[Summary view] [Print] [Text view]

   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_slice, count;
  12  
  13  /**
  14  * Replaces (?:axx|ayy) with a(?:xx|yy)
  15  */
  16  class MergePrefix extends AbstractPass
  17  {
  18      /**
  19      * {@inheritdoc}
  20      */
  21  	protected function runPass(array $strings): array
  22      {
  23          $newStrings = [];
  24          foreach ($this->getStringsByPrefix($strings) as $prefix => $strings)
  25          {
  26              $newStrings[] = (isset($strings[1])) ? $this->mergeStrings($strings) : $strings[0];
  27          }
  28  
  29          return $newStrings;
  30      }
  31  
  32      /**
  33      * Get the number of leading elements common to all given strings
  34      *
  35      * @param  array[] $strings
  36      * @return integer
  37      */
  38  	protected function getPrefixLength(array $strings): int
  39      {
  40          $len = 1;
  41          $cnt = count($strings[0]);
  42          while ($len < $cnt && $this->stringsMatch($strings, $len))
  43          {
  44              ++$len;
  45          }
  46  
  47          return $len;
  48      }
  49  
  50      /**
  51      * Return given strings grouped by their first element
  52      *
  53      * NOTE: assumes that this pass is run before the first element of any string could be replaced
  54      *
  55      * @param  array[] $strings
  56      * @return array[]
  57      */
  58  	protected function getStringsByPrefix(array $strings): array
  59      {
  60          $byPrefix = [];
  61          foreach ($strings as $string)
  62          {
  63              $byPrefix[$string[0]][] = $string;
  64          }
  65  
  66          return $byPrefix;
  67      }
  68  
  69      /**
  70      * Merge given strings into a new single string
  71      *
  72      * @param  array[] $strings
  73      * @return array
  74      */
  75  	protected function mergeStrings(array $strings): array
  76      {
  77          $len       = $this->getPrefixLength($strings);
  78          $newString = array_slice($strings[0], 0, $len);
  79          foreach ($strings as $string)
  80          {
  81              $newString[$len][] = array_slice($string, $len);
  82          }
  83  
  84          return $newString;
  85      }
  86  
  87      /**
  88      * Test whether all given strings' elements match at given position
  89      *
  90      * @param  array[] $strings
  91      * @param  integer $pos
  92      * @return bool
  93      */
  94  	protected function stringsMatch(array $strings, int $pos): bool
  95      {
  96          $value = $strings[0][$pos];
  97          foreach ($strings as $string)
  98          {
  99              if (!isset($string[$pos]) || $string[$pos] !== $value)
 100              {
 101                  return false;
 102              }
 103          }
 104  
 105          return true;
 106      }
 107  }