function FunctionExtension::translateNthChild

Throws

ExpressionErrorException

4 calls to FunctionExtension::translateNthChild()

FunctionExtension::getFunctionTranslators in vendor/symfony/css-selector/XPath/Extension/FunctionExtension.php: Returns function translators.
FunctionExtension::translateNthLastChild in vendor/symfony/css-selector/XPath/Extension/FunctionExtension.php
FunctionExtension::translateNthLastOfType in vendor/symfony/css-selector/XPath/Extension/FunctionExtension.php
FunctionExtension::translateNthOfType in vendor/symfony/css-selector/XPath/Extension/FunctionExtension.php

File

vendor/symfony/css-selector/XPath/Extension/FunctionExtension.php, line 48

Class

FunctionExtension: XPath expression translator function extension.

Namespace

Symfony\Component\CssSelector\XPath\Extension

Code

public function translateNthChild(XPathExpr $xpath, FunctionNode $function, bool $last = false, bool $addNameTest = true) : XPathExpr {
    try {
        [
            $a,
            $b,
        ] = Parser::parseSeries($function->getArguments());
    } catch (SyntaxErrorException $e) {
        throw new ExpressionErrorException(\sprintf('Invalid series: "%s".', implode('", "', $function->getArguments())), 0, $e);
    }
    $xpath->addStarPrefix();
    if ($addNameTest) {
        $xpath->addNameTest();
    }
    if (0 === $a) {
        return $xpath->addCondition('position() = ' . ($last ? 'last() - ' . ($b - 1) : $b));
    }
    if ($a < 0) {
        if ($b < 1) {
            return $xpath->addCondition('false()');
        }
        $sign = '<=';
    }
    else {
        $sign = '>=';
    }
    $expr = 'position()';
    if ($last) {
        $expr = 'last() - ' . $expr;
        --$b;
    }
    if (0 !== $b) {
        $expr .= ' - ' . $b;
    }
    $conditions = [
        \sprintf('%s %s 0', $expr, $sign),
    ];
    if (1 !== $a && -1 !== $a) {
        $conditions[] = \sprintf('(%s) mod %d = 0', $expr, $a);
    }
    return $xpath->addCondition(implode(' and ', $conditions));
    // todo: handle an+b, odd, even
    // an+b means every-a, plus b, e.g., 2n+1 means odd
    // 0n+b means b
    // n+0 means a=1, i.e., all elements
    // an means every a elements, i.e., 2n means even
    // -n means -1n
    // -1n+6 means elements 6 and previous
}