/**
 * Posimai Tech Events - /api/events
 *
 * GET /api/events?q=keyword -> Connpass APIを呼び出して整形したイベント一覧を返す。
 *
 * Connpass API: https://connpass.com/about/api/
 */

export default async function handler(req, res) {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
    res.setHeader('Cache-Control', 's-maxage=1800, stale-while-revalidate=3600');

    if (req.method === 'OPTIONS') {
        return res.status(200).end();
    }

    if (req.method !== 'GET') {
        return res.status(405).json({ error: 'Method not allowed' });
    }

    try {
        const { q } = req.query;
        // Search either specific query from UI or broad default queries for tech events
        const fetchKeyword = q && q.trim().length > 0 ? q.trim() : 'IT,エンジニア,デザイン,Web,AI,アプリ';
        const urlObj = new URL('https://connpass.com/api/v1/event/');
        // ConnpassのOR検索仕様に合わせて keyword_or を使用する
        urlObj.searchParams.append('keyword_or', fetchKeyword);
        urlObj.searchParams.append('order', '2'); // 開催降順（新着イベント）
        urlObj.searchParams.append('count', '50');

        // Connpass APIはUser-Agentが必須
        const response = await fetch(urlObj.toString(), {
            headers: {
                'User-Agent': 'PosimaiTechEvents/1.0 (https://posimai-tech-events.vercel.app)'
            }
        });

        if (!response.ok) {
            console.error('Connpass API Error', await response.text());
            res.status(502).json({ error: 'Failed to fetch events from Connpass' });
            return;
        }

        const data = await response.json();

        // Map to Posimai Events structure
        const events = (data.events || []).map(ev => {
            const startStr = ev.started_at || '';
            const endStr = ev.ended_at || '';

            const startDate = startStr.slice(0, 10);
            const startTime = startStr.slice(11, 16);
            const endDate = endStr.slice(0, 10);
            const endTime = endStr.slice(11, 16);

            let location = ev.place || 'オンライン';
            if (!ev.address && !ev.place) {
                if (ev.event_url && ev.event_type === 'online') location = 'オンライン開催';
                else location = '会場未定 / オンライン';
            }

            return {
                id: String(ev.event_id),
                title: ev.title,
                startDate: startDate,
                startTime: startTime,
                endDate: endDate,
                endTime: endTime,
                location: location,
                address: ev.address || '',
                description: ev.catch || '詳細説明はリンク先をご覧ください。',
                category: ev.series ? ev.series.title : 'IT/テック',
                url: ev.event_url,
                source: 'Connpass',
                // To be enhanced: derive tags based on title/description
                interestTags: [],
                audienceTags: []
            };
        });

        return res.status(200).json({
            events: events,
            updatedAt: new Date().toISOString(),
            source: 'connpass'
        });

    } catch (e) {
        console.error('API /events error:', e);
        return res.status(500).json({ error: 'Internal Server Error' });
    }
}