<?php

/**
 * Shared markdown utilities.
 */
class MarkdownHelper
{
    /**
     * Extract h1–h3 headings from raw markdown content as TOC items.
     *
     * Each heading gets an anchor id matching CommonMark's default slugification
     * (lowercase, spaces → hyphens, punctuation stripped).
     *
     * @return array<int, array{label: string, href: string}>
     */
    public static function extractToc(string $content): array
    {
        $items = [];
        $lines = explode("\n", $content);

        // Use CommonMark's own SlugNormalizer so TOC links match the rendered heading IDs exactly.
        $normalizer = new \League\CommonMark\Normalizer\SlugNormalizer();

        foreach ($lines as $line) {
            if (preg_match('/^#{1,3}\s+(.+)$/', $line, $m)) {
                $label = trim($m[1]);
                $id = $normalizer->normalize($label);
                $items[] = ['label' => $label, 'href' => '#' . $id];
            }
        }
        return $items;
    }
}