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<?php |
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namespace FunctionalPHP\PatternMatching; |
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class Parser |
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{ |
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protected $reserved = ['true', 'false']; |
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protected $rules = [ |
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'/^(true|false)$/i' => '_parseBooleanConstant', |
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'/^([\'"])(?:(?!\\1).)*\\1$/' => '_parseStringConstant', |
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'/^[a-zA-Z]+$/' => '_parseIdentifier', |
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'/^_$/' => '_parseWildcard', |
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'/^\\[.*\\]$/' => '_parseArray', |
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'/^\\(.+:.+\\)$/' => '_parseCons', |
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'/^[a-zA-Z]+@.+$/' => '_parseAs', |
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]; |
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protected function _parseBooleanConstant($value, $pattern) |
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{ |
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$pattern_value = strtoupper($pattern) === 'TRUE' ? true : false; |
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return is_bool($value) && $value === $pattern_value ? [] : false; |
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} |
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protected function _parseStringConstant($value, $pattern) |
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{ |
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$string_pattern = substr($pattern, 1, -1); |
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return is_string($value) && $string_pattern == $value ? [] : false; |
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} |
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protected function _parseIdentifier($value, $pattern) |
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{ |
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return in_array(strtolower($pattern), $this->reserved) ? false : [$pattern => $value]; |
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} |
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protected function _parseWildcard() |
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{ |
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return []; |
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} |
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protected function _parseArray($value, $pattern) |
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{ |
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$patterns = $this->_split(',', '[', ']', substr($pattern, 1, -1)); |
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if(count($patterns) === 0) { |
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return count($value) === 0 ? [] : false; |
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} |
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return $this->_recurse($value, $patterns); |
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} |
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protected function _parseCons($value, $pattern) |
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{ |
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$patterns = $this->_split(':', '(', ')', substr($pattern, 1, -1)); |
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$last_pattern = array_pop($patterns); |
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$results = $this->_recurse($value, $patterns); |
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if($results !== false) { |
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$last_result = $this->parse(array_splice($value, count($patterns)), $last_pattern); |
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$results = $last_result === false ? false : array_merge($results, $last_result); |
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} |
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return $results; |
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} |
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protected function _parseAs($value, $pattern) |
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{ |
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$patterns = explode('@', $pattern, 2); |
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$rest = $this->parse($value, $patterns[1]); |
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return $rest === false ? false : array_merge([$patterns[0] => $value], $rest); |
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} |
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/** |
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* @param mixed $value |
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* @param string $pattern |
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* @return bool|array |
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*/ |
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public function parse($value, $pattern) |
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{ |
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$pattern = trim($pattern); |
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if(is_numeric($pattern)) { |
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return is_numeric($value) && $pattern == $value ? [] : false; |
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} |
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$matched = false; |
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foreach($this->rules as $regex => $method) { |
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if(preg_match($regex, $pattern)) { |
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$matched = true; |
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$arguments = call_user_func_array([$this, $method], [$value, $pattern]); |
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if($arguments !== false) { |
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return $arguments; |
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} |
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} |
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} |
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if(! $matched) { |
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$this->_invalidPattern($pattern); |
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} |
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return false; |
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} |
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protected function _split($delimiter, $start, $stop, $pattern) |
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{ |
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$result = split_enclosed($delimiter, $start, $stop, $pattern); |
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if($result === false) { |
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$this->_invalidPattern($pattern); |
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} |
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return $result; |
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} |
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protected function _recurse($value, $patterns) |
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{ |
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if(! is_array($value) || count($patterns) > count($value)) { |
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return false; |
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} |
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$results = []; |
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foreach($patterns as $p) { |
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$new = $this->parse(array_shift($value), $p); |
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if($new === false) { |
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return false; |
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} |
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$results = array_merge($results, $new); |
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} |
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return $results; |
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} |
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protected function _invalidPattern($pattern) |
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{ |
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throw new \RuntimeException(sprintf('Invalid pattern "%s".', $pattern)); |
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} |
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} |
functional-php /
pattern-matching
Our type inference engine in quite powerful, but sometimes the code does not provide enough clues to go by. In these cases we request you to add a
@returnannotation as described here.