fx_cast/ext/src/cast/export.ts

"use strict";

import { Message } from "../messaging";

import { BridgeInfo } from "../lib/bridge";
import { TypedMessagePort } from "../lib/TypedMessagePort";

import CastSDK from "./sdk";

import { PageEventMessenger, ExtensionEventMessenger } from "./eventMessaging";

// Create messengers manually instead of relying on getters
const eventMessaging = {
    page: new PageEventMessenger(),
    extension: new ExtensionEventMessenger()
};

let initializedBridgeInfo: BridgeInfo;
let initializedBackgroundPort: MessagePort;

/**
 * To support exporting an API from a module, we need to
 * retain the event-based message passing despite not
 * actually crossing any context boundaries. The cast instance
 * listens for and emits these messages, and changing that
 * behavior is too messy.
 */
export function ensureInit(): Promise<TypedMessagePort<Message>> {
    return new Promise(async (resolve, reject) => {
        // If already initialized, just return existing bridge info
        if (initializedBridgeInfo) {
            if (initializedBridgeInfo.isVersionCompatible) {
                resolve(initializedBackgroundPort);
            } else {
                reject();
            }

            return;
        }

        const channel = new MessageChannel();
        initializedBackgroundPort = channel.port1;

        /**
         * If the module is imported into a background script
         * context, the location will be the internal extension URL,
         * whereas in a content script, it will be the content page
         * URL.
         */
        if (window.location.protocol === "moz-extension:") {
            const { default: castManager } = await import(
                "../background/castManager"
            );

            // port2 will post bridge messages to port 1
            await castManager.init();
            await castManager.createInstance(channel.port2);

            // bridge -> cast instance
            channel.port1.onmessage = ev => {
                const message = ev.data as Message;

                // Send message to cast instance
                eventMessaging.extension.sendMessage(message);
                handleIncomingMessageToCast(message);
            };

            // cast instance -> bridge
            eventMessaging.extension.addListener(message =>
                channel.port1.postMessage(message)
            );
        } else {
            /**
             * Import reference to message port created by contentBridge.
             * Creation of the port triggers side-effects in the
             * background script.
             */
            const { backgroundPort } = await import("./contentBridge");

            // backgroundPort -> channel.port2
            backgroundPort.onMessage.addListener((message: Message) => {
                channel.port2.postMessage(message);
            });

            // channel.port2 -> backgroundPort
            channel.port2.onmessage = ev => {
                const message = ev.data as Message;
                backgroundPort.postMessage(message);
            };

            // Handle cast messages
            eventMessaging.page.addListener(message =>
                handleIncomingMessageToCast(message)
            );
        }

        function handleIncomingMessageToCast(message: Message) {
            switch (message.subject) {
                case "cast:initialized": {
                    initializedBridgeInfo = message.data;

                    if (initializedBridgeInfo.isVersionCompatible) {
                        resolve(initializedBackgroundPort);
                    } else {
                        reject();
                    }
                }
            }
        }
    });
}

export default new CastSDK();