// ════════════════════════════════════════════════════════════════════════
//  useForecast — fetches the weather forecast and air quality for the
//  given location and keeps them fresh.
//
//  Responsibilities:
//    1. Fetch /v1/forecast on location change.
//    2. Fetch /v1/air-quality on location change, with a 6-hour
//       localStorage cache (AQI / pollen update slowly).
//    3. Auto-refresh both every 5 minutes so the displayed data stays
//       current as time passes. Air quality only refetches if cache is
//       stale.
//
//  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 5 minutes (drives the "current row")
// ════════════════════════════════════════════════════════════════════════

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

const SIX_HOURS_MS = 6 * 60 * 60 * 1000;
const FIVE_MIN     = 5 * 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`;
}

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());

  // Air quality loader — also used by the 5-minute refresh below.
  async function loadAirQuality(loc) {
    const cacheKey = `sunscope_aq_${loc.lat.toFixed(4)}_${loc.lon.toFixed(4)}`;
    try {
      const cached = localStorage.getItem(cacheKey);
      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; // silently fail — these columns just show '—'
      const data = await r.json();
      setAirQuality(data);
      try {
        localStorage.setItem(cacheKey, JSON.stringify({ ts: Date.now(), data }));
      } catch (e) { /* ignore storage errors */ }
    } catch (_) { /* silently ignore */ }
  }

  // ─── INITIAL FETCH on location change ─────────────────────────────
  useEffect(() => {
    async function load() {
      setLoading(true); setError(null);
      try {
        const r = await fetch(buildForecastUrl(location));
        if (!r.ok) throw new Error(`Open-Meteo HTTP ${r.status}`);
        setForecast(await r.json());
      } catch (e) { setError(e.message); }
      finally { setLoading(false); }
    }
    load();
    loadAirQuality(location);
  }, [location]);

  // ─── AUTO-REFRESH every 5 minutes ─────────────────────────────────
  // Updates `now` (drives the "current hour" highlight) and refetches
  // the forecast so fresh API data comes in automatically. Air quality
  // only refetches if its 6-hour cache has expired.
  useEffect(() => {
    const id = setInterval(() => {
      setNow(new Date());
      async function refresh() {
        try {
          const r = await fetch(buildForecastUrl(location));
          if (r.ok) setForecast(await r.json());
        } catch (_) { /* silently ignore refresh errors */ }
        const cacheKey = `sunscope_aq_${location.lat.toFixed(4)}_${location.lon.toFixed(4)}`;
        try {
          const cached = localStorage.getItem(cacheKey);
          if (cached) {
            const { ts } = JSON.parse(cached);
            if (Date.now() - ts < SIX_HOURS_MS) return; // still fresh
          }
        } catch (e) { /* ignore */ }
        loadAirQuality(location);
      }
      refresh();
    }, FIVE_MIN);
    return () => clearInterval(id);
  }, [location]);

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