Spaces:
Sleeping
Sleeping
File size: 2,880 Bytes
57a889c | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 | /**
* Live exchange rates for the Costs/Budget money conversion.
*
* Fetches from api.frankfurter.dev (no key, already CSP-allowlisted for the
* dashboard widget) and caches per base currency in-memory for a few hours so a
* settlement request never hammers the upstream. Rates are "units of X per 1
* base", so an amount in currency C converts to base as `amount / rates[C]`.
*
* Everything degrades gracefully: if the fetch fails (offline, upstream down),
* callers get `null`/identity conversion and amounts are treated as already in
* the base currency rather than throwing.
*/
const TTL_MS = 6 * 60 * 60 * 1000; // 6h
const cache = new Map<string, { rates: Record<string, number>; ts: number }>();
const inflight = new Map<string, Promise<Record<string, number> | null>>();
async function fetchRates(base: string): Promise<Record<string, number> | null> {
try {
const res = await fetch(`https://api.frankfurter.dev/v2/rates?base=${encodeURIComponent(base)}`);
if (!res.ok) return null;
// Frankfurter returns an array of { date, base, quote, rate } and omits the
// base's own self-rate, so seed the map with `base = 1` then index by quote.
const data = (await res.json()) as Array<{ quote?: string; rate?: number }>;
if (!Array.isArray(data)) return null;
const rates: Record<string, number> = { [base.toUpperCase()]: 1 };
for (const r of data) {
if (r && typeof r.quote === 'string' && typeof r.rate === 'number') rates[r.quote] = r.rate;
}
return Object.keys(rates).length > 1 ? rates : null;
} catch {
return null;
}
}
/** Rates map for `base` (cached). Returns null if unavailable. */
export async function getRates(base: string): Promise<Record<string, number> | null> {
const key = (base || 'EUR').toUpperCase();
const hit = cache.get(key);
const now = Date.now();
if (hit && now - hit.ts < TTL_MS) return hit.rates;
// Coalesce concurrent fetches for the same base.
let p = inflight.get(key);
if (!p) {
p = fetchRates(key).then(rates => {
if (rates) cache.set(key, { rates, ts: Date.now() });
inflight.delete(key);
return rates;
});
inflight.set(key, p);
}
const rates = await p;
// On failure fall back to the last cached value if we have one.
if (!rates && hit) return hit.rates;
return rates;
}
/**
* Convert `amount` from `from` currency into `base` using a rates map obtained
* from getRates(base). Identity when same currency or the rate is missing.
*/
export function convertWithRates(
amount: number,
from: string | null | undefined,
base: string,
rates: Record<string, number> | null,
): number {
const fromCur = (from || base).toUpperCase();
const baseCur = base.toUpperCase();
if (fromCur === baseCur || !rates) return amount;
const r = rates[fromCur];
if (!r || r <= 0) return amount;
return amount / r;
}
|