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});
		if (siteStatus.mode !== "allow"){
			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;
								}
							}
						}
					);
				}
			});
		}
	};
}());