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src/api/currency.ts

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+// Currency exchange rate API
+// Uses free exchangerate.host API
+
+interface ExchangeRates {
+  USD: number
+  CNY: number
+  IRR: number
+}
+
+interface CachedRates {
+  rates: ExchangeRates
+  timestamp: number
+}
+
+const CACHE_DURATION = 60 * 60 * 1000 // 1 hour in milliseconds
+
+// Fallback rates if API fails (approximate)
+const FALLBACK_RATES: ExchangeRates = {
+  USD: 100,      // 1 USD = 100 RUB
+  CNY: 14,       // 1 CNY = 14 RUB
+  IRR: 0.0024,   // 1 IRR = 0.0024 RUB (or 1 RUB = ~420 IRR)
+}
+
+let cachedRates: CachedRates | null = null
+
+export const currencyApi = {
+  // Get all exchange rates (RUB to other currencies)
+  getExchangeRates: async (): Promise<ExchangeRates> => {
+    // Check cache first
+    if (cachedRates && Date.now() - cachedRates.timestamp < CACHE_DURATION) {
+      return cachedRates.rates
+    }
+
+    try {
+      // Try primary API (exchangerate.host) - get RUB based rates
+      const response = await fetch(
+        'https://api.exchangerate.host/latest?base=RUB&symbols=USD,CNY,IRR'
+      )
+
+      if (response.ok) {
+        const data = await response.json()
+        if (data.success && data.rates) {
+          // API returns how much of each currency equals 1 RUB
+          // We need the inverse: how many RUB equals 1 of each currency
+          const rates: ExchangeRates = {
+            USD: data.rates.USD ? 1 / data.rates.USD : FALLBACK_RATES.USD,
+            CNY: data.rates.CNY ? 1 / data.rates.CNY : FALLBACK_RATES.CNY,
+            IRR: data.rates.IRR ? 1 / data.rates.IRR : FALLBACK_RATES.IRR,
+          }
+          cachedRates = { rates, timestamp: Date.now() }
+          return rates
+        }
+      }
+
+      // Try backup API (open.er-api.com)
+      const backupResponse = await fetch('https://open.er-api.com/v6/latest/RUB')
+
+      if (backupResponse.ok) {
+        const backupData = await backupResponse.json()
+        if (backupData.rates) {
+          const rates: ExchangeRates = {
+            USD: backupData.rates.USD ? 1 / backupData.rates.USD : FALLBACK_RATES.USD,
+            CNY: backupData.rates.CNY ? 1 / backupData.rates.CNY : FALLBACK_RATES.CNY,
+            IRR: backupData.rates.IRR ? 1 / backupData.rates.IRR : FALLBACK_RATES.IRR,
+          }
+          cachedRates = { rates, timestamp: Date.now() }
+          return rates
+        }
+      }
+
+      // Return fallback rates if both APIs fail
+      return FALLBACK_RATES
+    } catch (error) {
+      console.warn('Failed to fetch exchange rates, using fallback:', error)
+      return FALLBACK_RATES
+    }
+  },
+
+  // Convert RUB to target currency
+  convertFromRub: (rubAmount: number, targetCurrency: keyof ExchangeRates, rates: ExchangeRates): number => {
+    const rate = rates[targetCurrency]
+    if (!rate || rate <= 0) {
+      return rubAmount / FALLBACK_RATES[targetCurrency]
+    }
+    return rubAmount / rate
+  },
+
+  // Convert from target currency to RUB
+  convertToRub: (amount: number, sourceCurrency: keyof ExchangeRates, rates: ExchangeRates): number => {
+    const rate = rates[sourceCurrency]
+    if (!rate || rate <= 0) {
+      return amount * FALLBACK_RATES[sourceCurrency]
+    }
+    return amount * rate
+  },
+}
+
+export type { ExchangeRates }