/**
    * 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 org.apache.commons.lang3.StringUtils;
  
  import java.util.*;
  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 {
  
      // 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;
  
      // 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 record LinesToCharsResult(String chars1, String chars2, List<String> 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.
       * @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.isEmpty()
                         && 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.isEmpty()) {
                             pointer.add(new Diff(Operation.DELETE, textDelete.toString()));
                         }
                         if (!textInsert.isEmpty()) {
                             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);
         }
     }
 }