peers/peerjs-server

import { MessageType } from "../../../enums.ts";
import type { IClient } from "../../../models/client.ts";
import type { IMessage } from "../../../models/message.ts";
import type { IRealm } from "../../../models/realm.ts";

export const TransmissionHandler = ({
    realm,
}: {
    realm: IRealm;
}): ((client: IClient | undefined, message: IMessage) => boolean) => {
    const handle = (client: IClient | undefined, message: IMessage) => {
        const type = message.type;
        const srcId = message.src;
        const dstId = message.dst;

        const destinationClient = realm.getClientById(dstId);

        // User is connected!
        if (destinationClient) {
            const socket = destinationClient.getSocket();
            try {
                if (socket) {
                    const data = JSON.stringify(message);

                    socket.send(data);
                } else {
                    // Neither socket no res available. Peer dead?
                    throw new Error("Peer dead");
                }
            } catch (e) {
                // This happens when a peer disconnects without closing connections and
                // the associated WebSocket has not closed.
                // Tell other side to stop trying.
                if (socket) {
                    socket.close();
                } else {
                    realm.removeClientById(destinationClient.getId());
                }

                handle(client, {
                    type: MessageType.LEAVE,
                    src: dstId,
                    dst: srcId,
                });
            }
        } else {
            // Wait for this client to connect/reconnect (XHR) for important
            // messages.
            const ignoredTypes = [MessageType.LEAVE, MessageType.EXPIRE];

            if (!ignoredTypes.includes(type) && dstId) {
                realm.addMessageToQueue(dstId, message);
            } else if (type === MessageType.LEAVE && !dstId) {
                realm.removeClientById(srcId);
            } else {
                // Unavailable destination specified with message LEAVE or EXPIRE
                // Ignore
            }
        }

        return true;
    };

    return handle;
};