ematrix/js/vapi-messaging.js

/*******************************************************************************

    ηMatrix - a browser extension to black/white list requests.
    Copyright (C) 2014-2019 The uMatrix/uBlock Origin authors
    Copyright (C) 2019-2022 Alessio Vanni

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see {http://www.gnu.org/licenses/}.

    Home: https://gitlab.com/vannilla/ematrix
    uMatrix Home: https://github.com/gorhill/uMatrix
*/

'use strict';

/******************************************************************************/

(function () {
    Cu.import('chrome://ematrix/content/lib/CallbackWrapper.jsm');

    vAPI.messaging = {
	get globalMessageManager() {
            return Cc['@mozilla.org/globalmessagemanager;1']
                .getService(Ci.nsIMessageListenerManager);
	},
	frameScript: vAPI.getURL('frameScript.js'),
	listeners: {},
	defaultHandler: null,
	NOOPFUNC: function(){},
	UNHANDLED: 'vAPI.messaging.notHandled'
    };

    vAPI.messaging.listen = function (listenerName, callback) {
	this.listeners[listenerName] = callback;
    };

    vAPI.messaging.onMessage = function ({target, data}) {
	let messageManager = target.messageManager;

	if (!messageManager) {
            // Message came from a popup, and its message manager is
            // not usable.  So instead we broadcast to the parent
            // window.
            messageManager =
		vAPI.browser.
		getOwnerWindow(target.webNavigation
			       .QueryInterface(Ci.nsIDocShell)
			       .chromeEventHandler).messageManager;
	}

	let channelNameRaw = data.channelName;
	let pos = channelNameRaw.indexOf('|');
	let channelName = channelNameRaw.slice(pos + 1);

	let callback = vAPI.messaging.NOOPFUNC;
	if (data.requestId !== undefined) {
            callback = CallbackWrapper.factory(messageManager,
					       channelName,
					       channelNameRaw.slice(0, pos),
					       data.requestId).callback;
	}

	let sender = {
            tab: {
		id: vAPI.tabs.manager.tabIdFromTarget(target)
            }
	};

	// Specific handler
	let r = vAPI.messaging.UNHANDLED;
	let listener = vAPI.messaging.listeners[channelName];

	if (typeof listener === 'function') {
            r = listener(data.msg, sender, callback);
	}
	if (r !== vAPI.messaging.UNHANDLED) {
            return;
	}

	// Default handler
	r = vAPI.messaging.defaultHandler(data.msg, sender, callback);
	if (r !== vAPI.messaging.UNHANDLED) {
            return;
	}

	console.error('eMatrix> messaging > unknown request: %o', data);

	// Unhandled: Need to callback anyways in case caller expected
	// an answer, or else there is a memory leak on caller's side
	callback();
    };

    vAPI.messaging.setup = function (defaultHandler) {
	// Already setup?
	if (this.defaultHandler !== null) {
            return;
	}

	if (typeof defaultHandler !== 'function') {
            defaultHandler = function () {
		return vAPI.messaging.UNHANDLED;
	    };
	}

	this.defaultHandler = defaultHandler;
	this.globalMessageManager.addMessageListener(location.host
						     + ':background',
						     this.onMessage);
	this.globalMessageManager.loadFrameScript(this.frameScript, true);

	vAPI.addCleanUpTask(function () {
            let gmm = vAPI.messaging.globalMessageManager;

            gmm.removeDelayedFrameScript(vAPI.messaging.frameScript);
            gmm.removeMessageListener(location.host + ':background',
				      vAPI.messaging.onMessage);
	});
    };

    vAPI.messaging.broadcast = function (message) {
	this.globalMessageManager
	    .broadcastAsyncMessage(location.host + ':broadcast',
				   JSON.stringify({
				       broadcast: true,
				       msg: message}));
    };
})();