html diff in revision view

@@ -12,6 +12,7 @@ use BookStack\Repos\ChapterRepo;
 use BookStack\Repos\PageRepo;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Views;
+use Icap\HtmlDiff\HtmlDiff;
 
 class PageController extends Controller
 {
@@ -332,9 +333,19 @@ class PageController extends Controller
         $book = $this->bookRepo->getBySlug($bookSlug);
         $page = $this->pageRepo->getBySlug($pageSlug, $book->id);
         $revision = $this->pageRepo->getRevisionById($revisionId);
+        
+        $next     = $revision->getNext() ?: $page;
+        $htmlDiff = new HtmlDiff($revision->html, $next->html, true);
+        $diff     = $htmlDiff->outputDiff()->toString();
+
         $page->fill($revision->toArray());
         $this->setPageTitle('Page Revision For ' . $page->getShortName());
-        return view('pages/revision', ['page' => $page, 'book' => $book]);
+        
+        return view('pages/revision', [
+            'page' => $page,
+            'book' => $book,
+            'diff' => $diff,
+        ]);
     }
 
     /**

@@ -32,4 +32,25 @@ class PageRevision extends Model
         return $this->page->getUrl() . '/revisions/' . $this->id;
     }
 
+    /**
+     * Get previous revision
+     * @return \BookStack\PageRevision
+     */
+    public function getPrevious()
+    {
+        if ($id = PageRevision::where('id', '<', $this->id)->max('id')) {
+            return PageRevision::find($id);
+        }
+    }
+
+    /**
+     * Get next revision
+     * @return \BookStack\PageRevision
+     */
+    public function getNext()
+    {
+        if ($id = PageRevision::where('id', '>', $this->id)->min('id')) {
+            return PageRevision::find($id);
+        }
+    }
 }

@@ -13,7 +13,8 @@
         "barryvdh/laravel-debugbar": "^2.0",
         "league/flysystem-aws-s3-v3": "^1.0",
         "barryvdh/laravel-dompdf": "0.6.*",
-        "predis/predis": "^1.0"
+        "predis/predis": "^1.0",
+        "icap/html-diff": "^1.1"
     },
     "require-dev": {
         "fzaninotto/faker": "~1.4",

@@ -60,6 +60,18 @@
     word-break: break-word;
     hyphens: auto;
   }
+
+  // diffs
+  .diff-html-removed,
+  .diff-html-added {
+    text-decoration: none;
+  }
+  .diff-html-added {
+    background: rgba(45, 255, 0, 0.2);
+  }
+  .diff-html-removed {
+    background: rgba(255, 0, 0, 0.2);
+  }
 }
 
 // Page content pointers

@@ -18,5 +18,9 @@
 
     <div style="clear:left;"></div>
 
-    {!! $page->html !!}
+    @if (isset($diff) && $diff)
+        {!! $diff !!}
+    @else
+        {!! $page->html !!}
+    @endif
 </div>
\ No newline at end of file