Group class term dates, single-class embed mode, and offering editing

Group class offerings now carry real dates: the add/edit form takes a
start date plus a sessions control (one-off, or weekly for N sessions;
the end date is computed as start + (N-1) weeks via
Offering::weeklyTermEnd). Dates are validated strictly (Y-m-d) and shown
in the offerings list and on the student-facing class card, including
the weekly session count.

[us_group_classes offering="<id>"] (block attribute offeringId, chosen
from a dropdown of active classes fetched from the public offerings
endpoint) restricts the page to a single class so the enrolment flow can
be embedded on a page dedicated to that class; a pinned class that is no
longer offered reports itself closed instead of falling back to the
catalog.

Offerings are now editable from the admin screen: an Edit button
prefills the shared add/edit form and saving posts usc_action=update.
Updates always preserve the original owner and currency, and non-admin
instructors can only load and update their own offerings. The form also
gains the previously missing description field and an Active toggle (the
admin-UI counterpart of the REST is_active flag) so an edit cannot wipe
data the form never collected.

Closes #59

Co-Authored-By: Claude Fable 5 <[email protected]>

assets/js/blocks.js

@@ -3,10 +3,11 @@
     'use strict';
 
     const { registerBlockType } = wp.blocks;
-    const { createElement: el } = wp.element;
+    const { createElement: el, useState, useEffect } = wp.element;
     const { useBlockProps, InspectorControls } = wp.blockEditor;
     const { PanelBody, SelectControl, ToggleControl } = wp.components;
     const { useSelect } = wp.data;
+    const apiFetch = wp.apiFetch;
     const ServerSideRender = wp.serverSideRender;
     const { __ } = wp.i18n;
 
@@ -42,6 +43,46 @@
         });
     }
 
+    /**
+     * Dropdown of active group classes fetched from the plugin's public
+     * offerings endpoint. Values are offering IDs; 0 means all classes.
+     */
+    function GroupClassSelect(props) {
+        const [offerings, setOfferings] = useState(null);
+
+        useEffect(() => {
+            apiFetch({ path: '/us-scheduler/v1/offerings?kind=group_class' })
+                .then(setOfferings)
+                .catch(() => setOfferings([]));
+        }, []);
+
+        const options = [{ label: __('All classes', 'unsupervised-schedular'), value: '0' }].concat(
+            (offerings || []).map((o) => ({
+                label: o.title || __('(no title)', 'unsupervised-schedular'),
+                value: String(o.id),
+            }))
+        );
+
+        // A previously chosen class that is no longer offered (deleted or
+        // deactivated) keeps its stored id visible instead of silently
+        // pretending "All classes" is selected.
+        const value = String(props.value || 0);
+        if (offerings !== null && !options.some((opt) => opt.value === value)) {
+            options.push({
+                label: __('Unavailable class #', 'unsupervised-schedular') + value,
+                value: value,
+            });
+        }
+
+        return el(SelectControl, {
+            label: props.label,
+            help: props.help,
+            value: value,
+            options: options,
+            onChange: (newValue) => props.onChange(parseInt(newValue, 10) || 0),
+        });
+    }
+
     const blocks = [
         {
             name: 'us-scheduler/booking',
@@ -116,6 +157,19 @@
             icon: 'groups',
             keywords: ['group', 'class', 'enrol'],
             shortcode: 'us_group_classes',
+            attributes: {
+                offeringId: { type: 'number', default: 0 },
+            },
+            inspector: (attributes, setAttributes) => el(
+                PanelBody,
+                { title: __('Classes shown', 'unsupervised-schedular') },
+                el(GroupClassSelect, {
+                    label: __('Class', 'unsupervised-schedular'),
+                    help: __('Show only one group class, for embedding on a page dedicated to it.', 'unsupervised-schedular'),
+                    value: attributes.offeringId,
+                    onChange: (offeringId) => setAttributes({ offeringId }),
+                })
+            ),
         },
     ];