sset($this->registered[$handle]) )
				$keep_going = false; // Item doesn't exist.
			elseif ( $this->registered[$handle]->deps && array_diff($this->registered[$handle]->deps, array_keys($this->registered)) )
				$keep_going = false; // Item requires dependencies that don't exist.
			elseif ( $this->registered[$handle]->deps && !$this->all_deps( $this->registered[$handle]->deps, true, $new_group ) )
				$keep_going = false; // Item requires dependencies that don't exist.

			if ( ! $keep_going ) { // Either item or its dependencies don't exist.
				if ( $recursion )
					return false; // Abort this branch.
				else
					continue; // We're at the top level. Move on to the next one.
			}

			if ( $queued ) // Already grabbed it and its dependencies.
				continue;

			if ( isset($handle_parts[1]) )
				$this->args[$handle] = $handle_parts[1];

			$this->to_do[] = $handle;
		}

		return true;
	}

	/**
	 * Register an item.
	 *
	 * Registers the item if no item of that name already exists.
	 *
	 * @access public
	 * @since 2.1.0
	 * @since 2.6.0 Moved from `WP_Scripts`.
	 *
	 * @param string           $handle Name of the item. Should be unique.
	 * @param string           $src    Full URL of the item, or path of the item relative to the WordPress root directory.
	 * @param array            $deps   Optional. An array of registered item handles this item depends on. Default empty array.
	 * @param string|bool|null $ver    Optional. String specifying item version number, if it has one, which is added to the URL
	 *                                 as a query string for cache busting purposes. If version is set to false, a version
	 *                                 number is automatically added equal to current installed WordPress version.
	 *                                 If set to null, no version is added.
	 * @param mixed            $args   Optional. Custom property of the item. NOT the class property $args. Examples: $media, $in_footer.
	 * @return bool Whether the item has been registered. True on success, false on failure.
	 */
	public function add( $handle, $src, $deps = array(), $ver = false, $args = null ) {
		if ( isset($this->registered[$handle]) )
			return false;
		$this->registered[$handle] = new _WP_Dependency( $handle, $src, $deps, $ver, $args );
		return true;
	}

	/**
	 * Add extra item data.
	 *
	 * Adds data to a registered item.
	 *
	 * @access public
	 * @since 2.6.0
	 *
	 * @param string $handle Name of the item. Should be unique.
	 * @param string $key    The data key.
	 * @param mixed  $value  The data value.
	 * @return bool True on success, false on failure.
	 */
	public function add_data( $handle, $key, $value ) {
		if ( !isset( $this->registered[$handle] ) )
			return false;

		return $this->registered[$handle]->add_data( $key, $value );
	}

	/**
	 * Get extra item data.
	 *
	 * Gets data associated with a registered item.
	 *
	 * @access public
	 * @since 3.3.0
	 *
	 * @param string $handle Name of the item. Should be unique.
	 * @param string $key    The data key.
	 * @return mixed Extra item data (string), false otherwise.
	 */
	public function get_data( $handle, $key ) {
		if ( !isset( $this->registered[$handle] ) )
			return false;

		if ( !isset( $this->registered[$handle]->extra[$key] ) )
			return false;

		return $this->registered[$handle]->extra[$key];
	}

	/**
	 * Un-register an item or items.
	 *
	 * @access public
	 * @since 2.1.0
	 * @since 2.6.0 Moved from `WP_Scripts`.
	 *
	 * @param mixed $handles Item handle and argument (string) or item handles and arguments (array of strings).
	 * @return void
	 */
	public function remove( $handles ) {
		foreach ( (array) $handles as $handle )
			unset($this->registered[$handle]);
	}

	/**
	 * Queue an item or items.
	 *
	 * Decodes handles and arguments, then queues handles and stores
	 * arguments in the class property $args. For example in extending
	 * classes, $args is appended to the item url as a query string.
	 * Note $args is NOT the $args property of items in the $registered array.
	 *
	 * @access public
	 * @since 2.1.0
	 * @since 2.6.0 Moved from `WP_Scripts`.
	 *
	 * @param mixed $handles Item handle and argument (string) or item handles and arguments (array of strings).
	 */
	public function enqueue( $handles ) {
		foreach ( (array) $handles as $handle ) {
			$handle = explode('?', $handle);
			if ( !in_array($handle[0], $this->queue) && isset($this->registered[$handle[0]]) ) {
				$this->queue[] = $handle[0];
				if ( isset($handle[1]) )
					$this->args[$handle[0]] = $handle[1];
			}
		}
	}

	/**
	 * Dequeue an item or items.
	 *
	 * Decodes handles and arguments, then dequeues handles
	 * and removes arguments from the class property $args.
	 *
	 * @access public
	 * @since 2.1.0
	 * @since 2.6.0 Moved from `WP_Scripts`.
	 *
	 * @param mixed $handles Item handle and argument (string) or item handles and arguments (array of strings).
	 */
	public function dequeue( $handles ) {
		foreach ( (array) $handles as $handle ) {
			$handle = explode('?', $handle);
			$key = array_search($handle[0], $this->queue);
			if ( false !== $key ) {
				unset($this->queue[$key]);
				unset($this->args[$handle[0]]);
			}
		}
	}

	/**
	 * Recursively search the passed dependency tree for $handle
	 *
	 * @since 4.0.0
	 *
	 * @param array  $queue  An array of queued _WP_Dependency handle objects.
	 * @param string $handle Name of the item. Should be unique.
	 * @return bool Whether the handle is found after recursively searching the dependency tree.
	 */
	protected function recurse_deps( $queue, $handle ) {
		foreach ( $queue as $queued ) {
			if ( ! isset( $this->registered[ $queued ] ) ) {
				continue;
			}

			if ( in_array( $handle, $this->registered[ $queued ]->deps ) ) {
				return true;
			} elseif ( $this->recurse_deps( $this->registered[ $queued ]->deps, $handle ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Query list for an item.
	 *
	 * @access public
	 * @since 2.1.0
	 * @since 2.6.0 Moved from `WP_Scripts`.
	 *
	 * @param string $handle Name of the item. Should be unique.
	 * @param string $list   Property name of list array.
	 * @return bool|_WP_Dependency Found, or object Item data.
	 */
	public function query( $handle, $list = 'registered' ) {
		switch ( $list ) {
			case 'registered' :
			case 'scripts': // back compat
				if ( isset( $this->registered[ $handle ] ) )
					return $this->registered[ $handle ];
				return false;

			case 'enqueued' :
			case 'queue' :
				if ( in_array( $handle, $this->queue ) ) {
					return true;
				}
				return $this->recurse_deps( $this->queue, $handle );

			case 'to_do' :
			case 'to_print': // back compat
				return in_array( $handle, $this->to_do );

			case 'done' :
			case 'printed': // back compat
				return in_array( $handle, $this->done );
		}
		return false;
	}

	/**
	 * Set item group, unless already in a lower group.
	 *
	 * @access public
	 * @since 2.8.0
	 *
	 * @param string $handle    Name of the item. Should be unique.
	 * @param bool   $recursion Internal flag that calling function was called recursively.
	 * @param mixed  $group     Group level.
	 * @return bool Not already in the group or a lower group
	 */
	public function set_group( $handle, $recursion, $group ) {
		$group = (int) $group;

		if ( isset( $this->groups[ $handle ] ) && $this->groups[ $handle ] <= $group ) {
			return false;
		}

		$this->groups[ $handle ] = $group;

		return true;
	}

}