CanvasBlocker/lib/intercept.js

/* jslint moz: true */
/* 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/. */
(function(){
	"use strict";
	
	const {changedFunctions, setRandomSupply} = require("./modifiedAPI");
	const randomSupplies = require("./randomSupplies");
	setRandomSupply(randomSupplies.nonPersistent);
	var apiNames = Object.keys(changedFunctions);
	var undef;
	var exportFunction = require("chrome").Cu.exportFunction;
	function setRandomSupplyByType(type){
		switch (type){
			case "persistent":
				setRandomSupply(randomSupplies.persistent);
				break;
			default:
				setRandomSupply(randomSupplies.nonPersistent);
		}
	}
	exports.setRandomSupplyByType = setRandomSupplyByType;
	exports.intercept = function intercept({subject: window}, {check, checkStack, ask, notify, prefs}){
		var siteStatus = check({url: window.location.href});
		apiNames.forEach(function(name){
			var changedFunction = changedFunctions[name];
			var original = window.wrappedJSObject[changedFunction.object].prototype[name];
			
			if (changedFunction.getStatus(undefined, siteStatus).active){
				Object.defineProperty(
					window.wrappedJSObject[changedFunction.object].prototype,
					name,
					{
						enumerable: true,
						configureable: false,
						get: function(){
							if (!window.location.href){
								return undef;
							}
							var error = new Error();
							if (checkStack(error.stack)){
								return original;
							}
							var funcStatus = changedFunction.getStatus(this, siteStatus);
							
							if (funcStatus.active){
								if (funcStatus.mode === "ask"){
									funcStatus.mode = ask({window: window, type: changedFunction.type, canvas: this, errorStack: error.stack});
								}
								switch (funcStatus.mode){
									case "allow":
										return original;
									case "fake":
										setRandomSupplyByType(prefs("rng"));
										var fake = changedFunction.fakeGenerator(prefs, function(messageId){
											notify({url: window.location.href, errorStack: error.stack, messageId});
										});
										switch (fake){
											case true:
												return original;
											case false:
												return undef;
											default:
												return exportFunction(fake, window.wrappedJSObject);
										}
									//case "block":
									default:
										return undef;
								}
							}
							else {
								return original;
							}
						}
					}
				);
			}
		});
	};
}());