'use strict';

var d              = require('d')
  , validateSymbol = require('./validate-symbol')

  , create = Object.create, defineProperties = Object.defineProperties
  , defineProperty = Object.defineProperty, objPrototype = Object.prototype
  , NativeSymbol, SymbolPolyfill, HiddenSymbol, globalSymbols = create(null);

if (typeof Symbol === 'function') NativeSymbol = Symbol;

var generateName = (function () {
	var created = create(null);
	return function (desc) {
		var postfix = 0, name;
		while (created[desc + (postfix || '')]) ++postfix;
		desc += (postfix || '');
		created[desc] = true;
		name = '@@' + desc;
		defineProperty(objPrototype, name, d.gs(null, function (value) {
			defineProperty(this, name, d(value));
		}));
		return name;
	};
}());

HiddenSymbol = function Symbol(description) {
	if (this instanceof HiddenSymbol) throw new TypeError('TypeError: Symbol is not a constructor');
	return SymbolPolyfill(description);
};
module.exports = SymbolPolyfill = function Symbol(description) {
	var symbol;
	if (this instanceof Symbol) throw new TypeError('TypeError: Symbol is not a constructor');
	symbol = create(HiddenSymbol.prototype);
	description = (description === undefined ? '' : String(description));
	return defineProperties(symbol, {
		__description__: d('', description),
		__name__: d('', generateName(description))
	});
};
defineProperties(SymbolPolyfill, {
	for: d(function (key) {
		if (globalSymbols[key]) return globalSymbols[key];
		return (globalSymbols[key] = SymbolPolyfill(String(key)));
	}),
	keyFor: d(function (s) {
		var key;
		validateSymbol(s);
		for (key in globalSymbols) if (globalSymbols[key] === s) return key;
	}),
	hasInstance: d('', (NativeSymbol && NativeSymbol.hasInstance) || SymbolPolyfill('hasInstance')),
	isConcatSpreadable: d('', (NativeSymbol && NativeSymbol.isConcatSpreadable) ||
		SymbolPolyfill('isConcatSpreadable')),
	iterator: d('', (NativeSymbol && NativeSymbol.iterator) || SymbolPolyfill('iterator')),
	match: d('', (NativeSymbol && NativeSymbol.match) || SymbolPolyfill('match')),
	replace: d('', (NativeSymbol && NativeSymbol.replace) || SymbolPolyfill('replace')),
	search: d('', (NativeSymbol && NativeSymbol.search) || SymbolPolyfill('search')),
	species: d('', (NativeSymbol && NativeSymbol.species) || SymbolPolyfill('species')),
	split: d('', (NativeSymbol && NativeSymbol.split) || SymbolPolyfill('split')),
	toPrimitive: d('', (NativeSymbol && NativeSymbol.toPrimitive) || SymbolPolyfill('toPrimitive')),
	toStringTag: d('', (NativeSymbol && NativeSymbol.toStringTag) || SymbolPolyfill('toStringTag')),
	unscopables: d('', (NativeSymbol && NativeSymbol.unscopables) || SymbolPolyfill('unscopables'))
});
defineProperties(HiddenSymbol.prototype, {
	constructor: d(SymbolPolyfill),
	toString: d('', function () { return this.__name__; })
});

defineProperties(SymbolPolyfill.prototype, {
	toString: d(function () { return 'Symbol (' + validateSymbol(this).__description__ + ')'; }),
	valueOf: d(function () { return validateSymbol(this); })
});
defineProperty(SymbolPolyfill.prototype, SymbolPolyfill.toPrimitive, d('',
	function () { return validateSymbol(this); }));
defineProperty(SymbolPolyfill.prototype, SymbolPolyfill.toStringTag, d('c', 'Symbol'));

defineProperty(HiddenSymbol.prototype, SymbolPolyfill.toPrimitive,
	d('c', SymbolPolyfill.prototype[SymbolPolyfill.toPrimitive]));
defineProperty(HiddenSymbol.prototype, SymbolPolyfill.toStringTag,
	d('c', SymbolPolyfill.prototype[SymbolPolyfill.toStringTag]));