import { fetchJson, maybe } from "../http";
import type { AirQuality } from "../types";

/**
 * Air quality from Open-Meteo's free air-quality API (CAMS data), used for
 * every provider so the AQI always means the same thing.
 * Docs: https://open-meteo.com/en/docs/air-quality-api
 *
 * The same call also tells us the location's IANA time zone, which some
 * providers (Tomorrow.io, OpenWeather free) don't give us.
 */

interface AirQualityResponse {
  timezone: string;
  current: {
    us_aqi: number | null;
    pm2_5: number | null;
    pm10: number | null;
    ozone: number | null;
    nitrogen_dioxide: number | null;
  };
}

export interface LocalContext {
  timeZone: string;
  airQuality: AirQuality | null;
}

export async function getLocalContext(lat: number, lon: number): Promise<LocalContext> {
  const params = new URLSearchParams({
    latitude: String(lat),
    longitude: String(lon),
    current: "us_aqi,pm2_5,pm10,ozone,nitrogen_dioxide",
    timezone: "auto",
  });
  const data = await fetchJson<AirQualityResponse>(
    `https://air-quality-api.open-meteo.com/v1/air-quality?${params}`,
    "Open-Meteo air quality",
    { cacheSeconds: 1800 }, // air quality updates hourly at most
  );

  const c = data.current;
  return {
    timeZone: data.timezone,
    airQuality:
      c.us_aqi === null
        ? null
        : { usAqi: Math.round(c.us_aqi), pm25: maybe(c.pm2_5), pm10: maybe(c.pm10), ozone: maybe(c.ozone), no2: maybe(c.nitrogen_dioxide) },
  };
}