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import { DataError, NetworkError, ServerError } from "./errors"; |
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interface ExchangeRateResponse { |
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chart: { |
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result: [ |
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{ |
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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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} |
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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; |
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} |
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const YAHOO_FINANCE_BASE_URL = |
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"https://query1.finance.yahoo.com/v8/finance/chart/"; |
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const YAHOO_FINANCE_QUERY_PARAMS = |
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"=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 = new Map<string, CachedRate>(); |
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function buildRateUrl(fromCurrency: string, toCurrency: string): string { |
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return `${YAHOO_FINANCE_BASE_URL}${fromCurrency.toUpperCase()}${toCurrency.toUpperCase()}${YAHOO_FINANCE_QUERY_PARAMS}`; |
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} |
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function isCacheValid( |
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cachedRate: CachedRate, |
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cacheDurationMs: number, |
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): boolean { |
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return Date.now() - cachedRate.timestamp < cacheDurationMs; |
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} |
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function getCachedRate( |
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fromCurrency: string, |
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toCurrency: string, |
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cacheDurationMs?: number, |
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): number | null { |
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if (!cacheDurationMs) return null; |
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const cacheKey = `${fromCurrency}-${toCurrency}`; |
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const cachedRate = rateCache.get(cacheKey); |
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return cachedRate && isCacheValid(cachedRate, cacheDurationMs) |
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? cachedRate.value |
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: null; |
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} |
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async function fetchExchangeRateResponse(rateUrl: string): Promise<Response> { |
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const response = await fetch(rateUrl); |
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if (!response.ok) { |
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throw new ServerError(`HTTP ${response.status}: ${response.statusText}`); |
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} |
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return response; |
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} |
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function extractRateFromResponse(response: ExchangeRateResponse): number { |
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const rate = response.chart?.result[0]?.meta?.regularMarketPrice; |
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if (typeof rate !== "number" || isNaN(rate)) { |
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throw new DataError('Invalid or missing "regularMarketPrice" in response.'); |
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} |
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return rate; |
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} |
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async function fetchExchangeRate(rateUrl: string): Promise<number> { |
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try { |
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const response = await fetchExchangeRateResponse(rateUrl); |
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const responseData: ExchangeRateResponse = await response.json(); |
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return extractRateFromResponse(responseData); |
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} catch (error) { |
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if (error instanceof ServerError || error instanceof DataError) { |
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throw error; |
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} |
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throw new NetworkError( |
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`Failed to fetch exchange rate: ${error instanceof Error ? error.message : String(error)}`, |
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); |
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} |
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} |
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export async function getExchangeRate( |
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fromCurrency: string, |
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toCurrency: string, |
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options: ExchangeRateOptions = {}, |
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): Promise<number> { |
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const { cacheDurationMs } = options; |
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const cachedRate = getCachedRate(fromCurrency, toCurrency, cacheDurationMs); |
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if (cachedRate !== null) { |
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return cachedRate; |
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} |
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const rateUrl = buildRateUrl(fromCurrency, toCurrency); |
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const rate = await fetchExchangeRate(rateUrl); |
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if (cacheDurationMs) { |
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const cacheKey = `${fromCurrency}-${toCurrency}`; |
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rateCache.set(cacheKey, { value: rate, timestamp: Date.now() }); |
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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
