Fis-Retransmission/test/socket.ts

import { Observable, Subject, takeWhile } from "rxjs";
import { prepareResponseMessages } from "../services/utility/prepareFISmessage";
import { BaseMessage } from "../dependencies/logging/interface/export";
import { WrappedMessage } from "../services/retransmission.service";
import { io, Socket } from "socket.io-client";

let onHoldMessagesSubject: Subject<WrappedMessage> = new Subject()
let toBePassedOverToApp: Subject<BaseMessage> = new Subject()
// Serve static files (optional)
let sender: Subject<BaseMessage> = prepareResponseMessages(1, 2000)
let serverSocketUrl: string = 'http://localhost:3000'
let socket: Socket
establishSocketConnection(serverSocketUrl)
// interval(1000).subscribe(value => { // just to test if the emission is in sequence after reconnection
//     console.log(value)
//     socket.emit('interval', value)
// })
sender.subscribe({
    next: message => {
        makeRequest(message).subscribe({
            complete: () => console.log(`Request ${message.header.messageID} has acquired all responses.`)
        })
    }
})

// the interface the client Program will make without having to decide transport protocol
function makeRequest(request: BaseMessage): Observable<any> {
    return new Observable((response) => {
        sendMessage(request)
        toBePassedOverToApp.subscribe({
            next: (message: BaseMessage) => {
                // The identification of responses mapping to the request be adjusted accordingly
                // For now it's a simple demulti-plexing
                if (message.header.messageID == request.header.messageID && message.header.messageName == 'ResponseData') {
                    response.next(message)
                }
                if (message.header.messageID == request.header.messageID && message.header.messageName == 'Complete') {
                    response.complete()
                }
            },
            error: err => console.error(err),
            complete: () => { }
        })
    })
}

// socket util: Assuming that the client program would already have something like this in place
function establishSocketConnection(serverUrl: string) {
    socket = io(serverUrl, {
        reconnection: true,              // Enable automatic reconnections
        reconnectionAttempts: 100,        // Retry up to 10 times
        reconnectionDelay: 500,          // Start with a 500ms delay
        reconnectionDelayMax: 10000,     // Delay can grow to a max of 10 seconds
        randomizationFactor: 0.3,
    })

    // Listen for a connection event
    socket.on('connect', () => {
        // socket.emit('Hello from the client!')
        console.log('Connected to the server:', socket.id)
        // receiverConnectionState.next('ONLINE')
    });

    // Listen for messages from the server
    socket.on('message', (msg: WrappedMessage) => {
        console.log('Message from server:', msg.payload.header.messageID);

        // Check the sequence by ensuring the message value before the current message exists, then pass them over to "App"
        onHoldMessagesSubject.next(msg)
        checkMessage(msg).then(() => [
            toBePassedOverToApp.next(msg.payload as BaseMessage)
        ]).catch((err) => console.error(err))
    })

    socket.on('notification', (msg: string) => {
        console.log(msg)
    })

    // Handle disconnection
    socket.on('disconnect', () => {
        console.log('Disconnected from the server');
        // receiverConnectionState.next('OFFLINE')
    });
}



async function sendMessage(message: BaseMessage): Promise<any> {
    return new Promise((resolve, reject) => {
        try {
            // extra precaution: According to chatgpt, if disconnected, then the payload will be loaded back in event queue whilst the socket will try to reestablish connection
            // https://socket.io/docs/v4/client-offline-behavior/
            socket.emit('message', message); // inherently an aysnc
            console.log(`SocketEmit() for message to event queue ${message.header.messageID}`)
            resolve('')
        } catch (error) {
            console.error('Error emitting message:', error);
            this.wrappedMessage.next(message)
            reject(error)
        } ``
    })
}


// SO concept will be that if the message behind it is received, then 
async function checkMessage(message: WrappedMessage): Promise<any> {
    return new Promise((resolve, reject) => {
        if (message.previousMessageID) {
            onHoldMessagesSubject.pipe(
                takeWhile(item => item.payload.header.messageID == message.previousMessageID)
            ).subscribe({
                complete: () => {
                    resolve('previousMessageID matched')
                    // console.log(`${message.payload.header.messageID} : Previous messageID(${message.previousMessageID}) matched`)
                    console.log(`matched`)
                }
            })
        } else {
            console.log('No previous messageID. This should be the first message')
            resolve('No previous message ID. Please Proceed.')
        }
    })
}