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<?php |
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declare(strict_types=1); |
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/** |
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* @license http://opensource.org/licenses/mit-license.php MIT |
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* @link https://github.com/nicoSWD |
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* @author Nicolas Oelgart <[email protected]> |
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*/ |
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namespace nicoSWD\Rules; |
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use nicoSWD\Rules\Expressions\ExpressionFactory; |
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use nicoSWD\Rules\Tokens\BaseToken; |
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use SplStack; |
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class Parser |
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{ |
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/** @var AST */ |
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private $ast; |
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/** @var ExpressionFactory */ |
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private $expressionFactory; |
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/** @var Compiler */ |
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private $compiler; |
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/** @var null|BaseToken */ |
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private $operator = null; |
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/** @var SplStack */ |
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private $values; |
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public function __construct(AST $ast, ExpressionFactory $expressionFactory, Compiler $compiler) |
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{ |
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$this->ast = $ast; |
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$this->expressionFactory = $expressionFactory; |
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$this->compiler = $compiler; |
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$this->values = new SplStack(); |
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} |
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public function parse(string $rule): string |
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{ |
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$this->compiler->clear(); |
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$this->operator = null; |
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foreach ($this->ast->getStream($rule) as $token) { |
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switch ($token->getType()) { |
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case TokenType::VALUE: |
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$this->assignVariableValueFromToken($token); |
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break; |
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case TokenType::LOGICAL: |
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$this->compiler->addLogical($token); |
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continue 2; |
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case TokenType::PARENTHESIS: |
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$this->compiler->addParentheses($token); |
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continue 2; |
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case TokenType::OPERATOR: |
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$this->assignOperator($token); |
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continue 2; |
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case TokenType::COMMENT: |
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case TokenType::SPACE: |
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continue 2; |
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default: |
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throw Exceptions\ParserException::unknownToken($token); |
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} |
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$this->evaluateExpression(); |
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} |
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return $this->compiler->getCompiledRule(); |
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} |
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private function assignVariableValueFromToken(BaseToken $token) |
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{ |
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$this->compiler->flipOperatorRequired($token); |
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$this->values->push($token->getValue()); |
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} |
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private function assignOperator(BaseToken $token) |
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{ |
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if (isset($this->operator)) { |
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throw Exceptions\ParserException::unexpectedToken($token); |
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} elseif ($this->values->isEmpty()) { |
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throw Exceptions\ParserException::incompleteExpression($token); |
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} |
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$this->compiler->operatorRequired(false); |
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$this->operator = $token; |
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} |
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private function evaluateExpression() |
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{ |
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if (!isset($this->operator) || $this->values->count() !== 2) { |
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return; |
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} |
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list ($rightValue, $leftValue) = $this->values; |
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$this->compiler->addBoolean($this->getExpression()->evaluate($leftValue, $rightValue)); |
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$this->values->pop(); |
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$this->values->pop(); |
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unset($this->operator); |
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} |
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private function getExpression(): Expressions\BaseExpression |
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{ |
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return $this->expressionFactory->createFromOperator($this->operator); |
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} |
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} |
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Unless you are absolutely sure that the expression can never be null because of other conditions, we strongly recommend to add an additional type check to your code: