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import { BackendError, FetchError, MalformedError } from './errors' |
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export type CurrencyCode = string; |
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interface YFResponse { |
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chart: { |
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result: { |
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meta: { |
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regularMarketPrice: number |
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} |
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}[] |
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} |
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} |
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interface CachedRate { |
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value: number; |
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timestamp: number; |
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} |
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interface ExchangeRateOptions { |
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cacheDurationMs?: number; // Defaults to undefined (no caching) |
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} |
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const YF_BASE = 'https://query1.finance.yahoo.com/v8/finance/chart/' |
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const YF_PARAMS = '=X?region=US&lang=en-US&includePrePost=false&interval=2m&useYfid=true&range=1d&corsDomain=finance.yahoo.com&.tsrc=finance' |
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const rateCache: Record<string, CachedRate> = {} |
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function getRateUrl (from: CurrencyCode, to: CurrencyCode): string { |
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return `${YF_BASE}${from.toUpperCase()}${to.toUpperCase()}${YF_PARAMS}` |
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} |
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function isCacheValid (cachedRate: CachedRate, cacheDurationMs: number): boolean { |
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return Date.now() - cachedRate.timestamp < cacheDurationMs |
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} |
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function getCachedRate (from: CurrencyCode, to: CurrencyCode, cacheDurationMs?: number): number | null { |
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const cacheKey = `${from}-${to}` |
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const cachedRate = rateCache[cacheKey] |
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return (cacheDurationMs && cachedRate && isCacheValid(cachedRate, cacheDurationMs)) ? cachedRate.value : null |
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} |
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async function fetchRate (rateUrl: string): Promise<number> { |
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let response: Response |
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try { |
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response = await fetch(rateUrl) |
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if (!response.ok) { |
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throw new BackendError(`Service did not return HTTP 200 response. Status: ${response.status}`) |
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} |
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const result: YFResponse = await response.json() |
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const rate = result.chart?.result[0]?.meta?.regularMarketPrice |
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if (!rate) { |
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throw new MalformedError('Unexpected response structure. Missing "regularMarketPrice".') |
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} |
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return rate |
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} catch (error) { |
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if (error instanceof BackendError || error instanceof MalformedError) { |
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throw error |
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} |
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throw new FetchError(`Failed to fetch data from ${rateUrl}`) |
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} |
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} |
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export async function getExchangeRate ( |
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from: CurrencyCode, |
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to: CurrencyCode, |
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options: ExchangeRateOptions = {} |
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): Promise<number> { |
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const cachedRate = getCachedRate(from, to, options.cacheDurationMs) |
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if (cachedRate !== null) { |
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return cachedRate |
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} |
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const rateUrl = getRateUrl(from, to) |
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const rate = await fetchRate(rateUrl) |
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if (options.cacheDurationMs) { |
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const cacheKey = `${from}-${to}` |
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rateCache[cacheKey] = { value: rate, timestamp: Date.now() } // Cache the result with a timestamp |
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} |
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return rate |
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} |
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export * from './errors' |
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tamtamchik /
exchanger
