Authenticates the user using an application password.

function wp_authenticate_application_password( $input_user, $username, $password ) {
	if ( $input_user instanceof WP_User ) {
		return $input_user;
	}

	if ( ! WP_Application_Passwords::is_in_use() ) {
		return $input_user;
	}

	$is_api_request = ( ( defined( 'XMLRPC_REQUEST' ) && XMLRPC_REQUEST ) || ( defined( 'REST_REQUEST' ) && REST_REQUEST ) );

	/**
	 * Filters whether this is an API request that Application Passwords can be used on.
	 *
	 * By default, Application Passwords is available for the REST API and XML-RPC.
	 *
	 * @since 5.6.0
	 *
	 * @param bool $is_api_request If this is an acceptable API request.
	 */
	$is_api_request = apply_filters( 'application_password_is_api_request', $is_api_request );

	if ( ! $is_api_request ) {
		return $input_user;
	}

	$error = null;
	$user  = get_user_by( 'login', $username );

	if ( ! $user && is_email( $username ) ) {
		$user = get_user_by( 'email', $username );
	}

	// If the login name is invalid, short circuit.
	if ( ! $user ) {
		if ( is_email( $username ) ) {
			$error = new WP_Error(
				'invalid_email',
				__( 'Error: Unknown email address. Check again or try your username.' )
			);
		} else {
			$error = new WP_Error(
				'invalid_username',
				__( 'Error: Unknown username. Check again or try your email address.' )
			);
		}
	} elseif ( ! wp_is_application_passwords_available() ) {
		$error = new WP_Error(
			'application_passwords_disabled',
			__( 'Application passwords are not available.' )
		);
	} elseif ( ! wp_is_application_passwords_available_for_user( $user ) ) {
		$error = new WP_Error(
			'application_passwords_disabled_for_user',
			__( 'Application passwords are not available for your account. Please contact the site administrator for assistance.' )
		);
	}

	if ( $error ) {
		/**
		 * Fires when an application password failed to authenticate the user.
		 *
		 * @since 5.6.0
		 *
		 * @param WP_Error $error The authentication error.
		 */
		do_action( 'application_password_failed_authentication', $error );

		return $error;
	}

	/*
	 * Strips out anything non-alphanumeric. This is so passwords can be used with
	 * or without spaces to indicate the groupings for readability.
	 *
	 * Generated application passwords are exclusively alphanumeric.
	 */
	$password = preg_replace( '/[^a-zd]/i', '', $password );

	$hashed_passwords = WP_Application_Passwords::get_user_application_passwords( $user->ID );

	foreach ( $hashed_passwords as $key => $item ) {
		if ( ! wp_check_password( $password, $item['password'], $user->ID ) ) {
			continue;
		}

		$error = new WP_Error();

		/**
		 * Fires when an application password has been successfully checked as valid.
		 *
		 * This allows for plugins to add additional constraints to prevent an application password from being used.
		 *
		 * @since 5.6.0
		 *
		 * @param WP_Error $error    The error object.
		 * @param WP_User  $user     The user authenticating.
		 * @param array    $item     The details about the application password.
		 * @param string   $password The raw supplied password.
		 */
		do_action( 'wp_authenticate_application_password_errors', $error, $user, $item, $password );

		if ( is_wp_error( $error ) && $error->has_errors() ) {
			/** This action is documented in wp-includes/user.php */
			do_action( 'application_password_failed_authentication', $error );

			return $error;
		}

		WP_Application_Passwords::record_application_password_usage( $user->ID, $item['uuid'] );

		/**
		 * Fires after an application password was used for authentication.
		 *
		 * @since 5.6.0
		 *
		 * @param WP_User $user The user who was authenticated.
		 * @param array   $item The application password used.
		 */
		do_action( 'application_password_did_authenticate', $user, $item );

		return $user;
	}

	$error = new WP_Error(
		'incorrect_password',
		__( 'The provided password is an invalid application password.' )
	);

	/** This action is documented in wp-includes/user.php */
	do_action( 'application_password_failed_authentication', $error );

	return $error;
}