liftie/lib/weather/openweather.js

Clean, simple, easy to read, fast ski resort lift status

import Debug from 'debug';
import limiter from '../tools/limiter.js';
import * as millis from '../tools/millis.js';
import { iconsFrom } from './icons.js';

const debug = Debug('liftie:weather');

// not more than 30 a minute (60 per documentation)
const limit = limiter(30, millis.minute);

function tempInF(kelvins) {
  return Math.round((kelvins - 273.15) * 1.8) + 32;
}

function snowInInches(snow) {
  if (!snow) {
    return 0;
  }
  snow *= 0.0393701; // millimeters to inches
  return Math.round(snow);
}

const PERIODS = {
  d: 'day',
  n: 'night'
};

// see: https://openweathermap.org/weather-conditions
const KEYS = {
  '01': 'skc', // clear sky
  '02': 'few', // few clouds
  '03': 'sct', // scattered clouds
  '04': 'bkn', // broken clouds
  '09': 'rain_showers', // shower rain
  10: 'rain', // rain
  11: 'tsra', // thunderstorm
  13: 'snow', // snow
  50: 'fog' // mist
};

function icons(code) {
  const match = code.match(/(\d+)(d|n)/);
  if (!match) {
    return ['', ''];
  }
  const [, key, period] = match;
  return iconsFrom(PERIODS[period], KEYS[key]);
}

function sanitize({ city, list }) {
  const { dt_txt, main, weather, snow = {} } = list[0];

  debug(dt_txt, main, weather, snow);

  const notice = {
    href: `https://openweathermap.org/city/${city.id}`,
    img: 'https://openweathermap.org/themes/openweathermap/assets/vendor/owm/img/logo_OpenWeatherMap_orange.svg',
    width: 160,
    site: 'openweathermap.org'
  };
  return {
    date: dt_txt.slice(0, 10),
    icon: icons(weather[0].icon),
    text: weather[0].description,
    conditions: weather[0].main,
    temperature: {
      min: tempInF(main.temp_min),
      max: tempInF(main.temp_min)
    },
    snow: snowInInches(snow['3h']),
    notice
  };
}

export default function fetchForecast(resort, appid, fn) {
  limit(err => {
    if (err) {
      debug('Weather API limit %s', resort.id);
      return fn(err);
    }
    debug('request weather for %s', resort.id);

    const url = new URL('https://api.openweathermap.org/data/2.5/forecast');
    url.searchParams.set('lon', resort.ll[0]);
    url.searchParams.set('lat', resort.ll[1]);
    url.searchParams.set('appid', appid);

    fetch(url)
      .then(res => res.json())
      .then(body => fn(null, sanitize(body)))
      .catch(err => {
        console.error('Weather fetch error', resort.name, err.status);
        return fn(err.status);
      });
  });
}