First pass at Gutenberg support.

See #6.

assets/gutenberg.css

@@ -0,0 +1,9 @@
+.ray-unlisted {
+	position: relative;
+}
+
+.ray-unlisted input[type="checkbox"] {
+	position: absolute;
+	top: 3px;
+	right: -12px;
+}

assets/gutenberg.js

@@ -0,0 +1,60 @@
+( function( wp, $ ) {
+	var registerPlugin = wp.plugins.registerPlugin;
+	var PluginPostStatusInfo = wp.editPost.PluginPostStatusInfo;
+	var el = wp.element.createElement;
+	var __ = wp.i18n.__;
+
+	var checkBox = wp.components.CheckboxControl;
+	var withSelect = wp.data.withSelect;
+	var withDispatch = wp.data.withDispatch;
+	var compose = wp.compose.compose;
+
+	var metaCheckbox = compose(
+		withDispatch( function( dispatch, props ) {
+			return {
+				setMetaFieldValue: function( value ) {
+					dispatch( 'core/editor' ).editPost(
+						{ meta: { [ props.fieldName ]: value } }
+					);
+				}
+			}
+		} ),
+		withSelect( function( select, props ) {
+			return {
+				metaFieldValue: select( 'core/editor' ).getEditedPostAttribute( 'meta' )[ props.fieldName ],
+			}
+		} )
+
+	)( function( props ) {
+		// https://github.com/WordPress/gutenberg/tree/master/packages/components/src/checkbox-control
+		return el( checkBox, {
+			label: props.label,
+			checked: props.metaFieldValue,
+			onChange: function( retVal ) {
+				props.updater( retVal );
+				props.setMetaFieldValue( retVal );
+			},
+		} );
+	} );
+
+	var unlistedUpdater = function( retVal ) {
+		// If unlisted, switch post status to 'private'.
+		if ( retVal ) {
+			wp.data.dispatch( 'core/editor' ).editPost( { status: 'private' } );
+		}
+	};
+
+	registerPlugin( 'ray-unlisted-posts', {
+		render: function() {
+			return el( PluginPostStatusInfo, {
+				className: 'ray-unlisted'
+			},
+				el( metaCheckbox, {
+					label: __( 'Unlisted?' ),
+					fieldName: 'ray_unlisted',
+					updater: unlistedUpdater
+				} )
+			);
+		},
+	} );
+} )( window.wp, jQuery );

plugin.php

@@ -99,26 +99,38 @@ function rest_oembed( $retval, $server, $request ) {
 }
 add_filter( 'rest_request_before_callbacks', __NAMESPACE__ . '\\rest_oembed', 10, 3 );
 
+
+/* GUTENBERG ********************************************************/
+
 /**
- * Add compatibility for the Classic Editor.
+ * Register our post meta for Gutenberg support.
  */
-function load_classic() {
-	require_once  DIR . '/hooks/classic.php';
+function register_meta() {
+	\register_meta( 'post', 'ray_unlisted', array(
+		'show_in_rest' => true,
+		'single'       => true,
+		'type'         => 'boolean',
+	) );
 }
-add_action( 'post_submitbox_minor_actions', __NAMESPACE__ . '\\load_classic' );
+add_action( 'init', __NAMESPACE__ . '\\register_meta' );
 
 /**
- * Saves our unlisted option if selected in the Classic Editor.
- *
- * @todo This needs an audit to see if it conflicts with Gutenberg.
- *
- * @param int $post_id Post ID.
+ * Register our assets for Gutenberg support.
  */
-function save_unlisted_option( $post_id ) {
-	if ( empty( $_POST['ray_unlisted'] ) ) {
-		delete_post_meta( $post_id, 'ray_unlisted' );
-	} else {
-		update_post_meta( $post_id, 'ray_unlisted', 1 );
-	}
+function register_assets() {
+	wp_register_script( 'ray-unlisted-posts', plugin_dir_url( __FILE__ ) . 'assets/gutenberg.js', array(
+		'wp-plugins', 'wp-edit-post', 'wp-element', 'wp-compose', 'wp-data'
+	) );
+
+	wp_register_style( 'ray-unlisted-posts', plugin_dir_url( __FILE__ ) . 'assets/gutenberg.css' );
+}
+add_action( 'init', __NAMESPACE__ . '\\register_assets' );
+
+/**
+ * Enqueue our assets for Gutenberg support.
+ */
+function block_enqueue_assets() {
+	wp_enqueue_script( 'ray-unlisted-posts' );
+	wp_enqueue_style( 'ray-unlisted-posts' );
 }
-add_action( 'wp_insert_post', __NAMESPACE__ . '\\save_unlisted_option' );
+add_action( 'enqueue_block_editor_assets', __NAMESPACE__ . '\\block_enqueue_assets' );