Is winter coming? `seasoning.js` adds season awareness to your programs.

seasoning.js

/*
  `seasoning.js` adds season awareness to your programs. Help finding out what season it is.

  Usage:
    // Get the season using the user's browser location (NOTE: it requires the user's authorisation)
    seasoning.getSeason()
    .then(console.log);

    // Get the season using the user's geoip
    seasoning.getSeason({ locationProvider: 'ipinfo' })
    .then(console.log);

    // Get the season providing the location (NOTE: only the latitude matters)
    seasoning.getSeason({ latLng: { lat: -123 } })
    .then(console.log);

    // Get the season giving the date
    const date = new Date();
    date.setMonth((date.getMonth()+6)%12);

    seasoning.getSeason({ date })
    .then(console.log);

    // Get the "opposite" season
    seasoning.getOppositeSeason({ date: new Date() })
    .then(console.log);

    // Create your own helpers;
    const isWinterComing = () => {
      return seasoning.getSeason()
      .then(season => season === 'autumn');
    };

    isWinterComing().then(winterComing => {
      if (winterComing) {
        console.log("The ennemy of my ennemy is my friend? Naaaah let's just keep killing the Starks.");
      } else {
        console.log("Either this is already winter and the undead are unleashed, or we're good for another  scene with either incest, or boobs, or both... I feel like watching season 1.");
      }
    });

*/

const HEMISPHERES = {
  north: [
    { month: 'jan', season: 'winter' },
    { month: 'feb', season: 'winter' },
    { month: 'mar', season: 'spring' },
    { month: 'apr', season: 'spring' },
    { month: 'may', season: 'spring' },
    { month: 'jun', season: 'summer' },
    { month: 'jul', season: 'summer' },
    { month: 'aug', season: 'summer' },
    { month: 'sep', season: 'autumn' },
    { month: 'oct', season: 'autumn' },
    { month: 'nov', season: 'autumn' },
    { month: 'dev', season: 'winter' },
  ],
  south: [
    { month: 'jan', season: 'summer' },
    { month: 'feb', season: 'summer' },
    { month: 'mar', season: 'autumn' },
    { month: 'apr', season: 'autumn' },
    { month: 'may', season: 'autumn' },
    { month: 'jun', season: 'winter' },
    { month: 'jul', season: 'winter' },
    { month: 'aug', season: 'winter' },
    { month: 'sep', season: 'spring' },
    { month: 'oct', season: 'spring' },
    { month: 'nov', season: 'spring' },
    { month: 'dev', season: 'summer' },
  ],
};

const GEOLOCATION_OPTIONS = {
  enableHighAccuracy: true,
  timeout: 5000,
  maximumAge: 0,
};

const makeRemoteProvider = (url, transform) => () => fetch(url, {
    headers: { Accept: 'application/json' },
  })
  .then(r => r.json())
  .then(makeRemoteProvider);

const locationProviders = {
  browser() {
    return new Promise((res, rej) => {
      navigator.geolocation.getCurrentPosition(
        ({ coords }) => res({ lat: coords.latitude, lng: coords.longitude }),
        error => rej(error),
        GEOLOCATION_OPTIONS
      );
    });
  },
  ipinfo: makeRemoteProvider('https://ipinfo.io/json', ({ loc }) => {
    const latLng = loc.split(',');
    return { lat: latLng[0], lng: latLng[1] };
  }),
};

const getLatLng = provider => {
  let p = provider;
  if (!provider) {
    p = navigator.geolocation ? 'browser' : 'ipinfo';
  }
  return locationProviders[p]();
};

const seasoning = {
  async getHemisphere(latLng, locationProvider) {
    const { lat: latitude } = latLng || await getLatLng(locationProvider);
    return Promise.resolve(latitude > 0 ? 'north' : 'south');
  },
  async getSeason({ date, latLng, locationProvider } = {}) {
    const hemisphere = await this.getHemisphere(latLng, locationProvider);
    const monthIndex = (date || new Date()).getMonth();
    return Promise.resolve(HEMISPHERES[hemisphere][monthIndex].season);
  },
  getOppositeSeason({ date, ...params }) {
    const newDate = date ? new Date(date) : new Date();
    newDate.setMonth((date.getMonth()+6)%12); // the following only works with 12 months' years
    return this.getSeason(Object.assign(params, { date: newDate }));
  },
};

export default seasoning;