content: /*
   * Diff Match and Patch
   * Copyright 2018 The diff-match-patch Authors.
   * https://github.com/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 org.alephium.util;
  //package name.fraser.neil.plaintext;
  
  import java.io.UnsupportedEncodingException;
  import java.net.URLDecoder;
  import java.net.URLEncoder;
  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 {
  
      // 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 float Diff_Timeout = 1.0f;
      /**
       * Cost of an empty edit operation in terms of edit characters.
       */
      public short Diff_EditCost = 4;
      /**
       * At what point is no match declared (0.0 = perfection, 1.0 = very loose).
       */
      public 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 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 float Patch_DeleteThreshold = 0.5f;
      /**
       * Chunk size for context length.
       */
      public short Patch_Margin = 4;
  
      /**
       * The number of bits in an int.
       */
      private short Match_MaxBits = 32;
  
      /**
       * Internal class for returning results from diff_linesToChars().
       * Other less paranoid languages just use a three-element array.
       */
      protected static class LinesToCharsResult {
          protected String chars1;
          protected String chars2;
          protected 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 LinkedList<Diff> diff_main(String text1, String text2) {
          return diff_main(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> diff_main(String text1, String text2,
                                        boolean checklines) {
          // Set a deadline by which time the diff must be complete.
          long deadline;
          if (Diff_Timeout <= 0) {
              deadline = Long.MAX_VALUE;
          } else {
              deadline = System.currentTimeMillis() + (long) (Diff_Timeout * 1000);
          }
          return diff_main(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 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.  Used
       *     internally for recursive calls.  Users should set DiffTimeout instead.
       * @return Linked List of Diff objects.
       */
      private LinkedList<Diff> diff_main(String text1, String text2,
                                         boolean checklines, long deadline) {
          // 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<Diff>();
              if (text1.length() != 0) {
                  diffs.add(new Diff(Operation.EQUAL, text1));
              }
              return diffs;
          }
  
          // Trim off common prefix (speedup).
          int commonlength = diff_commonPrefix(text1, text2);
          String commonprefix = text1.substring(0, commonlength);
          text1 = text1.substring(commonlength);
          text2 = text2.substring(commonlength);
  
          // Trim off common suffix (speedup).
          commonlength = diff_commonSuffix(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 = diff_compute(text1, text2, checklines, deadline);
  
          // Restore the prefix and suffix.
          if (commonprefix.length() != 0) {
              diffs.addFirst(new Diff(Operation.EQUAL, commonprefix));
          }
          if (commonsuffix.length() != 0) {
              diffs.addLast(new Diff(Operation.EQUAL, commonsuffix));
          }
  
          diff_cleanupMerge(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> diff_compute(String text1, String text2,
                                            boolean checklines, long deadline) {
          LinkedList<Diff> diffs = new LinkedList<Diff>();
  
          if (text1.length() == 0) {
              // Just add some text (speedup).
              diffs.add(new Diff(Operation.INSERT, text2));
              return diffs;
          }
  
          if (text2.length() == 0) {
              // Just delete some text (speedup).
              diffs.add(new Diff(Operation.DELETE, text1));
              return diffs;
          }
  
          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 = diff_halfMatch(text1, text2);
          if (hm != null) {
              // A half-match was found, sort out the return data.
              String text1_a = hm[0];
              String text1_b = hm[1];
              String text2_a = hm[2];
              String text2_b = hm[3];
              String mid_common = hm[4];
              // Send both pairs off for separate processing.
              LinkedList<Diff> diffs_a = diff_main(text1_a, text2_a,
                      checklines, deadline);
              LinkedList<Diff> diffs_b = diff_main(text1_b, text2_b,
                      checklines, deadline);
              // Merge the results.
              diffs = diffs_a;
              diffs.add(new Diff(Operation.EQUAL, mid_common));
              diffs.addAll(diffs_b);
              return diffs;
          }
  
          if (checklines && text1.length() > 100 && text2.length() > 100) {
              return diff_lineMode(text1, text2, deadline);
          }
  
          return diff_bisect(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 text1 Old string to be diffed.
       * @param text2 New string to be diffed.
       * @param deadline Time when the diff should be complete by.
       * @return Linked List of Diff objects.
       */
      private LinkedList<Diff> diff_lineMode(String text1, String text2,
                                             long deadline) {
          // Scan the text on a line-by-line basis first.
          LinesToCharsResult a = diff_linesToChars(text1, text2);
          text1 = a.chars1;
          text2 = a.chars2;
          List<String> linearray = a.lineArray;
  
          LinkedList<Diff> diffs = diff_main(text1, text2, false, deadline);
  
          // Convert the diff back to original text.
          diff_charsToLines(diffs, linearray);
          // Eliminate freak matches (e.g. blank lines)
          diff_cleanupSemantic(diffs);
  
          // Rediff any replacement blocks, this time character-by-character.
          // Add a dummy entry at the end.
          diffs.add(new Diff(Operation.EQUAL, ""));
          int count_delete = 0;
          int count_insert = 0;
          String text_delete = "";
          String text_insert = "";
          ListIterator<Diff> pointer = diffs.listIterator();
          Diff thisDiff = pointer.next();
          while (thisDiff != null) {
              switch (thisDiff.operation) {
                  case INSERT:
                      count_insert++;
                      text_insert += thisDiff.text;
                      break;
                  case DELETE:
                      count_delete++;
                      text_delete += thisDiff.text;
                      break;
                  case EQUAL:
                      // Upon reaching an equality, check for prior redundancies.
                      if (count_delete >= 1 && count_insert >= 1) {
                          // Delete the offending records and add the merged ones.
                          pointer.previous();
                          for (int j = 0; j < count_delete + count_insert; j++) {
                              pointer.previous();
                              pointer.remove();
                          }
                          for (Diff subDiff : diff_main(text_delete, text_insert, false,
                                  deadline)) {
                              pointer.add(subDiff);
                          }
                      }
                      count_insert = 0;
                      count_delete = 0;
                      text_delete = "";
                      text_insert = "";
                      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> diff_bisect(String text1, String text2,
                                             long deadline) {
          // Cache the text lengths to prevent multiple calls.
          int text1_length = text1.length();
          int text2_length = text2.length();
          int max_d = (text1_length + text2_length + 1) / 2;
          int v_offset = max_d;
          int v_length = 2 * max_d;
          int[] v1 = new int[v_length];
          int[] v2 = new int[v_length];
          for (int x = 0; x < v_length; x++) {
              v1[x] = -1;
              v2[x] = -1;
          }
          v1[v_offset + 1] = 0;
          v2[v_offset + 1] = 0;
          int delta = text1_length - text2_length;
          // 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 < max_d; 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 k1_offset = v_offset + k1;
                  int x1;
                  if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {
                      x1 = v1[k1_offset + 1];
                  } else {
                      x1 = v1[k1_offset - 1] + 1;
                  }
                  int y1 = x1 - k1;
                  while (x1 < text1_length && y1 < text2_length
                          && text1.charAt(x1) == text2.charAt(y1)) {
                      x1++;
                      y1++;
                  }
                  v1[k1_offset] = x1;
                  if (x1 > text1_length) {
                      // Ran off the right of the graph.
                      k1end += 2;
                  } else if (y1 > text2_length) {
                      // Ran off the bottom of the graph.
                      k1start += 2;
                  } else if (front) {
                      int k2_offset = v_offset + delta - k1;
                      if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
                          // Mirror x2 onto top-left coordinate system.
                          int x2 = text1_length - v2[k2_offset];
                          if (x1 >= x2) {
                              // Overlap detected.
                              return diff_bisectSplit(text1, text2, x1, y1, deadline);
                          }
                      }
                  }
              }
  
              // Walk the reverse path one step.
              for (int k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
                  int k2_offset = v_offset + k2;
                  int x2;
                  if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {
                      x2 = v2[k2_offset + 1];
                  } else {
                      x2 = v2[k2_offset - 1] + 1;
                  }
                  int y2 = x2 - k2;
                  while (x2 < text1_length && y2 < text2_length
                          && text1.charAt(text1_length - x2 - 1)
                          == text2.charAt(text2_length - y2 - 1)) {
                      x2++;
                      y2++;
                  }
                  v2[k2_offset] = x2;
                  if (x2 > text1_length) {
                      // Ran off the left of the graph.
                      k2end += 2;
                  } else if (y2 > text2_length) {
                      // Ran off the top of the graph.
                      k2start += 2;
                  } else if (!front) {
                      int k1_offset = v_offset + delta - k2;
                      if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
                          int x1 = v1[k1_offset];
                          int y1 = v_offset + x1 - k1_offset;
                          // Mirror x2 onto top-left coordinate system.
                          x2 = text1_length - x2;
                          if (x1 >= x2) {
                              // Overlap detected.
                              return diff_bisectSplit(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<Diff>();
          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> diff_bisectSplit(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 = diff_main(text1a, text2a, false, deadline);
          LinkedList<Diff> diffsb = diff_main(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 diff_linesToChars(String text1, String text2) {
          List<String> lineArray = new ArrayList<String>();
          Map<String, Integer> lineHash = new HashMap<String, Integer>();
          // 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("");
  
          // Allocate 2/3rds of the space for text1, the rest for text2.
          String chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash, 40000);
          String chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash, 65535);
          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.
       * @param maxLines Maximum length of lineArray.
       * @return Encoded string.
       */
      private String diff_linesToCharsMunge(String text, List<String> lineArray,
                                            Map<String, Integer> lineHash, int maxLines) {
          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);
  
              if (lineHash.containsKey(line)) {
                  chars.append(String.valueOf((char) (int) lineHash.get(line)));
              } else {
                  if (lineArray.size() == maxLines) {
                      // Bail out at 65535 because
                      // String.valueOf((char) 65536).equals(String.valueOf(((char) 0)))
                      line = text.substring(lineStart);
                      lineEnd = text.length();
                  }
                  lineArray.add(line);
                  lineHash.put(line, lineArray.size() - 1);
                  chars.append(String.valueOf((char) (lineArray.size() - 1)));
              }
              lineStart = lineEnd + 1;
          }
          return chars.toString();
      }
  
      /**
       * Rehydrate the text in a diff from a string of line hashes to real lines of
       * text.
       * @param diffs List of Diff objects.
       * @param lineArray List of unique strings.
       */
      protected void diff_charsToLines(List<Diff> diffs,
                                       List<String> lineArray) {
          StringBuilder text;
          for (Diff diff : diffs) {
              text = new StringBuilder();
              for (int j = 0; j < diff.text.length(); j++) {
                  text.append(lineArray.get(diff.text.charAt(j)));
              }
              diff.text = 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 diff_commonPrefix(String text1, String text2) {
          // Performance analysis: https://neil.fraser.name/news/2007/10/09/
          int n = java.lang.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 diff_commonSuffix(String text1, String text2) {
          // Performance analysis: https://neil.fraser.name/news/2007/10/09/
          int text1_length = text1.length();
          int text2_length = text2.length();
          int n = java.lang.Math.min(text1_length, text2_length);
          for (int i = 1; i <= n; i++) {
              if (text1.charAt(text1_length - i) != text2.charAt(text2_length - i)) {
                  return i - 1;
              }
          }
          return n;
      }
  
      /**
       * Determine if the suffix of one string is the prefix of another.
       * @param text1 First string.
       * @param text2 Second string.
       * @return The number of characters common to the end of the first
       *     string and the start of the second string.
       */
      protected int diff_commonOverlap(String text1, String text2) {
          // Cache the text lengths to prevent multiple calls.
          int text1_length = text1.length();
          int text2_length = text2.length();
          // Eliminate the null case.
          if (text1_length == 0 || text2_length == 0) {
              return 0;
          }
          // Truncate the longer string.
          if (text1_length > text2_length) {
              text1 = text1.substring(text1_length - text2_length);
          } else if (text1_length < text2_length) {
              text2 = text2.substring(0, text1_length);
          }
          int text_length = java.lang.Math.min(text1_length, text2_length);
          // Quick check for the worst case.
          if (text1.equals(text2)) {
              return text_length;
          }
  
          // Start by looking for a single character match
          // and increase length until no match is found.
          // Performance analysis: https://neil.fraser.name/news/2010/11/04/
          int best = 0;
          int length = 1;
          while (true) {
              String pattern = text1.substring(text_length - length);
              int found = text2.indexOf(pattern);
              if (found == -1) {
                  return best;
              }
              length += found;
              if (found == 0 || text1.substring(text_length - 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[] diff_halfMatch(String text1, String text2) {
          if (Diff_Timeout <= 0) {
              // Don't risk returning a non-optimal diff if we have unlimited time.
              return null;
          }
          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 = diff_halfMatchI(longtext, shorttext,
                  (longtext.length() + 3) / 4);
          // Check again based on the third quarter.
          String[] hm2 = diff_halfMatchI(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;
              //return new String[]{hm[0], hm[1], hm[2], hm[3], hm[4]};
          } 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[] diff_halfMatchI(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 best_common = "";
          String best_longtext_a = "", best_longtext_b = "";
          String best_shorttext_a = "", best_shorttext_b = "";
          while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
              int prefixLength = diff_commonPrefix(longtext.substring(i),
                      shorttext.substring(j));
              int suffixLength = diff_commonSuffix(longtext.substring(0, i),
                      shorttext.substring(0, j));
              if (best_common.length() < suffixLength + prefixLength) {
                  best_common = shorttext.substring(j - suffixLength, j)
                          + shorttext.substring(j, j + prefixLength);
                  best_longtext_a = longtext.substring(0, i - suffixLength);
                  best_longtext_b = longtext.substring(i + prefixLength);
                  best_shorttext_a = shorttext.substring(0, j - suffixLength);
                  best_shorttext_b = shorttext.substring(j + prefixLength);
              }
          }
          if (best_common.length() * 2 >= longtext.length()) {
              return new String[]{best_longtext_a, best_longtext_b,
                      best_shorttext_a, best_shorttext_b, best_common};
          } else {
              return null;
          }
      }
  
      /**
       * Reduce the number of edits by eliminating semantically trivial equalities.
       * @param diffs LinkedList of Diff objects.
       */
      public void diff_cleanupSemantic(LinkedList<Diff> diffs) {
          if (diffs.isEmpty()) {
              return;
          }
          boolean changes = false;
          Deque<Diff> equalities = new ArrayDeque<Diff>();  // Double-ended queue of qualities.
          String lastEquality = null; // Always equal to equalities.peek().text
          ListIterator<Diff> pointer = diffs.listIterator();
          // Number of characters that changed prior to the equality.
          int length_insertions1 = 0;
          int length_deletions1 = 0;
          // Number of characters that changed after the equality.
          int length_insertions2 = 0;
          int length_deletions2 = 0;
          Diff thisDiff = pointer.next();
          while (thisDiff != null) {
              if (thisDiff.operation == Operation.EQUAL) {
                  // Equality found.
                  equalities.push(thisDiff);
                  length_insertions1 = length_insertions2;
                  length_deletions1 = length_deletions2;
                  length_insertions2 = 0;
                  length_deletions2 = 0;
                  lastEquality = thisDiff.text;
              } else {
                  // An insertion or deletion.
                  if (thisDiff.operation == Operation.INSERT) {
                      length_insertions2 += thisDiff.text.length();
                  } else {
                      length_deletions2 += thisDiff.text.length();
                  }
                  // Eliminate an equality that is smaller or equal to the edits on both
                  // sides of it.
                  if (lastEquality != null && (lastEquality.length()
                          <= java.lang.Math.max(length_insertions1, length_deletions1))
                          && (lastEquality.length()
                          <= java.lang.Math.max(length_insertions2, length_deletions2))) {
                      //System.out.println("Splitting: '" + lastEquality + "'");
                      // Walk back to offending equality.
                      while (thisDiff != equalities.peek()) {
                          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.isEmpty()) {
                          // Throw away the previous equality (it needs to be reevaluated).
                          equalities.pop();
                      }
                      if (equalities.isEmpty()) {
                          // 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.peek();
                          while (thisDiff != pointer.previous()) {
                              // Intentionally empty loop.
                          }
                      }
  
                      length_insertions1 = 0;  // Reset the counters.
                      length_insertions2 = 0;
                      length_deletions1 = 0;
                      length_deletions2 = 0;
                      lastEquality = null;
                      changes = true;
                  }
              }
              thisDiff = pointer.hasNext() ? pointer.next() : null;
          }
  
          // Normalize the diff.
          if (changes) {
              diff_cleanupMerge(diffs);
          }
          diff_cleanupSemanticLossless(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.operation == Operation.DELETE &&
                      thisDiff.operation == Operation.INSERT) {
                  String deletion = prevDiff.text;
                  String insertion = thisDiff.text;
                  int overlap_length1 = this.diff_commonOverlap(deletion, insertion);
                  int overlap_length2 = this.diff_commonOverlap(insertion, deletion);
                  if (overlap_length1 >= overlap_length2) {
                      if (overlap_length1 >= deletion.length() / 2.0 ||
                              overlap_length1 >= 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, overlap_length1)));
                          prevDiff.text =
                                  deletion.substring(0, deletion.length() - overlap_length1);
                          thisDiff.text = insertion.substring(overlap_length1);
                          // pointer.add inserts the element before the cursor, so there is
                          // no need to step past the new element.
                      }
                  } else {
                      if (overlap_length2 >= deletion.length() / 2.0 ||
                              overlap_length2 >= 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, overlap_length2)));
                          prevDiff.operation = Operation.INSERT;
                          prevDiff.text =
                                  insertion.substring(0, insertion.length() - overlap_length2);
                          thisDiff.operation = Operation.DELETE;
                          thisDiff.text = deletion.substring(overlap_length2);
                          // 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 diff_cleanupSemanticLossless(LinkedList<Diff> diffs) {
          String equality1, edit, equality2;
          String commonString;
          int commonOffset;
          int score, bestScore;
          String bestEquality1, bestEdit, 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.operation == Operation.EQUAL &&
                      nextDiff.operation == Operation.EQUAL) {
                  // This is a single edit surrounded by equalities.
                  equality1 = prevDiff.text;
                  edit = thisDiff.text;
                  equality2 = nextDiff.text;
  
                  // First, shift the edit as far left as possible.
                  commonOffset = diff_commonSuffix(equality1, edit);
                  if (commonOffset != 0) {
                      commonString = edit.substring(edit.length() - commonOffset);
                      equality1 = equality1.substring(0, equality1.length() - commonOffset);
                      edit = commonString + edit.substring(0, edit.length() - commonOffset);
                      equality2 = commonString + equality2;
                  }
  
                  // Second, step character by character right, looking for the best fit.
                  bestEquality1 = equality1;
                  bestEdit = edit;
                  bestEquality2 = equality2;
                  bestScore = diff_cleanupSemanticScore(equality1, edit)
                          + diff_cleanupSemanticScore(edit, equality2);
                  while (edit.length() != 0 && equality2.length() != 0
                          && edit.charAt(0) == equality2.charAt(0)) {
                      equality1 += edit.charAt(0);
                      edit = edit.substring(1) + equality2.charAt(0);
                      equality2 = equality2.substring(1);
                      score = diff_cleanupSemanticScore(equality1, edit)
                              + diff_cleanupSemanticScore(edit, equality2);
                      // The >= encourages trailing rather than leading whitespace on edits.
                      if (score >= bestScore) {
                          bestScore = score;
                          bestEquality1 = equality1;
                          bestEdit = edit;
                          bestEquality2 = equality2;
                      }
                  }
  
                  if (!prevDiff.text.equals(bestEquality1)) {
                      // We have an improvement, save it back to the diff.
                      if (bestEquality1.length() != 0) {
                          prevDiff.text = 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.text = bestEdit;
                      if (bestEquality2.length() != 0) {
                          nextDiff.text = 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 diff_cleanupSemanticScore(String one, String two) {
          if (one.length() == 0 || two.length() == 0) {
              // 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 && BLANKLINEEND.matcher(one).find();
          boolean blankLine2 = lineBreak2 && BLANKLINESTART.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;
      }
  
      // Define some regex patterns for matching boundaries.
      private Pattern BLANKLINEEND
              = Pattern.compile("\\n\\r?\\n\\Z", Pattern.DOTALL);
      private Pattern BLANKLINESTART
              = Pattern.compile("\\A\\r?\\n\\r?\\n", Pattern.DOTALL);
  
      /**
       * Reduce the number of edits by eliminating operationally trivial equalities.
       * @param diffs LinkedList of Diff objects.
       */
      public void diff_cleanupEfficiency(LinkedList<Diff> diffs) {
          if (diffs.isEmpty()) {
              return;
          }
          boolean changes = false;
          Deque<Diff> equalities = new ArrayDeque<Diff>();  // Double-ended queue of equalities.
          String lastEquality = null; // Always equal to equalities.peek().text
          ListIterator<Diff> pointer = diffs.listIterator();
          // Is there an insertion operation before the last equality.
          boolean pre_ins = false;
          // Is there a deletion operation before the last equality.
          boolean pre_del = false;
          // Is there an insertion operation after the last equality.
          boolean post_ins = false;
          // Is there a deletion operation after the last equality.
          boolean post_del = false;
          Diff thisDiff = pointer.next();
          Diff safeDiff = thisDiff;  // The last Diff that is known to be unsplittable.
          while (thisDiff != null) {
              if (thisDiff.operation == Operation.EQUAL) {
                  // Equality found.
                  if (thisDiff.text.length() < Diff_EditCost && (post_ins || post_del)) {
                      // Candidate found.
                      equalities.push(thisDiff);
                      pre_ins = post_ins;
                      pre_del = post_del;
                      lastEquality = thisDiff.text;
                  } else {
                      // Not a candidate, and can never become one.
                      equalities.clear();
                      lastEquality = null;
                      safeDiff = thisDiff;
                  }
                  post_ins = post_del = false;
              } else {
                  // An insertion or deletion.
                  if (thisDiff.operation == Operation.DELETE) {
                      post_del = true;
                  } else {
                      post_ins = 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
                          && ((pre_ins && pre_del && post_ins && post_del)
                          || ((lastEquality.length() < Diff_EditCost / 2)
                          && ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0)
                          + (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3))) {
                      //System.out.println("Splitting: '" + lastEquality + "'");
                      // Walk back to offending equality.
                      while (thisDiff != equalities.peek()) {
                          thisDiff = pointer.previous();
                      }
                      pointer.next();
  
                      // Replace equality with a delete.
                      pointer.set(new Diff(Operation.DELETE, lastEquality));
                      // Insert a corresponding an insert.
                      pointer.add(thisDiff = new Diff(Operation.INSERT, lastEquality));
  
                      equalities.pop();  // Throw away the equality we just deleted.
                      lastEquality = null;
                      if (pre_ins && pre_del) {
                          // No changes made which could affect previous entry, keep going.
                          post_ins = post_del = true;
                          equalities.clear();
                          safeDiff = thisDiff;
                      } else {
                          if (!equalities.isEmpty()) {
                              // Throw away the previous equality (it needs to be reevaluated).
                              equalities.pop();
                          }
                          if (equalities.isEmpty()) {
                              // 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.peek();
                          }
                          while (thisDiff != pointer.previous()) {
                              // Intentionally empty loop.
                          }
                          post_ins = post_del = false;
                      }
  
                      changes = true;
                  }
              }
              thisDiff = pointer.hasNext() ? pointer.next() : null;
          }
  
          if (changes) {
              diff_cleanupMerge(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 diff_cleanupMerge(LinkedList<Diff> diffs) {
          diffs.add(new Diff(Operation.EQUAL, ""));  // Add a dummy entry at the end.
          ListIterator<Diff> pointer = diffs.listIterator();
          int count_delete = 0;
          int count_insert = 0;
          String text_delete = "";
          String text_insert = "";
          Diff thisDiff = pointer.next();
          Diff prevEqual = null;
          int commonlength;
          while (thisDiff != null) {
              switch (thisDiff.operation) {
                  case INSERT:
                      count_insert++;
                      text_insert += thisDiff.text;
                      prevEqual = null;
                      break;
                  case DELETE:
                      count_delete++;
                      text_delete += thisDiff.text;
                      prevEqual = null;
                      break;
                  case EQUAL:
                      if (count_delete + count_insert > 1) {
                          boolean both_types = count_delete != 0 && count_insert != 0;
                          // Delete the offending records.
                          pointer.previous();  // Reverse direction.
                          while (count_delete-- > 0) {
                              pointer.previous();
                              pointer.remove();
                          }
                          while (count_insert-- > 0) {
                              pointer.previous();
                              pointer.remove();
                          }
                          if (both_types) {
                              // Factor out any common prefixies.
                              commonlength = diff_commonPrefix(text_insert, text_delete);
                              if (commonlength != 0) {
                                  if (pointer.hasPrevious()) {
                                      thisDiff = pointer.previous();
                                      assert thisDiff.operation == Operation.EQUAL
                                              : "Previous diff should have been an equality.";
                                      thisDiff.text += text_insert.substring(0, commonlength);
                                      pointer.next();
                                  } else {
                                      pointer.add(new Diff(Operation.EQUAL,
                                              text_insert.substring(0, commonlength)));
                                  }
                                  text_insert = text_insert.substring(commonlength);
                                  text_delete = text_delete.substring(commonlength);
                              }
                              // Factor out any common suffixies.
                              commonlength = diff_commonSuffix(text_insert, text_delete);
                              if (commonlength != 0) {
                                  thisDiff = pointer.next();
                                  thisDiff.text = text_insert.substring(text_insert.length()
                                          - commonlength) + thisDiff.text;
                                  text_insert = text_insert.substring(0, text_insert.length()
                                          - commonlength);
                                  text_delete = text_delete.substring(0, text_delete.length()
                                          - commonlength);
                                  pointer.previous();
                              }
                          }
                          // Insert the merged records.
                          if (text_delete.length() != 0) {
                              pointer.add(new Diff(Operation.DELETE, text_delete));
                          }
                          if (text_insert.length() != 0) {
                              pointer.add(new Diff(Operation.INSERT, text_insert));
                          }
                          // Step forward to the equality.
                          thisDiff = pointer.hasNext() ? pointer.next() : null;
                      } else if (prevEqual != null) {
                          // Merge this equality with the previous one.
                          prevEqual.text += thisDiff.text;
                          pointer.remove();
                          thisDiff = pointer.previous();
                          pointer.next();  // Forward direction
                      }
                      count_insert = 0;
                      count_delete = 0;
                      text_delete = "";
                      text_insert = "";
                      prevEqual = thisDiff;
                      break;
              }
              thisDiff = pointer.hasNext() ? pointer.next() : null;
          }
          if (diffs.getLast().text.length() == 0) {
              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.operation == Operation.EQUAL &&
                      nextDiff.operation == Operation.EQUAL) {
                  // This is a single edit surrounded by equalities.
                  if (thisDiff.text.endsWith(prevDiff.text)) {
                      // Shift the edit over the previous equality.
                      thisDiff.text = prevDiff.text
                              + thisDiff.text.substring(0, thisDiff.text.length()
                              - prevDiff.text.length());
                      nextDiff.text = prevDiff.text + nextDiff.text;
                      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.text.startsWith(nextDiff.text)) {
                      // Shift the edit over the next equality.
                      prevDiff.text += nextDiff.text;
                      thisDiff.text = thisDiff.text.substring(nextDiff.text.length())
                              + nextDiff.text;
                      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) {
              diff_cleanupMerge(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 diff_xIndex(List<Diff> diffs, int loc) {
          int chars1 = 0;
          int chars2 = 0;
          int last_chars1 = 0;
          int last_chars2 = 0;
          Diff lastDiff = null;
          for (Diff aDiff : diffs) {
              if (aDiff.operation != Operation.INSERT) {
                  // Equality or deletion.
                  chars1 += aDiff.text.length();
              }
              if (aDiff.operation != Operation.DELETE) {
                  // Equality or insertion.
                  chars2 += aDiff.text.length();
              }
              if (chars1 > loc) {
                  // Overshot the location.
                  lastDiff = aDiff;
                  break;
              }
              last_chars1 = chars1;
              last_chars2 = chars2;
          }
          if (lastDiff != null && lastDiff.operation == Operation.DELETE) {
              // The location was deleted.
              return last_chars2;
          }
          // Add the remaining character length.
          return last_chars2 + (loc - last_chars1);
      }
  
      /**
       * Convert a Diff list into a pretty HTML report.
       * @param diffs List of Diff objects.
       * @return HTML representation.
       */
      public String diff_prettyHtml(List<Diff> diffs) {
          StringBuilder html = new StringBuilder();
          for (Diff aDiff : diffs) {
              String text = aDiff.text.replace("&", "&amp;").replace("<", "&lt;")
                      .replace(">", "&gt;").replace("\n", "&para;<br>");
              switch (aDiff.operation) {
                  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 diff_text1(List<Diff> diffs) {
          StringBuilder text = new StringBuilder();
          for (Diff aDiff : diffs) {
              if (aDiff.operation != Operation.INSERT) {
                  text.append(aDiff.text);
              }
          }
          return text.toString();
      }
  
      /**
       * Compute and return the destination text (all equalities and insertions).
       * @param diffs List of Diff objects.
       * @return Destination text.
       */
      public String diff_text2(List<Diff> diffs) {
          StringBuilder text = new StringBuilder();
          for (Diff aDiff : diffs) {
              if (aDiff.operation != Operation.DELETE) {
                  text.append(aDiff.text);
              }
          }
          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 diff_levenshtein(List<Diff> diffs) {
          int levenshtein = 0;
          int insertions = 0;
          int deletions = 0;
          for (Diff aDiff : diffs) {
              switch (aDiff.operation) {
                  case INSERT:
                      insertions += aDiff.text.length();
                      break;
                  case DELETE:
                      deletions += aDiff.text.length();
                      break;
                  case EQUAL:
                      // A deletion and an insertion is one substitution.
                      levenshtein += java.lang.Math.max(insertions, deletions);
                      insertions = 0;
                      deletions = 0;
                      break;
              }
          }
          levenshtein += java.lang.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 List of Diff objects.
       * @return Delta text.
       */
      public String diff_toDelta(List<Diff> diffs) {
          StringBuilder text = new StringBuilder();
          for (Diff aDiff : diffs) {
              switch (aDiff.operation) {
                  case INSERT:
                      try {
                          text.append("+").append(URLEncoder.encode(aDiff.text, "UTF-8")
                                  .replace('+', ' ')).append("\t");
                      } catch (UnsupportedEncodingException e) {
                          // Not likely on modern system.
                          throw new Error("This system does not support UTF-8.", e);
                      }
                      break;
                  case DELETE:
                      text.append("-").append(aDiff.text.length()).append("\t");
                      break;
                  case EQUAL:
                      text.append("=").append(aDiff.text.length()).append("\t");
                      break;
              }
          }
          String delta = text.toString();
          if (delta.length() != 0) {
              // Strip off trailing tab character.
              delta = delta.substring(0, delta.length() - 1);
              delta = 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 Array of Diff objects or null if invalid.
       * @throws IllegalArgumentException If invalid input.
       */
      public LinkedList<Diff> diff_fromDelta(String text1, String delta)
              throws IllegalArgumentException {
          LinkedList<Diff> diffs = new LinkedList<Diff>();
          int pointer = 0;  // Cursor in text1
          String[] tokens = delta.split("\t");
          for (String token : tokens) {
              if (token.length() == 0) {
                  // 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, "UTF-8");
                      } catch (UnsupportedEncodingException e) {
                          // Not likely on modern system.
                          throw new Error("This system does not support UTF-8.", e);
                      } 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 {
                          text = text1.substring(pointer, pointer += n);
                      } 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 loc The location to search around.
       * @return Best match index or -1.
       */
      public int match_main(String text, String pattern, int loc) {
          // Check for null inputs.
          if (text == null || pattern == null) {
              throw new IllegalArgumentException("Null inputs. (match_main)");
          }
  
          loc = java.lang.Math.max(0, java.lang.Math.min(loc, text.length()));
          if (text.equals(pattern)) {
              // Shortcut (potentially not guaranteed by the algorithm)
              return 0;
          } else if (text.length() == 0) {
              // 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 match_bitap(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 match_bitap(String text, String pattern, int loc) {
          assert (Match_MaxBits == 0 || pattern.length() <= Match_MaxBits)
                  : "Pattern too long for this application.";
  
          // Initialise the alphabet.
          Map<Character, Integer> s = match_alphabet(pattern);
  
          // Highest score beyond which we give up.
          double score_threshold = Match_Threshold;
          // Is there a nearby exact match? (speedup)
          int best_loc = text.indexOf(pattern, loc);
          if (best_loc != -1) {
              score_threshold = java.lang.Math.min(match_bitapScore(0, best_loc, loc, pattern),
                      score_threshold);
              // What about in the other direction? (speedup)
              best_loc = text.lastIndexOf(pattern, loc + pattern.length());
              if (best_loc != -1) {
                  score_threshold = java.lang.Math.min(match_bitapScore(0, best_loc, loc, pattern),
                          score_threshold);
              }
          }
  
          // Initialise the bit arrays.
          int matchmask = 1 << (pattern.length() - 1);
          best_loc = -1;
  
          int bin_min, bin_mid;
          int bin_max = pattern.length() + text.length();
          // Empty initialization added to appease Java compiler.
          int[] last_rd = 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.
              bin_min = 0;
              bin_mid = bin_max;
              while (bin_min < bin_mid) {
                  if (match_bitapScore(d, loc + bin_mid, loc, pattern)
                          <= score_threshold) {
                      bin_min = bin_mid;
                  } else {
                      bin_max = bin_mid;
                  }
                  bin_mid = (bin_max - bin_min) / 2 + bin_min;
              }
              // Use the result from this iteration as the maximum for the next.
              bin_max = bin_mid;
              int start = java.lang.Math.max(1, loc - bin_mid + 1);
              int finish = java.lang.Math.min(loc + bin_mid, 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)
                              | (((last_rd[j + 1] | last_rd[j]) << 1) | 1) | last_rd[j + 1];
                  }
                  if ((rd[j] & matchmask) != 0) {
                      double score = match_bitapScore(d, j - 1, loc, pattern);
                      // This match will almost certainly be better than any existing
                      // match.  But check anyway.
                      if (score <= score_threshold) {
                          // Told you so.
                          score_threshold = score;
                          best_loc = j - 1;
                          if (best_loc > loc) {
                              // When passing loc, don't exceed our current distance from loc.
                              start = java.lang.Math.max(1, 2 * loc - best_loc);
                          } else {
                              // Already passed loc, downhill from here on in.
                              break;
                          }
                      }
                  }
              }
              if (match_bitapScore(d + 1, loc, loc, pattern) > score_threshold) {
                  // No hope for a (better) match at greater error levels.
                  break;
              }
              last_rd = rd;
          }
          return best_loc;
      }
  
      /**
       * 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 match_bitapScore(int e, int x, int loc, String pattern) {
          float accuracy = (float) e / pattern.length();
          int proximity = java.lang.Math.abs(loc - x);
          if (Match_Distance == 0) {
              // Dodge divide by zero error.
              return proximity == 0 ? accuracy : 1.0;
          }
          return accuracy + (proximity / (float) Match_Distance);
      }
  
      /**
       * Initialise the alphabet for the Bitap algorithm.
       * @param pattern The text to encode.
       * @return Hash of character locations.
       */
      protected Map<Character, Integer> match_alphabet(String pattern) {
          Map<Character, Integer> s = new HashMap<Character, Integer>();
          char[] char_pattern = pattern.toCharArray();
          for (char c : char_pattern) {
              s.put(c, 0);
          }
          int i = 0;
          for (char c : char_pattern) {
              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 patch_addContext(Patch patch, String text) {
          if (text.length() == 0) {
              return;
          }
          String pattern = text.substring(patch.start2, patch.start2 + patch.length1);
          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() < Match_MaxBits - Patch_Margin - Patch_Margin) {
              padding += Patch_Margin;
              pattern = text.substring(java.lang.Math.max(0, patch.start2 - padding),
                      java.lang.Math.min(text.length(), patch.start2 + patch.length1 + padding));
          }
          // Add one chunk for good luck.
          padding += Patch_Margin;
  
          // Add the prefix.
          String prefix = text.substring(java.lang.Math.max(0, patch.start2 - padding),
                  patch.start2);
          if (prefix.length() != 0) {
              patch.diffs.addFirst(new Diff(Operation.EQUAL, prefix));
          }
          // Add the suffix.
          String suffix = text.substring(patch.start2 + patch.length1,
                  java.lang.Math.min(text.length(), patch.start2 + patch.length1 + padding));
          if (suffix.length() != 0) {
              patch.diffs.addLast(new Diff(Operation.EQUAL, suffix));
          }
  
          // Roll back the start points.
          patch.start1 -= prefix.length();
          patch.start2 -= prefix.length();
          // Extend the lengths.
          patch.length1 += prefix.length() + suffix.length();
          patch.length2 += 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 LinkedList<Patch> patch_make(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 = diff_main(text1, text2, true);
          if (diffs.size() > 2) {
              diff_cleanupSemantic(diffs);
              diff_cleanupEfficiency(diffs);
          }
          return patch_make(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 LinkedList<Patch> patch_make(LinkedList<Diff> diffs) {
          if (diffs == null) {
              throw new IllegalArgumentException("Null inputs. (patch_make)");
          }
          // No origin string provided, compute our own.
          String text1 = diff_text1(diffs);
          return patch_make(text1, diffs);
      }
  
      /**
       * Compute a list of patches to turn text1 into text2.
       * text2 is ignored, diffs are the delta between text1 and text2.
       * @param text1 Old text
       * @param text2 Ignored.
       * @param diffs Array of Diff objects for text1 to text2.
       * @return LinkedList of Patch objects.
       * @deprecated Prefer patch_make(String text1, LinkedList<Diff> diffs).
       */
      @Deprecated public LinkedList<Patch> patch_make(String text1, String text2,
                                                      LinkedList<Diff> diffs) {
          return patch_make(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 LinkedList of Patch objects.
       */
      public LinkedList<Patch> patch_make(String text1, LinkedList<Diff> diffs) {
          if (text1 == null || diffs == null) {
              throw new IllegalArgumentException("Null inputs. (patch_make)");
          }
  
          LinkedList<Patch> patches = new LinkedList<Patch>();
          if (diffs.isEmpty()) {
              return patches;  // Get rid of the null case.
          }
          Patch patch = new Patch();
          int char_count1 = 0;  // Number of characters into the text1 string.
          int char_count2 = 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 prepatch_text = text1;
          String postpatch_text = text1;
          for (Diff aDiff : diffs) {
              if (patch.diffs.isEmpty() && aDiff.operation != Operation.EQUAL) {
                  // A new patch starts here.
                  patch.start1 = char_count1;
                  patch.start2 = char_count2;
              }
  
              switch (aDiff.operation) {
                  case INSERT:
                      patch.diffs.add(aDiff);
                      patch.length2 += aDiff.text.length();
                      postpatch_text = postpatch_text.substring(0, char_count2)
                              + aDiff.text + postpatch_text.substring(char_count2);
                      break;
                  case DELETE:
                      patch.length1 += aDiff.text.length();
                      patch.diffs.add(aDiff);
                      postpatch_text = postpatch_text.substring(0, char_count2)
                              + postpatch_text.substring(char_count2 + aDiff.text.length());
                      break;
                  case EQUAL:
                      if (aDiff.text.length() <= 2 * Patch_Margin
                              && !patch.diffs.isEmpty() && aDiff != diffs.getLast()) {
                          // Small equality inside a patch.
                          patch.diffs.add(aDiff);
                          patch.length1 += aDiff.text.length();
                          patch.length2 += aDiff.text.length();
                      }
  
                      if (aDiff.text.length() >= 2 * Patch_Margin && !patch.diffs.isEmpty()) {
                          // Time for a new patch.
                          if (!patch.diffs.isEmpty()) {
                              patch_addContext(patch, prepatch_text);
                              patches.add(patch);
                              patch = new Patch();
                              // Unlike Unidiff, our patch lists have a rolling context.
                              // https://github.com/google/diff-match-patch/wiki/Unidiff
                              // Update prepatch text & pos to reflect the application of the
                              // just completed patch.
                              prepatch_text = postpatch_text;
                              char_count1 = char_count2;
                          }
                      }
                      break;
              }
  
              // Update the current character count.
              if (aDiff.operation != Operation.INSERT) {
                  char_count1 += aDiff.text.length();
              }
              if (aDiff.operation != Operation.DELETE) {
                  char_count2 += aDiff.text.length();
              }
          }
          // Pick up the leftover patch if not empty.
          if (!patch.diffs.isEmpty()) {
              patch_addContext(patch, prepatch_text);
              patches.add(patch);
          }
  
          return patches;
      }
  
      /**
       * Given an array of patches, return another array that is identical.
       * @param patches Array of Patch objects.
       * @return Array of Patch objects.
       */
      public LinkedList<Patch> patch_deepCopy(LinkedList<Patch> patches) {
          LinkedList<Patch> patchesCopy = new LinkedList<Patch>();
          for (Patch aPatch : patches) {
              Patch patchCopy = new Patch();
              for (Diff aDiff : aPatch.diffs) {
                  Diff diffCopy = new Diff(aDiff.operation, aDiff.text);
                  patchCopy.diffs.add(diffCopy);
              }
              patchCopy.start1 = aPatch.start1;
              patchCopy.start2 = aPatch.start2;
              patchCopy.length1 = aPatch.length1;
              patchCopy.length2 = aPatch.length2;
              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 patches Array of Patch objects
       * @param text Old text.
       * @return Two element Object array, containing the new text and an array of
       *      boolean values.
       */
      public Object[] patch_apply(LinkedList<Patch> patches, String text) {
          if (patches.isEmpty()) {
              return new Object[]{text, new boolean[0]};
          }
  
          // Deep copy the patches so that no changes are made to originals.
          patches = patch_deepCopy(patches);
  
          String nullPadding = patch_addPadding(patches);
          text = nullPadding + text + nullPadding;
          patch_splitMax(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 expected_loc = aPatch.start2 + delta;
              String text1 = diff_text1(aPatch.diffs);
              int start_loc;
              int end_loc = -1;
              if (text1.length() > this.Match_MaxBits) {
                  // patch_splitMax will only provide an oversized pattern in the case of
                  // a monster delete.
                  start_loc = match_main(text,
                          text1.substring(0, this.Match_MaxBits), expected_loc);
                  if (start_loc != -1) {
                      end_loc = match_main(text,
                              text1.substring(text1.length() - this.Match_MaxBits),
                              expected_loc + text1.length() - this.Match_MaxBits);
                      if (end_loc == -1 || start_loc >= end_loc) {
                          // Can't find valid trailing context.  Drop this patch.
                          start_loc = -1;
                      }
                  }
              } else {
                  start_loc = match_main(text, text1, expected_loc);
              }
              if (start_loc == -1) {
                  // No match found.  :(
                  results[x] = false;
                  // Subtract the delta for this failed patch from subsequent patches.
                  delta -= aPatch.length2 - aPatch.length1;
              } else {
                  // Found a match.  :)
                  results[x] = true;
                  delta = start_loc - expected_loc;
                  String text2;
                  if (end_loc == -1) {
                      text2 = text.substring(start_loc,
                              java.lang.Math.min(start_loc + text1.length(), text.length()));
                  } else {
                      text2 = text.substring(start_loc,
                              java.lang.Math.min(end_loc + this.Match_MaxBits, text.length()));
                  }
                  if (text1.equals(text2)) {
                      // Perfect match, just shove the replacement text in.
                      text = text.substring(0, start_loc) + diff_text2(aPatch.diffs)
                              + text.substring(start_loc + text1.length());
                  } else {
                      // Imperfect match.  Run a diff to get a framework of equivalent
                      // indices.
                      LinkedList<Diff> diffs = diff_main(text1, text2, false);
                      if (text1.length() > this.Match_MaxBits
                              && diff_levenshtein(diffs) / (float) text1.length()
                              > this.Patch_DeleteThreshold) {
                          // The end points match, but the content is unacceptably bad.
                          results[x] = false;
                      } else {
                          diff_cleanupSemanticLossless(diffs);
                          int index1 = 0;
                          for (Diff aDiff : aPatch.diffs) {
                              if (aDiff.operation != Operation.EQUAL) {
                                  int index2 = diff_xIndex(diffs, index1);
                                  if (aDiff.operation == Operation.INSERT) {
                                      // Insertion
                                      text = text.substring(0, start_loc + index2) + aDiff.text
                                              + text.substring(start_loc + index2);
                                  } else if (aDiff.operation == Operation.DELETE) {
                                      // Deletion
                                      text = text.substring(0, start_loc + index2)
                                              + text.substring(start_loc + diff_xIndex(diffs,
                                              index1 + aDiff.text.length()));
                                  }
                              }
                              if (aDiff.operation != Operation.DELETE) {
                                  index1 += aDiff.text.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 patch_addPadding(LinkedList<Patch> patches) {
          short paddingLength = this.Patch_Margin;
          String nullPadding = "";
          for (short x = 1; x <= paddingLength; x++) {
              nullPadding += String.valueOf((char) x);
          }
  
          // Bump all the patches forward.
          for (Patch aPatch : patches) {
              aPatch.start1 += paddingLength;
              aPatch.start2 += paddingLength;
          }
  
          // Add some padding on start of first diff.
          Patch patch = patches.getFirst();
          LinkedList<Diff> diffs = patch.diffs;
          if (diffs.isEmpty() || diffs.getFirst().operation != Operation.EQUAL) {
              // Add nullPadding equality.
              diffs.addFirst(new Diff(Operation.EQUAL, nullPadding));
              patch.start1 -= paddingLength;  // Should be 0.
              patch.start2 -= paddingLength;  // Should be 0.
              patch.length1 += paddingLength;
              patch.length2 += paddingLength;
          } else if (paddingLength > diffs.getFirst().text.length()) {
              // Grow first equality.
              Diff firstDiff = diffs.getFirst();
              int extraLength = paddingLength - firstDiff.text.length();
              firstDiff.text = nullPadding.substring(firstDiff.text.length())
                      + firstDiff.text;
              patch.start1 -= extraLength;
              patch.start2 -= extraLength;
              patch.length1 += extraLength;
              patch.length2 += extraLength;
          }
  
          // Add some padding on end of last diff.
          patch = patches.getLast();
          diffs = patch.diffs;
          if (diffs.isEmpty() || diffs.getLast().operation != Operation.EQUAL) {
              // Add nullPadding equality.
              diffs.addLast(new Diff(Operation.EQUAL, nullPadding));
              patch.length1 += paddingLength;
              patch.length2 += paddingLength;
          } else if (paddingLength > diffs.getLast().text.length()) {
              // Grow last equality.
              Diff lastDiff = diffs.getLast();
              int extraLength = paddingLength - lastDiff.text.length();
              lastDiff.text += nullPadding.substring(0, extraLength);
              patch.length1 += extraLength;
              patch.length2 += extraLength;
          }
  
          return nullPadding;
      }
  
      /**
       * 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 LinkedList of Patch objects.
       */
      public void patch_splitMax(LinkedList<Patch> patches) {
          short patch_size = Match_MaxBits;
          String precontext, postcontext;
          Patch patch;
          int start1, start2;
          boolean empty;
          Operation diff_type;
          String diff_text;
          ListIterator<Patch> pointer = patches.listIterator();
          Patch bigpatch = pointer.hasNext() ? pointer.next() : null;
          while (bigpatch != null) {
              if (bigpatch.length1 <= Match_MaxBits) {
                  bigpatch = pointer.hasNext() ? pointer.next() : null;
                  continue;
              }
              // Remove the big old patch.
              pointer.remove();
              start1 = bigpatch.start1;
              start2 = bigpatch.start2;
              precontext = "";
              while (!bigpatch.diffs.isEmpty()) {
                  // Create one of several smaller patches.
                  patch = new Patch();
                  empty = true;
                  patch.start1 = start1 - precontext.length();
                  patch.start2 = start2 - precontext.length();
                  if (precontext.length() != 0) {
                      patch.length1 = patch.length2 = precontext.length();
                      patch.diffs.add(new Diff(Operation.EQUAL, precontext));
                  }
                  while (!bigpatch.diffs.isEmpty()
                          && patch.length1 < patch_size - Patch_Margin) {
                      diff_type = bigpatch.diffs.getFirst().operation;
                      diff_text = bigpatch.diffs.getFirst().text;
                      if (diff_type == Operation.INSERT) {
                          // Insertions are harmless.
                          patch.length2 += diff_text.length();
                          start2 += diff_text.length();
                          patch.diffs.addLast(bigpatch.diffs.removeFirst());
                          empty = false;
                      } else if (diff_type == Operation.DELETE && patch.diffs.size() == 1
                              && patch.diffs.getFirst().operation == Operation.EQUAL
                              && diff_text.length() > 2 * patch_size) {
                          // This is a large deletion.  Let it pass in one chunk.
                          patch.length1 += diff_text.length();
                          start1 += diff_text.length();
                          empty = false;
                          patch.diffs.add(new Diff(diff_type, diff_text));
                          bigpatch.diffs.removeFirst();
                      } else {
                          // Deletion or equality.  Only take as much as we can stomach.
                          diff_text = diff_text.substring(0, java.lang.Math.min(diff_text.length(),
                                  patch_size - patch.length1 - Patch_Margin));
                          patch.length1 += diff_text.length();
                          start1 += diff_text.length();
                          if (diff_type == Operation.EQUAL) {
                              patch.length2 += diff_text.length();
                              start2 += diff_text.length();
                          } else {
                              empty = false;
                          }
                          patch.diffs.add(new Diff(diff_type, diff_text));
                          if (diff_text.equals(bigpatch.diffs.getFirst().text)) {
                              bigpatch.diffs.removeFirst();
                          } else {
                              bigpatch.diffs.getFirst().text = bigpatch.diffs.getFirst().text
                                      .substring(diff_text.length());
                          }
                      }
                  }
                  // Compute the head context for the next patch.
                  precontext = diff_text2(patch.diffs);
                  precontext = precontext.substring(java.lang.Math.max(0, precontext.length()
                          - Patch_Margin));
                  // Append the end context for this patch.
                  if (diff_text1(bigpatch.diffs).length() > Patch_Margin) {
                      postcontext = diff_text1(bigpatch.diffs).substring(0, Patch_Margin);
                  } else {
                      postcontext = diff_text1(bigpatch.diffs);
                  }
                  if (postcontext.length() != 0) {
                      patch.length1 += postcontext.length();
                      patch.length2 += postcontext.length();
                      if (!patch.diffs.isEmpty()
                              && patch.diffs.getLast().operation == Operation.EQUAL) {
                          patch.diffs.getLast().text += postcontext;
                      } else {
                          patch.diffs.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 patch_toText(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.
       * @throws IllegalArgumentException If invalid input.
       */
      public List<Patch> patch_fromText(String textline)
              throws IllegalArgumentException {
          List<Patch> patches = new LinkedList<Patch>();
          if (textline.length() == 0) {
              return patches;
          }
          List<String> textList = Arrays.asList(textline.split("\n"));
          LinkedList<String> text = new LinkedList<String>(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.start1 = Integer.parseInt(m.group(1));
              if (m.group(2).length() == 0) {
                  patch.start1--;
                  patch.length1 = 1;
              } else if (m.group(2).equals("0")) {
                  patch.length1 = 0;
              } else {
                  patch.start1--;
                  patch.length1 = Integer.parseInt(m.group(2));
              }
  
              patch.start2 = Integer.parseInt(m.group(3));
              if (m.group(4).length() == 0) {
                  patch.start2--;
                  patch.length2 = 1;
              } else if (m.group(4).equals("0")) {
                  patch.length2 = 0;
              } else {
                  patch.start2--;
                  patch.length2 = Integer.parseInt(m.group(4));
              }
              text.removeFirst();
  
              while (!text.isEmpty()) {
                  try {
                      sign = text.getFirst().charAt(0);
                  } catch (IndexOutOfBoundsException 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, "UTF-8");
                  } catch (UnsupportedEncodingException e) {
                      // Not likely on modern system.
                      throw new Error("This system does not support UTF-8.", e);
                  } catch (IllegalArgumentException e) {
                      // Malformed URI sequence.
                      throw new IllegalArgumentException(
                              "Illegal escape in patch_fromText: " + line, e);
                  }
                  if (sign == '-') {
                      // Deletion.
                      patch.diffs.add(new Diff(Operation.DELETE, line));
                  } else if (sign == '+') {
                      // Insertion.
                      patch.diffs.add(new Diff(Operation.INSERT, line));
                  } else if (sign == ' ') {
                      // Minor equality.
                      patch.diffs.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;
      }
  
  
      /**
       * Class representing one diff operation.
       */
      public static class Diff {
          /**
           * One of: INSERT, DELETE or EQUAL.
           */
          public Operation operation;
          /**
           * The text associated with this diff operation.
           */
          public String text;
  
          /**
           * Constructor.  Initializes the diff with the provided values.
           * @param operation One of INSERT, DELETE or EQUAL.
           * @param text The text being applied.
           */
          public Diff(Operation operation, String text) {
              // Construct a diff with the specified operation and text.
              this.operation = operation;
              this.text = text;
          }
  
          /**
           * Display a human-readable version of this Diff.
           * @return text version.
           */
          public String toString() {
              String prettyText = this.text.replace('\n', '\u00b6');
              return "Diff(" + this.operation + ",\"" + prettyText + "\")";
          }
  
          /**
           * Create a numeric hash value for a Diff.
           * This function is not used by DMP.
           * @return Hash value.
           */
          @Override
          public int hashCode() {
              final int prime = 31;
              int result = (operation == null) ? 0 : operation.hashCode();
              result += prime * ((text == null) ? 0 : text.hashCode());
              return result;
          }
  
          /**
           * Is this Diff equivalent to another Diff?
           * @param obj Another Diff to compare against.
           * @return true or false.
           */
          @Override
          public boolean equals(Object obj) {
              if (this == obj) {
                  return true;
              }
              if (obj == null) {
                  return false;
              }
              if (getClass() != obj.getClass()) {
                  return false;
              }
              Diff other = (Diff) obj;
              if (operation != other.operation) {
                  return false;
              }
              if (text == null) {
                  if (other.text != null) {
                      return false;
                  }
              } else if (!text.equals(other.text)) {
                  return false;
              }
              return true;
          }
      }
  
  
      /**
       * Class representing one patch operation.
       */
      public static class Patch {
          public LinkedList<Diff> diffs;
          public int start1;
          public int start2;
          public int length1;
          public int length2;
  
          /**
           * Constructor.  Initializes with an empty list of diffs.
           */
          public Patch() {
              this.diffs = new LinkedList<Diff>();
          }
  
          /**
           * Emulate GNU diff's format.
           * Header: @@ -382,8 +481,9 @@
           * Indices are printed as 1-based, not 0-based.
           * @return The GNU diff string.
           */
          public String toString() {
              String coords1, coords2;
              if (this.length1 == 0) {
                  coords1 = this.start1 + ",0";
              } else if (this.length1 == 1) {
                  coords1 = Integer.toString(this.start1 + 1);
              } else {
                  coords1 = (this.start1 + 1) + "," + this.length1;
              }
              if (this.length2 == 0) {
                  coords2 = this.start2 + ",0";
              } else if (this.length2 == 1) {
                  coords2 = Integer.toString(this.start2 + 1);
              } else {
                  coords2 = (this.start2 + 1) + "," + this.length2;
              }
              StringBuilder text = new StringBuilder();
              text.append("@@ -").append(coords1).append(" +").append(coords2)
                      .append(" @@\n");
              // Escape the body of the patch with %xx notation.
              for (Diff aDiff : this.diffs) {
                  switch (aDiff.operation) {
                      case INSERT:
                          text.append('+');
                          break;
                      case DELETE:
                          text.append('-');
                          break;
                      case EQUAL:
                          text.append(' ');
                          break;
                  }
                  try {
                      text.append(URLEncoder.encode(aDiff.text, "UTF-8").replace('+', ' '))
                              .append("\n");
                  } catch (UnsupportedEncodingException e) {
                      // Not likely on modern system.
                      throw new Error("This system does not support UTF-8.", e);
                  }
              }
              return unescapeForEncodeUriCompatability(text.toString());
          }
      }
  
      /**
       * Unescape selected chars for compatability with JavaScript's encodeURI.
       * In speed critical applications this could be dropped since the
       * receiving application will certainly decode these fine.
       * Note that this function is case-sensitive.  Thus "%3f" would not be
       * unescaped.  But this is ok because it is only called with the output of
       * URLEncoder.encode which returns uppercase hex.
       *
       * Example: "%3F" -> "?", "%24" -> "$", etc.
       *
       * @param str The string to escape.
       * @return The escaped string.
       */
      private static String unescapeForEncodeUriCompatability(String str) {
          return str.replace("%21", "!").replace("%7E", "~")
                  .replace("%27", "'").replace("%28", "(").replace("%29", ")")
                  .replace("%3B", ";").replace("%2F", "/").replace("%3F", "?")
                  .replace("%3A", ":").replace("%40", "@").replace("%26", "&")
                  .replace("%3D", "=").replace("%2B", "+").replace("%24", "$")
                  .replace("%2C", ",").replace("%23", "#");
      }
  }