sunscope/assets/js/hooks/useForecast.js

// ------------------------------------------------------------------------
//  useForecast - fetches the weather forecast and air quality for the
//  given location and keeps them fresh.
//
//  Responsibilities:
//    1. Fetch /v1/forecast on location change, with a 15-minute
//       localStorage cache. fetchedAt reflects the cache timestamp.
//    2. Fetch /v1/air-quality on location change, with a 6-hour
//       localStorage cache (AQI / pollen update slowly).
//    3. Auto-refresh forecast every 15 minutes (matches Open-Meteo
//       update cadence). Air quality only refetches if cache is stale.
//    4. Tick `now` every 2 minutes to keep the current-row highlight
//       accurate without any API cost.
//
//  Inputs:
//    location  - { lat, lon, name, country }
//
//  Outputs:
//    forecast    - raw /v1/forecast response, or null
//    airQuality  - raw /v1/air-quality response, or null
//    loading     - true while the forecast fetch is in flight
//    error       - fetch error message, or null
//    now         - Date that ticks every 2 minutes (drives the current row)
//    fetchedAt   - Date the forecast data was last fetched or read from cache
// ------------------------------------------------------------------------

import { useState, useEffect } from '../../vendor/preact-hooks.js';

const FIFTEEN_MIN_MS = 15 * 60 * 1000;
const SIX_HOURS_MS   =  6 * 60 * 60 * 1000;
const TWO_MIN_MS     =  2 * 60 * 1000;

function buildForecastUrl(loc) {
  return `https://api.open-meteo.com/v1/forecast` +
    `?latitude=${loc.lat}&longitude=${loc.lon}` +
    `&hourly=temperature_2m,relative_humidity_2m,dew_point_2m,` +
    `wind_speed_10m,wind_direction_10m,wind_gusts_10m,` +
    `direct_radiation,diffuse_radiation,shortwave_radiation,` +
    `cloud_cover,cloud_cover_low,cloud_cover_mid,cloud_cover_high,` +
    `uv_index,precipitation,snowfall,visibility,` +
    `soil_temperature_0cm,soil_temperature_6cm,soil_moisture_0_to_1cm` +
    `&wind_speed_unit=ms&timezone=auto&forecast_days=14`;
}

function buildAirQualityUrl(loc) {
  return `https://air-quality-api.open-meteo.com/v1/air-quality` +
    `?latitude=${loc.lat}&longitude=${loc.lon}` +
    `&hourly=european_aqi,` +
    `grass_pollen,birch_pollen,alder_pollen,` +
    `mugwort_pollen,olive_pollen,ragweed_pollen` +
    `&timezone=auto&forecast_days=5`;
}

function forecastCacheKey(loc) {
  return `sunscope_fc_${loc.lat.toFixed(4)}_${loc.lon.toFixed(4)}`;
}

function airQualityCacheKey(loc) {
  return `sunscope_aq_${loc.lat.toFixed(4)}_${loc.lon.toFixed(4)}`;
}

export function useForecast(location) {
  const [forecast,  setForecast]  = useState(null);
  const [airQuality, setAirQuality] = useState(null);
  const [loading,   setLoading]   = useState(false);
  const [error,     setError]     = useState(null);
  const [now,       setNow]       = useState(new Date());
  const [fetchedAt, setFetchedAt] = useState(null);

  // ─── FORECAST LOADER ──────────────────────────────────────────────
  async function loadForecast(loc) {
    const key = forecastCacheKey(loc);
    try {
      const cached = localStorage.getItem(key);
      if (cached) {
        const { ts, data } = JSON.parse(cached);
        if (Date.now() - ts < FIFTEEN_MIN_MS) {
          setForecast(data);
          setFetchedAt(new Date(ts));
          return;
        }
      }
    } catch (e) { /* ignore bad cache */ }

    setLoading(true); setError(null);
    try {
      const r = await fetch(buildForecastUrl(loc));
      if (!r.ok) throw new Error(`Open-Meteo HTTP ${r.status}`);
      const data = await r.json();
      const ts = Date.now();
      setForecast(data);
      setFetchedAt(new Date(ts));
      try {
        localStorage.setItem(key, JSON.stringify({ ts, data }));
      } catch (e) { /* ignore storage errors */ }
    } catch (e) { setError(e.message); }
    finally { setLoading(false); }
  }

  // ─── AIR QUALITY LOADER ───────────────────────────────────────────
  async function loadAirQuality(loc) {
    const key = airQualityCacheKey(loc);
    try {
      const cached = localStorage.getItem(key);
      if (cached) {
        const { ts, data } = JSON.parse(cached);
        if (Date.now() - ts < SIX_HOURS_MS) {
          setAirQuality(data);
          return;
        }
      }
    } catch (e) { /* ignore bad cache */ }
    try {
      const r = await fetch(buildAirQualityUrl(loc));
      if (!r.ok) return;
      const data = await r.json();
      setAirQuality(data);
      try {
        localStorage.setItem(airQualityCacheKey(loc), JSON.stringify({ ts: Date.now(), data }));
      } catch (e) { /* ignore storage errors */ }
    } catch (_) { /* silently ignore */ }
  }

  // ─── INITIAL FETCH on location change ─────────────────────────────
  useEffect(() => {
    loadForecast(location);
    loadAirQuality(location);
  }, [location]);

  // ─── 2-MINUTE CLOCK TICK (current-row highlight only) ─────────────
  useEffect(() => {
    const id = setInterval(() => setNow(new Date()), TWO_MIN_MS);
    return () => clearInterval(id);
  }, []);

  // ─── 15-MINUTE REFRESH (matches Open-Meteo update cadence) ────────
  useEffect(() => {
    const id = setInterval(() => {
      async function refresh() {
        const key = forecastCacheKey(location);
        try { localStorage.removeItem(key); } catch (e) { /* ignore */ }
        await loadForecast(location);

        const aqKey = airQualityCacheKey(location);
        try {
          const cached = localStorage.getItem(aqKey);
          if (cached) {
            const { ts } = JSON.parse(cached);
            if (Date.now() - ts < SIX_HOURS_MS) return;
          }
        } catch (e) { /* ignore */ }
        loadAirQuality(location);
      }
      refresh();
    }, FIFTEEN_MIN_MS);
    return () => clearInterval(id);
  }, [location]);

  return { forecast, airQuality, loading, error, now, fetchedAt };
}