/*
 
* 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 java.util.Objects;

/**
 
* An engine that performs match operations on a {@linkplain java.lang.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
 
* method or, if a new input sequence is desired, its {@link
 
* #reset(java.lang.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.
     
*/
    
Pattern 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;

    
/**
     
* No default constructor.
     
*/
    
Matcher() {
    
}

    
/**
     
* All matchers have the state used by Pattern during a match.
     
*/

    
Matcher(Pattern parent, CharSequence text) {
        
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();
    
}

    
/**
     
* 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() {
        
Matcher result = new Matcher(this.parentPattern, text.toString());
        
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 Matcher usePattern(Pattern 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 Matcher 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 Matcher 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
     
*/

    
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
     
*/

    
public boolean find() {
        
int nextSearchIndex = last;
        
if (nextSearchIndex == first)
            
nextSearchIndex++;

        
// If next search starts before region, start it at region
        
if (nextSearchIndex < from)
            
nextSearchIndex = from;

        
// If next search starts beyond region then it fails
        
if (nextSearchIndex > to) {
            
for (int i = 0; i < groups.length; i++)
                
groups[i] = -1;
            
return false;
        
}
        
return search(nextSearchIndex);
    
}

    
/**
     
* 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
 
 
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();
        
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
     
*/

    
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 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
 
.
     
*
   
</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) {

        
// 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
     
*/

    
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) {
        
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 Matcher 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 Matcher 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);
        
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);
        
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
  
endIndexthe 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);
    
}
}