Part 6

.swift

// Use of the dataTaskPublisher API to implement Publisher with the decoded data
struct Token: Codable {
    let string: String
}

// We'll use the following function to validate our dataTaskPublisher output in the pipeline
func validate(_ data: Data, _ response: URLResponse) throws -> Data {
    guard let httpResponse = response as? HTTPURLResponse else {
        throw APIError.invalidResponse
    }
    guard (200..<300).contains(httpResponse.statusCode) else {
        throw APIError.statusCode(httpResponse.statusCode)
    }
    return data
}

func create(user: User) -> AnyPublisher<CreateUserResponse, Error>? {
    return try? postUser(user: user)
        .tryMap{ try validate($0.data, $0.response) }
        .decode(type: CreateUserResponse.self, decoder: JSONDecoder())
        .eraseToAnyPublisher()
}
        
func login(email: String, password: String) -> AnyPublisher<Token, Error> {
    return postLogin(email: email, password: password)
            .tryMap{ try validate($0.data, $0.response) }
            .decode(type: Token.self, decoder: JSONDecoder())
            .eraseToAnyPublisher()
}

func postTodo(authToken: String, todo: Todo) -> AnyPublisher<Todo, Error> {
    return  postTodo(authToken: authToken, body: todo)
            .tryMap{ try validate($0.data, $0.response) }
            .decode(type: Todo.self, decoder: JSONDecoder())
            .eraseToAnyPublisher()
}

func getTodo(authToken: String) -> AnyPublisher<[Todo], Error> {
    return getTodo(authToken: authToken)
            .tryMap{ try validate($0.data, $0.response) }
            .decode(type: [Todo].self, decoder: JSONDecoder())
            .eraseToAnyPublisher()
}

func deleteTodo(authToken: String, id: Int) -> AnyPublisher<Todo, Error> {
    return deleteTodo(authToken: authToken, id: id)
            .tryMap{ try validate($0.data, $0.response) }
            .decode(type: Todo.self, decoder: JSONDecoder())
            .eraseToAnyPublisher()
}