Implement Fever sync

lib/REST/Fever/API.php

@@ -138,6 +138,12 @@ class API extends \JKingWeb\Arsse\REST\AbstractHandler {
             // TODO: implement hot links
             $out['inks'] = [];
         }
+        if ($G['unread_item_ids']) {
+            $out['unread_item_ids'] = $this->getItemIds((new Context)->unread(true));
+        }
+        if ($G['saved_item_ids']) {
+            $out['saved_item_ids'] = $this->getItemIds((new Context)->starred(true));
+        }
         return $out;
     }
 
@@ -262,4 +268,12 @@ class API extends \JKingWeb\Arsse\REST\AbstractHandler {
         }
         return $out;
     }
+
+    protected function getItemIds(Context $c = null): array {
+        $out = [];
+        foreach (Arsse::$db->articleList(Arsse::$user->id, $c) as $r) {
+            $out[] = (int) $r['id'];
+        }
+        return $out;
+    }
 }