Fis-MessageTransmission/src/transport/websocket.ts

import { BehaviorSubject, filter, Observable, Subject } from "rxjs";
import { Socket as ClientSocket } from 'socket.io-client'
import { Socket as SocketForConnectedClient } from "socket.io"
import { handleClientSocketConnection, handleNewSocketClient, startClientSocketConnection, startSocketServer } from "../utils/socket.utils";
import { ClientObject, ConnectionState, Info, Transport, TransportEvent, TransportMessage, TransportService } from "../interface/connector.interface";

/* Just code in the context that this websocket service will be handling multiple UI clients. Can think about the server communication at a later time. */
export class WebsocketTransportService implements TransportService {
    private info: Transport = Transport.Websocket 
    private connectedServer: ConnectedServerSocket[] = [] // to allow the possibility of having to communicate with multiple servers as a client
    private connectedClientSocket: ConnectedClientSocket[] = [] // to keep track of the all the clients that are connected
    // private incomingMessage: Subject<TransportMessage> = new Subject() // this is only for client roles only atm
    private transportEvent: Subject<TransportEvent> = new Subject()

    constructor() {
        console.log(`WebsocketTransportService: Constructing socket transport service....`)
        // logic here
    }

    public startServer(port: number): void {
        // logic here
        startSocketServer(port).subscribe({
            next: (connectedClient: SocketForConnectedClient) => {
                console.log(`WebsocketTransport Server Started...`)
                handleNewSocketClient(connectedClient, this.connectedClientSocket).subscribe(this.transportEvent)
            },
            error: error => console.error(error),
        })
    }

    public startClient(url: string): void {
        // logic here
        startClientSocketConnection(url).then((socket: ClientSocket) => {
            handleClientSocketConnection(socket, this.connectedServer).subscribe(this.transportEvent)
        }).catch((error) => {
            console.error(`WebsocketTransport ERROR:`, error) 
        })
    }

    public getTransportEvent(): Observable<TransportEvent> {
        return this.transportEvent.asObservable()
    }


    // for transmission(Server Only, not applicable for client Socket)
    public emit(message: TransportMessage): void {
        /* Just a rough idea, Because this service still needs to be direct the mesage to be emiteed based on the client that send it earlier.
        For example, if it'd doing a request response, obviosuly, it needs to be identified whose respnses it belong to. */
        let clientObj: ConnectedClientSocket | undefined = this.connectedClientSocket.find(obj => obj.id == message.target)
        if(clientObj && clientObj.connectionState.getValue() == 'ONLINE') {
            clientObj.socketInstance.emit(`message`, message)
        }
    }

    public subscribe(): Observable<TransportEvent> {
        return this.transportEvent.asObservable()
    }

    public getInfo(): Transport {
        return this.info
    }
}

export interface ConnectedClientSocket extends ClientObject {
    socketInstance: SocketForConnectedClient
}

export interface ConnectedServerSocket extends ClientObject {
    socketInstance: ClientSocket
}