ram string $key  The key to check if exists.
	 * @return bool  Whether the key exists in the current data registry.
	 */
	public function exists( $key ) {
		return array_key_exists( $key, $this->data );
	}

	/**
	 * Interface for adding data to the registry.
	 *
	 * You can only register data that is not already in the registry identified by the given key. If there is a
	 * duplicate found, unless $ignore_duplicates is true, an exception will be thrown.
	 *
	 * @param string  $key              The key used to reference the data being registered. This should use camelCase.
	 * @param mixed   $data             If not a function, registered to the registry as is. If a function, then the
	 *                                  callback is invoked right before output to the screen.
	 * @param boolean $check_key_exists If set to true, duplicate data will be ignored if the key exists.
	 *                                  If false, duplicate data will cause an exception.
	 *
	 * @throws InvalidArgumentException  Only throws when site is in debug mode. Always logs the error.
	 */
	public function add( $key, $data, $check_key_exists = false ) {
		if ( $check_key_exists && $this->exists( $key ) ) {
			return;
		}
		try {
			$this->add_data( $key, $data );
		} catch ( Exception $e ) {
			if ( $this->debug() ) {
				// bubble up.
				throw $e;
			}
			wc_caught_exception( $e, __METHOD__, [ $key, $data ] );
		}
	}

	/**
	 * Hydrate from the API.
	 *
	 * @param string $path REST API path to preload.
	 */
	public function hydrate_api_request( $path ) {
		if ( ! isset( $this->preloaded_api_requests[ $path ] ) ) {
			$this->preloaded_api_requests[ $path ] = Package::container()->get( Hydration::class )->get_rest_api_response_data( $path );
		}
	}

	/**
	 * Hydrate some data from the API.
	 *
	 * @param string  $key  The key used to reference the data being registered.
	 * @param string  $path REST API path to preload.
	 * @param boolean $check_key_exists If set to true, duplicate data will be ignored if the key exists.
	 *                                  If false, duplicate data will cause an exception.
	 *
	 * @throws InvalidArgumentException  Only throws when site is in debug mode. Always logs the error.
	 */
	public function hydrate_data_from_api_request( $key, $path, $check_key_exists = false ) {
		$this->add(
			$key,
			function() use ( $path ) {
				if ( isset( $this->preloaded_api_requests[ $path ], $this->preloaded_api_requests[ $path ]['body'] ) ) {
					return $this->preloaded_api_requests[ $path ]['body'];
				}
				$response = Package::container()->get( Hydration::class )->get_rest_api_response_data( $path );
				return $response['body'] ?? '';
			},
			$check_key_exists
		);
	}

	/**
	 * Adds a page permalink to the data registry.
	 *
	 * @param integer $page_id Page ID to add to the registry.
	 */
	public function register_page_id( $page_id ) {
		$permalink = $page_id ? get_permalink( $page_id ) : false;

		if ( $permalink ) {
			$this->data[ 'page-' . $page_id ] = $permalink;
		}
	}

	/**
	 * Callback for registering the data script via WordPress API.
	 *
	 * @return void
	 */
	public function register_data_script() {
		$this->api->register_script(
			$this->handle,
			'assets/client/blocks/wc-settings.js',
			[ 'wp-api-fetch' ],
			true
		);
	}

	/**
	 * Callback for enqueuing asset data via the WP api.
	 *
	 * Note: while this is hooked into print/admin_print_scripts, it still only
	 * happens if the script attached to `wc-settings` handle is enqueued. This
	 * is done to allow for any potentially expensive data generation to only
	 * happen for routes that need it.
	 */
	public function enqueue_asset_data() {
		if ( wp_script_is( $this->handle, 'enqueued' ) ) {
			$this->initialize_core_data();
			$this->execute_lazy_data();

			$data                          = rawurlencode( wp_json_encode( $this->data ) );
			$wc_settings_script            = "var wcSettings = wcSettings || JSON.parse( decodeURIComponent( '" . esc_js( $data ) . "' ) );";
			$preloaded_api_requests_script = '';

			if ( count( $this->preloaded_api_requests ) > 0 ) {
				$preloaded_api_requests        = rawurlencode( wp_json_encode( $this->preloaded_api_requests ) );
				$preloaded_api_requests_script = "wp.apiFetch.use( wp.apiFetch.createPreloadingMiddleware( JSON.parse( decodeURIComponent( '" . esc_js( $preloaded_api_requests ) . "' ) ) ) );";
			}

			wp_add_inline_script(
				$this->handle,
				$wc_settings_script . $preloaded_api_requests_script,
				'before'
			);
		}
	}

	/**
	 * See self::add() for docs.
	 *
	 * @param   string $key   Key for the data.
	 * @param   mixed  $data  Value for the data.
	 *
	 * @throws InvalidArgumentException  If key is not a string or already
	 *                                   exists in internal data cache.
	 */
	protected function add_data( $key, $data ) {
		if ( ! is_string( $key ) ) {
			if ( $this->debug() ) {
				throw new InvalidArgumentException(
					'Key for the data being registered must be a string'
				);
			}
		}
		if ( isset( $this->data[ $key ] ) ) {
			if ( $this->debug() ) {
				throw new InvalidArgumentException(
					'Overriding existing data with an already registered key is not allowed'
				);
			}
			return;
		}
		if ( \is_callable( $data ) ) {
			$this->lazy_data[ $key ] = $data;
			return;
		}
		$this->data[ $key ] = $data;
	}

	/**
	 * Exposes whether the current site is in debug mode or not.
	 *
	 * @return boolean  True means the site is in debug mode.
	 */
	protected function debug() {
		return defined( 'WP_DEBUG' ) && WP_DEBUG;
	}
}