Started addition of favourite system

app/Http/Controllers/FavouriteController.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace BookStack\Http\Controllers;
+
+use BookStack\Entities\Models\Entity;
+use BookStack\Interfaces\Favouritable;
+use BookStack\Model;
+use Illuminate\Http\Request;
+
+class FavouriteController extends Controller
+{
+    /**
+     * Add a new item as a favourite.
+     */
+    public function add(Request $request)
+    {
+        $favouritable = $this->getValidatedModelFromRequest($request);
+        $favouritable->favourites()->firstOrCreate([
+            'user_id' => user()->id,
+        ]);
+
+        $this->showSuccessNotification(trans('activities.favourite_add_notification', [
+            'name' => $favouritable->name,
+        ]));
+        return redirect()->back();
+    }
+
+    /**
+     * Remove an item as a favourite.
+     */
+    public function remove(Request $request)
+    {
+        $favouritable = $this->getValidatedModelFromRequest($request);
+        $favouritable->favourites()->where([
+            'user_id' => user()->id,
+        ])->delete();
+
+        $this->showSuccessNotification(trans('activities.favourite_remove_notification', [
+            'name' => $favouritable->name,
+        ]));
+        return redirect()->back();
+    }
+
+    /**
+     * @throws \Illuminate\Validation\ValidationException
+     * @throws \Exception
+     */
+    protected function getValidatedModelFromRequest(Request $request): Favouritable
+    {
+        $modelInfo = $this->validate($request, [
+            'type' => 'required|string',
+            'id' => 'required|integer',
+        ]);
+
+        if (!class_exists($modelInfo['type'])) {
+            throw new \Exception('Model not found');
+        }
+
+        /** @var Model $model */
+        $model = new $modelInfo['type'];
+        if (! $model instanceof Favouritable) {
+            throw new \Exception('Model not favouritable');
+        }
+
+        $modelInstance = $model->newQuery()
+            ->where('id', '=', $modelInfo['id'])
+            ->first(['id', 'name']);
+
+        $inaccessibleEntity = ($modelInstance instanceof Entity && !userCan('view', $modelInstance));
+        if (is_null($modelInstance) || $inaccessibleEntity) {
+            throw new \Exception('Model instance not found');
+        }
+
+        return $modelInstance;
+    }
+}