/**
 * Proxies Tomorrow.io daily weather forecast for the Plano TX area.
 * Set TOMORROW_API_KEY in Vercel env vars (and .env locally for vercel dev).
 *
 * Response: array of 7-day daily forecast objects, normalised for the frontend.
 * Cached 1 hour — free tier allows 500 calls/day.
 */

const PLANO_LAT = 33.055;
const PLANO_LNG = -96.752;

// Tomorrow.io weather code → label + hail risk flag
function interpretCode(code) {
    const map = {
        1000: { label: 'Clear',            hailRisk: false },
        1001: { label: 'Cloudy',           hailRisk: false },
        1100: { label: 'Mostly Clear',     hailRisk: false },
        1101: { label: 'Partly Cloudy',    hailRisk: false },
        1102: { label: 'Mostly Cloudy',    hailRisk: false },
        2000: { label: 'Fog',              hailRisk: false },
        4000: { label: 'Drizzle',          hailRisk: false },
        4001: { label: 'Rain',             hailRisk: false },
        4200: { label: 'Light Rain',       hailRisk: false },
        4201: { label: 'Heavy Rain',       hailRisk: false },
        5000: { label: 'Snow',             hailRisk: false },
        5001: { label: 'Flurries',         hailRisk: false },
        5100: { label: 'Light Snow',       hailRisk: false },
        5101: { label: 'Heavy Snow',       hailRisk: false },
        6000: { label: 'Freezing Drizzle', hailRisk: true  },
        6001: { label: 'Freezing Rain',    hailRisk: true  },
        6200: { label: 'Lt Freezing Rain', hailRisk: true  },
        6201: { label: 'Hvy Freezing Rain',hailRisk: true  },
        7000: { label: 'Ice Pellets',      hailRisk: true  },
        7101: { label: 'Heavy Hail',       hailRisk: true  },
        7102: { label: 'Light Hail',       hailRisk: true  },
        8000: { label: 'Thunderstorm',     hailRisk: true  },
    };
    return map[code] ?? { label: 'Mixed', hailRisk: false };
}

export default async function handler(req, res) {
    res.setHeader('Cache-Control', 's-maxage=3600, stale-while-revalidate=7200');
    res.setHeader('Access-Control-Allow-Origin', '*');

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

    // Trim to tolerate a stray trailing space/newline in the env var value.
    const key = (process.env.TOMORROW_API_KEY || '').trim();
    if (!key) {
        console.warn('[storm-forecast] TOMORROW_API_KEY not set');
        return res.status(200).json([]);
    }

    try {
        const fields = [
            'precipitationProbability',
            'weatherCode',
            'windSpeedAvg',
            'windGustMax',
            'temperatureAvg',
            'precipitationIntensityAvg',
            'humidityAvg',
        ].join(',');

        const url = `https://api.tomorrow.io/v4/weather/forecast?location=${PLANO_LAT},${PLANO_LNG}&apikey=${key}&timesteps=1d&units=imperial&fields=${fields}`;
        const resp = await fetch(url, {
            headers: { Accept: 'application/json' },
        });

        if (!resp.ok) {
            const txt = await resp.text();
            console.warn('[storm-forecast] Tomorrow.io error', resp.status, txt);
            return res.status(200).json([]);
        }

        const data = await resp.json();
        const daily = data?.timelines?.daily ?? [];

        const forecast = daily.slice(0, 7).map(day => {
            const v = day.values ?? {};
            // Daily aggregated fields may come back as plain names or with Avg/Max suffix
            const precipProb = v.precipitationProbability ?? v.precipitationProbabilityAvg ?? 0;
            const weatherCode = v.weatherCode ?? v.weatherCodeMax ?? 1000;
            const windGust    = v.windGustMax ?? v.windGustAvg ?? 0;
            const windSpeed   = v.windSpeedAvg ?? 0;
            const temp        = v.temperatureAvg ?? 0;
            const humidity    = v.humidityAvg ?? 0;
            const { label, hailRisk } = interpretCode(weatherCode);

            // Storm severity: 0–100 score for how dangerous this day looks
            const stormScore = Math.min(100, Math.round(
                precipProb * 0.5 +
                (hailRisk ? 35 : 0) +
                (windGust > 40 ? 15 : windGust > 25 ? 8 : 0)
            ));

            return {
                date:        day.time,
                precipProb:  Math.round(precipProb),
                weatherCode,
                weatherLabel: label,
                hailRisk,
                windGust:    Math.round(windGust),
                windSpeed:   Math.round(windSpeed),
                tempF:       Math.round(temp),
                humidity:    Math.round(humidity),
                stormScore,
            };
        });

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