shootismoke/common

import * as aqiCodes from './aqi';
import { AqiCode } from './types';
import { Pollutant } from './util/pollutant';
import { ugm3 } from './util/unit';

/**
 * For any pollutant, convert an AQI to its ugm3 concentration, or vice versa,
 * or convert an AQI to another AQI
 *
 * @param pollutant - The pollutant to convert
 * @param from - The type to convert from (either ugm3, or an AQI)
 * @param to - The type to convert to (either ugm3, or an AQI)
 * @param value - The value to convert
 */
export function convert(
    pollutant: Pollutant,
    from: AqiCode | 'µg/m³' | 'ppm' | 'particles/cm³' | 'ppb',
    to: AqiCode | 'µg/m³' | 'ppm' | 'particles/cm³' | 'ppb',
    value: number
): number {
    if (
        from === 'ppb' ||
        from === 'ppm' ||
        from === 'particles/cm³' ||
        to === 'ppb' ||
        to === 'ppm' ||
        to === 'particles/cm³'
    ) {
        throw new Error(`Conversion from ${from} to ${to} not supported yet.`);
    }

    if (from === to) {
        return value;
    }

    // Convert ugm3 to AQI
    if (from === ugm3) {
        return aqiCodes[to as AqiCode].fromUgm3(pollutant, value);
    }

    // Convert AQI to ugm3
    if (to === ugm3) {
        return aqiCodes[from].toUgm3(pollutant, value);
    }

    // Convert AQI to AQI
    const ugm3Value = aqiCodes[from].toUgm3(pollutant, value);
    return aqiCodes[to].fromUgm3(pollutant, ugm3Value);
}