<?php

declare(strict_types=1);

class FeedFetcher
{
    private const MIN_TTL  = 900;    // 15 min
    private const MAX_TTL  = 86400;  // 24 h

    public function __construct(private string $cacheDir)
    {
    }

    /**
     * Retourne les items du feed (depuis le cache si valide, sinon refetch).
     * @return array{items: array, feed_title: string, fetched_at: int, ttl: int}|null
     */
    public function get(string $url): ?array
    {
        $cached = $this->cacheRead($url);
        if ($cached !== null && time() < (int)$cached['fetched_at'] + (int)$cached['ttl']) {
            return $cached;
        }
        return $this->fetch($url);
    }

    /** Force le refetch et met le cache à jour. */
    public function fetch(string $url): ?array
    {
        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_FOLLOWLOCATION => true,
            CURLOPT_MAXREDIRS      => 5,
            CURLOPT_TIMEOUT        => 10,
            CURLOPT_USERAGENT      => 'varlog/1.0 FeedFetcher (+' . (defined('APP_URL') ? APP_URL : '') . ')',
            CURLOPT_HEADER         => true,
        ]);
        $raw      = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $hSize    = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
        curl_close($ch);

        if ($raw === false || !is_int($httpCode) || $httpCode < 200 || $httpCode >= 400) {
            return null;
        }

        $headers = substr((string)$raw, 0, $hSize);
        $body    = substr((string)$raw, $hSize);

        libxml_use_internal_errors(true);
        $xml = simplexml_load_string($body);
        libxml_clear_errors();
        if ($xml === false) {
            return null;
        }

        $isAtom = ($xml->getName() === 'feed');
        $items  = $isAtom ? $this->parseAtom($xml) : $this->parseRss($xml);
        $feedTitle = $isAtom
            ? (string)($xml->title ?? '')
            : (string)($xml->channel->title ?? '');

        $ttl = $this->resolveTtl($xml, $isAtom, $headers);

        $data = [
            'feed_title' => $feedTitle,
            'fetched_at' => time(),
            'ttl'        => $ttl,
            'items'      => $items,
        ];
        $this->cacheWrite($url, $data);
        return $data;
    }

    // ------------------------------------------------------------------ //

    private function parseRss(\SimpleXMLElement $xml): array
    {
        $items = [];
        foreach ($xml->channel->item ?? [] as $item) {
            $date = (string)($item->pubDate ?? '');
            $items[] = [
                'title'   => trim((string)($item->title ?? '')),
                'url'     => trim((string)($item->link ?? '')),
                'summary' => $this->cleanSummary((string)($item->description ?? '')),
                'date'    => $date !== '' ? (int)strtotime($date) : 0,
                'author'  => trim((string)($item->author ?? '')),
            ];
        }
        return $this->sortItems($items);
    }

    private function parseAtom(\SimpleXMLElement $xml): array
    {
        $ns    = $xml->getNamespaces(true);
        $items = [];
        foreach ($xml->entry ?? [] as $entry) {
            $url  = '';
            foreach ($entry->link ?? [] as $link) {
                $rel = (string)($link['rel'] ?? 'alternate');
                if ($rel === 'alternate' || $rel === '') {
                    $url = (string)($link['href'] ?? '');
                    break;
                }
            }
            $date    = (string)($entry->published ?? $entry->updated ?? '');
            $author  = (string)($entry->author->name ?? '');
            $summary = (string)($entry->summary ?? $entry->content ?? '');
            $items[] = [
                'title'   => trim((string)($entry->title ?? '')),
                'url'     => trim($url),
                'summary' => $this->cleanSummary($summary),
                'date'    => $date !== '' ? (int)strtotime($date) : 0,
                'author'  => trim($author),
            ];
        }
        return $this->sortItems($items);
    }

    private function cleanSummary(string $html): string
    {
        $text = strip_tags($html);
        $text = preg_replace('/\s+/', ' ', $text) ?? $text;
        return mb_strimwidth(trim($text), 0, 200, '…');
    }

    private function sortItems(array $items): array
    {
        usort($items, static fn ($a, $b) => $b['date'] <=> $a['date']);
        return $items;
    }

    private function resolveTtl(\SimpleXMLElement $xml, bool $isAtom, string $headers): int
    {
        // 1. TTL déclaré dans le flux RSS (<ttl> en minutes)
        if (!$isAtom) {
            $rssttl = (int)($xml->channel->ttl ?? 0);
            if ($rssttl > 0) {
                return $this->clampTtl($rssttl * 60);
            }
        }

        // 2. Cache-Control: max-age depuis les headers HTTP
        if (preg_match('/max-age=(\d+)/i', $headers, $m)) {
            return $this->clampTtl((int)$m[1]);
        }

        // 3. Valeur par défaut : 1 heure
        return 3600;
    }

    private function clampTtl(int $seconds): int
    {
        return max(self::MIN_TTL, min(self::MAX_TTL, $seconds));
    }

    // ------------------------------------------------------------------ //

    private function cachePath(string $url): string
    {
        return $this->cacheDir . '/' . md5($url) . '.json';
    }

    private function cacheRead(string $url): ?array
    {
        $path = $this->cachePath($url);
        if (!file_exists($path)) {
            return null;
        }
        $data = json_decode((string)file_get_contents($path), true);
        return is_array($data) ? $data : null;
    }

    private function cacheWrite(string $url, array $data): void
    {
        if (!is_dir($this->cacheDir)) {
            mkdir($this->cacheDir, 0755, true);
        }
        file_put_contents(
            $this->cachePath($url),
            json_encode($data, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES)
        );
    }
}