import Foundation

func loadExchangeRates(currencyCode: String = "USD") {
    let urlString = "https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest" +
        "/v1/currencies/\(currencyCode.lowercased()).json"
    load(from: urlString) { result in
        switch result {
        case .success(let data):
            let jsonString = String(data: data, encoding: .utf8)!
            print(jsonString)
            
        case .failure:
            break
        }
    }
}

func load(
    from urlString: String,
    completionHandler: @escaping (Result<Data, Error>) -> Void) {
    
    if let url = URL(string: urlString) {
        let config = URLSessionConfiguration.default
        config.requestCachePolicy = .reloadIgnoringLocalCacheData
        
        let urlSession = URLSession(configuration: config)
            .dataTask(with: url) { (data, _, error) in
                if let error = error {
                    completionHandler(.failure(error))
                } else if let data = data {
                    completionHandler(.success(data))
                }
            }
        
        urlSession.resume()
    } else {
        completionHandler(.failure("Invalid URL".toError()))
    }
}

extension String {
    func toError() -> Error {
        return StringError(self)
    }
}

struct StringError: Error {
    let message: String
    init(_ message: String) {
        self.message = message
    }
}