/**
 * Proxy für newsdata.io API.
 * Endpoint: https://newsdata.io/api/1/news?apikey=...&language=...&category=...
 * Pagination: counter = wievieltes Widget dieser Art (0 = erste Seite, 1 = zweite, …), damit News nicht doppelt gezeigt werden.
 */

const NEWS_BASE = 'https://newsdata.io/api/1/news';

// Cache für News-Ergebnisse (pro Sprache/Kategorie)
const newsCache = new Map();
const CACHE_TTL = 5 * 60 * 1000; // 5 Minuten Cache

/**
 * @param {object} options
 * @param {number} options.counter - 0 = erste Seite, 1 = zweite, … (für Pagination/nextPage)
 * @param {string} [options.language] - z. B. de, en
 * @param {string} [options.category] - z. B. top, technology
 * @returns {Promise<{ results: Array, nextPage: string|null }>}
 */
async function fetchNewsPage({ language = 'de', category = 'top', nextPageToken = null }) {
    const apiKey = process.env.NEWSDATA_IO_API_KEY;
    if (!apiKey || !apiKey.trim()) {
        throw new Error('NEWSDATA_IO_API_KEY is not set in .env');
    }
    const params = new URLSearchParams();
    params.set('apikey', apiKey.trim());
    params.set('language', String(language));
    params.set('category', String(category));
    if (nextPageToken) params.set('page', nextPageToken);

    const url = `${NEWS_BASE}?${params.toString()}`;
    const res = await fetch(url);
    if (!res.ok) {
        const text = await res.text();
        throw new Error(`newsdata.io: ${res.status} ${text.slice(0, 200)}`);
    }
    const data = await res.json();
    return {
        results: data.results ?? [],
        nextPage: data.nextPage ?? null
    };
}

/**
 * Holt gecachte Artikel oder lädt sie von der API
 */
async function getCachedNews({ language = 'de', category = 'top', minArticles = 10 }) {
    const cacheKey = `${language}:${category}`;
    const cached = newsCache.get(cacheKey);
    
    // Cache gültig?
    if (cached && (Date.now() - cached.timestamp) < CACHE_TTL) {
        // Wenn wir mehr Artikel brauchen, erweitern
        if (cached.articles.length >= minArticles) {
            return cached.articles;
        }
    }
    
    // Neue Daten laden
    const collected = cached?.articles || [];
    let nextPageToken = cached?.nextPage || null;
    
    while (collected.length < minArticles) {
        try {
            const page = await fetchNewsPage({
                language,
                category,
                nextPageToken: nextPageToken || undefined
            });
            const items = page.results ?? [];
            
            // Duplikate vermeiden (nach title)
            const existingTitles = new Set(collected.map(a => a.title));
            for (const item of items) {
                if (!existingTitles.has(item.title)) {
                    collected.push(item);
                    existingTitles.add(item.title);
                }
            }
            
            nextPageToken = page.nextPage ?? null;
            if (items.length === 0 || !nextPageToken) break;
        } catch (error) {
            console.error('News fetch error:', error);
            break;
        }
    }
    
    // Cache aktualisieren
    newsCache.set(cacheKey, {
        articles: collected,
        nextPage: nextPageToken,
        timestamp: Date.now()
    });
    
    return collected;
}

/**
 * Liefert den N-ten Artikel (counter = 0, 1, 2, …) für das N-te News-Widget.
 * Nutzt Cache, damit mehrere Widgets unterschiedliche Artikel bekommen.
 *
 * @param {object} options
 * @param {number} options.counter - Index des Artikels (0 = erster, 1 = zweiter, …)
 * @param {string} [options.language]
 * @param {string} [options.category]
 * @returns {Promise<{ results: Array, nextPage: string|null }>}
 */
async function getNews({ counter = 0, language = 'de', category = 'top' }) {
    const neededIndex = Math.max(0, counter);
    
    // Mindestens so viele Artikel laden wie benötigt
    const articles = await getCachedNews({
        language,
        category,
        minArticles: neededIndex + 1
    });

    const single = articles[neededIndex] ? [articles[neededIndex]] : [];
    return { results: single, nextPage: null };
}

export default { getNews };