crnc/x/ecommerce/remember-or-download-exchange-rates.js

currency conversion and functionality for the web

import { cache } from "../toolbox/cache.js";
export async function rememberOrDownloadExchangeRates({ currencies, persistence: { storage, storageKeys, cacheLifespan }, downloadExchangeRates, }) {
    const ratesCache = cache({
        storage,
        lifespan: cacheLifespan,
        storageKey: storageKeys.exchangeRatesCache,
        load: async () => downloadExchangeRates({ currencies }),
    });
    let results = await ratesCache.readCache();
    const shouldDownloadFreshResults = results
        ? !ratesAreSufficient(results.exchangeRates, currencies)
        : true;
    if (shouldDownloadFreshResults)
        results = await ratesCache.readFresh();
    const validAndSufficient = ((results === null || results === void 0 ? void 0 : results.exchangeRates)
        && ratesAreSufficient(results.exchangeRates, currencies));
    const exchangeRates = validAndSufficient
        ? trimOffIrrelevantRates(results.exchangeRates, currencies)
        : undefined;
    return exchangeRates;
}
function ratesAreSufficient(rates, currencies) {
    const exchangeKeys = Object.keys(rates);
    const currenciesMissingInRates = currencies.filter(currency => exchangeKeys.indexOf(currency) === -1);
    return currenciesMissingInRates.length
        ? false
        : true;
}
function trimOffIrrelevantRates(rates, currencies) {
    const relevant = {};
    for (const code of currencies)
        relevant[code] = rates[code];
    return relevant;
}
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