CurrencyConverter.h

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#pragma once
#include <string>
#include <map>
#include <vector>
#include <chrono>
#include <functional>
 
class CurrencyConverter {
public:
    std::string baseCurrency = "USD";
    std::map<std::string, double> exchangeRate;
 
    std::string apiKey;
    std::string apiUrl = "https://api.exchangerate-api.com/v4/latest/";  // Default free API
 
    std::chrono::system_clock::time_point lastUpdate;
    std::chrono::minutes cacheTimeout{60};
 
    double convert(double amount, const std::string &from, const std::string &to);
    void updateRate(const std::string &currency, double rate);
    
    bool fetchRatesFromAPI(const std::string &base = "");
    
    bool fetchRatesForCurrencies(const std::vector<std::string> &currencies, const std::string &base = "");
    
    void fetchRatesFromAPIAsync(std::function<void(bool)> callback, const std::string &base = "");
 
    bool updateRatesIfNeeded();
    
    void setApiUrl(const std::string &url);
    
    void setApiKey(const std::string &key);
    
    bool isCacheValid() const;
};
 
inline double CurrencyConverter::convert(double amount, const std::string &from, const std::string &to) {
    if (from == to) return amount;
    double fromRate = (exchangeRate.count(from) ? exchangeRate[from] : 1.0);
    double toRate = (exchangeRate.count(to) ? exchangeRate[to] : 1.0);
    if (from == baseCurrency) return amount * toRate;
    if (to == baseCurrency) return amount / fromRate;
    double inBase = amount / fromRate;
    return inBase * toRate;
}
 
inline void CurrencyConverter::updateRate(const std::string &currency, double rate) { 
    exchangeRate[currency] = rate; 
}
 
inline void CurrencyConverter::setApiUrl(const std::string &url) {
    apiUrl = url;
}
 
inline void CurrencyConverter::setApiKey(const std::string &key) {
    apiKey = key;
}
 
inline bool CurrencyConverter::isCacheValid() const {
    auto now = std::chrono::system_clock::now();
    auto elapsed = std::chrono::duration_cast<std::chrono::minutes>(now - lastUpdate);
    return elapsed < cacheTimeout;
}