/**
    * Diff Match and Patch
    *
    * Copyright 2006 Google Inc.
    * http://code.google.com/p/google-diff-match-patch/
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.jsql.model.injection.strategy.blind.patch;
  
  import com.jsql.util.LogLevelUtil;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  import java.net.URLDecoder;
  import java.net.URLEncoder;
  import java.nio.charset.StandardCharsets;
  import java.util.*;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /*
   * Functions for diff, match and patch.
   * Computes the difference between two texts to create a patch.
   * Applies the patch onto another text, allowing for errors.
   *
   * @author fraser@google.com (Neil Fraser)
   */
  
  /**
   * Class containing the diff, match and patch methods.
   * Also contains the behaviour settings.
   */
  public class DiffMatchPatch {
  
      /**
       * Log4j logger sent to view.
       */
      private static final Logger LOGGER = LogManager.getRootLogger();
  
      // Defaults.
      // Set these on your diff_match_patch instance to override the defaults.
  
      /**
       * Number of seconds to map a diff before giving up (0 for infinity).
       */
      public static final float DIFF_TIMEOUT = 1.0f;
  
      /**
       * Cost of an empty edit operation in terms of edit characters.
       */
      public static final short DIFF_EDIT_COST = 4;
  
      /**
       * At what point is no match declared (0.0 = perfection, 1.0 = very loose).
       */
      public static final float MATCH_THRESHOLD = 0.5f;
  
      /**
       * How far to search for a match (0 = exact location, 1000+ = broad match).
       * A match this many characters away from the expected location will add
       * 1.0 to the score (0.0 is a perfect match).
       */
      public static final int MATCH_DISTANCE = 1000;
  
      /**
       * When deleting a large block of text (over ~64 characters), how close do
       * the contents have to be to match the expected contents. (0.0 = perfection,
       * 1.0 = very loose).  Note that Match_Threshold controls how closely the
       * end points of a delete need to match.
       */
      public static final float PATCH_DELETE_THRESHOLD = 0.5f;
  
      /**
       * Chunk size for context length.
       */
      public static final short PATCH_MARGIN = 4;
  
      /**
       * The number of bits in an int.
       */
      private static final short MATCH_MAX_BITS = 32;
  
      // Define some regex patterns for matching boundaries.
      private static final Pattern BLANK_LINE_END = Pattern.compile("\\n\\r?\\n\\Z", Pattern.DOTALL);
      private static final Pattern BLANK_LINE_START = Pattern.compile("\\A\\r?\\n\\r?\\n", Pattern.DOTALL);
  
      /**
      * Internal class for returning results from diff_linesToChars().
      * Other less paranoid languages just use a three-element array.
      */
     protected static class LinesToCharsResult {
         protected final String chars1;
         protected final String chars2;
         protected final List<String> lineArray;
 
         protected LinesToCharsResult(String chars1, String chars2,
                                      List<String> lineArray) {
             this.chars1 = chars1;
             this.chars2 = chars2;
             this.lineArray = lineArray;
         }
     }
 
     //  DIFF FUNCTIONS
 
     /**
      * The data structure representing a diff is a Linked list of Diff objects:
      * {Diff(Operation.DELETE, "Hello"), Diff(Operation.INSERT, "Goodbye"),
      *  Diff(Operation.EQUAL, " world.")}
      * which means: delete "Hello", add "Goodbye" and keep " world."
      */
     public enum Operation {
         DELETE, INSERT, EQUAL
     }
 
     /**
      * Find the differences between two texts.
      * Run a faster, slightly less optimal diff.
      * This method allows the 'checklines' of diff_main() to be optional.
      * Most of the time checklines is wanted, so default to true.
      * @param text1 Old string to be diffed.
      * @param text2 New string to be diffed.
      * @return Linked List of Diff objects.
      */
     public List<Diff> diffMain(String text1, String text2) {
         return this.diffMain(text1, text2, true);
     }
 
     /**
      * Find the differences between two texts.
      * @param text1 Old string to be diffed.
      * @param text2 New string to be diffed.
      * @param checklines Speedup flag.  If false, then don't run a
      *     line-level diff first to identify the changed areas.
      *     If true, then run a faster slightly less optimal diff.
      * @return Linked List of Diff objects.
      */
     public LinkedList<Diff> diffMain(String text1, String text2, boolean checklines) {
         // Set a deadline by which time the diff must be complete.
         long deadline = System.currentTimeMillis() + (long) (DiffMatchPatch.DIFF_TIMEOUT * 1000);
         return this.diffMain(text1, text2, checklines, deadline);
     }
 
     /**
      * Find the differences between two texts.  Simplifies the problem by
      * stripping any common prefix or suffix off the texts before diffing.
      * @param valueText1 Old string to be diffed.
      * @param valueText2 New string to be diffed.
      * @param checklines Speedup flag.  If false, then don't run a
      *     line-level diff first to identify the changed areas.
      *     If true, then run a faster slightly less optimal diff.
      * @param deadline Time when the diff should be complete by.  Used
      *     internally for recursive calls.  Users should set DiffTimeout instead.
      * @return Linked List of Diff objects.
      */
     private LinkedList<Diff> diffMain(String valueText1, String valueText2, boolean checklines, long deadline) {
 
         String text1 = valueText1;
         String text2 = valueText2;
 
         // Check for null inputs.
         if (text1 == null || text2 == null) {
             throw new IllegalArgumentException("Null inputs. (diff_main)");
         }
 
         // Check for equality (speedup).
         LinkedList<Diff> diffs;
         if (text1.equals(text2)) {
             diffs = new LinkedList<>();
             if (!text1.isEmpty()) {
                 diffs.add(new Diff(Operation.EQUAL, text1));
             }
             return diffs;
         }
 
         // Trim off common prefix (speedup).
         int commonlength = this.diffCommonPrefix(text1, text2);
         String commonprefix = text1.substring(0, commonlength);
         text1 = text1.substring(commonlength);
         text2 = text2.substring(commonlength);
 
         // Trim off common suffix (speedup).
         commonlength = this.diffCommonSuffix(text1, text2);
         String commonsuffix = text1.substring(text1.length() - commonlength);
         text1 = text1.substring(0, text1.length() - commonlength);
         text2 = text2.substring(0, text2.length() - commonlength);
 
         // Compute the diff on the middle block.
         diffs = this.diffCompute(text1, text2, checklines, deadline);
 
         // Restore the prefix and suffix.
         if (!commonprefix.isEmpty()) {
             diffs.addFirst(new Diff(Operation.EQUAL, commonprefix));
         }
         if (!commonsuffix.isEmpty()) {
             diffs.addLast(new Diff(Operation.EQUAL, commonsuffix));
         }
 
         this.diffCleanupMerge(diffs);
         return diffs;
     }
 
     /**
      * Find the differences between two texts.  Assumes that the texts do not
      * have any common prefix or suffix.
      * @param text1 Old string to be diffed.
      * @param text2 New string to be diffed.
      * @param checklines Speedup flag.  If false, then don't run a
      *     line-level diff first to identify the changed areas.
      *     If true, then run a faster slightly less optimal diff.
      * @param deadline Time when the diff should be complete by.
      * @return Linked List of Diff objects.
      */
     private LinkedList<Diff> diffCompute(String text1, String text2, boolean checklines, long deadline) {
 
         LinkedList<Diff> diffs = new LinkedList<>();
 
         if (text1.isEmpty()) {
             // Just add some text (speedup).
             diffs.add(new Diff(Operation.INSERT, text2));
             return diffs;
         }
 
         if (text2.isEmpty()) {
             // Just delete some text (speedup).
             diffs.add(new Diff(Operation.DELETE, text1));
             return diffs;
         }
 
         {
             // New scope to garbage collect longtext and shorttext.
             String longtext = text1.length() > text2.length() ? text1 : text2;
             String shorttext = text1.length() > text2.length() ? text2 : text1;
             int i = longtext.indexOf(shorttext);
             if (i != -1) {
                 // Shorter text is inside the longer text (speedup).
                 Operation op = (text1.length() > text2.length()) ?
                         Operation.DELETE : Operation.INSERT;
                 diffs.add(new Diff(op, longtext.substring(0, i)));
                 diffs.add(new Diff(Operation.EQUAL, shorttext));
                 diffs.add(new Diff(op, longtext.substring(i + shorttext.length())));
                 return diffs;
             }
 
             if (shorttext.length() == 1) {
                 // Single character string.
                 // After the previous speedup, the character can't be an equality.
                 diffs.add(new Diff(Operation.DELETE, text1));
                 diffs.add(new Diff(Operation.INSERT, text2));
                 return diffs;
             }
         }
 
         // Check to see if the problem can be split in two.
         String[] hm = this.diffHalfMatch(text1, text2);
         if (hm != null) {
             // A half-match was found, sort out the return data.
             String text1A = hm[0];
             String text1B = hm[1];
             String text2A = hm[2];
             String text2B = hm[3];
             String midCommon = hm[4];
             // Send both pairs off for separate processing.
             LinkedList<Diff> diffsA = this.diffMain(text1A, text2A, checklines, deadline);
             List<Diff> diffsB = this.diffMain(text1B, text2B, checklines, deadline);
             // Merge the results.
             diffs = diffsA;
             diffs.add(new Diff(Operation.EQUAL, midCommon));
             diffs.addAll(diffsB);
             return diffs;
         }
 
         if (checklines && text1.length() > 100 && text2.length() > 100) {
             return this.diffLineMode(text1, text2, deadline);
         }
 
         return this.diffBisect(text1, text2, deadline);
     }
 
     /**
      * Do a quick line-level diff on both strings, then rediff the parts for
      * greater accuracy.
      * This speedup can produce non-minimal diffs.
      * @param valueText1 Old string to be diffed.
      * @param valueText2 New string to be diffed.
      * @param deadline Time when the diff should be complete by.
      * @return Linked List of Diff objects.
      */
     private LinkedList<Diff> diffLineMode(String valueText1, String valueText2, long deadline) {
 
         // Scan the text on a line-by-line basis first.
         LinesToCharsResult b = this.diffLinesToChars(valueText1, valueText2);
         String text1 = b.chars1;
         String text2 = b.chars2;
         List<String> linearray = b.lineArray;
 
         LinkedList<Diff> diffs = this.diffMain(text1, text2, false, deadline);
 
         // Convert the diff back to original text.
         this.diffCharsToLines(diffs, linearray);
         // Eliminate freak matches (e.g. blank lines)
         this.diffCleanupSemantic(diffs);
 
         // Rediff any replacement blocks, this time character-by-character.
         // Add a dummy entry at the end.
         diffs.add(new Diff(Operation.EQUAL, StringUtils.EMPTY));
         int countDelete = 0;
         int countInsert = 0;
         StringBuilder textDelete = new StringBuilder();
         StringBuilder textInsert = new StringBuilder();
         ListIterator<Diff> pointer = diffs.listIterator();
         Diff thisDiff = pointer.next();
 
         while (thisDiff != null) {
             switch (thisDiff.getOperation()) {
                 case INSERT:
                     countInsert++;
                     textInsert.append(thisDiff.getText());
                     break;
                 case DELETE:
                     countDelete++;
                     textDelete.append(thisDiff.getText());
                     break;
                 case EQUAL:
                     // Upon reaching an equality, check for prior redundancies.
                     if (countDelete >= 1 && countInsert >= 1) {
                         // Delete the offending records and add the merged ones.
                         pointer.previous();
                         for (int j = 0; j < countDelete + countInsert; j++) {
                             pointer.previous();
                             pointer.remove();
                         }
                         for (Diff newDiff : this.diffMain(textDelete.toString(), textInsert.toString(), false, deadline)) {
                             pointer.add(newDiff);
                         }
                     }
                     countInsert = 0;
                     countDelete = 0;
                     textDelete.setLength(0);
                     textInsert.setLength(0);
                     break;
             }
             thisDiff = pointer.hasNext() ? pointer.next() : null;
         }
         diffs.removeLast();  // Remove the dummy entry at the end.
 
         return diffs;
     }
 
     /**
      * Find the 'middle snake' of a diff, split the problem in two
      * and return the recursively constructed diff.
      * See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
      * @param text1 Old string to be diffed.
      * @param text2 New string to be diffed.
      * @param deadline Time at which to bail if not yet complete.
      * @return LinkedList of Diff objects.
      */
     protected LinkedList<Diff> diffBisect(String text1, String text2, long deadline) {
 
         // Cache the text lengths to prevent multiple calls.
         int text1Length = text1.length();
         int text2Length = text2.length();
         int maxD = (text1Length + text2Length + 1) / 2;
         int vLength = 2 * maxD;
         int[] v1 = new int[vLength];
         int[] v2 = new int[vLength];
         for (int x = 0; x < vLength; x++) {
             v1[x] = -1;
             v2[x] = -1;
         }
         v1[maxD + 1] = 0;
         v2[maxD + 1] = 0;
         int delta = text1Length - text2Length;
         // If the total number of characters is odd, then the front path will
         // collide with the reverse path.
         boolean front = delta % 2 != 0;
         // Offsets for start and end of k loop.
         // Prevents mapping of space beyond the grid.
         int k1start = 0;
         int k1end = 0;
         int k2start = 0;
         int k2end = 0;
 
         for (int d = 0; d < maxD; d++) {
             // Bail out if deadline is reached.
             if (System.currentTimeMillis() > deadline) {
                 break;
             }
 
             // Walk the front path one step.
             for (int k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
                 int k1Offset = maxD + k1;
                 int x1;
                 if (k1 == -d || (k1 != d && v1[k1Offset - 1] < v1[k1Offset + 1])) {
                     x1 = v1[k1Offset + 1];
                 } else {
                     x1 = v1[k1Offset - 1] + 1;
                 }
                 int y1 = x1 - k1;
                 while (x1 < text1Length && y1 < text2Length
                         && text1.charAt(x1) == text2.charAt(y1)) {
                     x1++;
                     y1++;
                 }
                 v1[k1Offset] = x1;
                 if (x1 > text1Length) {
                     // Ran off the right of the graph.
                     k1end += 2;
                 } else if (y1 > text2Length) {
                     // Ran off the bottom of the graph.
                     k1start += 2;
                 } else if (front) {
                     int k2Offset = maxD + delta - k1;
                     if (k2Offset >= 0 && k2Offset < vLength && v2[k2Offset] != -1) {
                         // Mirror x2 onto top-left coordinate system.
                         int x2 = text1Length - v2[k2Offset];
                         if (x1 >= x2) {
                             // Overlap detected.
                             return this.diffBisectSplit(text1, text2, x1, y1, deadline);
                         }
                     }
                 }
             }
 
             // Walk the reverse path one step.
             for (int k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
                 int k2Offset = maxD + k2;
                 int x2;
                 if (k2 == -d || (k2 != d && v2[k2Offset - 1] < v2[k2Offset + 1])) {
                     x2 = v2[k2Offset + 1];
                 } else {
                     x2 = v2[k2Offset - 1] + 1;
                 }
                 int y2 = x2 - k2;
                 while (x2 < text1Length && y2 < text2Length
                         && text1.charAt(text1Length - x2 - 1)
                         == text2.charAt(text2Length - y2 - 1)) {
                     x2++;
                     y2++;
                 }
                 v2[k2Offset] = x2;
                 if (x2 > text1Length) {
                     // Ran off the left of the graph.
                     k2end += 2;
                 } else if (y2 > text2Length) {
                     // Ran off the top of the graph.
                     k2start += 2;
                 } else if (!front) {
                     int k1Offset = maxD + delta - k2;
                     if (k1Offset >= 0 && k1Offset < vLength && v1[k1Offset] != -1) {
                         int x1 = v1[k1Offset];
                         int y1 = maxD + x1 - k1Offset;
                         // Mirror x2 onto top-left coordinate system.
                         x2 = text1Length - x2;
                         if (x1 >= x2) {
                             // Overlap detected.
                             return this.diffBisectSplit(text1, text2, x1, y1, deadline);
                         }
                     }
                 }
             }
         }
         // Diff took too long and hit the deadline or
         // number of diffs equals number of characters, no commonality at all.
         LinkedList<Diff> diffs = new LinkedList<>();
         diffs.add(new Diff(Operation.DELETE, text1));
         diffs.add(new Diff(Operation.INSERT, text2));
         return diffs;
     }
 
     /**
      * Given the location of the 'middle snake', split the diff in two parts
      * and recurse.
      * @param text1 Old string to be diffed.
      * @param text2 New string to be diffed.
      * @param x Index of split point in text1.
      * @param y Index of split point in text2.
      * @param deadline Time at which to bail if not yet complete.
      * @return LinkedList of Diff objects.
      */
     private LinkedList<Diff> diffBisectSplit(String text1, String text2, int x, int y, long deadline) {
         String text1a = text1.substring(0, x);
         String text2a = text2.substring(0, y);
         String text1b = text1.substring(x);
         String text2b = text2.substring(y);
 
         // Compute both diffs serially.
         LinkedList<Diff> diffs = this.diffMain(text1a, text2a, false, deadline);
         List<Diff> diffsb = this.diffMain(text1b, text2b, false, deadline);
 
         diffs.addAll(diffsb);
         return diffs;
     }
 
     /**
      * Split two texts into a list of strings.  Reduce the texts to a string of
      * hashes where each Unicode character represents one line.
      * @param text1 First string.
      * @param text2 Second string.
      * @return An object containing the encoded text1, the encoded text2 and
      *     the List of unique strings.  The zeroth element of the List of
      *     unique strings is intentionally blank.
      */
     protected LinesToCharsResult diffLinesToChars(String text1, String text2) {
         List<String> lineArray = new ArrayList<>();
         Map<String, Integer> lineHash = new HashMap<>();
         // e.g. linearray[4] == "Hello\n"
         // e.g. linehash.get("Hello\n") == 4
 
         // "\x00" is a valid character, but various debuggers don't like it.
         // So we'll insert a junk entry to avoid generating a null character.
         lineArray.add(StringUtils.EMPTY);
 
         String chars1 = this.diffLinesToCharsMunge(text1, lineArray, lineHash);
         String chars2 = this.diffLinesToCharsMunge(text2, lineArray, lineHash);
         return new LinesToCharsResult(chars1, chars2, lineArray);
     }
 
     /**
      * Split a text into a list of strings.  Reduce the texts to a string of
      * hashes where each Unicode character represents one line.
      * @param text String to encode.
      * @param lineArray List of unique strings.
      * @param lineHash Map of strings to indices.
      * @return Encoded string.
      */
     private String diffLinesToCharsMunge(String text, List<String> lineArray,
                                          Map<String, Integer> lineHash) {
 
         int lineStart = 0;
         int lineEnd = -1;
         String line;
         StringBuilder chars = new StringBuilder();
         // Walk the text, pulling out a substring for each line.
         // text.split('\n') would would temporarily double our memory footprint.
         // Modifying text would create many large strings to garbage collect.
         while (lineEnd < text.length() - 1) {
             lineEnd = text.indexOf('\n', lineStart);
             if (lineEnd == -1) {
                 lineEnd = text.length() - 1;
             }
             line = text.substring(lineStart, lineEnd + 1);
             lineStart = lineEnd + 1;
 
             if (lineHash.containsKey(line)) {
                 chars.append((char) (int) lineHash.get(line));
             } else {
                 lineArray.add(line);
                 lineHash.put(line, lineArray.size() - 1);
                 chars.append((char) (lineArray.size() - 1));
             }
         }
         return chars.toString();
     }
 
     /**
      * Rehydrate the text in a diff from a string of line hashes to real lines of
      * text.
      * @param diffs LinkedList of Diff objects.
      * @param lineArray List of unique strings.
      */
     protected void diffCharsToLines(List<Diff> diffs, List<String> lineArray) {
         StringBuilder text;
         for (Diff diff : diffs) {
             text = new StringBuilder();
             for (int y = 0; y < diff.getText().length(); y++) {
                 text.append(lineArray.get(diff.getText().charAt(y)));
             }
             diff.setText(text.toString());
         }
     }
 
     /**
      * Determine the common prefix of two strings
      * @param text1 First string.
      * @param text2 Second string.
      * @return The number of characters common to the start of each string.
      */
     public int diffCommonPrefix(String text1, String text2) {
         // Performance analysis: http://neil.fraser.name/news/2007/10/09/
         int n = Math.min(text1.length(), text2.length());
         for (int i = 0; i < n; i++) {
             if (text1.charAt(i) != text2.charAt(i)) {
                 return i;
             }
         }
         return n;
     }
 
     /**
      * Determine the common suffix of two strings
      * @param text1 First string.
      * @param text2 Second string.
      * @return The number of characters common to the end of each string.
      */
     public int diffCommonSuffix(String text1, String text2) {
         // Performance analysis: http://neil.fraser.name/news/2007/10/09/
         int text1Length = text1.length();
         int text2Length = text2.length();
         int n = Math.min(text1Length, text2Length);
         for (int i = 1; i <= n; i++) {
             if (text1.charAt(text1Length - i) != text2.charAt(text2Length - i)) {
                 return i - 1;
             }
         }
         return n;
     }
 
     /**
      * Determine if the suffix of one string is the prefix of another.
      * @param valueText1 First string.
      * @param valueText2 Second string.
      * @return The number of characters common to the end of the first
      *     string and the start of the second string.
      */
     protected int diffCommonOverlap(String valueText1, String valueText2) {
 
         String text1 = valueText1;
         String text2 = valueText2;
 
         // Cache the text lengths to prevent multiple calls.
         int text1Length = text1.length();
         int text2Length = text2.length();
         // Eliminate the null case.
         if (text1Length == 0 || text2Length == 0) {
             return 0;
         }
         // Truncate the longer string.
         if (text1Length > text2Length) {
             text1 = text1.substring(text1Length - text2Length);
         } else if (text1Length < text2Length) {
             text2 = text2.substring(0, text1Length);
         }
         int textLength = Math.min(text1Length, text2Length);
         // Quick check for the worst case.
         if (text1.equals(text2)) {
             return textLength;
         }
 
         // Start by looking for a single character match
         // and increase length until no match is found.
         // Performance analysis: http://neil.fraser.name/news/2010/11/04/
         int best = 0;
         int length = 1;
         while (true) {
             String pattern = text1.substring(textLength - length);
             int found = text2.indexOf(pattern);
             if (found == -1) {
                 return best;
             }
             length += found;
             if (found == 0 || text1.substring(textLength - length).equals(
                     text2.substring(0, length))) {
                 best = length;
                 length++;
             }
         }
     }
 
     /**
      * Do the two texts share a substring which is at least half the length of
      * the longer text?
      * This speedup can produce non-minimal diffs.
      * @param text1 First string.
      * @param text2 Second string.
      * @return Five element String array, containing the prefix of text1, the
      *     suffix of text1, the prefix of text2, the suffix of text2 and the
      *     common middle.  Or null if there was no match.
      */
     protected String[] diffHalfMatch(String text1, String text2) {
 
         String longtext = text1.length() > text2.length() ? text1 : text2;
         String shorttext = text1.length() > text2.length() ? text2 : text1;
         if (longtext.length() < 4 || shorttext.length() * 2 < longtext.length()) {
             return null;  // Pointless.
         }
 
         // First check if the second quarter is the seed for a half-match.
         String[] hm1 = this.diffHalfMatchI(longtext, shorttext, (longtext.length() + 3) / 4);
         // Check again based on the third quarter.
         String[] hm2 = this.diffHalfMatchI(longtext, shorttext, (longtext.length() + 1) / 2);
         String[] hm;
         if (hm1 == null && hm2 == null) {
             return null;
         } else if (hm2 == null) {
             hm = hm1;
         } else if (hm1 == null) {
             hm = hm2;
         } else {
             // Both matched.  Select the longest.
             hm = hm1[4].length() > hm2[4].length() ? hm1 : hm2;
         }
 
         // A half-match was found, sort out the return data.
         if (text1.length() > text2.length()) {
             return hm;
         } else {
             return new String[]{hm[2], hm[3], hm[0], hm[1], hm[4]};
         }
     }
 
     /**
      * Does a substring of shorttext exist within longtext such that the
      * substring is at least half the length of longtext?
      * @param longtext Longer string.
      * @param shorttext Shorter string.
      * @param i Start index of quarter length substring within longtext.
      * @return Five element String array, containing the prefix of longtext, the
      *     suffix of longtext, the prefix of shorttext, the suffix of shorttext
      *     and the common middle.  Or null if there was no match.
      */
     private String[] diffHalfMatchI(String longtext, String shorttext, int i) {
 
         // Start with a 1/4 length substring at position i as a seed.
         String seed = longtext.substring(i, i + longtext.length() / 4);
         int j = -1;
         String bestCommon = StringUtils.EMPTY;
         String bestLongtextA = StringUtils.EMPTY;
         String bestLongtextB = StringUtils.EMPTY;
         String bestShorttextA = StringUtils.EMPTY;
         String bestShorttextB = StringUtils.EMPTY;
         while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
             int prefixLength = this.diffCommonPrefix(longtext.substring(i),
                     shorttext.substring(j));
             int suffixLength = this.diffCommonSuffix(longtext.substring(0, i),
                     shorttext.substring(0, j));
             if (bestCommon.length() < suffixLength + prefixLength) {
                 bestCommon = shorttext.substring(j - suffixLength, j)
                         + shorttext.substring(j, j + prefixLength);
                 bestLongtextA = longtext.substring(0, i - suffixLength);
                 bestLongtextB = longtext.substring(i + prefixLength);
                 bestShorttextA = shorttext.substring(0, j - suffixLength);
                 bestShorttextB = shorttext.substring(j + prefixLength);
             }
         }
         if (bestCommon.length() * 2 >= longtext.length()) {
             return new String[]{bestLongtextA, bestLongtextB,
                     bestShorttextA, bestShorttextB, bestCommon};
         } else {
             return null;
         }
     }
 
     /**
      * Reduce the number of edits by eliminating semantically trivial equalities.
      * @param diffs LinkedList of Diff objects.
      */
     public void diffCleanupSemantic(LinkedList<Diff> diffs) {
 
         if (diffs.isEmpty()) {
             return;
         }
         boolean changes = false;
         // Synchronized Stack to avoid Exception
         Stack<Diff> equalities = new Stack<>();  // Stack of qualities.
         String lastequality = null; // Always equal to equalities.lastElement().text
         ListIterator<Diff> pointer = diffs.listIterator();
         // Number of characters that changed prior to the equality.
         int lengthInsertions1 = 0;
         int lengthDeletions1 = 0;
         // Number of characters that changed after the equality.
         int lengthInsertions2 = 0;
         int lengthDeletions2 = 0;
         Diff thisDiff = pointer.next();
 
         while (thisDiff != null) {
             if (thisDiff.getOperation() == Operation.EQUAL) {
                 // Equality found.
                 equalities.push(thisDiff);
                 lengthInsertions1 = lengthInsertions2;
                 lengthDeletions1 = lengthDeletions2;
                 lengthInsertions2 = 0;
                 lengthDeletions2 = 0;
                 lastequality = thisDiff.getText();
             } else {
                 // An insertion or deletion.
                 if (thisDiff.getOperation() == Operation.INSERT) {
                     lengthInsertions2 += thisDiff.getText().length();
                 } else {
                     lengthDeletions2 += thisDiff.getText().length();
                 }
                 // Eliminate an equality that is smaller or equal to the edits on both
                 // sides of it.
                 if (
                         lastequality != null
                                 && lastequality.length() <= Math.max(lengthInsertions1, lengthDeletions1)
                                 && lastequality.length() <= Math.max(lengthInsertions2, lengthDeletions2)
                 ) {
                     // Walk back to offending equality.
                     while (thisDiff != equalities.lastElement()) {
                         thisDiff = pointer.previous();
                     }
                     pointer.next();
 
                     // Replace equality with a delete.
                     pointer.set(new Diff(Operation.DELETE, lastequality));
                     // Insert a corresponding an insert.
                     pointer.add(new Diff(Operation.INSERT, lastequality));
 
                     equalities.pop();  // Throw away the equality we just deleted.
                     if (!equalities.empty()) {
                         // Throw away the previous equality (it needs to be reevaluated).
                         equalities.pop();
                     }
                     if (equalities.empty()) {
                         // There are no previous equalities, walk back to the start.
                         while (pointer.hasPrevious()) {
                             pointer.previous();
                         }
                     } else {
                         // There is a safe equality we can fall back to.
                         thisDiff = equalities.lastElement();
                         while (thisDiff != pointer.previous()) {
                             // Intentionally empty loop.
                         }
                     }
 
                     lengthInsertions1 = 0;  // Reset the counters.
                     lengthInsertions2 = 0;
                     lengthDeletions1 = 0;
                     lengthDeletions2 = 0;
                     lastequality = null;
                     changes = true;
                 }
             }
             thisDiff = pointer.hasNext() ? pointer.next() : null;
         }
 
         // Normalize the diff.
         if (changes) {
             this.diffCleanupMerge(diffs);
         }
         this.diffCleanupSemanticLossless(diffs);
 
         // Find any overlaps between deletions and insertions.
         // e.g: <del>abcxxx</del><ins>xxxdef</ins>
         //   -> <del>abc</del>xxx<ins>def</ins>
         // e.g: <del>xxxabc</del><ins>defxxx</ins>
         //   -> <ins>def</ins>xxx<del>abc</del>
         // Only extract an overlap if it is as big as the edit ahead or behind it.
         pointer = diffs.listIterator();
         Diff prevDiff = null;
         thisDiff = null;
         if (pointer.hasNext()) {
             prevDiff = pointer.next();
             if (pointer.hasNext()) {
                 thisDiff = pointer.next();
             }
         }
 
         while (thisDiff != null) {
             if (prevDiff.getOperation() == Operation.DELETE &&
                     thisDiff.getOperation() == Operation.INSERT) {
                 String deletion = prevDiff.getText();
                 String insertion = thisDiff.getText();
                 int overlapLength1 = this.diffCommonOverlap(deletion, insertion);
                 int overlapLength2 = this.diffCommonOverlap(insertion, deletion);
                 if (overlapLength1 >= overlapLength2) {
                     if (overlapLength1 >= deletion.length() / 2.0 ||
                             overlapLength1 >= insertion.length() / 2.0) {
                         // Overlap found.  Insert an equality and trim the surrounding edits.
                         pointer.previous();
                         pointer.add(new Diff(Operation.EQUAL,
                                 insertion.substring(0, overlapLength1)));
                         prevDiff.setText(deletion.substring(0, deletion.length() - overlapLength1));
                         thisDiff.setText(insertion.substring(overlapLength1));
                         // pointer.add inserts the element before the cursor, so there is
                         // no need to step past the new element.
                     }
                 } else {
                     if (overlapLength2 >= deletion.length() / 2.0 ||
                             overlapLength2 >= insertion.length() / 2.0) {
                         // Reverse overlap found.
                         // Insert an equality and swap and trim the surrounding edits.
                         pointer.previous();
                         pointer.add(new Diff(Operation.EQUAL,
                                 deletion.substring(0, overlapLength2)));
                         prevDiff.setOperation(Operation.INSERT);
                         prevDiff.setText(insertion.substring(0, insertion.length() - overlapLength2));
                         thisDiff.setOperation(Operation.DELETE);
                         thisDiff.setText(deletion.substring(overlapLength2));
                         // pointer.add inserts the element before the cursor, so there is
                         // no need to step past the new element.
                     }
                 }
                 thisDiff = pointer.hasNext() ? pointer.next() : null;
             }
             prevDiff = thisDiff;
             thisDiff = pointer.hasNext() ? pointer.next() : null;
         }
     }
 
     /**
      * Look for single edits surrounded on both sides by equalities
      * which can be shifted sideways to align the edit to a word boundary.
      * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
      * @param diffs LinkedList of Diff objects.
      */
     public void diffCleanupSemanticLossless(List<Diff> diffs) {
 
         StringBuilder equality1 = new StringBuilder();
         String edit;
         StringBuilder equality2 = new StringBuilder();
         String commonString;
         int commonOffset;
         int score;
         int bestScore;
         String bestEquality1;
         String bestEdit;
         String bestEquality2;
         // Create a new iterator at the start.
         ListIterator<Diff> pointer = diffs.listIterator();
         Diff prevDiff = pointer.hasNext() ? pointer.next() : null;
         Diff thisDiff = pointer.hasNext() ? pointer.next() : null;
         Diff nextDiff = pointer.hasNext() ? pointer.next() : null;
 
         // Intentionally ignore the first and last element (don't need checking).
         while (nextDiff != null) {
             if (prevDiff.getOperation() == Operation.EQUAL &&
                     nextDiff.getOperation() == Operation.EQUAL) {
                 // This is a single edit surrounded by equalities.
                 equality1.setLength(0);
                 equality1.append(prevDiff.getText());
                 edit = thisDiff.getText();
                 equality2.setLength(0);
                 equality2.append(nextDiff.getText());
 
                 // First, shift the edit as far left as possible.
                 commonOffset = this.diffCommonSuffix(equality1.toString(), edit);
                 if (commonOffset != 0) {
                     commonString = edit.substring(edit.length() - commonOffset);
                     String substring = equality1.substring(0, equality1.length() - commonOffset);
                     equality1.setLength(0);
                     equality1.append(substring);
                     edit = commonString + edit.substring(0, edit.length() - commonOffset);
                     equality2.insert(0, commonString);
                 }
 
                 // Second, step character by character right, looking for the best fit.
                 bestEquality1 = equality1.toString();
                 bestEdit = edit;
                 bestEquality2 = equality2.toString();
                 bestScore = this.diffCleanupSemanticScore(equality1.toString(), edit)
                         + this.diffCleanupSemanticScore(edit, equality2.toString());
                 while (!edit.isEmpty() && equality2.length() != 0
                         && edit.charAt(0) == equality2.charAt(0)) {
                     equality1.append(edit.charAt(0));
                     edit = edit.substring(1) + equality2.charAt(0);
                     String substring = equality2.substring(1);
                     equality2.setLength(0);
                     equality2.append(substring);
                     score = this.diffCleanupSemanticScore(equality1.toString(), edit)
                             + this.diffCleanupSemanticScore(edit, equality2.toString());
                     // The >= encourages trailing rather than leading whitespace on edits.
                     if (score >= bestScore) {
                         bestScore = score;
                         bestEquality1 = equality1.toString();
                         bestEdit = edit;
                         bestEquality2 = equality2.toString();
                     }
                 }
 
                 if (!prevDiff.getText().equals(bestEquality1)) {
                     // We have an improvement, save it back to the diff.
                     if (!bestEquality1.isEmpty()) {
                         prevDiff.setText(bestEquality1);
                     } else {
                         pointer.previous(); // Walk past nextDiff.
                         pointer.previous(); // Walk past thisDiff.
                         pointer.previous(); // Walk past prevDiff.
                         pointer.remove(); // Delete prevDiff.
                         pointer.next(); // Walk past thisDiff.
                         pointer.next(); // Walk past nextDiff.
                     }
                     thisDiff.setText(bestEdit);
                     if (!bestEquality2.isEmpty()) {
                         nextDiff.setText(bestEquality2);
                     } else {
                         pointer.remove(); // Delete nextDiff.
                         nextDiff = thisDiff;
                         thisDiff = prevDiff;
                     }
                 }
             }
             prevDiff = thisDiff;
             thisDiff = nextDiff;
             nextDiff = pointer.hasNext() ? pointer.next() : null;
         }
     }
 
     /**
      * Given two strings, compute a score representing whether the internal
      * boundary falls on logical boundaries.
      * Scores range from 6 (best) to 0 (worst).
      * @param one First string.
      * @param two Second string.
      * @return The score.
      */
     private int diffCleanupSemanticScore(String one, String two) {
 
         if (one.isEmpty() || two.isEmpty()) {
             // Edges are the best.
             return 6;
         }
 
         // Each port of this function behaves slightly differently due to
         // subtle differences in each language's definition of things like
         // 'whitespace'.  Since this function's purpose is largely cosmetic,
         // the choice has been made to use each language's native features
         // rather than force total conformity.
         char char1 = one.charAt(one.length() - 1);
         char char2 = two.charAt(0);
         boolean nonAlphaNumeric1 = !Character.isLetterOrDigit(char1);
         boolean nonAlphaNumeric2 = !Character.isLetterOrDigit(char2);
         boolean whitespace1 = nonAlphaNumeric1 && Character.isWhitespace(char1);
         boolean whitespace2 = nonAlphaNumeric2 && Character.isWhitespace(char2);
         boolean lineBreak1 = whitespace1
                 && Character.getType(char1) == Character.CONTROL;
         boolean lineBreak2 = whitespace2
                 && Character.getType(char2) == Character.CONTROL;
         boolean blankLine1 = lineBreak1 && DiffMatchPatch.BLANK_LINE_END.matcher(one).find();
         boolean blankLine2 = lineBreak2 && DiffMatchPatch.BLANK_LINE_START.matcher(two).find();
 
         if (blankLine1 || blankLine2) {
             // Five points for blank lines.
             return 5;
         } else if (lineBreak1 || lineBreak2) {
             // Four points for line breaks.
             return 4;
         } else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
             // Three points for end of sentences.
             return 3;
         } else if (whitespace1 || whitespace2) {
             // Two points for whitespace.
             return 2;
         } else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
             // One point for non-alphanumeric.
             return 1;
         }
         return 0;
     }
 
     /**
      * Reduce the number of edits by eliminating operationally trivial equalities.
      * @param diffs LinkedList of Diff objects.
      */
     public void diffCleanupEfficiency(LinkedList<Diff> diffs) {
 
         if (diffs.isEmpty()) {
             return;
         }
         boolean changes = false;
         // Synchronized Stack to avoid Exception
         Stack<Diff> equalities = new Stack<>();  // Stack of equalities.
         String lastequality = null; // Always equal to equalities.lastElement().text
         ListIterator<Diff> pointer = diffs.listIterator();
         // Is there an insertion operation before the last equality.
         boolean preIns = false;
         // Is there a deletion operation before the last equality.
         boolean preDel = false;
         // Is there an insertion operation after the last equality.
         boolean postIns = false;
         // Is there a deletion operation after the last equality.
         boolean postDel = false;
         Diff thisDiff = pointer.next();
         Diff safeDiff = thisDiff;  // The last Diff that is known to be unsplitable.
         while (thisDiff != null) {
 
             if (thisDiff.getOperation() == Operation.EQUAL) {
 
                 // Equality found.
                 if (thisDiff.getText().length() < DiffMatchPatch.DIFF_EDIT_COST && (postIns || postDel)) {
                     // Candidate found.
                     equalities.push(thisDiff);
                     preIns = postIns;
                     preDel = postDel;
                     lastequality = thisDiff.getText();
                 } else {
                     // Not a candidate, and can never become one.
                     equalities.clear();
                     lastequality = null;
                     safeDiff = thisDiff;
                 }
                 postIns = postDel = false;
             } else {
                 // An insertion or deletion.
                 if (thisDiff.getOperation() == Operation.DELETE) {
                     postDel = true;
                 } else {
                     postIns = true;
                 }
 
                 /*
                  * Five types to be split:
                  * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
                  * <ins>A</ins>X<ins>C</ins><del>D</del>
                  * <ins>A</ins><del>B</del>X<ins>C</ins>
                  * <ins>A</del>X<ins>C</ins><del>D</del>
                  * <ins>A</ins><del>B</del>X<del>C</del>
                  */
                 if (
                         lastequality != null
                                 && (
                                 (preIns && preDel && postIns && postDel)
                                         || (
                                         (lastequality.length() < DiffMatchPatch.DIFF_EDIT_COST / 2)
                                                 && ((preIns ? 1 : 0) + (preDel ? 1 : 0) + (postIns ? 1 : 0) + (postDel ? 1 : 0)) == 3
                                 )
                         )
                 ) {
                     // Walk back to offending equality.
                     while (thisDiff != equalities.lastElement()) {
                         thisDiff = pointer.previous();
                     }
                     pointer.next();
 
                     // Replace equality with a delete.
                     pointer.set(new Diff(Operation.DELETE, lastequality));
                     // Insert a corresponding an insert.
                     thisDiff = new Diff(Operation.INSERT, lastequality);
                     pointer.add(thisDiff);
 
                     equalities.pop();  // Throw away the equality we just deleted.
                     lastequality = null;
                     if (preIns && preDel) {
                         // No changes made which could affect previous entry, keep going.
                         postIns = postDel = true;
                         equalities.clear();
                         safeDiff = thisDiff;
                     } else {
                         if (!equalities.empty()) {
                             // Throw away the previous equality (it needs to be reevaluated).
                             equalities.pop();
                         }
                         if (equalities.empty()) {
                             // There are no previous questionable equalities,
                             // walk back to the last known safe diff.
                             thisDiff = safeDiff;
                         } else {
                             // There is an equality we can fall back to.
                             thisDiff = equalities.lastElement();
                         }
                         while (thisDiff != pointer.previous()) {
                             // Intentionally empty loop.
                         }
                         postIns = postDel = false;
                     }
 
                     changes = true;
                 }
             }
             thisDiff = pointer.hasNext() ? pointer.next() : null;
         }
 
         if (changes) {
             this.diffCleanupMerge(diffs);
         }
     }
 
     /**
      * Reorder and merge like edit sections.  Merge equalities.
      * Any edit section can move as long as it doesn't cross an equality.
      * @param diffs LinkedList of Diff objects.
      */
     public void diffCleanupMerge(LinkedList<Diff> diffs) {
 
         diffs.add(new Diff(Operation.EQUAL, StringUtils.EMPTY));  // Add a dummy entry at the end.
         ListIterator<Diff> pointer = diffs.listIterator();
         int countDelete = 0;
         int countInsert = 0;
         StringBuilder textDelete = new StringBuilder();
         StringBuilder textInsert = new StringBuilder();
         Diff thisDiff = pointer.next();
         Diff prevEqual = null;
         int commonlength;
         while (thisDiff != null) {
             switch (thisDiff.getOperation()) {
                 case INSERT:
                     countInsert++;
                     textInsert.append(thisDiff.getText());
                     prevEqual = null;
                     break;
                 case DELETE:
                     countDelete++;
                     textDelete.append(thisDiff.getText());
                     prevEqual = null;
                     break;
                 case EQUAL:
                     if (countDelete + countInsert > 1) {
 
                         boolean bothTypes = countDelete != 0 && countInsert != 0;
                         // Delete the offending records.
                         pointer.previous();  // Reverse direction.
                         while (countDelete-- > 0) {
                             pointer.previous();
                             pointer.remove();
                         }
                         while (countInsert-- > 0) {
                             pointer.previous();
                             pointer.remove();
                         }
 
                         if (bothTypes) {
                             // Factor out any common prefixies.
                             commonlength = this.diffCommonPrefix(textInsert.toString(), textDelete.toString());
                             if (commonlength != 0) {
                                 if (pointer.hasPrevious()) {
                                     thisDiff = pointer.previous();
                                     // Previous diff should have been an equality: thisDiff.getOperation() == Operation.EQUAL")
                                     thisDiff.setText(thisDiff.getText() + textInsert.substring(0, commonlength));
                                     pointer.next();
                                 } else {
                                     pointer.add(new Diff(Operation.EQUAL,
                                             textInsert.substring(0, commonlength)));
                                 }
                                 String substringIns = textInsert.substring(commonlength);
                                 textInsert.setLength(0);
                                 textInsert.append(substringIns);
                                 String substringDel = textDelete.substring(commonlength);
                                 textDelete.setLength(0);
                                 textDelete.append(substringDel);
                             }
                             // Factor out any common suffixies.
                             commonlength = this.diffCommonSuffix(textInsert.toString(), textDelete.toString());
                             if (commonlength != 0) {
                                 thisDiff = pointer.next();
                                 thisDiff.setText(textInsert.substring(textInsert.length() - commonlength) + thisDiff.getText());
                                 String substringIns = textInsert.substring(0, textInsert.length() - commonlength);
                                 textInsert.setLength(0);
                                 textInsert.append(substringIns);
                                 String substringDel = textDelete.substring(0, textDelete.length() - commonlength);
                                 textDelete.setLength(0);
                                 textDelete.append(substringDel);
                                 pointer.previous();
                             }
                         }
                         // Insert the merged records.
                         if (textDelete.length() != 0) {
                             pointer.add(new Diff(Operation.DELETE, textDelete.toString()));
                         }
                         if (textInsert.length() != 0) {
                             pointer.add(new Diff(Operation.INSERT, textInsert.toString()));
                         }
                         // Step forward to the equality.
                         thisDiff = pointer.hasNext() ? pointer.next() : null;
                     } else if (prevEqual != null) {
                         // Merge this equality with the previous one.
                         prevEqual.setText(prevEqual.getText() + thisDiff.getText());
                         pointer.remove();
                         thisDiff = pointer.previous();
                         pointer.next();  // Forward direction
                     }
                     countInsert = 0;
                     countDelete = 0;
                     textDelete.setLength(0);
                     textInsert.setLength(0);
                     prevEqual = thisDiff;
                     break;
             }
             thisDiff = pointer.hasNext() ? pointer.next() : null;
         }
         if (diffs.getLast().getText().isEmpty()) {
             diffs.removeLast();  // Remove the dummy entry at the end.
         }
 
         /*
          * Second pass: look for single edits surrounded on both sides by equalities
          * which can be shifted sideways to eliminate an equality.
          * e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
          */
         boolean changes = false;
         // Create a new iterator at the start.
         // (As opposed to walking the current one back.)
         pointer = diffs.listIterator();
         Diff prevDiff = pointer.hasNext() ? pointer.next() : null;
         thisDiff = pointer.hasNext() ? pointer.next() : null;
         Diff nextDiff = pointer.hasNext() ? pointer.next() : null;
 
         // Intentionally ignore the first and last element (don't need checking).
         while (nextDiff != null) {
             if (prevDiff.getOperation() == Operation.EQUAL &&
                     nextDiff.getOperation() == Operation.EQUAL) {
                 // This is a single edit surrounded by equalities.
                 if (thisDiff.getText().endsWith(prevDiff.getText())) {
                     // Shift the edit over the previous equality.
                     thisDiff.setText(prevDiff.getText()
                             + thisDiff.getText().substring(0, thisDiff.getText().length()
                             - prevDiff.getText().length()));
                     nextDiff.setText(prevDiff.getText() + nextDiff.getText());
                     pointer.previous(); // Walk past nextDiff.
                     pointer.previous(); // Walk past thisDiff.
                     pointer.previous(); // Walk past prevDiff.
                     pointer.remove(); // Delete prevDiff.
                     pointer.next(); // Walk past thisDiff.
                     thisDiff = pointer.next(); // Walk past nextDiff.
                     nextDiff = pointer.hasNext() ? pointer.next() : null;
                     changes = true;
                 } else if (thisDiff.getText().startsWith(nextDiff.getText())) {
                     // Shift the edit over the next equality.
                     prevDiff.setText(prevDiff.getText() + nextDiff.getText());
                     thisDiff.setText(thisDiff.getText().substring(nextDiff.getText().length())
                             + nextDiff.getText());
                     pointer.remove(); // Delete nextDiff.
                     nextDiff = pointer.hasNext() ? pointer.next() : null;
                     changes = true;
                 }
             }
             prevDiff = thisDiff;
             thisDiff = nextDiff;
             nextDiff = pointer.hasNext() ? pointer.next() : null;
         }
         // If shifts were made, the diff needs reordering and another shift sweep.
         if (changes) {
             this.diffCleanupMerge(diffs);
         }
     }
 
     /**
      * loc is a location in text1, compute and return the equivalent location in
      * text2.
      * e.g. "The cat" vs "The big cat", 1->1, 5->8
      * @param diffs List of Diff objects.
      * @param loc Location within text1.
      * @return Location within text2.
      */
     public int diffXIndex(List<Diff> diffs, int loc) {
         int chars1 = 0;
         int chars2 = 0;
         int lastChars1 = 0;
         int lastChars2 = 0;
         Diff lastDiff = null;
         for (Diff aDiff : diffs) {
             if (aDiff.getOperation() != Operation.INSERT) {
                 // Equality or deletion.
                 chars1 += aDiff.getText().length();
             }
             if (aDiff.getOperation() != Operation.DELETE) {
                 // Equality or insertion.
                 chars2 += aDiff.getText().length();
             }
             if (chars1 > loc) {
                 // Overshot the location.
                 lastDiff = aDiff;
                 break;
             }
             lastChars1 = chars1;
             lastChars2 = chars2;
         }
         if (lastDiff != null && lastDiff.getOperation() == Operation.DELETE) {
             // The location was deleted.
             return lastChars2;
         }
         // Add the remaining character length.
         return lastChars2 + loc - lastChars1;
     }
 
     /**
      * Convert a Diff list into a pretty HTML report.
      * @param diffs List of Diff objects.
      * @return HTML representation.
      */
     public String diffPrettyHtml(List<Diff> diffs) {
         StringBuilder html = new StringBuilder();
         for (Diff aDiff : diffs) {
             String text = aDiff.getText().replace("&", "&amp;").replace("<", "&lt;")
                     .replace(">", "&gt;").replace("\n", "&para;<br>");
             switch (aDiff.getOperation()) {
                 case INSERT:
                     html.append("<ins style=\"background:#e6ffe6;\">").append(text)
                             .append("</ins>");
                     break;
                 case DELETE:
                     html.append("<del style=\"background:#ffe6e6;\">").append(text)
                             .append("</del>");
                     break;
                 case EQUAL:
                     html.append("<span>").append(text).append("</span>");
                     break;
             }
         }
         return html.toString();
     }
 
     /**
      * Compute and return the source text (all equalities and deletions).
      * @param diffs List of Diff objects.
      * @return Source text.
      */
     public String diffText1(List<Diff> diffs) {
         StringBuilder text = new StringBuilder();
         for (Diff aDiff : diffs) {
             if (aDiff.getOperation() != Operation.INSERT) {
                 text.append(aDiff.getText());
             }
         }
         return text.toString();
     }
 
     /**
      * Compute and return the destination text (all equalities and insertions).
      * @param diffs List of Diff objects.
      * @return Destination text.
      */
     public String diffText2(List<Diff> diffs) {
         StringBuilder text = new StringBuilder();
         for (Diff aDiff : diffs) {
             if (aDiff.getOperation() != Operation.DELETE) {
                 text.append(aDiff.getText());
             }
         }
         return text.toString();
     }
 
     /**
      * Compute the Levenshtein distance; the number of inserted, deleted or
      * substituted characters.
      * @param diffs List of Diff objects.
      * @return Number of changes.
      */
     public int diffLevenshtein(List<Diff> diffs) {
         int levenshtein = 0;
         int insertions = 0;
         int deletions = 0;
         for (Diff aDiff : diffs) {
             switch (aDiff.getOperation()) {
                 case INSERT:
                     insertions += aDiff.getText().length();
                     break;
                 case DELETE:
                     deletions += aDiff.getText().length();
                     break;
                 case EQUAL:
                     // A deletion and an insertion is one substitution.
                     levenshtein += Math.max(insertions, deletions);
                     insertions = 0;
                     deletions = 0;
                     break;
             }
         }
         levenshtein += Math.max(insertions, deletions);
         return levenshtein;
     }
 
     /**
      * Crush the diff into an encoded string which describes the operations
      * required to transform text1 into text2.
      * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
      * Operations are tab-separated.  Inserted text is escaped using %xx notation.
      * @param diffs Array of Diff objects.
      * @return Delta text.
      */
     public String diffToDelta(List<Diff> diffs) {
 
         StringBuilder text = new StringBuilder();
         for (Diff aDiff : diffs) {
             switch (aDiff.getOperation()) {
                 case INSERT:
                     text.append("+").append(URLEncoder.encode(aDiff.getText(), StandardCharsets.UTF_8)
                             .replace('+', ' ')).append("\t");
                     break;
                 case DELETE:
                     text.append("-").append(aDiff.getText().length()).append("\t");
                     break;
                 case EQUAL:
                     text.append("=").append(aDiff.getText().length()).append("\t");
                     break;
             }
         }
         String delta = text.toString();
         if (!delta.isEmpty()) {
             // Strip off trailing tab character.
             delta = delta.substring(0, delta.length() - 1);
             delta = Patch.unescapeForEncodeUriCompatability(delta);
         }
         return delta;
     }
 
     /**
      * Given the original text1, and an encoded string which describes the
      * operations required to transform text1 into text2, compute the full diff.
      * @param text1 Source string for the diff.
      * @param delta Delta text.
      * @return list of Diff objects or null if invalid.
      */
     public List<Diff> diffFromDelta(String text1, String delta) {
 
         List<Diff> diffs = new LinkedList<>();
         int pointer = 0;  // Cursor in text1
         String[] tokens = delta.split("\t");
 
         for (String token : tokens) {
             if (token.isEmpty()) {
                 // Blank tokens are ok (from a trailing \t).
                 continue;
             }
             // Each token begins with a one character parameter which specifies the
             // operation of this token (delete, insert, equality).
             String param = token.substring(1);
             switch (token.charAt(0)) {
                 case '+':
                     // decode would change all "+" to " "
                     param = param.replace("+", "%2B");
                     try {
                         param = URLDecoder.decode(param, StandardCharsets.UTF_8);
                     } catch (IllegalArgumentException e) {
                         // Malformed URI sequence.
                         throw new IllegalArgumentException(
                                 "Illegal escape in diff_fromDelta: " + param, e);
                     }
                     diffs.add(new Diff(Operation.INSERT, param));
                     break;
                 case '-':
                     // Fall through.
                 case '=':
                     int n;
                     try {
                         n = Integer.parseInt(param);
                     } catch (NumberFormatException e) {
                         throw new IllegalArgumentException(
                                 "Invalid number in diff_fromDelta: " + param, e);
                     }
                     if (n < 0) {
                         throw new IllegalArgumentException(
                                 "Negative number in diff_fromDelta: " + param);
                     }
                     String text;
                     try {
                         int p1 = pointer;
                         pointer += n;
                         int p2 = pointer;
                         text = text1.substring(p1, p2);
                     } catch (StringIndexOutOfBoundsException e) {
                         throw new IllegalArgumentException("Delta length (" + pointer
                                 + ") larger than source text length (" + text1.length()
                                 + ").", e);
                     }
                     if (token.charAt(0) == '=') {
                         diffs.add(new Diff(Operation.EQUAL, text));
                     } else {
                         diffs.add(new Diff(Operation.DELETE, text));
                     }
                     break;
                 default:
                     // Anything else is an error.
                     throw new IllegalArgumentException(
                             "Invalid diff operation in diff_fromDelta: " + token.charAt(0));
             }
         }
         if (pointer != text1.length()) {
             throw new IllegalArgumentException("Delta length (" + pointer
                     + ") smaller than source text length (" + text1.length() + ").");
         }
         return diffs;
     }
 
 
     //  MATCH FUNCTIONS
 
     /**
      * Locate the best instance of 'pattern' in 'text' near 'loc'.
      * Returns -1 if no match found.
      * @param text The text to search.
      * @param pattern The pattern to search for.
      * @param valueLoc The location to search around.
      * @return Best match index or -1.
      */
     public int matchMain(String text, String pattern, int valueLoc) {
         // Check for null inputs.
         if (text == null || pattern == null) {
             throw new IllegalArgumentException("Null inputs. (match_main)");
         }
 
         int loc = Math.max(0, Math.min(valueLoc, text.length()));
         if (text.equals(pattern)) {
             // Shortcut (potentially not guaranteed by the algorithm)
             return 0;
         } else if (text.isEmpty()) {
             // Nothing to match.
             return -1;
         } else if (loc + pattern.length() <= text.length()
                 && text.substring(loc, loc + pattern.length()).equals(pattern)) {
             // Perfect match at the perfect spot!  (Includes case of null pattern)
             return loc;
         } else {
             // Do a fuzzy compare.
             return this.matchBitap(text, pattern, loc);
         }
     }
 
     /**
      * Locate the best instance of 'pattern' in 'text' near 'loc' using the
      * Bitap algorithm.  Returns -1 if no match found.
      * @param text The text to search.
      * @param pattern The pattern to search for.
      * @param loc The location to search around.
      * @return Best match index or -1.
      */
     protected int matchBitap(String text, String pattern, int loc) {
 
         // Initialize the alphabet.
         Map<Character, Integer> s = this.matchAlphabet(pattern);
 
         // Highest score beyond which we give up.
         double scoreThreshold = DiffMatchPatch.MATCH_THRESHOLD;
         // Is there a nearby exact match? (speedup)
         int bestLoc = text.indexOf(pattern, loc);
         if (bestLoc != -1) {
             scoreThreshold = Math.min(this.matchBitapScore(0, bestLoc, loc, pattern),
                     scoreThreshold);
             // What about in the other direction? (speedup)
             bestLoc = text.lastIndexOf(pattern, loc + pattern.length());
             if (bestLoc != -1) {
                 scoreThreshold = Math.min(this.matchBitapScore(0, bestLoc, loc, pattern),
                         scoreThreshold);
             }
         }
 
         // Initialize the bit arrays.
         int matchmask = 1 << (pattern.length() - 1);
         bestLoc = -1;
 
         int binMin;
         int binMid;
         int binMax = pattern.length() + text.length();
         // Empty initialization added to appease Java compiler.
         int[] lastRd = new int[0];
         for (int d = 0; d < pattern.length(); d++) {
 
             // Scan for the best match; each iteration allows for one more error.
             // Run a binary search to determine how far from 'loc' we can stray at
             // this error level.
             binMin = 0;
             binMid = binMax;
             while (binMin < binMid) {
                 if (this.matchBitapScore(d, loc + binMid, loc, pattern)
                         <= scoreThreshold) {
                     binMin = binMid;
                 } else {
                     binMax = binMid;
                 }
                 binMid = (binMax - binMin) / 2 + binMin;
             }
             // Use the result from this iteration as the maximum for the next.
             binMax = binMid;
             int start = Math.max(1, loc - binMid + 1);
             int finish = Math.min(loc + binMid, text.length()) + pattern.length();
 
             int[] rd = new int[finish + 2];
             rd[finish + 1] = (1 << d) - 1;
             for (int j = finish; j >= start; j--) {
 
                 int charMatch;
                 if (text.length() <= j - 1 || !s.containsKey(text.charAt(j - 1))) {
                     // Out of range.
                     charMatch = 0;
                 } else {
                     charMatch = s.get(text.charAt(j - 1));
                 }
                 if (d == 0) {
                     // First pass: exact match.
                     rd[j] = ((rd[j + 1] << 1) | 1) & charMatch;
                 } else {
                     // Subsequent passes : fuzzy match.
                     rd[j] = (((rd[j + 1] << 1) | 1) & charMatch)
                             | (((lastRd[j + 1] | lastRd[j]) << 1) | 1) | lastRd[j + 1];
                 }
 
                 if ((rd[j] & matchmask) != 0) {
                     double score = this.matchBitapScore(d, j - 1, loc, pattern);
                     // This match will almost certainly be better than any existing
                     // match.  But check anyway.
                     if (score <= scoreThreshold) {
                         // Told you so.
                         scoreThreshold = score;
                         bestLoc = j - 1;
                         if (bestLoc > loc) {
                             // When passing loc, don't exceed our current distance from loc.
                             start = Math.max(1, 2 * loc - bestLoc);
                         } else {
                             // Already passed loc, downhill from here on in.
                             break;
                         }
                     }
                 }
             }
             if (this.matchBitapScore(d + 1, loc, loc, pattern) > scoreThreshold) {
                 // No hope for a (better) match at greater error levels.
                 break;
             }
             lastRd = rd;
         }
         return bestLoc;
     }
 
     /**
      * Compute and return the score for a match with e errors and x location.
      * @param e Number of errors in match.
      * @param x Location of match.
      * @param loc Expected location of match.
      * @param pattern Pattern being sought.
      * @return Overall score for match (0.0 = good, 1.0 = bad).
      */
     private double matchBitapScore(int e, int x, int loc, String pattern) {
         float accuracy = (float) e / pattern.length();
         int proximity = Math.abs(loc - x);
         return accuracy + (proximity / (float) DiffMatchPatch.MATCH_DISTANCE);
     }
 
     /**
      * Initialize the alphabet for the Bitap algorithm.
      * @param pattern The text to encode.
      * @return Hash of character locations.
      */
     protected Map<Character, Integer> matchAlphabet(String pattern) {
         Map<Character, Integer> s = new HashMap<>();
         char[] charPattern = pattern.toCharArray();
         for (char c : charPattern) {
             s.put(c, 0);
         }
         int i = 0;
         for (char c : charPattern) {
             s.put(c, s.get(c) | (1 << (pattern.length() - i - 1)));
             i++;
         }
         return s;
     }
 
 
     //  PATCH FUNCTIONS
 
     /**
      * Increase the context until it is unique,
      * but don't let the pattern expand beyond Match_MaxBits.
      * @param patch The patch to grow.
      * @param text Source text.
      */
     protected void patchAddContext(Patch patch, String text) {
 
         if (text.isEmpty()) {
             return;
         }
         String pattern = text.substring(patch.getStart2(), patch.getStart2() + patch.getLength1());
         int padding = 0;
 
         // Look for the first and last matches of pattern in text.  If two different
         // matches are found, increase the pattern length.
         while (text.indexOf(pattern) != text.lastIndexOf(pattern)
                 && pattern.length() < DiffMatchPatch.MATCH_MAX_BITS - DiffMatchPatch.PATCH_MARGIN - DiffMatchPatch.PATCH_MARGIN) {
             padding += DiffMatchPatch.PATCH_MARGIN;
             pattern = text.substring(Math.max(0, patch.getStart2() - padding),
                     Math.min(text.length(), patch.getStart2() + patch.getLength1() + padding));
         }
         // Add one chunk for good luck.
         padding += DiffMatchPatch.PATCH_MARGIN;
 
         // Add the prefix.
         String prefix = text.substring(Math.max(0, patch.getStart2() - padding),
                 patch.getStart2());
         if (!prefix.isEmpty()) {
             patch.getDiffs().addFirst(new Diff(Operation.EQUAL, prefix));
         }
         // Add the suffix.
         String suffix = text.substring(patch.getStart2() + patch.getLength1(),
                 Math.min(text.length(), patch.getStart2() + patch.getLength1() + padding));
         if (!suffix.isEmpty()) {
             patch.getDiffs().addLast(new Diff(Operation.EQUAL, suffix));
         }
 
         // Roll back the start points.
         patch.setStart1(patch.getStart1() - prefix.length());
         patch.setStart2(patch.getStart2() - prefix.length());
         // Extend the lengths.
         patch.setLength1(patch.getLength1() + prefix.length() + suffix.length());
         patch.setLength2(patch.getLength2() + prefix.length() + suffix.length());
     }
 
     /**
      * Compute a list of patches to turn text1 into text2.
      * A set of diffs will be computed.
      * @param text1 Old text.
      * @param text2 New text.
      * @return LinkedList of Patch objects.
      */
     public List<Patch> patchMake(String text1, String text2) {
         if (text1 == null || text2 == null) {
             throw new IllegalArgumentException("Null inputs. (patch_make)");
         }
         // No diffs provided, compute our own.
         LinkedList<Diff> diffs = this.diffMain(text1, text2, true);
         if (diffs.size() > 2) {
             this.diffCleanupSemantic(diffs);
             this.diffCleanupEfficiency(diffs);
         }
         return this.patchMake(text1, diffs);
     }
 
     /**
      * Compute a list of patches to turn text1 into text2.
      * text1 will be derived from the provided diffs.
      * @param diffs Array of Diff objects for text1 to text2.
      * @return LinkedList of Patch objects.
      */
     public List<Patch> patchMake(LinkedList<Diff> diffs) {
         if (diffs == null) {
             throw new IllegalArgumentException("Null inputs. (patch_make)");
         }
         // No origin string provided, compute our own.
         String text1 = this.diffText1(diffs);
         return this.patchMake(text1, diffs);
     }
 
     /**
      * Compute a list of patches to turn text1 into text2.
      * text2 is not provided, diffs are the delta between text1 and text2.
      * @param text1 Old text.
      * @param diffs Array of Diff objects for text1 to text2.
      * @return Deque of Patch objects.
      */
     public List<Patch> patchMake(String text1, Deque<Diff> diffs) {
 
         if (text1 == null || diffs == null) {
             throw new IllegalArgumentException("Null inputs. (patch_make)");
         }
 
         List<Patch> patches = new LinkedList<>();
         if (diffs.isEmpty()) {
             return patches;  // Get rid of the null case.
         }
         Patch patch = new Patch();
         int charCount1 = 0;  // Number of characters into the text1 string.
         int charCount2 = 0;  // Number of characters into the text2 string.
         // Start with text1 (prepatch_text) and apply the diffs until we arrive at
         // text2 (postpatch_text). We recreate the patches one by one to determine
         // context info.
         String prepatchText = text1;
         String postpatchText = text1;
 
         for (Diff aDiff : diffs) {
             if (patch.getDiffs().isEmpty() && aDiff.getOperation() != Operation.EQUAL) {
                 // A new patch starts here.
                 patch.setStart1(charCount1);
                 patch.setStart2(charCount2);
             }
 
             switch (aDiff.getOperation()) {
                 case INSERT:
                     patch.getDiffs().add(aDiff);
                     patch.setLength2(patch.getLength2() + aDiff.getText().length());
                     postpatchText = postpatchText.substring(0, charCount2)
                             + aDiff.getText() + postpatchText.substring(charCount2);
                     break;
                 case DELETE:
                     patch.setLength1(patch.getLength1() + aDiff.getText().length());
                     patch.getDiffs().add(aDiff);
                     postpatchText = postpatchText.substring(0, charCount2)
                             + postpatchText.substring(charCount2 + aDiff.getText().length());
                     break;
                 case EQUAL:
                     if (
                             aDiff.getText().length() <= 2 * DiffMatchPatch.PATCH_MARGIN
                                     && !patch.getDiffs().isEmpty() && aDiff != diffs.getLast()
                     ) {
                         // Small equality inside a patch.
                         patch.getDiffs().add(aDiff);
                         patch.setLength1(patch.getLength1() + aDiff.getText().length());
                         patch.setLength2(patch.getLength2() + aDiff.getText().length());
                     }
 
                     if (
                             aDiff.getText().length() >= 2 * DiffMatchPatch.PATCH_MARGIN
                                     && !patch.getDiffs().isEmpty()
                     ) {
                         // Time for a new patch.
                         this.patchAddContext(patch, prepatchText);
                         patches.add(patch);
                         patch = new Patch();
                         // Unlike Unidiff, our patch lists have a rolling context.
                         // http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
                         // Update prepatch text & pos to reflect the application of the
                         // just completed patch.
                         prepatchText = postpatchText;
                         charCount1 = charCount2;
                     }
                     break;
             }
 
             // Update the current character count.
             if (aDiff.getOperation() != Operation.INSERT) {
                 charCount1 += aDiff.getText().length();
             }
             if (aDiff.getOperation() != Operation.DELETE) {
                 charCount2 += aDiff.getText().length();
             }
         }
         // Pick up the leftover patch if not empty.
         if (!patch.getDiffs().isEmpty()) {
             this.patchAddContext(patch, prepatchText);
             patches.add(patch);
         }
 
         return patches;
     }
 
     /**
      * Given an array of patches, return another array that is identical.
      * @param patches Array of Patch objects.
      * @return list of Patch objects.
      */
     public LinkedList<Patch> patchDeepCopy(List<Patch> patches) {
         LinkedList<Patch> patchesCopy = new LinkedList<>();
         for (Patch aPatch : patches) {
             Patch patchCopy = new Patch();
             for (Diff aDiff : aPatch.getDiffs()) {
                 Diff diffCopy = new Diff(aDiff.getOperation(), aDiff.getText());
                 patchCopy.getDiffs().add(diffCopy);
             }
             patchCopy.setStart1(aPatch.getStart1());
             patchCopy.setStart2(aPatch.getStart2());
             patchCopy.setLength1(aPatch.getLength1());
             patchCopy.setLength2(aPatch.getLength2());
             patchesCopy.add(patchCopy);
         }
         return patchesCopy;
     }
 
     /**
      * Merge a set of patches onto the text.  Return a patched text, as well
      * as an array of true/false values indicating which patches were applied.
      * @param valuePatches Array of Patch objects
      * @param valueText Old text.
      * @return Two element Object array, containing the new text and an array of
      *      boolean values.
      */
     public Object[] patchApply(LinkedList<Patch> valuePatches, String valueText) {
 
         if (valuePatches.isEmpty()) {
             return new Object[]{valueText, new boolean[0]};
         }
 
         // Deep copy the patches so that no changes are made to originals.
         LinkedList<Patch> patches = this.patchDeepCopy(valuePatches);
 
         String nullPadding = this.patchAddPadding(patches);
         String text = nullPadding + valueText + nullPadding;
         this.patchSplitMax(patches);
 
         int x = 0;
         // delta keeps track of the offset between the expected and actual location
         // of the previous patch.  If there are patches expected at positions 10 and
         // 20, but the first patch was found at 12, delta is 2 and the second patch
         // has an effective expected position of 22.
         int delta = 0;
         boolean[] results = new boolean[patches.size()];
         for (Patch aPatch : patches) {
 
             int expectedLoc = aPatch.getStart2() + delta;
             String text1 = this.diffText1(aPatch.getDiffs());
             int startLoc;
             int endLoc = -1;
 
             if (text1.length() > DiffMatchPatch.MATCH_MAX_BITS) {
                 // patch_splitMax will only provide an oversized pattern in the case of
                 // a monster delete.
                 startLoc = this.matchMain(text,
                         text1.substring(0, DiffMatchPatch.MATCH_MAX_BITS), expectedLoc);
                 if (startLoc != -1) {
                     endLoc = this.matchMain(text,
                             text1.substring(text1.length() - DiffMatchPatch.MATCH_MAX_BITS),
                             expectedLoc + text1.length() - DiffMatchPatch.MATCH_MAX_BITS);
                     if (endLoc == -1 || startLoc >= endLoc) {
                         // Can't find valid trailing context.  Drop this patch.
                         startLoc = -1;
                     }
                 }
             } else {
                 startLoc = this.matchMain(text, text1, expectedLoc);
             }
 
             if (startLoc == -1) {
                 // No match found.  :(
                 results[x] = false;
                 // Subtract the delta for this failed patch from subsequent patches.
                 delta -= aPatch.getLength2() - aPatch.getLength1();
             } else {
                 // Found a match.  :)
                 results[x] = true;
                 delta = startLoc - expectedLoc;
                 String text2;
                 if (endLoc == -1) {
                     text2 = text.substring(startLoc,
                             Math.min(startLoc + text1.length(), text.length()));
                 } else {
                     text2 = text.substring(startLoc,
                             Math.min(endLoc + DiffMatchPatch.MATCH_MAX_BITS, text.length()));
                 }
 
                 if (text1.equals(text2)) {
                     // Perfect match, just shove the replacement text in.
                     text = text.substring(0, startLoc) + this.diffText2(aPatch.getDiffs())
                             + text.substring(startLoc + text1.length());
                 } else {
                     // Imperfect match.  Run a diff to get a framework of equivalent
                     // indices.
                     List<Diff> diffs = this.diffMain(text1, text2, false);
                     if (text1.length() > DiffMatchPatch.MATCH_MAX_BITS
                             && this.diffLevenshtein(diffs) / (float) text1.length()
                             > DiffMatchPatch.PATCH_DELETE_THRESHOLD) {
                         // The end points match, but the content is unacceptably bad.
                         results[x] = false;
                     } else {
                         this.diffCleanupSemanticLossless(diffs);
                         int index1 = 0;
                         for (Diff aDiff : aPatch.getDiffs()) {
                             if (aDiff.getOperation() != Operation.EQUAL) {
                                 int index2 = this.diffXIndex(diffs, index1);
                                 if (aDiff.getOperation() == Operation.INSERT) {
                                     // Insertion
                                     text = text.substring(0, startLoc + index2) + aDiff.getText()
                                             + text.substring(startLoc + index2);
                                 } else if (aDiff.getOperation() == Operation.DELETE) {
                                     // Deletion
                                     text = text.substring(0, startLoc + index2)
                                             + text.substring(startLoc + this.diffXIndex(diffs,
                                             index1 + aDiff.getText().length()));
                                 }
                             }
                             if (aDiff.getOperation() != Operation.DELETE) {
                                 index1 += aDiff.getText().length();
                             }
                         }
                     }
                 }
             }
             x++;
         }
         // Strip the padding off.
         text = text.substring(nullPadding.length(), text.length()
                 - nullPadding.length());
         return new Object[]{text, results};
     }
 
     /**
      * Add some padding on text start and end so that edges can match something.
      * Intended to be called only from within patch_apply.
      * @param patches Array of Patch objects.
      * @return The padding string added to each side.
      */
     public String patchAddPadding(Deque<Patch> patches) {
 
         short paddingLength = DiffMatchPatch.PATCH_MARGIN;
         StringBuilder nullPadding = new StringBuilder();
         for (short x = 1; x <= paddingLength; x++) {
             nullPadding.append((char) x);
         }
 
         // Bump all the patches forward.
         for (Patch aPatch : patches) {
             aPatch.setStart1(aPatch.getStart1() + paddingLength);
             aPatch.setStart2(aPatch.getStart2() + paddingLength);
         }
 
         // Add some padding on start of first diff.
         Patch patch = patches.getFirst();
         Deque<Diff> diffs = patch.getDiffs();
         if (diffs.isEmpty() || diffs.getFirst().getOperation() != Operation.EQUAL) {
             // Add nullPadding equality.
             diffs.addFirst(new Diff(Operation.EQUAL, nullPadding.toString()));
             patch.setStart1(patch.getStart1() - paddingLength);  // Should be 0.
             patch.setStart2(patch.getStart2() - paddingLength);  // Should be 0.
             patch.setLength1(patch.getLength1() + paddingLength);
             patch.setLength2(patch.getLength2() + paddingLength);
         } else if (paddingLength > diffs.getFirst().getText().length()) {
             // Grow first equality.
             Diff firstDiff = diffs.getFirst();
             int extraLength = paddingLength - firstDiff.getText().length();
             firstDiff.setText(nullPadding.substring(firstDiff.getText().length())
                     + firstDiff.getText());
             patch.setStart1(patch.getStart1() - extraLength);
             patch.setStart2(patch.getStart2() - extraLength);
             patch.setLength1(patch.getLength1() + extraLength);
             patch.setLength2(patch.getLength2() + extraLength);
         }
 
         // Add some padding on end of last diff.
         patch = patches.getLast();
         diffs = patch.getDiffs();
         if (diffs.isEmpty() || diffs.getLast().getOperation() != Operation.EQUAL) {
             // Add nullPadding equality.
             diffs.addLast(new Diff(Operation.EQUAL, nullPadding.toString()));
             patch.setLength1(patch.getLength1() + paddingLength);
             patch.setLength2(patch.getLength2() + paddingLength);
         } else if (paddingLength > diffs.getLast().getText().length()) {
             // Grow last equality.
             Diff lastDiff = diffs.getLast();
             int extraLength = paddingLength - lastDiff.getText().length();
             lastDiff.setText(lastDiff.getText() + nullPadding.substring(0, extraLength));
             patch.setLength1(patch.getLength1() + extraLength);
             patch.setLength2(patch.getLength2() + extraLength);
         }
 
         return nullPadding.toString();
     }
 
     /**
      * Look through the patches and break up any which are longer than the
      * maximum limit of the match algorithm.
      * Intended to be called only from within patch_apply.
      * @param patches List of Patch objects.
      */
     public void patchSplitMax(List<Patch> patches) {
 
         short patchSize = DiffMatchPatch.MATCH_MAX_BITS;
         String precontext;
         String postcontext;
         Patch patch;
         int start1;
         int start2;
         boolean empty;
         Operation diffType;
         String diffText;
         ListIterator<Patch> pointer = patches.listIterator();
         Patch bigpatch = pointer.hasNext() ? pointer.next() : null;
 
         while (bigpatch != null) {
             if (bigpatch.getLength1() <= DiffMatchPatch.MATCH_MAX_BITS) {
                 bigpatch = pointer.hasNext() ? pointer.next() : null;
                 continue;
             }
             // Remove the big old patch.
             pointer.remove();
             start1 = bigpatch.getStart1();
             start2 = bigpatch.getStart2();
             precontext = StringUtils.EMPTY;
 
             while (!bigpatch.getDiffs().isEmpty()) {
                 // Create one of several smaller patches.
                 patch = new Patch();
                 empty = true;
                 patch.setStart1(start1 - precontext.length());
                 patch.setStart2(start2 - precontext.length());
                 if (!precontext.isEmpty()) {
                     patch.setLength1(patch.setLength2(precontext.length()));
                     patch.getDiffs().add(new Diff(Operation.EQUAL, precontext));
                 }
                 while (!bigpatch.getDiffs().isEmpty()
                         && patch.getLength1() < patchSize - DiffMatchPatch.PATCH_MARGIN) {
                     diffType = bigpatch.getDiffs().getFirst().getOperation();
                     diffText = bigpatch.getDiffs().getFirst().getText();
 
                     if (diffType == Operation.INSERT) {
                         // Insertions are harmless.
                         patch.setLength2(patch.getLength2() + diffText.length());
                         start2 += diffText.length();
                         patch.getDiffs().addLast(bigpatch.getDiffs().removeFirst());
                         empty = false;
                     } else if (diffType == Operation.DELETE && patch.getDiffs().size() == 1
                             && patch.getDiffs().getFirst().getOperation() == Operation.EQUAL
                             && diffText.length() > 2 * patchSize) {
                         // This is a large deletion.  Let it pass in one chunk.
                         patch.setLength1(patch.getLength1() + diffText.length());
                         start1 += diffText.length();
                         empty = false;
                         patch.getDiffs().add(new Diff(diffType, diffText));
                         bigpatch.getDiffs().removeFirst();
                     } else {
                         // Deletion or equality.  Only take as much as we can stomach.
                         diffText = diffText.substring(0, Math.min(diffText.length(),
                                 patchSize - patch.getLength1() - DiffMatchPatch.PATCH_MARGIN));
                         patch.setLength1(patch.getLength1() + diffText.length());
                         start1 += diffText.length();
                         if (diffType == Operation.EQUAL) {
                             patch.setLength2(patch.getLength2() + diffText.length());
                             start2 += diffText.length();
                         } else {
                             empty = false;
                         }
                         patch.getDiffs().add(new Diff(diffType, diffText));
                         if (diffText.equals(bigpatch.getDiffs().getFirst().getText())) {
                             bigpatch.getDiffs().removeFirst();
                         } else {
                             bigpatch.getDiffs().getFirst().setText(bigpatch.getDiffs().getFirst().getText()
                                     .substring(diffText.length()));
                         }
                     }
                 }
                 // Compute the head context for the next patch.
                 precontext = this.diffText2(patch.getDiffs());
                 precontext = precontext.substring(Math.max(0, precontext.length()
                         - DiffMatchPatch.PATCH_MARGIN));
                 // Append the end context for this patch.
                 if (this.diffText1(bigpatch.getDiffs()).length() > DiffMatchPatch.PATCH_MARGIN) {
                     postcontext = this.diffText1(bigpatch.getDiffs()).substring(0, DiffMatchPatch.PATCH_MARGIN);
                 } else {
                     postcontext = this.diffText1(bigpatch.getDiffs());
                 }
 
                 if (!postcontext.isEmpty()) {
                     patch.setLength1(patch.getLength1() + postcontext.length());
                     patch.setLength2(patch.getLength2() + postcontext.length());
                     if (!patch.getDiffs().isEmpty()
                             && patch.getDiffs().getLast().getOperation() == Operation.EQUAL) {
                         patch.getDiffs().getLast().setText(patch.getDiffs().getLast().getText() + postcontext);
                     } else {
                         patch.getDiffs().add(new Diff(Operation.EQUAL, postcontext));
                     }
                 }
 
                 if (!empty) {
                     pointer.add(patch);
                 }
             }
             bigpatch = pointer.hasNext() ? pointer.next() : null;
         }
     }
 
     /**
      * Take a list of patches and return a textual representation.
      * @param patches List of Patch objects.
      * @return Text representation of patches.
      */
     public String patchToText(List<Patch> patches) {
         StringBuilder text = new StringBuilder();
         for (Patch aPatch : patches) {
             text.append(aPatch);
         }
         return text.toString();
     }
 
     /**
      * Parse a textual representation of patches and return a List of Patch
      * objects.
      * @param textline Text representation of patches.
      * @return List of Patch objects.
      */
     public List<Patch> patchFromText(String textline) {
 
         List<Patch> patches = new LinkedList<>();
         if (textline.isEmpty()) {
             return patches;
         }
         List<String> textList = Arrays.asList(textline.split("\n"));
         Deque<String> text = new LinkedList<>(textList);
         Patch patch;
         Pattern patchHeader = Pattern.compile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$");
         Matcher m;
         char sign;
         String line;
         while (!text.isEmpty()) {
 
             m = patchHeader.matcher(text.getFirst());
             if (!m.matches()) {
                 throw new IllegalArgumentException(
                         "Invalid patch string: " + text.getFirst());
             }
             patch = new Patch();
             patches.add(patch);
             patch.setStart1(Integer.parseInt(m.group(1)));
             if (m.group(2).isEmpty()) {
                 patch.setStart1(patch.getStart1() - 1);
                 patch.setLength1(1);
             } else if ("0".equals(m.group(2))) {
                 patch.setLength1(0);
             } else {
                 patch.setStart1(patch.getStart1() - 1);
                 patch.setLength1(Integer.parseInt(m.group(2)));
             }
 
             patch.setStart2(Integer.parseInt(m.group(3)));
             if (m.group(4).isEmpty()) {
                 patch.setStart2(patch.getStart2() - 1);
                 patch.setLength2(1);
             } else if ("0".equals(m.group(4))) {
                 patch.setLength2(0);
             } else {
                 patch.setStart2(patch.getStart2() - 1);
                 patch.setLength2(Integer.parseInt(m.group(4)));
             }
             text.removeFirst();
 
             while (!text.isEmpty()) {
 
                 try {
                     sign = text.getFirst().charAt(0);
                 } catch (IndexOutOfBoundsException e) {
                     LOGGER.log(LogLevelUtil.IGNORE, e);
 
                     // Blank line?  Whatever.
                     text.removeFirst();
                     continue;
                 }
 
                 line = text.getFirst().substring(1);
                 line = line.replace("+", "%2B");  // decode would change all "+" to " "
                 try {
                     line = URLDecoder.decode(line, StandardCharsets.UTF_8);
                 } catch (IllegalArgumentException e) {
                     // Malformed URI sequence.
                     throw new IllegalArgumentException(
                             "Illegal escape in patch_fromText: " + line, e);
                 }
 
                 if (sign == '-') {
                     // Deletion.
                     patch.getDiffs().add(new Diff(Operation.DELETE, line));
                 } else if (sign == '+') {
                     // Insertion.
                     patch.getDiffs().add(new Diff(Operation.INSERT, line));
                 } else if (sign == ' ') {
                     // Minor equality.
                     patch.getDiffs().add(new Diff(Operation.EQUAL, line));
                 } else if (sign == '@') {
                     // Start of next patch.
                     break;
                 } else {
                     // WTF?
                     throw new IllegalArgumentException(
                             "Invalid patch mode '" + sign + "' in: " + line);
                 }
                 text.removeFirst();
             }
         }
         return patches;
     }
 }