bridge.js

'use strict';

/**
 * __        ___    ____  _   _ ___ _   _  ____
 * \ \      / / \  |  _ \| \ | |_ _| \ | |/ ___|
 *  \ \ /\ / / _ \ | |_) |  \| || ||  \| | |  _
 *   \ V  V / ___ \|  _ <| |\  || || |\  | |_| |
 *    \_/\_/_/   \_\_| \_\_| \_|___|_| \_|\____|
 *
 * This file is critical for vm2. It implements the bridge between the host and the sandbox.
 * If you do not know exactly what you are doing, you should NOT edit this file.
 *
 * The file is loaded in the host and sandbox to handle objects in both directions.
 * This is done to ensure that RangeErrors are from the correct context.
 * The boundary between the sandbox and host might throw RangeErrors from both contexts.
 * Therefore, thisFromOther and friends can handle objects from both domains.
 *
 * Method parameters have comments to tell from which context they came.
 *
 */

const globalsList = [
	'Number',
	'String',
	'Boolean',
	'Date',
	'RegExp',
	'Map',
	'WeakMap',
	'Set',
	'WeakSet',
	'Promise',
	'Function'
];

const errorsList = [
	'RangeError',
	'ReferenceError',
	'SyntaxError',
	'TypeError',
	'EvalError',
	'URIError',
	'Error'
];

const OPNA = 'Operation not allowed on contextified object.';

const thisGlobalPrototypes = {
	__proto__: null,
	Object: Object.prototype,
	Array: Array.prototype
};

for (let i = 0; i < globalsList.length; i++) {
	const key = globalsList[i];
	const g = global[key];
	if (g) thisGlobalPrototypes[key] = g.prototype;
}

for (let i = 0; i < errorsList.length; i++) {
	const key = errorsList[i];
	const g = global[key];
	if (g) thisGlobalPrototypes[key] = g.prototype;
}

const {
	getPrototypeOf: thisReflectGetPrototypeOf,
	setPrototypeOf: thisReflectSetPrototypeOf,
	defineProperty: thisReflectDefineProperty,
	deleteProperty: thisReflectDeleteProperty,
	getOwnPropertyDescriptor: thisReflectGetOwnPropertyDescriptor,
	isExtensible: thisReflectIsExtensible,
	preventExtensions: thisReflectPreventExtensions,
	apply: thisReflectApply,
	construct: thisReflectConstruct,
	set: thisReflectSet,
	get: thisReflectGet,
	has: thisReflectHas,
	ownKeys: thisReflectOwnKeys,
	enumerate: thisReflectEnumerate,
} = Reflect;

const thisObject = Object;
const {
	freeze: thisObjectFreeze,
	prototype: thisObjectPrototype
} = thisObject;
const thisObjectHasOwnProperty = thisObjectPrototype.hasOwnProperty;
const ThisProxy = Proxy;
const ThisWeakMap = WeakMap;
const {
	get: thisWeakMapGet,
	set: thisWeakMapSet
} = ThisWeakMap.prototype;
const ThisMap = Map;
const thisMapGet = ThisMap.prototype.get;
const thisMapSet = ThisMap.prototype.set;
const thisFunction = Function;
const thisFunctionBind = thisFunction.prototype.bind;
const thisArrayIsArray = Array.isArray;
const thisErrorCaptureStackTrace = Error.captureStackTrace;

const thisSymbolToString = Symbol.prototype.toString;
const thisSymbolToStringTag = Symbol.toStringTag;
const thisSymbolIterator = Symbol.iterator;
const thisSymbolNodeJSUtilInspectCustom = Symbol.for('nodejs.util.inspect.custom');

/**
 * VMError.
 *
 * @public
 * @extends {Error}
 */
class VMError extends Error {

	/**
	 * Create VMError instance.
	 *
	 * @public
	 * @param {string} message - Error message.
	 * @param {string} code - Error code.
	 */
	constructor(message, code) {
		super(message);

		this.name = 'VMError';
		this.code = code;

		thisErrorCaptureStackTrace(this, this.constructor);
	}
}

thisGlobalPrototypes['VMError'] = VMError.prototype;

function thisUnexpected() {
	return new VMError('Unexpected');
}

if (!thisReflectSetPrototypeOf(exports, null)) throw thisUnexpected();

function thisSafeGetOwnPropertyDescriptor(obj, key) {
	const desc = thisReflectGetOwnPropertyDescriptor(obj, key);
	if (!desc) return desc;
	if (!thisReflectSetPrototypeOf(desc, null)) throw thisUnexpected();
	return desc;
}

function thisThrowCallerCalleeArgumentsAccess(key) {
	'use strict';
	thisThrowCallerCalleeArgumentsAccess[key];
	return thisUnexpected();
}

function thisIdMapping(factory, other) {
	return other;
}

const thisThrowOnKeyAccessHandler = thisObjectFreeze({
	__proto__: null,
	get(target, key, receiver) {
		if (typeof key === 'symbol') {
			key = thisReflectApply(thisSymbolToString, key, []);
		}
		throw new VMError(`Unexpected access to key '${key}'`);
	}
});

const emptyForzenObject = thisObjectFreeze({
	__proto__: null
});

const thisThrowOnKeyAccess = new ThisProxy(emptyForzenObject, thisThrowOnKeyAccessHandler);

function SafeBase() {}

if (!thisReflectDefineProperty(SafeBase, 'prototype', {
	__proto__: null,
	value: thisThrowOnKeyAccess
})) throw thisUnexpected();

function SHARED_FUNCTION() {}

const TEST_PROXY_HANDLER = thisObjectFreeze({
	__proto__: thisThrowOnKeyAccess,
	construct() {
		return this;
	}
});

function thisIsConstructor(obj) {
	// Note: obj@any(unsafe)
	const Func = new ThisProxy(obj, TEST_PROXY_HANDLER);
	try {
		// eslint-disable-next-line no-new
		new Func();
		return true;
	} catch (e) {
		return false;
	}
}

function thisCreateTargetObject(obj, proto) {
	// Note: obj@any(unsafe) proto@any(unsafe) returns@this(unsafe) throws@this(unsafe)
	let base;
	if (typeof obj === 'function') {
		if (thisIsConstructor(obj)) {
			// Bind the function since bound functions do not have a prototype property.
			base = thisReflectApply(thisFunctionBind, SHARED_FUNCTION, [null]);
		} else {
			base = () => {};
		}
	} else if (thisArrayIsArray(obj)) {
		base = [];
	} else {
		return {__proto__: proto};
	}
	if (!thisReflectSetPrototypeOf(base, proto)) throw thisUnexpected();
	return base;
}

function createBridge(otherInit, registerProxy) {

	const mappingOtherToThis = new ThisWeakMap();
	const protoMappings = new ThisMap();
	const protoName = new ThisMap();

	function thisAddProtoMapping(proto, other, name) {
		// Note: proto@this(unsafe) other@other(unsafe) name@this(unsafe) throws@this(unsafe)
		thisReflectApply(thisMapSet, protoMappings, [proto, thisIdMapping]);
		thisReflectApply(thisMapSet, protoMappings, [other,
			(factory, object) => thisProxyOther(factory, object, proto)]);
		if (name) thisReflectApply(thisMapSet, protoName, [proto, name]);
	}

	function thisAddProtoMappingFactory(protoFactory, other, name) {
		// Note: protoFactory@this(unsafe) other@other(unsafe) name@this(unsafe) throws@this(unsafe)
		let proto;
		thisReflectApply(thisMapSet, protoMappings, [other,
			(factory, object) => {
				if (!proto) {
					proto = protoFactory();
					thisReflectApply(thisMapSet, protoMappings, [proto, thisIdMapping]);
					if (name) thisReflectApply(thisMapSet, protoName, [proto, name]);
				}
				return thisProxyOther(factory, object, proto);
			}]);
	}

	const result = {
		__proto__: null,
		globalPrototypes: thisGlobalPrototypes,
		safeGetOwnPropertyDescriptor: thisSafeGetOwnPropertyDescriptor,
		fromArguments: thisFromOtherArguments,
		from: thisFromOther,
		fromWithFactory: thisFromOtherWithFactory,
		ensureThis: thisEnsureThis,
		mapping: mappingOtherToThis,
		connect: thisConnect,
		reflectSet: thisReflectSet,
		reflectGet: thisReflectGet,
		reflectDefineProperty: thisReflectDefineProperty,
		reflectDeleteProperty: thisReflectDeleteProperty,
		reflectApply: thisReflectApply,
		reflectConstruct: thisReflectConstruct,
		reflectHas: thisReflectHas,
		reflectOwnKeys: thisReflectOwnKeys,
		reflectEnumerate: thisReflectEnumerate,
		reflectGetPrototypeOf: thisReflectGetPrototypeOf,
		reflectIsExtensible: thisReflectIsExtensible,
		reflectPreventExtensions: thisReflectPreventExtensions,
		objectHasOwnProperty: thisObjectHasOwnProperty,
		weakMapSet: thisWeakMapSet,
		addProtoMapping: thisAddProtoMapping,
		addProtoMappingFactory: thisAddProtoMappingFactory,
		defaultFactory,
		protectedFactory,
		readonlyFactory,
		VMError
	};

	const isHost = typeof otherInit !== 'object';

	if (isHost) {
		otherInit = otherInit(result, registerProxy);
	}

	result.other = otherInit;

	const {
		globalPrototypes: otherGlobalPrototypes,
		safeGetOwnPropertyDescriptor: otherSafeGetOwnPropertyDescriptor,
		fromArguments: otherFromThisArguments,
		from: otherFromThis,
		mapping: mappingThisToOther,
		reflectSet: otherReflectSet,
		reflectGet: otherReflectGet,
		reflectDefineProperty: otherReflectDefineProperty,
		reflectDeleteProperty: otherReflectDeleteProperty,
		reflectApply: otherReflectApply,
		reflectConstruct: otherReflectConstruct,
		reflectHas: otherReflectHas,
		reflectOwnKeys: otherReflectOwnKeys,
		reflectEnumerate: otherReflectEnumerate,
		reflectGetPrototypeOf: otherReflectGetPrototypeOf,
		reflectIsExtensible: otherReflectIsExtensible,
		reflectPreventExtensions: otherReflectPreventExtensions,
		objectHasOwnProperty: otherObjectHasOwnProperty,
		weakMapSet: otherWeakMapSet
	} = otherInit;

	function thisOtherHasOwnProperty(object, key) {
		// Note: object@other(safe) key@prim throws@this(unsafe)
		try {
			return otherReflectApply(otherObjectHasOwnProperty, object, [key]) === true;
		} catch (e) { // @other(unsafe)
			throw thisFromOtherForThrow(e);
		}
	}

	function thisDefaultGet(handler, object, key, desc) {
		// Note: object@other(unsafe) key@prim desc@other(safe)
		let ret; // @other(unsafe)
		if (desc.get || desc.set) {
			const getter = desc.get;
			if (!getter) return undefined;
			try {
				ret = otherReflectApply(getter, object, [key]);
			} catch (e) {
				throw thisFromOtherForThrow(e);
			}
		} else {
			ret = desc.value;
		}
		return handler.fromOtherWithContext(ret);
	}

	function otherFromThisIfAvailable(to, from, key) {
		// Note: to@other(safe) from@this(safe) key@prim throws@this(unsafe)
		if (!thisReflectApply(thisObjectHasOwnProperty, from, [key])) return false;
		try {
			to[key] = otherFromThis(from[key]);
		} catch (e) { // @other(unsafe)
			throw thisFromOtherForThrow(e);
		}
		return true;
	}

	class BaseHandler extends SafeBase {

		constructor(object) {
			// Note: object@other(unsafe) throws@this(unsafe)
			super();
			this.objectWrapper = () => object;
		}

		getObject() {
			return this.objectWrapper();
		}

		getFactory() {
			return defaultFactory;
		}

		fromOtherWithContext(other) {
			// Note: other@other(unsafe) throws@this(unsafe)
			return thisFromOtherWithFactory(this.getFactory(), other);
		}

		doPreventExtensions(target, object, factory) {
			// Note: target@this(unsafe) object@other(unsafe) throws@this(unsafe)
			let keys; // @other(safe-array-of-prim)
			try {
				keys = otherReflectOwnKeys(object);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			for (let i = 0; i < keys.length; i++) {
				const key = keys[i]; // @prim
				let desc;
				try {
					desc = otherSafeGetOwnPropertyDescriptor(object, key);
				} catch (e) { // @other(unsafe)
					throw thisFromOtherForThrow(e);
				}
				if (!desc) continue;
				if (!desc.configurable) {
					const current = thisSafeGetOwnPropertyDescriptor(target, key);
					if (current && !current.configurable) continue;
					if (desc.get || desc.set) {
						desc.get = this.fromOtherWithContext(desc.get);
						desc.set = this.fromOtherWithContext(desc.set);
					} else if (typeof object === 'function' && (key === 'caller' || key === 'callee' || key === 'arguments')) {
						desc.value = null;
					} else {
						desc.value = this.fromOtherWithContext(desc.value);
					}
				} else {
					if (desc.get || desc.set) {
						desc = {
							__proto__: null,
							configurable: true,
							enumerable: desc.enumerable,
							writable: true,
							value: null
						};
					} else {
						desc.value = null;
					}
				}
				if (!thisReflectDefineProperty(target, key, desc)) throw thisUnexpected();
			}
			if (!thisReflectPreventExtensions(target)) throw thisUnexpected();
		}

		get(target, key, receiver) {
			// Note: target@this(unsafe) key@prim receiver@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			switch (key) {
				case 'constructor': {
					const desc = otherSafeGetOwnPropertyDescriptor(object, key);
					if (desc) return thisDefaultGet(this, object, key, desc);
					const proto = thisReflectGetPrototypeOf(target);
					return proto === null ? undefined : proto.constructor;
				}
				case '__proto__': {
					const desc = otherSafeGetOwnPropertyDescriptor(object, key);
					if (desc) return thisDefaultGet(this, object, key, desc);
					return thisReflectGetPrototypeOf(target);
				}
				case thisSymbolToStringTag:
					if (!thisOtherHasOwnProperty(object, thisSymbolToStringTag)) {
						const proto = thisReflectGetPrototypeOf(target);
						const name = thisReflectApply(thisMapGet, protoName, [proto]);
						if (name) return name;
					}
					break;
				case 'arguments':
				case 'caller':
				case 'callee':
					if (typeof object === 'function' && thisOtherHasOwnProperty(object, key)) {
						throw thisThrowCallerCalleeArgumentsAccess(key);
					}
					break;
			}
			let ret; // @other(unsafe)
			try {
				ret = otherReflectGet(object, key);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			return this.fromOtherWithContext(ret);
		}

		set(target, key, value, receiver) {
			// Note: target@this(unsafe) key@prim value@this(unsafe) receiver@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			if (key === '__proto__' && !thisOtherHasOwnProperty(object, key)) {
				return this.setPrototypeOf(target, value);
			}
			try {
				value = otherFromThis(value);
				return otherReflectSet(object, key, value) === true;
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
		}

		getPrototypeOf(target) {
			// Note: target@this(unsafe)
			return thisReflectGetPrototypeOf(target);
		}

		setPrototypeOf(target, value) {
			// Note: target@this(unsafe) throws@this(unsafe)
			throw new VMError(OPNA);
		}

		apply(target, context, args) {
			// Note: target@this(unsafe) context@this(unsafe) args@this(safe-array) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			let ret; // @other(unsafe)
			try {
				context = otherFromThis(context);
				args = otherFromThisArguments(args);
				ret = otherReflectApply(object, context, args);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			return thisFromOther(ret);
		}

		construct(target, args, newTarget) {
			// Note: target@this(unsafe) args@this(safe-array) newTarget@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			let ret; // @other(unsafe)
			try {
				args = otherFromThisArguments(args);
				ret = otherReflectConstruct(object, args);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			return thisFromOtherWithFactory(this.getFactory(), ret, thisFromOther(object));
		}

		getOwnPropertyDescriptorDesc(target, prop, desc) {
			// Note: target@this(unsafe) prop@prim desc@other{safe} throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			if (desc && typeof object === 'function' && (prop === 'arguments' || prop === 'caller' || prop === 'callee')) desc.value = null;
			return desc;
		}

		getOwnPropertyDescriptor(target, prop) {
			// Note: target@this(unsafe) prop@prim throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			let desc; // @other(safe)
			try {
				desc = otherSafeGetOwnPropertyDescriptor(object, prop);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}

			desc = this.getOwnPropertyDescriptorDesc(target, prop, desc);

			if (!desc) return undefined;

			let thisDesc;
			if (desc.get || desc.set) {
				thisDesc = {
					__proto__: null,
					get: this.fromOtherWithContext(desc.get),
					set: this.fromOtherWithContext(desc.set),
					enumerable: desc.enumerable === true,
					configurable: desc.configurable === true
				};
			} else {
				thisDesc = {
					__proto__: null,
					value: this.fromOtherWithContext(desc.value),
					writable: desc.writable === true,
					enumerable: desc.enumerable === true,
					configurable: desc.configurable === true
				};
			}
			if (!thisDesc.configurable) {
				const oldDesc = thisSafeGetOwnPropertyDescriptor(target, prop);
				if (!oldDesc || oldDesc.configurable || oldDesc.writable !== thisDesc.writable) {
					if (!thisReflectDefineProperty(target, prop, thisDesc)) throw thisUnexpected();
				}
			}
			return thisDesc;
		}

		definePropertyDesc(target, prop, desc) {
			// Note: target@this(unsafe) prop@prim desc@this(safe) throws@this(unsafe)
			return desc;
		}

		defineProperty(target, prop, desc) {
			// Note: target@this(unsafe) prop@prim desc@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			if (!thisReflectSetPrototypeOf(desc, null)) throw thisUnexpected();

			desc = this.definePropertyDesc(target, prop, desc);

			if (!desc) return false;

			let otherDesc = {__proto__: null};
			let hasFunc = true;
			let hasValue = true;
			let hasBasic = true;
			hasFunc &= otherFromThisIfAvailable(otherDesc, desc, 'get');
			hasFunc &= otherFromThisIfAvailable(otherDesc, desc, 'set');
			hasValue &= otherFromThisIfAvailable(otherDesc, desc, 'value');
			hasValue &= otherFromThisIfAvailable(otherDesc, desc, 'writable');
			hasBasic &= otherFromThisIfAvailable(otherDesc, desc, 'enumerable');
			hasBasic &= otherFromThisIfAvailable(otherDesc, desc, 'configurable');

			try {
				if (!otherReflectDefineProperty(object, prop, otherDesc)) return false;
				if (otherDesc.configurable !== true && (!hasBasic || !(hasFunc || hasValue))) {
					otherDesc = otherSafeGetOwnPropertyDescriptor(object, prop);
				}
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}

			if (!otherDesc.configurable) {
				let thisDesc;
				if (otherDesc.get || otherDesc.set) {
					thisDesc = {
						__proto__: null,
						get: this.fromOtherWithContext(otherDesc.get),
						set: this.fromOtherWithContext(otherDesc.set),
						enumerable: otherDesc.enumerable,
						configurable: otherDesc.configurable
					};
				} else {
					thisDesc = {
						__proto__: null,
						value: this.fromOtherWithContext(otherDesc.value),
						writable: otherDesc.writable,
						enumerable: otherDesc.enumerable,
						configurable: otherDesc.configurable
					};
				}
				if (!thisReflectDefineProperty(target, prop, thisDesc)) throw thisUnexpected();
			}
			return true;
		}

		deleteProperty(target, prop) {
			// Note: target@this(unsafe) prop@prim throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			try {
				return otherReflectDeleteProperty(object, prop) === true;
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
		}

		has(target, key) {
			// Note: target@this(unsafe) key@prim throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			try {
				return otherReflectHas(object, key) === true;
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
		}

		isExtensible(target) {
			// Note: target@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			try {
				if (otherReflectIsExtensible(object)) return true;
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			if (thisReflectIsExtensible(target)) {
				this.doPreventExtensions(target, object, this);
			}
			return false;
		}

		ownKeys(target) {
			// Note: target@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			let res; // @other(unsafe)
			try {
				res = otherReflectOwnKeys(object);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			return thisFromOther(res);
		}

		preventExtensions(target) {
			// Note: target@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			try {
				if (!otherReflectPreventExtensions(object)) return false;
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			if (thisReflectIsExtensible(target)) {
				this.doPreventExtensions(target, object, this);
			}
			return true;
		}

		enumerate(target) {
			// Note: target@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			let res; // @other(unsafe)
			try {
				res = otherReflectEnumerate(object);
			} catch (e) { // @other(unsafe)
				throw thisFromOtherForThrow(e);
			}
			return this.fromOtherWithContext(res);
		}

	}

	BaseHandler.prototype[thisSymbolNodeJSUtilInspectCustom] = undefined;
	BaseHandler.prototype[thisSymbolToStringTag] = 'VM2 Wrapper';
	BaseHandler.prototype[thisSymbolIterator] = undefined;

	function defaultFactory(object) {
		// Note: other@other(unsafe) returns@this(unsafe) throws@this(unsafe)
		return new BaseHandler(object);
	}

	class ProtectedHandler extends BaseHandler {

		getFactory() {
			return protectedFactory;
		}

		set(target, key, value, receiver) {
			// Note: target@this(unsafe) key@prim value@this(unsafe) receiver@this(unsafe) throws@this(unsafe)
			if (typeof value === 'function') {
				return thisReflectDefineProperty(receiver, key, {
					__proto__: null,
					value: value,
					writable: true,
					enumerable: true,
					configurable: true
				}) === true;
			}
			return super.set(target, key, value, receiver);
		}

		definePropertyDesc(target, prop, desc) {
			// Note: target@this(unsafe) prop@prim desc@this(safe) throws@this(unsafe)
			if (desc && (desc.set || desc.get || typeof desc.value === 'function')) return undefined;
			return desc;
		}

	}

	function protectedFactory(object) {
		// Note: other@other(unsafe) returns@this(unsafe) throws@this(unsafe)
		return new ProtectedHandler(object);
	}

	class ReadOnlyHandler extends BaseHandler {

		getFactory() {
			return readonlyFactory;
		}

		set(target, key, value, receiver) {
			// Note: target@this(unsafe) key@prim value@this(unsafe) receiver@this(unsafe) throws@this(unsafe)
			return thisReflectDefineProperty(receiver, key, {
				__proto__: null,
				value: value,
				writable: true,
				enumerable: true,
				configurable: true
			});
		}

		setPrototypeOf(target, value) {
			// Note: target@this(unsafe) throws@this(unsafe)
			return false;
		}

		defineProperty(target, prop, desc) {
			// Note: target@this(unsafe) prop@prim desc@this(unsafe) throws@this(unsafe)
			return false;
		}

		deleteProperty(target, prop) {
			// Note: target@this(unsafe) prop@prim throws@this(unsafe)
			return false;
		}

		isExtensible(target) {
			// Note: target@this(unsafe) throws@this(unsafe)
			return false;
		}

		preventExtensions(target) {
			// Note: target@this(unsafe) throws@this(unsafe)
			return false;
		}

	}

	function readonlyFactory(object) {
		// Note: other@other(unsafe) returns@this(unsafe) throws@this(unsafe)
		return new ReadOnlyHandler(object);
	}

	class ReadOnlyMockHandler extends ReadOnlyHandler {

		constructor(object, mock) {
			// Note: object@other(unsafe) mock:this(unsafe) throws@this(unsafe)
			super(object);
			this.mock = mock;
		}

		get(target, key, receiver) {
			// Note: target@this(unsafe) key@prim receiver@this(unsafe) throws@this(unsafe)
			const object = this.getObject(); // @other(unsafe)
			const mock = this.mock;
			if (thisReflectApply(thisObjectHasOwnProperty, mock, key) && !thisOtherHasOwnProperty(object, key)) {
				return mock[key];
			}
			return super.get(target, key, receiver);
		}

	}

	function thisFromOther(other) {
		// Note: other@other(unsafe) returns@this(unsafe) throws@this(unsafe)
		return thisFromOtherWithFactory(defaultFactory, other);
	}

	function thisProxyOther(factory, other, proto) {
		const target = thisCreateTargetObject(other, proto);
		const handler = factory(other);
		const proxy = new ThisProxy(target, handler);
		try {
			otherReflectApply(otherWeakMapSet, mappingThisToOther, [proxy, other]);
			registerProxy(proxy, handler);
		} catch (e) {
			throw new VMError('Unexpected error');
		}
		if (!isHost) {
			thisReflectApply(thisWeakMapSet, mappingOtherToThis, [other, proxy]);
			return proxy;
		}
		const proxy2 = new ThisProxy(proxy, emptyForzenObject);
		try {
			otherReflectApply(otherWeakMapSet, mappingThisToOther, [proxy2, other]);
			registerProxy(proxy2, handler);
		} catch (e) {
			throw new VMError('Unexpected error');
		}
		thisReflectApply(thisWeakMapSet, mappingOtherToThis, [other, proxy2]);
		return proxy2;
	}

	function thisEnsureThis(other) {
		const type = typeof other;
		switch (type) {
			case 'object':
				if (other === null) {
					return null;
				}
				// fallthrough
			case 'function':
				let proto = thisReflectGetPrototypeOf(other);
				if (!proto) {
					return other;
				}
				while (proto) {
					const mapping = thisReflectApply(thisMapGet, protoMappings, [proto]);
					if (mapping) {
						const mapped = thisReflectApply(thisWeakMapGet, mappingOtherToThis, [other]);
						if (mapped) return mapped;
						return mapping(defaultFactory, other);
					}
					proto = thisReflectGetPrototypeOf(proto);
				}
				return other;
			case 'undefined':
			case 'string':
			case 'number':
			case 'boolean':
			case 'symbol':
			case 'bigint':
				return other;

			default: // new, unknown types can be dangerous
				throw new VMError(`Unknown type '${type}'`);
		}
	}

	function thisFromOtherForThrow(other) {
		for (let loop = 0; loop < 10; loop++) {
			const type = typeof other;
			switch (type) {
				case 'object':
					if (other === null) {
						return null;
					}
					// fallthrough
				case 'function':
					const mapped = thisReflectApply(thisWeakMapGet, mappingOtherToThis, [other]);
					if (mapped) return mapped;
					let proto;
					try {
						proto = otherReflectGetPrototypeOf(other);
					} catch (e) { // @other(unsafe)
						other = e;
						break;
					}
					if (!proto) {
						return thisProxyOther(defaultFactory, other, null);
					}
					for (;;) {
						const mapping = thisReflectApply(thisMapGet, protoMappings, [proto]);
						if (mapping) return mapping(defaultFactory, other);
						try {
							proto = otherReflectGetPrototypeOf(proto);
						} catch (e) { // @other(unsafe)
							other = e;
							break;
						}
						if (!proto) return thisProxyOther(defaultFactory, other, thisObjectPrototype);
					}
					break;
				case 'undefined':
				case 'string':
				case 'number':
				case 'boolean':
				case 'symbol':
				case 'bigint':
					return other;

				default: // new, unknown types can be dangerous
					throw new VMError(`Unknown type '${type}'`);
			}
		}
		throw new VMError('Exception recursion depth');
	}

	function thisFromOtherWithFactory(factory, other, proto) {
		const type = typeof other;
		switch (type) {
			case 'object':
				if (other === null) {
					return null;
				}
				// fallthrough
			case 'function':
				const mapped = thisReflectApply(thisWeakMapGet, mappingOtherToThis, [other]);
				if (mapped) return mapped;
				if (proto) {
					return thisProxyOther(factory, other, proto);
				}
				try {
					proto = otherReflectGetPrototypeOf(other);
				} catch (e) { // @other(unsafe)
					throw thisFromOtherForThrow(e);
				}
				if (!proto) {
					return thisProxyOther(factory, other, null);
				}
				do {
					const mapping = thisReflectApply(thisMapGet, protoMappings, [proto]);
					if (mapping) return mapping(factory, other);
					try {
						proto = otherReflectGetPrototypeOf(proto);
					} catch (e) { // @other(unsafe)
						throw thisFromOtherForThrow(e);
					}
				} while (proto);
				return thisProxyOther(factory, other, thisObjectPrototype);
			case 'undefined':
			case 'string':
			case 'number':
			case 'boolean':
			case 'symbol':
			case 'bigint':
				return other;

			default: // new, unknown types can be dangerous
				throw new VMError(`Unknown type '${type}'`);
		}
	}

	function thisFromOtherArguments(args) {
		// Note: args@other(safe-array) returns@this(safe-array) throws@this(unsafe)
		const arr = [];
		for (let i = 0; i < args.length; i++) {
			const value = thisFromOther(args[i]);
			thisReflectDefineProperty(arr, i, {
				__proto__: null,
				value: value,
				writable: true,
				enumerable: true,
				configurable: true
			});
		}
		return arr;
	}

	function thisConnect(obj, other) {
		// Note: obj@this(unsafe) other@other(unsafe) throws@this(unsafe)
		try {
			otherReflectApply(otherWeakMapSet, mappingThisToOther, [obj, other]);
		} catch (e) {
			throw new VMError('Unexpected error');
		}
		thisReflectApply(thisWeakMapSet, mappingOtherToThis, [other, obj]);
	}

	thisAddProtoMapping(thisGlobalPrototypes.Object, otherGlobalPrototypes.Object);
	thisAddProtoMapping(thisGlobalPrototypes.Array, otherGlobalPrototypes.Array);

	for (let i = 0; i < globalsList.length; i++) {
		const key = globalsList[i];
		const tp = thisGlobalPrototypes[key];
		const op = otherGlobalPrototypes[key];
		if (tp && op) thisAddProtoMapping(tp, op, key);
	}

	for (let i = 0; i < errorsList.length; i++) {
		const key = errorsList[i];
		const tp = thisGlobalPrototypes[key];
		const op = otherGlobalPrototypes[key];
		if (tp && op) thisAddProtoMapping(tp, op, 'Error');
	}

	thisAddProtoMapping(thisGlobalPrototypes.VMError, otherGlobalPrototypes.VMError, 'Error');

	result.BaseHandler = BaseHandler;
	result.ProtectedHandler = ProtectedHandler;
	result.ReadOnlyHandler = ReadOnlyHandler;
	result.ReadOnlyMockHandler = ReadOnlyMockHandler;

	return result;
}

exports.createBridge = createBridge;
exports.VMError = VMError;