@anyit/messaging

Core Messaging Library

This library provides basic classes and decorators designed for streamlined messaging functionality. It's built with simplicity in mind, making it easy for developers to integrate and utilize within their projects to handle message-based interactions. Whether you're looking to process, route, or manage messages, this tool offers the essential building blocks to get started.

Table of Contents

• Message Base Class
• Additional message types
• Decorators
• Messages Factory
• Error Class
• Types and Helpers
• Example Message Type
• Conclusion

Message Base Class

Message

The Message class is an abstract class designed to act as the base for all custom message types.

Public Properties:

• messageId: A unique identifier for the message.
• traceId: An optional trace identifier. Its value will be taken from the reason if not directly provided.
• createdAt: Timestamp of message creation.
• reason: An optional reason message.
• reasonId: An optional reason message ID if for some reason providing of the whole message within the reason field is unwanted.
• sender: An optional sender field to identify who is sending this message
• type: Returns the constructor's name.
• code: Returns the code associated with the message.

Public Methods:

• toJSON(): Returns a JSON representation of the message.
• toString(): Returns a string representation of the message.

Additional Message Types

ErrorMessage

A custom message type for error-related messages. It extends the base Message class and includes:

Public Property:

• error: Stores the error information.

When using this message, it is advisable to provide a reason to detail the context or specifics of the error.

Type Guard:

Use the isErrorMessage function to check if a given message instance is of the ErrorMessage type.

if (isErrorMessage(someMessage)) {
    console.log("This is a error message.");
}

SuccessMessage

This message type indicates a successful operation and extends the base Message class. When using this message, it is advisable to provide a reason to detail the context or specifics of the success.

Type Guard:

Use the isSuccessMessage function to check if a given message instance is of the SuccessMessage type.

if (isSuccessMessage(someMessage)) {
    console.log("This is a success message.");
}

ProcessingComplete

This message type signifies the completion of a processing task and also extends the base Message class. Similarly, it's recommended to accompany this message with a reason to provide clarity on what processing was completed.

Type Guard:

Use the isProcessingComplete function to verify if a given message instance is of the ProcessingComplete type.

if (isProcessingComplete(someMessage)) {
    console.log("Processing is complete.");
}

Decorators

RegisterMessage(uniqueCode?: string)

A decorator that registers a message type with a unique code.

Parameters:

• uniqueCode: A string that acts as a unique identifier for the message type. If it is omitted then code wil be equal to the constructor name of a message class.

Messages Factory

MessageFactory

This class provides methods for message instantiation and registration.

Public Methods:

• create(input: { [key: string]: any }): Creates a message instance from given input.

Error Class

MessageDeserializeError

This error is thrown when the MessageFactory is unable to deserialize a message due to unknown types.

Types and Helpers

MessageArgs<T extends Message = Message>

A utility type for constructing a message.

MessageType<T extends Message = Message>

A type representing the message constructor with a code property.

Example Message Type

In this section, we'll introduce an example message type based on a real-world use-case, showcasing how you can derive from the Message base class.

TerminateAccount

A custom message type for deleting a specific account. It extends the base Message class.

import { Message, MessageArgs, RegisterMessage } from '@anyit/messaging';

type TerminateAccountArgs = MessageArgs<TerminateAccount>;

@RegisterMessage('01H7XYZT08AS2ABCDEQQNMHRQ2')
export class TerminateAccount extends Message {
  constructor(args: TerminateAccountArgs) {
    super(args);

    this.accountID = args.accountID;
  }

  readonly accountID: string;
}

export const isTerminateAccount = (message?: Message): message is TerminateAccount =>
  Boolean(message && message.code === TerminateAccount.code);

Conclusion

Utilize the Message class as a foundation for custom message types and leverage the MessageFactory for creation and deserialization of these custom types. Always use the RegisterMessage decorator to ensure custom messages are recognized by the system.