[Fix] Improve Class-Subclass Linkage (#1846)

* Initial thoughts

* .

* Fixed linting

* Continue work on updating identifier

* Change to uuid approach

* Localization and minor fix

* Fixed CompendiumBrowser Class filter for Subclass view

* Fixed the class name display in the subclass view

* Improved missing class visual for subclass

* Fixed character creation

* Rerender class sheets when subclass link is changed

* Use compendium source over actual uuid in search

---------

Co-authored-by: Carlos Fernandez <cfern1990@gmail.com>

module/applications/sheets/items/subclass.mjs

@@ -40,4 +40,36 @@ export default class SubclassSheet extends DHBaseItemSheet {
     get relatedDocs() {
         return this.document.system.features.map(x => x.item);
     }
+
+    async _prepareContext(options) {
+        const context = await super._prepareContext(options);
+        if (this.document.system.linkedClass) {
+            const classData = await fromUuid(this.document.system.linkedClass);
+            context.class = classData ?? {
+                name: _loc('DAGGERHEART.GENERAL.missingX', { x: _loc('TYPES.Item.class') }),
+                missing: true
+            };
+        }
+        return context;
+    }
+
+    async _onDrop(event) {
+        event.stopPropagation();
+        const data = TextEditor.getDragEventData(event);
+        const item = await fromUuid(data.uuid);
+        const itemType = data.type === 'ActiveEffect' ? data.type : item.type;
+        if (itemType === 'class') {
+            const uuid = item._stats.compendiumSource ?? item.uuid;
+            if (this.document.system.linkedClass !== uuid) {
+                await this.document.update({ 'system.linkedClass': uuid });
+                // Re-render all class sheets for instant feedback
+                for (const app of foundry.applications.instances.values()) {
+                    if (app.document?.type === 'class') app.render();
+                }
+            }
+            return;
+        }
+
+        return super._onDrop(event);
+    }
 }