masteringModule/node_modules/side-channel/index.js

'use strict';

var GetIntrinsic = require('get-intrinsic');
var callBound = require('call-bind/callBound');
var inspect = require('object-inspect');

var $TypeError = GetIntrinsic('%TypeError%');
var $WeakMap = GetIntrinsic('%WeakMap%', true);
var $Map = GetIntrinsic('%Map%', true);

var $weakMapGet = callBound('WeakMap.prototype.get', true);
var $weakMapSet = callBound('WeakMap.prototype.set', true);
var $weakMapHas = callBound('WeakMap.prototype.has', true);
var $mapGet = callBound('Map.prototype.get', true);
var $mapSet = callBound('Map.prototype.set', true);
var $mapHas = callBound('Map.prototype.has', true);

/*
 * This function traverses the list returning the node corresponding to the
 * given key.
 *
 * That node is also moved to the head of the list, so that if it's accessed
 * again we don't need to traverse the whole list. By doing so, all the recently
 * used nodes can be accessed relatively quickly.
 */
var listGetNode = function (list, key) { // eslint-disable-line consistent-return
	for (var prev = list, curr; (curr = prev.next) !== null; prev = curr) {
		if (curr.key === key) {
			prev.next = curr.next;
			curr.next = list.next;
			list.next = curr; // eslint-disable-line no-param-reassign
			return curr;
		}
	}
};

var listGet = function (objects, key) {
	var node = listGetNode(objects, key);
	return node && node.value;
};
var listSet = function (objects, key, value) {
	var node = listGetNode(objects, key);
	if (node) {
		node.value = value;
	} else {
		// Prepend the new node to the beginning of the list
		objects.next = { // eslint-disable-line no-param-reassign
			key: key,
			next: objects.next,
			value: value
		};
	}
};
var listHas = function (objects, key) {
	return !!listGetNode(objects, key);
};

module.exports = function getSideChannel() {
	var $wm;
	var $m;
	var $o;
	var channel = {
		assert: function (key) {
			if (!channel.has(key)) {
				throw new $TypeError('Side channel does not contain ' + inspect(key));
			}
		},
		get: function (key) { // eslint-disable-line consistent-return
			if ($WeakMap && key && (typeof key === 'object' || typeof key === 'function')) {
				if ($wm) {
					return $weakMapGet($wm, key);
				}
			} else if ($Map) {
				if ($m) {
					return $mapGet($m, key);
				}
			} else {
				if ($o) { // eslint-disable-line no-lonely-if
					return listGet($o, key);
				}
			}
		},
		has: function (key) {
			if ($WeakMap && key && (typeof key === 'object' || typeof key === 'function')) {
				if ($wm) {
					return $weakMapHas($wm, key);
				}
			} else if ($Map) {
				if ($m) {
					return $mapHas($m, key);
				}
			} else {
				if ($o) { // eslint-disable-line no-lonely-if
					return listHas($o, key);
				}
			}
			return false;
		},
		set: function (key, value) {
			if ($WeakMap && key && (typeof key === 'object' || typeof key === 'function')) {
				if (!$wm) {
					$wm = new $WeakMap();
				}
				$weakMapSet($wm, key, value);
			} else if ($Map) {
				if (!$m) {
					$m = new $Map();
				}
				$mapSet($m, key, value);
			} else {
				if (!$o) {
					/*
					 * Initialize the linked list as an empty node, so that we don't have
					 * to special-case handling of the first node: we can always refer to
					 * it as (previous node).next, instead of something like (list).head
					 */
					$o = { key: {}, next: null };
				}
				listSet($o, key, value);
			}
		}
	};
	return channel;
};