abstract class RecursiveArrayHelper {
	/**
	 * @var string
	 */
	static private $separator='.';
	
	/**
	 * @param array $array
	 * @param string $key
	 * @return bool
	 */
	static public function has(array $array, $key) {
		assert('is_scalar($key)');
		$keyParts = self::getKeyParts($key);
		return self::hasKeyParts($array, $keyParts);
	}
	
	/**
	 * @param array $array
	 * @param string $key
	 * @param mixed $default
	 * @return mixed
	 */
	static public function get(array $array, $key, $default=null) {
		assert('is_scalar($key)');
		$keyParts = self::getKeyParts($key);
		return self::getByKeyParts($array, $keyParts, $default);
	}
	
	/**
	 * @param array $array
	 * @param string $key
	 * @param mixed $value
	 * @return array
	 */
	static public function set(array $array, $key, $value) {
		assert('is_scalar($key)');
		$keyParts = self::getKeyParts($key);
		$array = self::setByKeyParts($array, $keyParts, $value);
		return $array;
	}
	
	/**
	 * @return string
	 */
	static public function getSeparator() {
		return self::$separator;
	}
	
	/**
	 * @param string $separator
	 * @return void
	 */
	static public function setSeparator($separator) {
		assert('is_string($key) && strlen($separator)>0');
		self::$separator = $separator;
	}
	
	/**
	 * @param array $array
	 * @param array $keyParts
	 * @return bool
	 */
	static private function hasKeyParts(array $array, array $keyParts) {
		$currentKey = array_shift($keyParts);
		if(array_key_exists($currentKey, $array)) {
			if(!count($keyParts)) {
				return true;
			} else {
				return self::hasKeyParts($array[$currentKey], $keyParts);
			}
		}
		return false;
	}
	
	/**
	 * @param array $array
	 * @param array $keyParts
	 * @param mixed $default
	 * @return mixed
	 */
	static private function getByKeyParts(array $array, array $keyParts, $default) {
		$currentKey = array_shift($keyParts);
		if(array_key_exists($currentKey, $array)) {
			if(!count($keyParts)) {
				return $array[$currentKey];
			} else {
				return self::getByKeyParts($array[$currentKey], $keyParts, $default);
			}
		}
		return $default;
	}
	
	/**
	 * @param array $array
	 * @param array $keyParts
	 * @param mixed $value
	 * @return array
	 */
	static private function setByKeyParts(array $array, array $keyParts, $value) {
		$currentKey = array_shift($keyParts);
		if(!array_key_exists($currentKey, $array)) {
			$array[$currentKey] = array();
		}
		if(!count($keyParts)) {
			$array[$currentKey] = $value;
			return $array;
		}
		$array[$currentKey] = self::setByKeyParts($array[$currentKey], $keyParts, $value);
		return $array;
	}
	
	/**
	 * @param string $key
	 * @return array
	 */
	static private function getKeyParts($key) {
		return explode(self::$separator, $key);
	}
}