class MacroTokenParser

final class MacroTokenParser extends AbstractTokenParser {
    public function parse(Token $token) : Node {
        $lineno = $token->getLine();
        $stream = $this->parser
            ->getStream();
        $name = $stream->expect(Token::NAME_TYPE)
            ->getValue();
        $arguments = $this->parseDefinition();
        $stream->expect(Token::BLOCK_END_TYPE);
        $this->parser
            ->pushLocalScope();
        $body = $this->parser
            ->subparse([
            $this,
            'decideBlockEnd',
        ], true);
        if ($token = $stream->nextIf(Token::NAME_TYPE)) {
            $value = $token->getValue();
            if ($value != $name) {
                throw new SyntaxError(\sprintf('Expected endmacro for macro "%s" (but "%s" given).', $name, $value), $stream->getCurrent()
                    ->getLine(), $stream->getSourceContext());
            }
        }
        $this->parser
            ->popLocalScope();
        $stream->expect(Token::BLOCK_END_TYPE);
        $this->parser
            ->setMacro($name, new MacroNode($name, new BodyNode([
            $body,
        ]), $arguments, $lineno));
        return new EmptyNode($lineno);
    }
    public function decideBlockEnd(Token $token) : bool {
        return $token->test('endmacro');
    }
    public function getTag() : string {
        return 'macro';
    }
    private function parseDefinition() : ArrayExpression {
        $arguments = new ArrayExpression([], $this->parser
            ->getCurrentToken()
            ->getLine());
        $stream = $this->parser
            ->getStream();
        $stream->expect(Token::PUNCTUATION_TYPE, '(', 'A list of arguments must begin with an opening parenthesis');
        while (!$stream->test(Token::PUNCTUATION_TYPE, ')')) {
            if (count($arguments)) {
                $stream->expect(Token::PUNCTUATION_TYPE, ',', 'Arguments must be separated by a comma');
                // if the comma above was a trailing comma, early exit the argument parse loop
                if ($stream->test(Token::PUNCTUATION_TYPE, ')')) {
                    break;
                }
            }
            $token = $stream->expect(Token::NAME_TYPE, null, 'An argument must be a name');
            $name = new LocalVariable($token->getValue(), $this->parser
                ->getCurrentToken()
                ->getLine());
            if ($token = $stream->nextIf(Token::OPERATOR_TYPE, '=')) {
                $default = $this->parser
                    ->getExpressionParser()
                    ->parseExpression();
            }
            else {
                $default = new ConstantExpression(null, $this->parser
                    ->getCurrentToken()
                    ->getLine());
                $default->setAttribute('is_implicit', true);
            }
            if (!$this->checkConstantExpression($default)) {
                throw new SyntaxError('A default value for an argument must be a constant (a boolean, a string, a number, a sequence, or a mapping).', $token->getLine(), $stream->getSourceContext());
            }
            $arguments->addElement($default, $name);
        }
        $stream->expect(Token::PUNCTUATION_TYPE, ')', 'A list of arguments must be closed by a parenthesis');
        return $arguments;
    }
    // checks that the node only contains "constant" elements
    private function checkConstantExpression(Node $node) : bool {
        if (!($node instanceof ConstantExpression || $node instanceof ArrayExpression || $node instanceof NegUnary || $node instanceof PosUnary)) {
            return false;
        }
        foreach ($node as $n) {
            if (!$this->checkConstantExpression($n)) {
                return false;
            }
        }
        return true;
    }

}