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@molecule/api-fx-rates-ecb

Provider bond · fx-rates · API (Node) · v1.0.1 · Apache-2.0

European Central Bank reference FX rates — keyless, free, EUR-pivot daily and 90-day-history XML feeds.

npm install @molecule/api-fx-rates-ecb

npm · Source on GitHub · Implements @molecule/api-fx-rates

How it works

@molecule/api-fx-rates-ecb is a provider bond on the API (Node) side: it implements the fx-rates core interface (@molecule/api-fx-rates) with a concrete vendor or library behind it.

Your code calls the core; you wire this provider once at startup. Swapping vendors later is one line in that wiring, not a rewrite.

import { setProvider } from '@molecule/api-fx-rates'
import { provider } from '@molecule/api-fx-rates-ecb'

setProvider(provider)

Works with: @molecule/api-bond, @molecule/api-fx-rates

Reference

Auto-generated, AI-first package reference for the molecule.dev ecosystem. It is written to be read by coding agents as much as by people, and is generated from this package's source — edit src/index.ts JSDoc, not this file.

ECB FX-rates provider for molecule.dev.

Implements the {@link import('@molecule/api-fx-rates').FxRatesProvider} interface against the European Central Bank's public reference-rate XML feeds (eurofxref-daily.xml and eurofxref-hist-90d.xml). Both feeds are keyless, free, and EUR-pivoted. Cross-rates are computed by pivoting through EUR (USD->GBP = rates[GBP] / rates[USD]).

Snapshots are cached in memory for a configurable TTL (default 1h) and, when the 'cache' bond is registered, written through to it as well.

Quick Start

import { setProvider } from '@molecule/api-fx-rates'
import { provider } from '@molecule/api-fx-rates-ecb'

setProvider(provider)

Type

provider

Installation

npm install @molecule/api-fx-rates-ecb @molecule/api-bond @molecule/api-fx-rates fast-xml-parser

API

Interfaces

EcbDailySnapshot

A single daily snapshot of EUR-pivot reference rates parsed from the ECB XML feed. The pivot (EUR) itself is included with rate 1.

interface EcbDailySnapshot {
  /**
   * The publication date of the snapshot (UTC midnight on the publication day).
   */
  asOf: Date

  /**
   * Map from currency code to rate, where `1 EUR = rates[code] units of code`.
   * Always contains the `EUR` entry with rate `1`.
   */
  rates: Record<string, number>
}

EcbFxRatesConfig

Configuration options for the ECB FX-rates provider.

The European Central Bank's daily and 90-day-history reference-rate XML feeds (https://www.ecb.europa.eu/stats/eurofxref/) are keyless and free, so every field is optional.

interface EcbFxRatesConfig {
  /**
   * Base URL override. Defaults to `'https://www.ecb.europa.eu/stats/eurofxref'`.
   */
  baseUrl?: string

  /**
   * Daily-feed XML filename. Defaults to `'eurofxref-daily.xml'`. Used when
   * the caller does not request an `asOf` date or requests a date the daily
   * snapshot already covers.
   */
  dailyPath?: string

  /**
   * Historical 90-day-feed XML filename. Defaults to
   * `'eurofxref-hist-90d.xml'`. Used when the caller requests an `asOf` date
   * older than the latest snapshot.
   */
  historicalPath?: string

  /**
   * Request timeout in milliseconds. Defaults to `10000`.
   */
  timeout?: number

  /**
   * TTL for the in-memory cache of parsed snapshots, in milliseconds.
   * Defaults to `3_600_000` (1 hour). Set to `0` to disable internal caching.
   *
   * If the `'cache'` bond is registered, snapshots are also written through
   * to it with the equivalent TTL in seconds.
   */
  cacheTtlMs?: number
}

Functions

computeRate(snapshot, from, to)

Computes the conversion rate 1 unit of from = rate units of to from a EUR-pivot snapshot. Both sides may equal the pivot.

function computeRate(snapshot: EcbDailySnapshot, from: string, to: string): number
  • snapshot — The dated snapshot to read.
  • from — Source currency.
  • to — Target currency.

Returns: The conversion ratio as a plain number.

createProvider(config)

Creates an ECB FX-rates provider.

function createProvider(config?: EcbFxRatesConfig): FxRatesProvider
  • config — Provider configuration. All fields are optional.

Returns: An {@link FxRatesProvider} backed by the ECB reference-rate feeds.

parseEcbXml(xml)

Parses the body of an ECB XML feed (daily or historical) into an array of snapshots, sorted newest-first.

function parseEcbXml(xml: string): EcbDailySnapshot[]
  • xml — Raw XML body fetched from the ECB endpoint.

Returns: Snapshots sorted newest-first.

Constants

provider

Default ECB FX-rates provider, lazily constructed on first access.

Reads the optional ECB_FX_BASE_URL environment variable to override the endpoint base URL (e.g. for a local mirror in tests). The public ECB endpoints require no key.

const provider: FxRatesProvider

Core Interface

Implements @molecule/api-fx-rates interface.

Bond Wiring

Setup function to register this provider with the core interface:

import { setProvider } from '@molecule/api-fx-rates'
import { provider } from '@molecule/api-fx-rates-ecb'

export function setupFxRatesEcb(): void {
  setProvider(provider)
}

Injection Notes

Requirements

Peer dependencies:

  • @molecule/api-bond ^1.0.1
  • @molecule/api-fx-rates ^1.0.1

Runtime Dependencies

  • @molecule/api-bond
  • @molecule/api-fx-rates
  • fast-xml-parser

E2E Tests

Integration checklist — drive the real UI (live preview, no mocks), adapt each item to this app's actual currency/pricing screens, and check every box off one by one. This is money: a wrong rate silently corrupts every price, so verify the NUMBERS the app computes, not just that a value rendered. A box you can't check is an integration bug to fix — not a skip:

  • A known pair returns a PLAUSIBLE rate: getRate('USD', 'EUR') yields a real ratio (roughly 0.8-1.0 for USD->EUR), never 0, null, NaN, negative, or an absurd value like 1e9 — and the UI shows it as an actual number.
  • convert does the CORRECT MATH: converting 100 USD (amountMinor 10_000 cents) USD->EUR returns approximately 10_000 * rate in the target's minor units, rounded sensibly for that currency (integer cents; JPY has 0 decimals), and the UI shows that converted amount — not the untouched original.
  • Round-trip consistency: the inverse pair is reciprocal — getRate('EUR', 'USD') is approximately 1 / getRate('USD', 'EUR') — and same-currency is identity: getRate('USD', 'USD') is exactly 1 and convert(x, 'USD', 'USD') returns x unchanged.
  • Changing the selected pair changes the displayed result (USD->EUR vs USD->JPY give visibly different converted amounts) — the screen is not pinned to one hardcoded rate.
  • An unknown/unsupported code (e.g. 'ZZZ', absent from listSupportedCurrencies()) surfaces a clear error in the UI — NEVER a silent rate of 0 (which zeroes the price) or a pass-through of 1.
  • If a historical lookup is exposed (options.asOf), a past date returns that day's rate (different from latest for a volatile pair), not today's.
  • A provider/network failure surfaces gracefully (a visible error or retry) and the amount is left unconverted — the app NEVER falls back to converting at rate 0 or 1, which would corrupt the price shown or charged.
  • The provider API key stays server-side — fx-rates is server-only; the key never appears in the browser bundle, the network tab, or any client response.