extension ServerManager {
    func createTransactionFromReceipt(_ receipt: ReceiptTask, _ completion: @escaping (String)-> Void, error: @escaping (String)-> Void) {
        let parameter = receipt.getParameter()

        // "Constants.Network.EndPoint.CreateTransaction" equals "ios/createTransactionFromReceipt"
        self.post(endpoint: Constants.Network.EndPoint.CreateTransaction, parameters: parameter, completion: { (json) in
            let obj = json["success"].stringValue
            completion(obj)
        }, error: error)
    }
}

/* --------------------------------- */
// "receipt.getParameter()" method

class ReceiptTask {
    var receipt: String
    var userID: String?
    var testReceipt: Bool = true

    init(receipt: String) {
        self.receipt = receipt
        if let user = DataManager.shared.getUser() {
            self.userID = user.userID
        }
    }

    func getParameter() -> [String: String] {
        var parameter = ["receipt": receipt, "testReceipt": "true"]
        if let _ = userID {
            parameter.updateValue(userID!, forKey: "userID")
        }

        return parameter
    }

}

/* --------------------------------- */
// "self.post" method

internal func post(endpoint: String, parameters: Parameter, completion: @escaping SuccessHandler, error: @escaping FailureHandler) {
    request(method: .post, endpoint: endpoint, parameters: parameters, completion: completion, error: error)
}


/* --------------------------------- */
// request(...) method
private func request(method: HTTPMethod,
                     endpoint: String,
                     parameters: Parameter,
                     completion: @escaping SuccessHandler,
                     error: @escaping FailureHandler) {

    var apiUrl = ""
    var parametersForBody = parameters
    if method == .get && parameters != nil {
        // GET request url with params in url
        apiUrl = ApiAddress(endpoint: endpoint, param: parameters).getURLString()
        parametersForBody = nil
    } else {
        // POST request url
        // apiUrl = https://dev-api.enotes.com/api/2.0/?apiKey=108516db726ae161f7ee9365bb79ab81b59133cd
        apiUrl = ApiAddress(endpoint: endpoint).getURLString()
    }

    var header: HTTPHeaders = [:]
    if let cookie = DataManager.shared.getSessionCookie() {
        header.updateValue(cookie, forKey: "Cookie")
    }

    DataManager.shared.dataRequest = Alamofire.request(apiUrl.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)!, method: method, parameters: parametersForBody, encoding: JSONEncoding.default , headers: header)
                .authenticate(user: "ios", password: "ios")
        .responseJSON { (response:DataResponse<Any>) in

        guard response.response != nil else {
            error(Constants.Network.ErrorMessage.UNABLE_LOAD_DATA)
            return
        }

        guard let statusCode = response.response?.statusCode else {
            error(Constants.Network.ErrorMessage.NO_HTTP_STATUS_CODE)
            return
        }

        switch(statusCode) {

        case HttpStatusCode.unauthorized.statusCode:
            //Catch json error
            error(Constants.Network.ErrorMessage.UNAUTHORIZED)
            break

        case HttpStatusCode.ok.statusCode,
             HttpStatusCode.accepted.statusCode,
             HttpStatusCode.created.statusCode:
                let json = JSON(data: response.data!)
                completion(json)
            //TODO: catch possible "errors" json key-value
                break;

        default:

            let json = JSON(data: response.data!)
            if !json.isEmpty && json["errors"].exists() {
                let err = ServerError(json: json)
                //need to test
                error(err.errors[0])
                break;
            }
        }
    }
}