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Diffstat (limited to 'remote/shared/messagehandler/EventsDispatcher.sys.mjs')
| -rw-r--r-- | remote/shared/messagehandler/EventsDispatcher.sys.mjs | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/remote/shared/messagehandler/EventsDispatcher.sys.mjs b/remote/shared/messagehandler/EventsDispatcher.sys.mjs new file mode 100644 index 0000000000..9620febcc1 --- /dev/null +++ b/remote/shared/messagehandler/EventsDispatcher.sys.mjs @@ -0,0 +1,260 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +const lazy = {}; + +ChromeUtils.defineESModuleGetters(lazy, { + ContextDescriptorType: + "chrome://remote/content/shared/messagehandler/MessageHandler.sys.mjs", + Log: "chrome://remote/content/shared/Log.sys.mjs", + SessionDataCategory: + "chrome://remote/content/shared/messagehandler/sessiondata/SessionData.sys.mjs", + SessionDataMethod: + "chrome://remote/content/shared/messagehandler/sessiondata/SessionData.sys.mjs", + TabManager: "chrome://remote/content/shared/TabManager.sys.mjs", +}); + +ChromeUtils.defineLazyGetter(lazy, "logger", () => lazy.Log.get()); + +/** + * Helper to listen to events which rely on SessionData. + * In order to support the EventsDispatcher, a module emitting events should + * subscribe and unsubscribe to those events based on SessionData updates + * and should use the "event" SessionData category. + */ +export class EventsDispatcher { + // The MessageHandler owning this EventsDispatcher. + #messageHandler; + + /** + * @typedef {object} EventListenerInfo + * @property {ContextDescriptor} contextDescriptor + * The ContextDescriptor to which those callbacks are associated + * @property {Set<Function>} callbacks + * The callbacks to trigger when an event matching the ContextDescriptor + * is received. + */ + + // Map from event name to map of strings (context keys) to EventListenerInfo. + #listenersByEventName; + + /** + * Create a new EventsDispatcher instance. + * + * @param {MessageHandler} messageHandler + * The MessageHandler owning this EventsDispatcher. + */ + constructor(messageHandler) { + this.#messageHandler = messageHandler; + + this.#listenersByEventName = new Map(); + } + + destroy() { + for (const event of this.#listenersByEventName.keys()) { + this.#messageHandler.off(event, this.#onMessageHandlerEvent); + } + + this.#listenersByEventName = null; + } + + /** + * Check for existing listeners for a given event name and a given context. + * + * @param {string} name + * Name of the event to check. + * @param {ContextInfo} contextInfo + * ContextInfo identifying the context to check. + * + * @returns {boolean} + * True if there is a registered listener matching the provided arguments. + */ + hasListener(name, contextInfo) { + if (!this.#listenersByEventName.has(name)) { + return false; + } + + const listeners = this.#listenersByEventName.get(name); + for (const { contextDescriptor } of listeners.values()) { + if (this.#matchesContext(contextInfo, contextDescriptor)) { + return true; + } + } + return false; + } + + /** + * Stop listening for an event relying on SessionData and relayed by the + * message handler. + * + * @param {string} event + * Name of the event to unsubscribe from. + * @param {ContextDescriptor} contextDescriptor + * Context descriptor for this event. + * @param {Function} callback + * Event listener callback. + * @returns {Promise} + * Promise which resolves when the event fully unsubscribed, including + * propagating the necessary session data. + */ + async off(event, contextDescriptor, callback) { + return this.update([{ event, contextDescriptor, callback, enable: false }]); + } + + /** + * Listen for an event relying on SessionData and relayed by the message + * handler. + * + * @param {string} event + * Name of the event to subscribe to. + * @param {ContextDescriptor} contextDescriptor + * Context descriptor for this event. + * @param {Function} callback + * Event listener callback. + * @returns {Promise} + * Promise which resolves when the event fully subscribed to, including + * propagating the necessary session data. + */ + async on(event, contextDescriptor, callback) { + return this.update([{ event, contextDescriptor, callback, enable: true }]); + } + + /** + * An object that holds information about subscription/unsubscription + * of an event. + * + * @typedef Subscription + * + * @param {string} event + * Name of the event to subscribe/unsubscribe to. + * @param {ContextDescriptor} contextDescriptor + * Context descriptor for this event. + * @param {Function} callback + * Event listener callback. + * @param {boolean} enable + * True, if we need to subscribe to an event. + * Otherwise false. + */ + + /** + * Start or stop listening to a list of events relying on SessionData + * and relayed by the message handler. + * + * @param {Array<Subscription>} subscriptions + * The list of information to subscribe/unsubscribe to. + * + * @returns {Promise} + * Promise which resolves when the events fully subscribed/unsubscribed to, + * including propagating the necessary session data. + */ + async update(subscriptions) { + const sessionDataItemUpdates = []; + subscriptions.forEach(({ event, contextDescriptor, callback, enable }) => { + if (enable) { + // Setup listeners. + if (!this.#listenersByEventName.has(event)) { + this.#listenersByEventName.set(event, new Map()); + this.#messageHandler.on(event, this.#onMessageHandlerEvent); + } + + const key = this.#getContextKey(contextDescriptor); + const listeners = this.#listenersByEventName.get(event); + if (listeners.has(key)) { + const { callbacks } = listeners.get(key); + callbacks.add(callback); + } else { + const callbacks = new Set([callback]); + listeners.set(key, { callbacks, contextDescriptor }); + + sessionDataItemUpdates.push({ + ...this.#getSessionDataItem(event, contextDescriptor), + method: lazy.SessionDataMethod.Add, + }); + } + } else { + // Remove listeners. + const listeners = this.#listenersByEventName.get(event); + if (!listeners) { + return; + } + + const key = this.#getContextKey(contextDescriptor); + if (!listeners.has(key)) { + return; + } + + const { callbacks } = listeners.get(key); + if (callbacks.has(callback)) { + callbacks.delete(callback); + if (callbacks.size === 0) { + listeners.delete(key); + if (listeners.size === 0) { + this.#messageHandler.off(event, this.#onMessageHandlerEvent); + this.#listenersByEventName.delete(event); + } + + sessionDataItemUpdates.push({ + ...this.#getSessionDataItem(event, contextDescriptor), + method: lazy.SessionDataMethod.Remove, + }); + } + } + } + }); + + // Update all sessionData at once. + await this.#messageHandler.updateSessionData(sessionDataItemUpdates); + } + + #getContextKey(contextDescriptor) { + const { id, type } = contextDescriptor; + return `${type}-${id}`; + } + + #getSessionDataItem(event, contextDescriptor) { + const [moduleName] = event.split("."); + return { + moduleName, + category: lazy.SessionDataCategory.Event, + contextDescriptor, + values: [event], + }; + } + + #matchesContext(contextInfo, contextDescriptor) { + if (contextDescriptor.type === lazy.ContextDescriptorType.All) { + return true; + } + + if ( + contextDescriptor.type === lazy.ContextDescriptorType.TopBrowsingContext + ) { + const eventBrowsingContext = lazy.TabManager.getBrowsingContextById( + contextInfo.contextId + ); + return eventBrowsingContext?.browserId === contextDescriptor.id; + } + + return false; + } + + #onMessageHandlerEvent = (name, event, contextInfo) => { + const listeners = this.#listenersByEventName.get(name); + for (const { callbacks, contextDescriptor } of listeners.values()) { + if (!this.#matchesContext(contextInfo, contextDescriptor)) { + continue; + } + + for (const callback of callbacks) { + try { + callback(name, event); + } catch (e) { + lazy.logger.debug( + `Error while executing callback for ${name}: ${e.message}` + ); + } + } + } + }; +} |