Livebeat/backend/lib/eventManager.ts

import { Response } from "express";
import { logger } from "../app";
import { ISeverity, NotificationType, PublicNotificationType } from "../models/notifications/notification.interface";
import { addNotification } from "../models/notifications/notification.model";
import { IPhone } from "../models/phone/phone.interface";
import { IUser } from "../models/user/user.interface";
import { User } from "../models/user/user.model";
import { randomString } from "./crypto";

/**
 * This class stores one specific client.
 */
export class Client {
    id: string;
    userId: string;
    stream: Response;

    constructor(stream: Response, userId: string) {
        this.id = randomString(16);
        this.userId = userId;
        this.stream = stream;
    }

    send(type: NotificationType, data: any) {
        this.stream.write(`event: ${type}\ndata: ${JSON.stringify(data)}\n\n`);
    }

    async getUser() {
        return await User.findById(this.userId);
    }
}

export class Clients {
    private clients: Client[];

    constructor(clients: Client[]) {
        this.clients = clients;
    }

    getClientsByUser(userId: string) {
        const userClients = [];
        for (let i = 0; i < this.clients.length; i++) {
            if (this.clients[i].userId === userId) {
                userClients.push(this.clients[i]);
            }
        }

        return userClients;
    }

    closeAllClientsByUser(userId: string) {
        this.getClientsByUser(userId).forEach(client => {
            client.stream.end();
        });
    }

    addClient(client: Client) {
        this.clients.push(client);

        return client;
    }

    getClients() {
        return this.clients;
    }
}

export class EventManager {
    constructor() {
        setInterval(() => {
            this.broadcast('info', { message: "Test" });
        }, 2000);
    }

    // This map stores a open data stream and it's associated room.
    private clients: Clients = new Clients([]);

    private addClient(stream: Response, userId: string) {
        this.clients.addClient(new Client(stream, userId));
    }

    /**
     * Add a client to a specific room
     * @param room Used as an id for the specific room
     * @param stream A open connection to the user
     */
    async join(userId: string, stream: Response) {
        if (stream.req == undefined) {
            stream.send(500);
            return;
        }

        // Check user
        const user = await User.findById(userId);
        if (user === null) {
            stream.send(401);
            return;
        }

        // Make sure to keep the connection open
        stream.writeHead(200, {
            'Content-Type': 'text/event-stream',
            'Cache-Control': 'no-cache',
            'Connection': 'keep-alive'
        });

        this.addClient(stream, userId);
        logger.debug(`Client ${stream.req.hostname} of user ${user.name} joined.`);
    }

    /**
     * Push a new event into a specific room
     * @param event Type of the event
     * @param data Content of the event
     * @param selector Room to push in. If empty then it will be a public broadcast to anyone.
     */
    push(type: NotificationType, data: any, user: IUser, severity = ISeverity.INFO) {
        let clients = this.clients.getClientsByUser(user.id);
        if (clients === undefined) return;

        /* Manage notifications */
        if (type != 'beat' && user !== undefined) {
            if (type == 'phone_alive' || type == 'phone_dead') {
                addNotification(type, severity, ((data as IPhone)._id), user);
            }
        }

        data = { type, severity, ...data };

        clients.forEach((client) => {
            client.stream.write(`event: ${type}\ndata: ${JSON.stringify(data)}\n\n`);
        });

        if (user === undefined) {
            logger.debug(`Broadcasted event ${type} to all users (${clients.length} clients affected)`);
        } else {
            logger.debug(`Broadcasted event ${type} to user ${user.id} (${clients.length} clients affected)`);
        }
    }

    /**
     * Very much like push() but it will send this message to **every connected client!**
     */
    broadcast(type: PublicNotificationType, data: any) {
        this.clients.getClients().forEach(async client => {
            console.log(`Send ${JSON.stringify(data)} (of type ${type}) to a client of user ${(await client.getUser())?.name}`);
            client.stream.write(`event: message\ndata: ${JSON.stringify(data)}\n\n`);
        });

        logger.debug(`Broadcasted event ${type} to all users (${this.clients.getClients().length} clients affected)`);
    }

    /**
     * End the communication with a specific client.
     */
    end(stream: Response, userId: string) {
        stream.end();

        logger.debug(`End connection with ${stream.req?.hostname} (user: ${userId})`);
    }

    static buildEventTypeName(type: EventType, user: IUser) {
        return `${type}-${user}`;
    }
}

export type EventType = 
    | 'tracker'     // Receive just the gps location of a specific user.
    | 'user'        // Receive user updates.
    | 'all';        // Receive all above events.