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<?php |
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namespace vanderlee\comprehend\parser\structure; |
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use vanderlee\comprehend\core\ArgumentsTrait; |
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use vanderlee\comprehend\core\Context; |
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use vanderlee\comprehend\directive\Prefer; |
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use vanderlee\comprehend\match\Match; |
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use vanderlee\comprehend\match\Success; |
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use vanderlee\comprehend\parser\Parser; |
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/** |
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* Match one of the provided parsers. |
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* |
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* @author Martijn |
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*/ |
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class Choice extends IterableParser |
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{ |
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use ArgumentsTrait; |
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use PreferTrait; |
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public function __construct(...$arguments) |
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{ |
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if (empty($arguments)) { |
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throw new \InvalidArgumentException('No arguments'); |
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} |
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$this->parsers = self::getArguments($arguments); |
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} |
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public static function first(...$arguments) |
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{ |
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return (new self(...$arguments))->preferFirst(); |
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} |
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public static function shortest(...$arguments) |
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{ |
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return (new self(...$arguments))->preferShortest(); |
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} |
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public static function longest(...$arguments) |
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{ |
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return (new self(...$arguments))->preferLongest(); |
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} |
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private function parseFirst(&$input, $offset, Context $context) |
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{ |
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$max = 0; |
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foreach ($this->parsers as $parser) { |
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$match = $parser->parse($input, $offset, $context); |
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if ($match->match) { |
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return $this->success($input, $offset, $match->length, $match); |
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} |
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$max = max($max, $match->length); |
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} |
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return $this->failure($input, $offset, $max); |
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} |
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private function parseLongest(&$input, $offset, Context $context) |
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{ |
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$max_match = $this->failure($input, $offset); |
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foreach ($this->parsers as $parser) { |
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$match = $parser->parse($input, $offset, $context); |
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if ($match->match == $max_match->match) { |
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if ($match->length > $max_match->length) { |
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$max_match = ($match instanceof Success) |
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? $this->success($input, $offset, $match->length, $match) |
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: $this->failure($input, $offset, $match->length); |
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} |
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} elseif ($match instanceof Success) { |
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$max_match = $this->success($input, $offset, $match->length, $match); |
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} |
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} |
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return $max_match; |
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} |
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private function parseShortest(&$input, $offset, Context $context) |
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{ |
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/** @var Match $match */ |
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$match = null; |
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foreach ($this->parsers as $parser) { |
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$attempt = $parser->parse($input, $offset, $context); |
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switch (true) { |
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case!$match: // Keep attempt if first. |
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case $attempt->match && !$match->match: // Keep attempt if first match |
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case $attempt->match === $match->match && $attempt->length < $match->length: // Keep attempt if equally successful but shorter |
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$match = $attempt; |
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} |
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} |
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// This will fail! $match is not necessarily the shortest |
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return ($match instanceof Success) |
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? $this->success($input, $offset, $match->length, $match) |
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: $this->failure($input, $offset, $match->length); |
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} |
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protected function parse(&$input, $offset, Context $context) |
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{ |
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$this->pushPreferenceToContext($context); |
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switch ($context->getPreference()) { |
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default: |
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case Prefer::FIRST: |
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$match = $this->parseFirst($input, $offset, $context); |
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break; |
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case Prefer::LONGEST: |
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$match = $this->parseLongest($input, $offset, $context); |
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break; |
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case Prefer::SHORTEST: |
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$match = $this->parseShortest($input,$offset, $context); |
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break; |
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} |
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$this->popPreferenceFromContext($context); |
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return $match; |
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} |
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/** |
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* Add one or more parsers as choices |
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* |
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* @param string[]|int[]|Parser[] $arguments |
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* @return $this |
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*/ |
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public function add(...$arguments) |
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{ |
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$this->parsers = array_merge($this->parsers, self::getArguments($arguments)); |
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return $this; |
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} |
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public function __toString() |
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{ |
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$prefix = $this->preference === Prefer::LONGEST |
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? 'longest-of' |
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: |
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($this->preference === Prefer::SHORTEST |
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? 'shortest-of' |
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: |
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''); |
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return $prefix . '( ' . join(' | ', $this->parsers) . ' )'; |
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} |
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} |
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vanderlee /
Comprehend
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