@comapeo/ipc/dist/lib/sub-channel.js

IPC wrappers for CoMapeo Core

import { isRelevantEventData } from './utils.js';
// Shared prefix on every channel id this library mints. It lets the server
// tell its own traffic from a foreign sender sharing the same port: an id
// without this prefix isn't ours and is ignored without warning.
export const COMAPEO_PREFIX = '@@comapeo/';
export const MANAGER_CHANNEL_ID = '@@comapeo/manager';
export const PROJECT_ROUTING_ID = '@@comapeo/project-routing';
export const SERVICES_ID = '@@comapeo/services';
// Prefix for per-project instance channel ids; the rest of the id is the
// project's public id plus a per-open counter (see `openProjectInstance`).
export const PROJECT_INSTANCE_PREFIX = '@@comapeo/project/';
/** @import {MessagePortLike, MessageEvent} from 'rpc-reflector' */
/**
 * @typedef {Object} Events
 * @property {(message: unknown) => void} message
 */
/** @implements {MessagePortLike} */
export class SubChannel {
    #id;
    #messagePort;
    /** @type {'idle' | 'active' | 'closed'} */
    #state;
    /** @type {Array<{id: string, message: unknown}>} */
    #queued;
    #handleMessageEvent;
    /** @type {Set<(message: MessageEvent) => void>} */
    #listeners = new Set();
    /**
     * @param {MessagePortLike} messagePort Parent channel to add namespace to
     * @param {string} id ID for the subchannel
     */
    constructor(messagePort, id) {
        this.#id = id;
        this.#messagePort = messagePort;
        this.#state = 'idle';
        this.#queued = [];
        /**
         * @param {{ data: unknown }} event
         */
        this.#handleMessageEvent = ({ data }) => {
            if (!isRelevantEventData(data))
                return;
            const { id, message } = data;
            if (this.#id !== id)
                return;
            switch (this.#state) {
                case 'idle': {
                    this.#queued.push(data);
                    break;
                }
                case 'active': {
                    this.dispatchEvent({ data: message });
                    break;
                }
                case 'closed': {
                    // no-op if closed (the event listener should be removed anyway)
                    break;
                }
            }
        };
        this.#messagePort.addEventListener('message', this.#handleMessageEvent);
    }
    /**
     * @param {'message'} type
     * @param {(event: MessageEvent) => void} listener
     */
    addEventListener(type, listener) {
        if (type !== 'message')
            return;
        this.#listeners.add(listener);
    }
    /**
     * @param {'message'} type
     * @param {(event: MessageEvent) => void} listener
     */
    removeEventListener(type, listener) {
        if (type !== 'message')
            return;
        this.#listeners.delete(listener);
    }
    get id() {
        return this.#id;
    }
    /**
     * Send messages with the subchannel's ID
     * @param {any} message
     */
    postMessage(message) {
        this.#messagePort.postMessage({ id: this.#id, message });
    }
    start() {
        if (this.#state !== 'idle')
            return;
        this.#state = 'active';
        /** @type {{id: string, message: unknown} | undefined} */
        let data;
        while ((data = this.#queued.shift())) {
            this.#handleMessageEvent({ data });
        }
    }
    close() {
        if (this.#state === 'closed')
            return;
        this.#state = 'closed';
        this.#queued = [];
        // Node types are incorrect (as of v14, Node's MessagePort should also extend [EventTarget](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget))
        this.#messagePort.removeEventListener('message', this.#handleMessageEvent);
    }
    /** @param {MessageEvent} event */
    dispatchEvent(event) {
        for (const listener of this.#listeners) {
            listener(event);
        }
    }
}