//: Playground - noun: a place where people can play

enum APIRequest {
    case userLogin(username: String, password: String)
    case userLoginWithData(username: String, password: String)
    case addPromo(username: String, password: String, code: String)
    func getRawResponse(completion: @escaping ([String:Any]?, Error?) -> Void) {
        let dict = self.serialize()
        // session send dict
        // call completion
    }
    func serialize() -> [String: Any] {
        if case .userLogin(let username, let password) = self {
            return ["username": username, "password": password, "method": "p1"]
        }
        else if case .userLoginWithData(let username, let password) = self {
            return ["username": username, "password": password, "method": "p2"]
        }
        else {
            return [:]
        }
    }
    func getMappedResponse<T>(mapper: @escaping ([String:Any]) -> T?, completion: @escaping (T?, Error?) -> Void) {
        getRawResponse { (rawResponse, error) in
            if let error = error {
                completion(nil, error)
                return
            }
            guard let rawResponse = rawResponse else {
                completion(nil, error)
                return
            }
            if let mappedResponse = mapper(rawResponse) {
                completion(mappedResponse, nil)
                return
            }
            completion(nil, error)
        }
    }
}


// Usage:

class UserModel {
    static func fromDictionary(_ dict: [String:Any]) -> UserModel {
        return UserModel()
    }
}

APIRequest.userLoginWithData(username: "test", password: "test").getMappedResponse(mapper: UserModel.fromDictionary) { (userModel, error) in

}