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   1  <?php declare(strict_types=1);
   2  
   3  /**
   4  * @package   s9e\RegexpBuilder
   5  * @copyright Copyright (c) 2016-2022 The s9e authors
   6  * @license   http://www.opensource.org/licenses/mit-license.php The MIT License
   7  */
   8  namespace s9e\RegexpBuilder\Passes;
   9  
  10  use const false, true;
  11  use function array_filter, array_pop, array_unshift, count, end;
  12  
  13  /**
  14  * Replaces (?:aax|bbx) with (?:aa|bb)x
  15  */
  16  class MergeSuffix extends AbstractPass
  17  {
  18      /**
  19      * {@inheritdoc}
  20      */
  21  	protected function canRun(array $strings): bool
  22      {
  23          return (count($strings) > 1 && $this->hasMatchingSuffix($strings));
  24      }
  25  
  26      /**
  27      * {@inheritdoc}
  28      */
  29  	protected function runPass(array $strings): array
  30      {
  31          $newString = [];
  32          while ($this->hasMatchingSuffix($strings))
  33          {
  34              array_unshift($newString, end($strings[0]));
  35              $strings = $this->pop($strings);
  36          }
  37          array_unshift($newString, $strings);
  38  
  39          return [$newString];
  40      }
  41  
  42      /**
  43      * Test whether all given strings have the same last element
  44      *
  45      * @param  array[] $strings
  46      * @return bool
  47      */
  48  	protected function hasMatchingSuffix(array $strings): bool
  49      {
  50          $suffix = end($strings[1]);
  51          foreach ($strings as $string)
  52          {
  53              if (end($string) !== $suffix)
  54              {
  55                  return false;
  56              }
  57          }
  58  
  59          return ($suffix !== false);
  60      }
  61  
  62      /**
  63      * Remove the last element of every string
  64      *
  65      * @param  array[] $strings Original strings
  66      * @return array[]          Processed strings
  67      */
  68  	protected function pop(array $strings): array
  69      {
  70          $cnt = count($strings);
  71          $i   = $cnt;
  72          while (--$i >= 0)
  73          {
  74              array_pop($strings[$i]);
  75          }
  76  
  77          // Remove empty elements then prepend one back at the start of the array if applicable
  78          $strings = array_filter($strings);
  79          if (count($strings) < $cnt)
  80          {
  81              array_unshift($strings, []);
  82          }
  83  
  84          return $strings;
  85      }
  86  }