les of items that have been processed.
	 */
	public function do_head_items() {
		$this->do_items( false, 0 );
		return $this->done;
	}

	/**
	 * Processes items and dependencies for the footer group.
	 *
	 * @since 2.8.0
	 *
	 * @see WP_Dependencies::do_items()
	 *
	 * @return string[] Handles of items that have been processed.
	 */
	public function do_footer_items() {
		$this->do_items( false, 1 );
		return $this->done;
	}

	/**
	 * Whether a handle's source is in a default directory.
	 *
	 * @since 2.8.0
	 *
	 * @param string $src The source of the enqueued script.
	 * @return bool True if found, false if not.
	 */
	public function in_default_dir( $src ) {
		if ( ! $this->default_dirs ) {
			return true;
		}

		if ( str_starts_with( $src, '/' . WPINC . '/js/l10n' ) ) {
			return false;
		}

		foreach ( (array) $this->default_dirs as $test ) {
			if ( str_starts_with( $src, $test ) ) {
				return true;
			}
		}
		return false;
	}

	/**
	 * This overrides the add_data method from WP_Dependencies, to support normalizing of $args.
	 *
	 * @since 6.3.0
	 *
	 * @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;
		}

		if ( 'strategy' === $key ) {
			if ( ! empty( $value ) && ! $this->is_delayed_strategy( $value ) ) {
				_doing_it_wrong(
					__METHOD__,
					sprintf(
						/* translators: 1: $strategy, 2: $handle */
						__( 'Invalid strategy `%1$s` defined for `%2$s` during script registration.' ),
						$value,
						$handle
					),
					'6.3.0'
				);
				return false;
			} elseif ( ! $this->registered[ $handle ]->src && $this->is_delayed_strategy( $value ) ) {
				_doing_it_wrong(
					__METHOD__,
					sprintf(
						/* translators: 1: $strategy, 2: $handle */
						__( 'Cannot supply a strategy `%1$s` for script `%2$s` because it is an alias (it lacks a `src` value).' ),
						$value,
						$handle
					),
					'6.3.0'
				);
				return false;
			}
		}
		return parent::add_data( $handle, $key, $value );
	}

	/**
	 * Gets all dependents of a script.
	 *
	 * @since 6.3.0
	 *
	 * @param string $handle The script handle.
	 * @return string[] Script handles.
	 */
	private function get_dependents( $handle ) {
		// Check if dependents map for the handle in question is present. If so, use it.
		if ( isset( $this->dependents_map[ $handle ] ) ) {
			return $this->dependents_map[ $handle ];
		}

		$dependents = array();

		// Iterate over all registered scripts, finding dependents of the script passed to this method.
		foreach ( $this->registered as $registered_handle => $args ) {
			if ( in_array( $handle, $args->deps, true ) ) {
				$dependents[] = $registered_handle;
			}
		}

		// Add the handles dependents to the map to ease future lookups.
		$this->dependents_map[ $handle ] = $dependents;

		return $dependents;
	}

	/**
	 * Checks if the strategy passed is a valid delayed (non-blocking) strategy.
	 *
	 * @since 6.3.0
	 *
	 * @param string $strategy The strategy to check.
	 * @return bool True if $strategy is one of the delayed strategies, otherwise false.
	 */
	private function is_delayed_strategy( $strategy ) {
		return in_array(
			$strategy,
			$this->delayed_strategies,
			true
		);
	}

	/**
	 * Gets the best eligible loading strategy for a script.
	 *
	 * @since 6.3.0
	 *
	 * @param string $handle The script handle.
	 * @return string The best eligible loading strategy.
	 */
	private function get_eligible_loading_strategy( $handle ) {
		$intended = (string) $this->get_data( $handle, 'strategy' );

		// Bail early if there is no intended strategy.
		if ( ! $intended ) {
			return '';
		}

		/*
		 * If the intended strategy is 'defer', limit the initial list of eligible
		 * strategies, since 'async' can fallback to 'defer', but not vice-versa.
		 */
		$initial = ( 'defer' === $intended ) ? array( 'defer' ) : null;

		$eligible = $this->filter_eligible_strategies( $handle, $initial );

		// Return early once we know the eligible strategy is blocking.
		if ( empty( $eligible ) ) {
			return '';
		}

		return in_array( 'async', $eligible, true ) ? 'async' : 'defer';
	}

	/**
	 * Filter the list of eligible loading strategies for a script.
	 *
	 * @since 6.3.0
	 *
	 * @param string              $handle   The script handle.
	 * @param string[]|null       $eligible Optional. The list of strategies to filter. Default null.
	 * @param array<string, true> $checked  Optional. An array of already checked script handles, used to avoid recursive loops.
	 * @return string[] A list of eligible loading strategies that could be used.
	 */
	private function filter_eligible_strategies( $handle, $eligible = null, $checked = array() ) {
		// If no strategies are being passed, all strategies are eligible.
		if ( null === $eligible ) {
			$eligible = $this->delayed_strategies;
		}

		// If this handle was already checked, return early.
		if ( isset( $checked[ $handle ] ) ) {
			return $eligible;
		}

		// Mark this handle as checked.
		$checked[ $handle ] = true;

		// If this handle isn't registered, don't filter anything and return.
		if ( ! isset( $this->registered[ $handle ] ) ) {
			return $eligible;
		}

		// If the handle is not enqueued, don't filter anything and return.
		if ( ! $this->query( $handle, 'enqueued' ) ) {
			return $eligible;
		}

		$is_alias          = (bool) ! $this->registered[ $handle ]->src;
		$intended_strategy = $this->get_data( $handle, 'strategy' );

		// For non-alias handles, an empty intended strategy filters all strategies.
		if ( ! $is_alias && empty( $intended_strategy ) ) {
			return array();
		}

		// Handles with inline scripts attached in the 'after' position cannot be delayed.
		if ( $this->has_inline_script( $handle, 'after' ) ) {
			return array();
		}

		// If the intended strategy is 'defer', filter out 'async'.
		if ( 'defer' === $intended_strategy ) {
			$eligible = array( 'defer' );
		}

		$dependents = $this->get_dependents( $handle );

		// Recursively filter eligible strategies for dependents.
		foreach ( $dependents as $dependent ) {
			// Bail early once we know the eligible strategy is blocking.
			if ( empty( $eligible ) ) {
				return array();
			}

			$eligible = $this->filter_eligible_strategies( $dependent, $eligible, $checked );
		}

		return $eligible;
	}

	/**
	 * Gets data for inline scripts registered for a specific handle.
	 *
	 * @since 6.3.0
	 *
	 * @param string $handle   Name of the script to get data for. Must be lowercase.
	 * @param string $position The position of the inline script.
	 * @return bool Whether the handle has an inline script (either before or after).
	 */
	private function has_inline_script( $handle, $position = null ) {
		if ( $position && in_array( $position, array( 'before', 'after' ), true ) ) {
			return (bool) $this->get_data( $handle, $position );
		}

		return (bool) ( $this->get_data( $handle, 'before' ) || $this->get_data( $handle, 'after' ) );
	}

	/**
	 * Resets class properties.
	 *
	 * @since 2.8.0
	 */
	public function reset() {
		$this->do_concat      = false;
		$this->print_code     = '';
		$this->concat         = '';
		$this->concat_version = '';
		$this->print_html     = '';
		$this->ext_version    = '';
		$this->ext_handles    = '';
	}
}