shootismoke/common

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packages/ui/src/util/station.ts

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// Sh**t! I Smoke
// Copyright (C) 2018-2021  Marcelo S. Coelho, Amaury M.

// Sh**t! I Smoke is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Sh**t! I Smoke is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Sh**t! I Smoke.  If not, see <http://www.gnu.org/licenses/>.

import {
    ACCURATE_RADIUS,
    LatLng,
    OpenAQResult,
} from '@shootismoke/dataproviders';
import haversine from 'haversine';

/**
 * Capitalize a string.
 *
 * @param s - The string to capitalize
 */
export function capitalize(s: string): string {
    return s.charAt(0).toUpperCase() + s.slice(1);
}

/**
 * We can show distances in these two units.
 */
export type DistanceUnit = 'km' | 'mile';

/**
 * Above this distance (km), we consider the station too far from the user
 */
export const MAX_DISTANCE_TO_STATION = ACCURATE_RADIUS / 1000;

/**
 * Station given by the AQICN API is fucked up. Sometimes it's [lat, lng],
 * sometimes it's [lng, lat].
 * We check here with the user's real currentLocation coordinates, and take the
 * "closest" one.
 *
 * @param currentLocation - An object containing {latitude, longitude}
 * representing the user's current location.
 * @param station - An object containing {latitude, longitude} representing
 * the station's location.
 */
export function getCorrectLatLng(
    currentLocation: LatLng,
    station: LatLng
): LatLng {
    const d1 =
        Math.abs(currentLocation.latitude - station.latitude) +
        Math.abs(currentLocation.longitude - station.longitude);

    const d2 =
        Math.abs(currentLocation.latitude - station.longitude) +
        Math.abs(currentLocation.longitude - station.latitude);

    if (d1 < d2) return station;
    return {
        ...station,
        latitude: station.longitude,
        longitude: station.latitude,
    };
}

/**
 * Get distance from current location to station.
 *
 * @param currentLocation - The current location of the user.
 * @param api - The api object returned by remote data.
 * @param unit - The unit of measure returned.
 */
export function distanceToStation(
    currentLocation: LatLng,
    pm25Measurement: OpenAQResult,
    unit: DistanceUnit = 'km'
): number {
    // This case should be very rare, only happens on OpenAQ that sometimes,
    // the `coordinates` field isn't returned. This field is actually optional
    // in the OpenAQ format.
    // FIXME Return something better than 0?
    if (!pm25Measurement.coordinates) {
        return 0;
    }

    return Math.round(
        haversine(
            currentLocation,
            getCorrectLatLng(currentLocation, pm25Measurement.coordinates),
            { unit }
        )
    );
}

/**
 * Returns true if the station is at more than {@link MAX_DISTANCE_TO_STATION}
 * kilometers away from the current location.
 *
 * @param currentLocation - The current location of the user.
 * @param api - The api object returned by remote data.
 */
export function isStationTooFar(
    currentLocation: LatLng,
    pm25Measurement: OpenAQResult
): boolean {
    return (
        distanceToStation(currentLocation, pm25Measurement) >
        MAX_DISTANCE_TO_STATION
    );
}