) {
                          if (cursor >= replacement.length()) {
                              break;
                          }
                          int nextDigit = replacement.charAt(cursor) - '0';
                          if ((nextDigit < 0)||(nextDigit > 9)) { // not a number
                              break;
                          }
                          int newRefNum = (refNum * 10) + nextDigit;
                          if (groupCount() < newRefNum) {
                              done = true;
                          } else {
                              refNum = newRefNum;
                              cursor++;
                          }
                      }
                  }
                  // Append group
                  if (start(refNum) != -1 && end(refNum) != -1)
                      result.append(text, start(refNum), end(refNum));
              } else {
                  result.append(nextChar);
                  cursor++;
              }
          }
          // Append the intervening text
          sb.append(text, lastAppendPosition, first);
          // Append the match substitution
          sb.append(result);
  
          lastAppendPosition = last;
          return this;
      }
  
      /**
       * 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) {
          sb.append(text, lastAppendPosition, getTextLength());
          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
       * @throws CatastrophicBacktrackingException 
       */
      public String replaceAll(String replacement){
          reset();
          boolean result = find().matchSuccess;
          if (result) {
              StringBuffer sb = new StringBuffer();
              do {
                  appendReplacement(sb, replacement);
                  result = find().matchSuccess;
              } 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
       * @throws CatastrophicBacktrackingException 
       */
      public String replaceFirst(String replacement){
          if (replacement == null)
              throw new NullPointerException("replacement");
          reset();
          if (!find().matchSuccess)
              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 ReScueMatcher region(int start, int end) {
          if ((start < 0) || (start > getTextLength()))
              throw new IndexOutOfBoundsException("start");
          if ((end < 0) || (end > getTextLength()))
              throw new IndexOutOfBoundsException("end");
          if (start > end)
              throw new IndexOutOfBoundsException("start > end");
          reset();
          from = start;
          to = end;
          return this;
      }
  
      /**
       * 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 java.util.regex.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 java.util.regex.Matcher#hasTransparentBounds
       * @since 1.5
       */
      public ReScueMatcher useTransparentBounds(boolean b) {
          transparentBounds = 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 java.util.regex.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 java.util.regex.Matcher#hasAnchoringBounds
       * @since 1.5
       */
      public ReScueMatcher useAnchoringBounds(boolean b) {
          anchoringBounds = 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 ((first >= 0) && (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() {
          return 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() {
          return requireEnd;
      }
  
      /**
       * Initiates a search to find a Pattern within the given bounds.
       * The groups are filled with default values and the match of the root
       * of the state machine is called. The state machine will hold the state
       * of the match as it proceeds in this matcher.
       *
       * Matcher.from is not set here, because it is the "hard" boundary
       * of the start of the search which anchors will set to. The from param
       * is the "soft" boundary of the start of the search, meaning that the
       * regex tries to match at that index but ^ won't match there. Subsequent
       * calls to the search methods start at a new "soft" boundary which is
       * the end of the previous match.
       */
      boolean search(int from){
          this.hitEnd = false;
          this.requireEnd = false;
          from        = from < 0 ? 0 : from;
          this.first  = from;
          this.oldLast = oldLast < 0 ? from : oldLast;
          for (int i = 0; i < groups.length; i++)
              groups[i] = -1;
          acceptMode = NOANCHOR;
          boolean result = parentPattern.root.match(this, from, text, true);
          if (!result)
              this.first = -1;
          this.oldLast = this.last;
          return result;
      }
  
      /**
       * Initiates a search for an anchored match to a Pattern within the given
       * bounds. The groups are filled with default values and the match of the
       * root of the state machine is called. The state machine will hold the
       * state of the match as it proceeds in this matcher.
       */
      boolean match(int from, int anchor){
          this.hitEnd = false;
          this.requireEnd = false;
          from        = from < 0 ? 0 : from;
          this.first  = from;
          this.oldLast = oldLast < 0 ? from : oldLast;
          for (int i = 0; i < groups.length; i++)
              groups[i] = -1;
          acceptMode = anchor;
          boolean result = parentPattern.matchRoot.match(this, from, text, true);
          if (!result)
              this.first = -1;
          this.oldLast = this.last;
          return result;
      }
  
      /**
       * 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);
      }
  
      /**
       * Returns this Matcher's input character at index i.
       *
       * @return A char from the specified index
       */
      char charAt(int i) {
          return text.charAt(i);
      }
  
      /**
       * Returns the group index of the matched capturing group.
       *
       * @return the index of the named-capturing group
       */
      int getMatchedGroupIndex(String name) {
          Objects.requireNonNull(name, "Group name");
          if (first < 0)
              throw new IllegalStateException("No match found");
          if (!parentPattern.namedGroups().containsKey(name))
              throw new IllegalArgumentException("No group with name <" + name + ">");
          return parentPattern.namedGroups().get(name);
      }
  }
  