<?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, level: int}>
     */
    public static function extractToc(string $content): array
    {
        $items = [];
        $lines = explode("\n", $content);

        // ── DEBUG: temporary TOC diagnostics ──────────────────────────
        error_log('[TOC-DEBUG] content length: ' . strlen($content));
        error_log('[TOC-DEBUG] line count: ' . count($lines));
        foreach (array_slice($lines, 0, 8) as $i => $line) {
            if ($line === '') {
                error_log('[TOC-DEBUG] line[' . $i . '] (empty)');
            } else {
                $hex = bin2hex($line);
                $preview = mb_substr($line, 0, 60);
                error_log('[TOC-DEBUG] line[' . $i . '] hex=' . $hex . ' raw=' . $preview);
            }
        }
        // ── END DEBUG ─────────────────────────────────────────────────

        // 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)) {
                $level = strlen($m[1]);
                $label = trim($m[2]);
                $id = $normalizer->normalize($label);
                $items[] = ['label' => $label, 'href' => '#' . $id, 'level' => $level];
                error_log('[TOC-DEBUG] MATCH: h' . $level . ' "' . $label . '" -> #' . $id);
            }
        }
        error_log('[TOC-DEBUG] total items found: ' . count($items));
        return $items;
    }
}