/**
 * Proxies active NWS severe weather alerts for Texas to the frontend.
 * No auth required — api.weather.gov is a free public endpoint.
 *
 * For historical data beyond 7 days, integrate NOAA Storm Events CSV API
 * or SWDI (https://www.ncei.noaa.gov/pub/data/swdi/) in a future iteration.
 *
 * Response: array of normalised storm event objects (same shape as MOCK_STORM_EVENTS)
 */

const NWS_HEADERS = {
    'User-Agent': 'PlanoRealtyCRM/1.0 (admin@plano-realty.com)',
    Accept: 'application/geo+json',
};

function severityFromSize(inches) {
    if (!inches || inches < 0.75) return 'none';
    if (inches < 1.00) return 'trace';
    if (inches < 1.50) return 'moderate';
    if (inches < 2.00) return 'significant';
    return 'severe';
}

function parseHailSize(text = '') {
    const m = text.match(/(\d+\.?\d*)\s*inch/i) || text.match(/(\d+\.?\d*)"/) ;
    return m ? parseFloat(m[1]) : null;
}

export default async function handler(req, res) {
    res.setHeader('Cache-Control', 's-maxage=3600, stale-while-revalidate=86400');
    res.setHeader('Access-Control-Allow-Origin', '*');

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

    try {
        // NWS active severe weather alerts for TX — hail + thunderstorm
        const url = 'https://api.weather.gov/alerts/active?area=TX&event=Hail,Severe+Thunderstorm,Tornado';
        const nwsRes = await fetch(url, { headers: NWS_HEADERS });

        if (!nwsRes.ok) {
            console.warn('[storm-events] NWS returned', nwsRes.status);
            return res.status(200).json([]);
        }

        const geojson = await nwsRes.json();
        const features = (geojson.features || []);

        const events = features
            .filter(f => {
                const evt = (f.properties?.event || '').toLowerCase();
                return evt.includes('hail') || evt.includes('thunderstorm') || evt.includes('tornado');
            })
            .map((f, i) => {
                const p = f.properties || {};
                const desc = p.description || p.headline || '';
                const hailSize = parseHailSize(desc) ?? parseHailSize(p.parameters?.hailSize?.[0] ?? '');

                // NWS GeoJSON polygon coordinates are [lng, lat] — swap for Leaflet
                let polygon = [];
                const geom = f.geometry;
                if (geom?.type === 'Polygon' && geom.coordinates?.[0]) {
                    polygon = geom.coordinates[0].map(([lng, lat]) => [lat, lng]);
                } else if (geom?.type === 'MultiPolygon' && geom.coordinates?.[0]?.[0]) {
                    polygon = geom.coordinates[0][0].map(([lng, lat]) => [lat, lng]);
                }

                const typeStr = (p.event || '').toLowerCase();
                const type = typeStr.includes('tornado') ? 'tornado'
                    : typeStr.includes('hail') ? 'hail'
                    : 'wind';

                return {
                    id: `NWS-${p.id || i}`,
                    date: p.onset || p.sent || new Date().toISOString(),
                    type,
                    severity: severityFromSize(hailSize),
                    maxHailSize: hailSize,
                    areaName: p.areaDesc || 'Unknown Area',
                    county: 'Collin',
                    estimatedHomes: null,
                    description: p.headline || desc.slice(0, 300),
                    source: 'NWS',
                    polygon,
                };
            })
            .filter(e => e.polygon.length >= 3); // require a valid polygon

        return res.status(200).json(events);
    } catch (err) {
        console.error('[storm-events] error:', err.message);
        return res.status(200).json([]);
    }
}