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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 function array_merge, array_slice, count, is_array, serialize;
  11  
  12  /**
  13  * Replaces (?:ab|bb|c) with (?:[ab]b|c)
  14  */
  15  class CoalesceSingleCharacterPrefix extends AbstractPass
  16  {
  17      /**
  18      * {@inheritdoc}
  19      */
  20  	protected function runPass(array $strings): array
  21      {
  22          $newStrings = [];
  23          foreach ($this->getEligibleKeys($strings) as $keys)
  24          {
  25              // Create a new string to hold the merged strings and replace the first element with
  26              // an empty character class
  27              $newString    = $strings[$keys[0]];
  28              $newString[0] = [];
  29  
  30              // Fill the character class with the prefix of each string in this group before removing
  31              // the original string
  32              foreach ($keys as $key)
  33              {
  34                  $newString[0][] = [$strings[$key][0]];
  35                  unset($strings[$key]);
  36              }
  37              $newStrings[] = $newString;
  38          }
  39  
  40          return array_merge($newStrings, $strings);
  41      }
  42  
  43      /**
  44      * Filter the list of eligible keys and keep those that have at least two matches
  45      *
  46      * @param  array[] $eligibleKeys List of lists of keys
  47      * @return array[]
  48      */
  49  	protected function filterEligibleKeys(array $eligibleKeys): array
  50      {
  51          $filteredKeys = [];
  52          foreach ($eligibleKeys as $k => $keys)
  53          {
  54              if (count($keys) > 1)
  55              {
  56                  $filteredKeys[] = $keys;
  57              }
  58          }
  59  
  60          return $filteredKeys;
  61      }
  62  
  63      /**
  64      * Get a list of keys of strings eligible to be merged together, grouped by suffix
  65      *
  66      * @param  array[] $strings
  67      * @return array[]
  68      */
  69  	protected function getEligibleKeys(array $strings): array
  70      {
  71          $eligibleKeys = [];
  72          foreach ($strings as $k => $string)
  73          {
  74              if (!is_array($string[0]) && isset($string[1]))
  75              {
  76                  $suffix = serialize(array_slice($string, 1));
  77                  $eligibleKeys[$suffix][] = $k;
  78              }
  79          }
  80  
  81          return $this->filterEligibleKeys($eligibleKeys);
  82      }
  83  }