Asset Price MCP Server

import { fetchJson } from "../utils.js"; import { apiCache } from "../cache.js"; const RATE_API_PRIMARY = 'https://open.er-api.com/v6/latest/USD'; const RATE_API_BACKUP = 'https://api.exchangerate-api.com/v4/latest/USD'; interface RatesResponse { base_code?: string; base?: string; rates: Record<string, number>; } export class ExchangeRateService { async getRate(from: string, to: string): Promise<number | null> { const fromUpper = from.toUpperCase(); const toUpper = to.toUpperCase(); if (fromUpper === toUpper) return 1; // Currently our APIs are USD based // If from is USD, we just look up the rate // If from is not USD, we might need cross rate (not implemented fully for efficiency, assuming base is USD) // Check cache for USD rates const cacheKey = "EXCHANGE_RATES_USD"; let rates = apiCache.get<Record<string, number>>(cacheKey); if (!rates) { rates = await this.fetchRates(); if (rates) { apiCache.set(cacheKey, rates); // Cache default TTL } } if (!rates) return null; // If source is USD if (fromUpper === 'USD') { return rates[toUpper] || null; } // If source is not USD, convert to USD then to Target // e.g. EUR -> CNY = (USD -> CNY) / (USD -> EUR) const usdToFrom = rates[fromUpper]; const usdToTo = rates[toUpper]; if (usdToFrom && usdToTo) { return usdToTo / usdToFrom; } return null; } private async fetchRates(): Promise<Record<string, number> | null> { // Try primary let data = await fetchJson<RatesResponse>(RATE_API_PRIMARY); if (!data) { // Try backup console.warn("Primary exchange rate API failed, trying backup..."); data = await fetchJson<RatesResponse>(RATE_API_BACKUP); } return data?.rates || null; } }