var namespace = 'expire_mixin'

module.exports = expirePlugin

function expirePlugin() {
	var expirations = this.createStore(this.storage, null, this._namespacePrefix+namespace)
	
	return {
		set: expire_set,
		get: expire_get,
		remove: expire_remove,
		getExpiration: getExpiration,
		removeExpiredKeys: removeExpiredKeys
	}
	
	function expire_set(super_fn, key, val, expiration) {
		if (!this.hasNamespace(namespace)) {
			expirations.set(key, expiration)
		}
		return super_fn()
	}
	
	function expire_get(super_fn, key) {
		if (!this.hasNamespace(namespace)) {
			_checkExpiration.call(this, key)
		}
		return super_fn()
	}
	
	function expire_remove(super_fn, key) {
		if (!this.hasNamespace(namespace)) {
			expirations.remove(key)
		}
		return super_fn()
	}
	
	function getExpiration(_, key) {
		return expirations.get(key)
	}
	
	function removeExpiredKeys(_) {
		var keys = []
		this.each(function(val, key) {
			keys.push(key)
		})
		for (var i=0; i<keys.length; i++) {
			_checkExpiration.call(this, keys[i])
		}
	}
	
	function _checkExpiration(key) {
		var expiration = expirations.get(key, Number.MAX_VALUE)
		if (expiration <= new Date().getTime()) {
			this.raw.remove(key)
			expirations.remove(key)
		}
	}
	
}