MockedMessagingService.swift

/**
 Service for mocking a message sending service
 Conforms to MessageSendable protocol
 */
struct MockedMessageService: MessageSendable {
    
    /**
     Mocked version of send message
     */
    func sendMessage(username: String, message: String, completion: @escaping (Result<String, Error>) -> Void) {
        
        // check for cases that will cause failure and mock them
        if username.isEmpty {
            completion(.failure(MessageError.emptyUsername))
        }
        
        if message.isEmpty {
            completion(.failure(MessageError.emptyMessage))
        }
        
        // mock successfully sending message
        completion(.success("Successfully sent message"))
    }
}