and adds the returned
	 * value to the data array.
	 *
	 * This method is executed right before preparing the data for printing to
	 * the rendered screen.
	 *
	 * @return void
	 */
	protected function execute_lazy_data() {
		foreach ( $this->lazy_data as $key => $callback ) {
			$this->data[ $key ] = $callback();
		}
	}

	/**
	 * Exposes private registered data to child classes.
	 *
	 * @return array  The registered data on the private data property
	 */
	protected function get() {
		return $this->data;
	}

	/**
	 * Allows checking whether a key exists.
	 *
	 * @param 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.
	 *
	 * @param string $key  The key used to reference the data being registered.
	 *                     You can only register data that is not already in the
	 *                     registry identified by the given key.
	 * @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.
	 *
	 * @throws InvalidArgumentException  Only throws when site is in debug mode.
	 *                                   Always logs the error.
	 */
	public function add( $key, $data ) {
		try {
			$this->add_data( $key, $data );
		} catch ( Exception $e ) {
			if ( $this->debug() ) {
				// bubble up.
				throw $e;
			}
			wc_caught_exception( $e, __METHOD__, [ $key, $data ] );
		}
	}

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

	/**
	 * 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 ) );
			wp_add_inline_script(
				$this->handle,
				"var wcSettings = wcSettings || JSON.parse( decodeURIComponent( '"
					. esc_js( $data )
					. "' ) );",
				'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;
	}
}