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   1  <?php
   2  
   3  /**
   4  * @package   s9e\TextFormatter
   5  * @copyright Copyright (c) 2010-2022 The s9e authors
   6  * @license   http://www.opensource.org/licenses/mit-license.php The MIT License
   7  */
   8  namespace s9e\TextFormatter\Configurator\TemplateNormalizations;
   9  
  10  use Exception;
  11  use s9e\TextFormatter\Utils\XPath;
  12  
  13  class FoldConstantXPathExpressions extends AbstractConstantFolding
  14  {
  15      /**
  16      * @var string[] List of supported XPath functions
  17      */
  18      protected $supportedFunctions = [
  19          'boolean',
  20          'ceiling',
  21          'concat',
  22          'contains',
  23          'floor',
  24          'normalize-space',
  25          'not',
  26          'number',
  27          'round',
  28          'starts-with',
  29          'string',
  30          'string-length',
  31          'substring',
  32          'substring-after',
  33          'substring-before',
  34          'translate'
  35      ];
  36  
  37      /**
  38      * {@inheritdoc}
  39      */
  40  	protected function getOptimizationPasses()
  41      {
  42          return [
  43              '(^(?:"[^"]*"|\'[^\']*\'|\\.[0-9]|[^"$&\'./:@[\\]])++$)' => 'foldConstantXPathExpression'
  44          ];
  45      }
  46  
  47      /**
  48      * Evaluate given expression without raising any warnings
  49      *
  50      * @param  string $expr
  51      * @return mixed
  52      */
  53  	protected function evaluate($expr)
  54      {
  55          $useErrors = libxml_use_internal_errors(true);
  56          $result    = $this->xpath->evaluate($expr);
  57          libxml_use_internal_errors($useErrors);
  58  
  59          return $result;
  60      }
  61  
  62      /**
  63      * Evaluate and replace a constant XPath expression
  64      *
  65      * @param  array  $m
  66      * @return string
  67      */
  68  	protected function foldConstantXPathExpression(array $m)
  69      {
  70          $expr = $m[0];
  71          if ($this->isConstantExpression($expr))
  72          {
  73              try
  74              {
  75                  $result     = $this->evaluate($expr);
  76                  $foldedExpr = XPath::export($result);
  77                  $expr       = $this->selectReplacement($expr, $foldedExpr);
  78              }
  79              catch (Exception $e)
  80              {
  81                  // Do nothing
  82              }
  83          }
  84  
  85          return $expr;
  86      }
  87  
  88      /**
  89      * Test whether given expression seems to be constant
  90      *
  91      * @param  string $expr
  92      * @return bool
  93      */
  94  	protected function isConstantExpression($expr)
  95      {
  96          // Replace strings to avoid false-positives
  97          $expr = preg_replace('("[^"]*"|\'[^\']*\')', '0', $expr);
  98  
  99          // Match function calls against the list of supported functions
 100          preg_match_all('(\\w[-\\w]+(?=\\())', $expr, $m);
 101          if (count(array_diff($m[0], $this->supportedFunctions)) > 0)
 102          {
 103              return false;
 104          }
 105  
 106          // Match unsupported characters and keywords, as well as function calls without arguments
 107          return !preg_match('([^\\s!\\-0-9<=>a-z\\(-.]|\\.(?![0-9])|\\b[-a-z](?![-\\w]+\\()|\\(\\s*\\))i', $expr);
 108      }
 109  
 110      /**
 111      * Select the best replacement for given expression
 112      *
 113      * @param  string $expr       Original expression
 114      * @param  string $foldedExpr Folded expression
 115      * @return string
 116      */
 117  	protected function selectReplacement($expr, $foldedExpr)
 118      {
 119          // Use the folded expression if it's smaller or it's a boolean
 120          if (strlen($foldedExpr) < strlen($expr) || $foldedExpr === 'false()' || $foldedExpr === 'true()')
 121          {
 122              return $foldedExpr;
 123          }
 124  
 125          return $expr;
 126      }
 127  }