fx_cast/app/src/bridge/components/cast/client.ts

import { Channel, Client } from "castv2";

import type { ReceiverMessage, SenderMessage } from "./types";

export const NS_CONNECTION = "urn:x-cast:com.google.cast.tp.connection";
export const NS_HEARTBEAT = "urn:x-cast:com.google.cast.tp.heartbeat";
export const NS_RECEIVER = "urn:x-cast:com.google.cast.receiver";

const DEFAULT_PORT = 8009;
const HEARTBEAT_INTERVAL_MS = 5000;

interface CastClientConnectOptions {
    port?: number;
    onReceiverMessage?: (message: ReceiverMessage) => void;
    onHeartbeat?: () => void;
}

export default class CastClient {
    protected client = new Client();

    protected connectionChannel?: Channel;
    protected heartbeatChannel?: Channel;
    protected heartbeatIntervalId?: NodeJS.Timeout;

    // Platform messaging
    private receiverChannel?: Channel;
    private receiverRequestId = Math.floor(Math.random() * 1e6);

    constructor(
        protected sourceId = "sender-0",
        protected destinationId = "receiver-0"
    ) {}

    /**
     * Create a channel on the client connection with a given
     * namespace.
     */
    protected createChannel(
        namespace: string,
        sourceId = this.sourceId,
        destinationId = this.destinationId
    ) {
        return this.client.createChannel(
            sourceId,
            destinationId,
            namespace,
            "JSON"
        );
    }

    /**
     * Sends a message on the receiver channel with the correct
     * request ID.
     */
    sendReceiverMessage(message: DistributiveOmit<SenderMessage, "requestId">) {
        if (!this.receiverChannel) return;

        const requestId = this.receiverRequestId++;
        this.receiverChannel.send({ ...message, requestId });
        return requestId;
    }

    /**
     * Connects to a cast receiver at a given host, returning a
     * promise that resolves once the client is connected.
     */
    connect(host: string, options?: CastClientConnectOptions) {
        return new Promise<void>((resolve, reject) => {
            // Handle errors
            this.client.on("error", reject);
            this.client.on("close", () => {
                if (this.heartbeatChannel && this.heartbeatIntervalId) {
                    clearInterval(this.heartbeatIntervalId);
                }
            });

            this.client.connect(
                {
                    host,
                    port: options?.port ?? DEFAULT_PORT
                },
                // On connection callback
                () => {
                    this.connectionChannel = this.createChannel(NS_CONNECTION);
                    this.heartbeatChannel = this.createChannel(NS_HEARTBEAT);

                    // Handle receiver messages
                    this.receiverChannel = this.createChannel(NS_RECEIVER);
                    this.receiverChannel.on("message", message => {
                        options?.onReceiverMessage?.(message);
                    });

                    this.connectionChannel.send({ type: "CONNECT" });
                    this.heartbeatChannel.send({ type: "PING" });

                    this.heartbeatIntervalId = setInterval(() => {
                        this.heartbeatChannel?.send({ type: "PING" });
                        options?.onHeartbeat?.();
                    }, HEARTBEAT_INTERVAL_MS);

                    resolve();
                }
            );
        });
    }

    disconnect() {
        if (this.heartbeatIntervalId) {
            clearInterval(this.heartbeatIntervalId);
        }

        this.connectionChannel?.send({ type: "CLOSE" });
        this.client.close();
    }
}