wayfarer-weather/lib/weather/providers/openmeteo.ts

import { CONDITION_LABELS } from "../describe";
import { fetchJson, fromUnix, maybe, MAX_DAYS, MAX_HOURS, nextHours, round1 } from "../http";
import type { Condition, WeatherProvider } from "../types";

/**
 * Open-Meteo — free, no key, and the deepest data: hourly and daily out to 16 days.
 * Docs: https://open-meteo.com/en/docs
 *
 * We ask for `timeformat=unixtime` so every time comes back as a plain number.
 */

const HOURLY_VARS = [
  "temperature_2m", "apparent_temperature", "precipitation_probability", "precipitation",
  "weather_code", "wind_speed_10m", "wind_gusts_10m", "wind_direction_10m",
  "relative_humidity_2m", "uv_index", "is_day",
] as const;

const DAILY_VARS = [
  "weather_code", "temperature_2m_max", "temperature_2m_min", "precipitation_probability_max",
  "precipitation_sum", "wind_speed_10m_max", "wind_gusts_10m_max", "wind_direction_10m_dominant",
  "uv_index_max", "sunrise", "sunset",
] as const;

const CURRENT_VARS = [
  "temperature_2m", "apparent_temperature", "relative_humidity_2m", "is_day", "precipitation",
  "weather_code", "cloud_cover", "pressure_msl", "wind_speed_10m", "wind_direction_10m",
  "wind_gusts_10m", "dew_point_2m", "visibility", "uv_index",
] as const;

// Each section is "variable name → value" (current) or "variable name → array of values".
type Row<Names extends readonly string[]> = Record<Names[number], number>;
type Columns<Names extends readonly string[]> = Record<Names[number], (number | null)[]> & { time: number[] };

interface OpenMeteoResponse {
  timezone: string;
  current: Row<typeof CURRENT_VARS> & { time: number };
  hourly: Columns<typeof HOURLY_VARS>;
  daily: Columns<typeof DAILY_VARS>;
}

/** WMO weather codes, listed at the bottom of the Open-Meteo docs page. */
function toCondition(code: number | null): Condition {
  if (code === null || code <= 1) return "clear";
  if (code <= 3) return "clouds";
  if (code === 45 || code === 48) return "fog";
  if ((code >= 71 && code <= 77) || code === 85 || code === 86) return "snow";
  if (code >= 95) return "storm";
  return "rain"; // drizzle (51–57), rain (61–67), showers (80–82)
}

const TWELVE_HOURS = 12 * 60 * 60;

export const openMeteo: WeatherProvider = {
  id: "openmeteo",
  label: "Open-Meteo",
  envKey: null,
  limits: () => ({ forecastDays: 14, hourlyStepHours: 1 }),

  async getForecast(lat, lon) {
    const params = new URLSearchParams({
      latitude: String(lat),
      longitude: String(lon),
      current: CURRENT_VARS.join(","),
      hourly: HOURLY_VARS.join(","),
      daily: DAILY_VARS.join(","),
      timezone: "auto",
      timeformat: "unixtime",
      forecast_days: String(MAX_DAYS),
    });
    const { current: c, hourly: h, daily: d, timezone } = await fetchJson<OpenMeteoResponse>(
      `https://api.open-meteo.com/v1/forecast?${params}`,
      "Open-Meteo",
    );

    const condition = toCondition(c.weather_code);

    const hourly = h.time.map((t, i) => ({
      time: fromUnix(t),
      tempC: round1(h.temperature_2m[i] ?? 0),
      feelsLikeC: maybe(h.apparent_temperature[i]),
      condition: toCondition(h.weather_code[i]),
      isDay: h.is_day[i] === 1,
      precipChance: maybe(h.precipitation_probability[i]),
      precipMm: maybe(h.precipitation[i]),
      windKph: round1(h.wind_speed_10m[i] ?? 0),
      gustKph: maybe(h.wind_gusts_10m[i]),
      windDeg: maybe(h.wind_direction_10m[i]),
      humidity: maybe(h.relative_humidity_2m[i]),
      uvIndex: maybe(h.uv_index[i]),
    }));

    return {
      timeZone: timezone,
      hourlyStepHours: 1,
      alerts: [], // Open-Meteo has no alerts; the API route adds NWS alerts for US locations
      current: {
        time: fromUnix(c.time),
        tempC: round1(c.temperature_2m),
        feelsLikeC: round1(c.apparent_temperature),
        condition,
        description: CONDITION_LABELS[condition],
        isDay: c.is_day === 1,
        humidity: c.relative_humidity_2m,
        windKph: round1(c.wind_speed_10m),
        gustKph: maybe(c.wind_gusts_10m),
        windDeg: maybe(c.wind_direction_10m),
        pressureHpa: maybe(c.pressure_msl),
        dewPointC: maybe(c.dew_point_2m),
        visibilityKm: c.visibility == null ? null : round1(c.visibility / 1000),
        uvIndex: maybe(c.uv_index),
        cloudCover: maybe(c.cloud_cover),
        precipMm: maybe(c.precipitation),
      },
      hourly: nextHours(hourly, MAX_HOURS),
      daily: d.time.map((t, i) => ({
        time: fromUnix(t + TWELVE_HOURS), // daily times are local midnight; use midday
        highC: round1(d.temperature_2m_max[i] ?? 0),
        lowC: round1(d.temperature_2m_min[i] ?? 0),
        condition: toCondition(d.weather_code[i]),
        summary: null,
        precipChance: maybe(d.precipitation_probability_max[i]),
        precipMm: maybe(d.precipitation_sum[i]),
        windKph: maybe(d.wind_speed_10m_max[i]),
        gustKph: maybe(d.wind_gusts_10m_max[i]),
        windDeg: maybe(d.wind_direction_10m_dominant[i]),
        uvIndexMax: maybe(d.uv_index_max[i]),
        humidity: null,
        sunrise: d.sunrise[i] ? fromUnix(d.sunrise[i]!) : null,
        sunset: d.sunset[i] ? fromUnix(d.sunset[i]!) : null,
      })),
    };
  },
};