utils_diff.class.php

<?php
/* Copyright (C) 2016      Jean-François Ferry  <hello@librethic.io>
 *
 * A class containing a diff implementation
 *
 * Created by Stephen Morley - http://stephenmorley.org/ - and released under the
 * terms of the CC0 1.0 Universal legal code:
 *
 * http://creativecommons.org/publicdomain/zero/1.0/legalcode
 */


class Diff
{
  // define the constants
  const UNMODIFIED = 0;
  const DELETED = 1;
  const INSERTED = 2;

  public static function compare($string1, $string2, $compareCharacters = false)
  {
    // initialise the sequences and comparison start and end positions
    $start = 0;
    if ($compareCharacters) {
      $sequence1 = $string1;
      $sequence2 = $string2;
      $end1 = strlen($string1) - 1;
      $end2 = strlen($string2) - 1;
    } else {
      $sequence1 = preg_split('/\R/', $string1);
      $sequence2 = preg_split('/\R/', $string2);
      $end1 = count($sequence1) - 1;
      $end2 = count($sequence2) - 1;
    }

    // skip any common prefix
    while ($start <= $end1 && $start <= $end2
      && $sequence1[$start] == $sequence2[$start]) {
      $start++;
    }

    // skip any common suffix
    while ($end1 >= $start && $end2 >= $start
      && $sequence1[$end1] == $sequence2[$end2]) {
      $end1--;
      $end2--;
    }

    // compute the table of longest common subsequence lengths
    $table = self::computeTable($sequence1, $sequence2, $start, $end1, $end2);

    // generate the partial diff
    $partialDiff = self::generatePartialDiff($table, $sequence1, $sequence2, $start);

    // generate the full diff
    $diff = array();
    for ($index = 0; $index < $start; $index++) {
      $diff[] = array($sequence1[$index], self::UNMODIFIED);
    }
    while (count($partialDiff) > 0) {
      $diff[] = array_pop($partialDiff);
    }

    $end2 = ($compareCharacters ? strlen($sequence1) : count($sequence1));
    for ($index = $end1 + 1; $index < $end2; $index++)
    {
      $diff[] = array($sequence1[$index], self::UNMODIFIED);
    }

    // return the diff
    return $diff;
  }

  public static function compareFiles(
    $file1,
    $file2,
    $compareCharacters = false
  ) {

    // return the diff of the files
    return self::compare(
      file_get_contents($file1),
      file_get_contents($file2),
      $compareCharacters
    );
  }

  private static function computeTable($sequence1, $sequence2, $start, $end1, $end2)
  {
    // determine the lengths to be compared
    $length1 = $end1 - $start + 1;
    $length2 = $end2 - $start + 1;

    // initialise the table
    $table = array(array_fill(0, $length2 + 1, 0));

    // loop over the rows
    for ($index1 = 1; $index1 <= $length1; $index1++) {
      // create the new row
      $table[$index1] = array(0);

      // loop over the columns
      for ($index2 = 1; $index2 <= $length2; $index2++) {
        // store the longest common subsequence length
        if ($sequence1[$index1 + $start - 1] == $sequence2[$index2 + $start - 1]
        ) {
          $table[$index1][$index2] = $table[$index1 - 1][$index2 - 1] + 1;
        } else {
          $table[$index1][$index2] = max($table[$index1 - 1][$index2], $table[$index1][$index2 - 1]);
        }
      }
    }

    // return the table
    return $table;
  }

  private static function generatePartialDiff($table, $sequence1, $sequence2, $start)
  {
    //  initialise the diff
    $diff = array();

    // initialise the indices
    $index1 = count($table) - 1;
    $index2 = count($table[0]) - 1;

    // loop until there are no items remaining in either sequence
    while ($index1 > 0 || $index2 > 0) {
      // check what has happened to the items at these indices
      if ($index1 > 0 && $index2 > 0
        && $sequence1[$index1 + $start - 1] == $sequence2[$index2 + $start - 1]
      ) {
        // update the diff and the indices
        $diff[] = array($sequence1[$index1 + $start - 1], self::UNMODIFIED);
        $index1--;
        $index2--;
      } elseif ($index2 > 0
        && $table[$index1][$index2] == $table[$index1][$index2 - 1]
      ) {
        // update the diff and the indices
        $diff[] = array($sequence2[$index2 + $start - 1], self::INSERTED);
        $index2--;
      } else {
        // update the diff and the indices
        $diff[] = array($sequence1[$index1 + $start - 1], self::DELETED);
        $index1--;
      }
    }

    // return the diff
    return $diff;
  }

  public static function toString($diff, $separator = "\n")
  {
    // initialise the string
    $string = '';

    // loop over the lines in the diff
    foreach ($diff as $line) {
      // extend the string with the line
      switch ($line[1]) {
        case self::UNMODIFIED:
          $string .= '  '.$line[0];
          break;
        case self::DELETED:
          $string .= '- '.$line[0];
          break;
        case self::INSERTED:
          $string .= '+ '.$line[0];
          break;
      }

      // extend the string with the separator
      $string .= $separator;
    }

    // return the string
    return $string;
  }

  public static function toHTML($diff, $separator = '<br>')
  {
    // initialise the HTML
    $html = '';

    // loop over the lines in the diff
    foreach ($diff as $line) {
      // extend the HTML with the line
      switch ($line[1]) {
        case self::UNMODIFIED:
          $element = 'span';
          break;
        case self::DELETED:
          $element = 'del';
          break;
        case self::INSERTED:
          $element = 'ins';
          break;
      }
      $html .=
      '<'.$element.'>'
      . htmlspecialchars($line[0])
        . '</'.$element.'>';

      // extend the HTML with the separator
      $html .= $separator;
    }

    // return the HTML
    return $html;
  }

  public static function toTable($diff, $indentation = '', $separator = '<br>')
  {
    // initialise the HTML
    $html = $indentation."<table class=\"diff\">\n";

    // loop over the lines in the diff
    $index = 0;
    while ($index < count($diff)) {
      // determine the line type
      switch ($diff[$index][1]) {
        // display the content on the left and right
        case self::UNMODIFIED:
          $leftCell = self::getCellContent(
            $diff,
            $indentation,
            $separator,
            $index,
            self::UNMODIFIED
          );
          $rightCell = $leftCell;
          break;

        // display the deleted on the left and inserted content on the right
        case self::DELETED:
          $leftCell = self::getCellContent(
            $diff,
            $indentation,
            $separator,
            $index,
            self::DELETED
          );
          $rightCell = self::getCellContent(
              $diff,
              $indentation,
              $separator,
              $index,
              self::INSERTED
            );
          break;

        // display the inserted content on the right
        case self::INSERTED:
          $leftCell = '';
          $rightCell = self::getCellContent(
            $diff,
            $indentation,
            $separator,
            $index,
            self::INSERTED
          );
          break;
      }

      // extend the HTML with the new row
      $html .=
        $indentation
        . "  <tr>\n"
        . $indentation
        . '    <td class="diff'
        . ($leftCell == $rightCell
        ? 'Unmodified'
        : ($leftCell == '' ? 'Blank' : 'Deleted'))
        . '">'
        . $leftCell
        . "</td>\n"
        . $indentation
        . '    <td class="diff'
        . ($leftCell == $rightCell
        ? 'Unmodified'
        : ($rightCell == '' ? 'Blank' : 'Inserted'))
        . '">'
        . $rightCell
        . "</td>\n"
        . $indentation
        . "  </tr>\n";
    }

    // return the HTML
    return $html.$indentation."</table>\n";
  }

  private static function getCellContent($diff, $indentation, $separator, &$index, $type)
  {
    // initialise the HTML
    $html = '';

    // loop over the matching lines, adding them to the HTML
    while ($index < count($diff) && $diff[$index][1] == $type) {
      $html .=
      '<span>'
      . htmlspecialchars($diff[$index][0])
        . '</span>'
        . $separator;
      $index++;
    }

    // return the HTML
    return $html;
  }
}