Tweak notification grouping

Notifications that are of the same type but are separated by a groupable
notification of a different type are now considered groupable. For
example:

favorite 1 (status 1)
reblog 1 (status 1)
favorite 2 (status 1)
reblog 2 (status 1)
mention 1
reblog 3 (status 1)

will be grouped into:

favorite 1, 2 (status 1)
reblog 1, 2 (status 1)
mention 1
reblog 3 (status 1)

Pachyderm/Utilities/NotificationGroup.swift

@@ -27,18 +27,24 @@ public class NotificationGroup {
     }
 
     public static func createGroups(notifications: [Notification], only allowedTypes: [Notification.Kind]) -> [NotificationGroup] {
-        return notifications.reduce(into: [[Notification]]()) { (groups, notification) in
+        var groups = [[Notification]]()
-            if allowedTypes.contains(notification.kind),
+        for notification in notifications {
-                let lastGroup = groups.last,
+            if allowedTypes.contains(notification.kind) {
-                let firstStatus = lastGroup.first,
+                if let lastGroup = groups.last, let firstNotification = lastGroup.first, firstNotification.kind == notification.kind, firstNotification.status?.id == notification.status?.id {
-                firstStatus.kind == notification.kind,
+                    groups[groups.count - 1].append(notification)
-                firstStatus.status?.id == notification.status?.id {
+                    continue
-                
+                } else if groups.count >= 2 {
-                groups[groups.count - 1].append(notification)
+                    let secondToLastGroup = groups[groups.count - 2]
-            } else {
+                    if allowedTypes.contains(groups[groups.count - 1][0].kind), let firstNotification = secondToLastGroup.first, firstNotification.kind == notification.kind, firstNotification.status?.id == notification.status?.id {
-                groups.append([notification])
+                        groups[groups.count - 2].append(notification)
+                        continue
+                    }
+                }
             }
-        }.map {
+            
+            groups.append([notification])
+        }
+        return groups.map {
             NotificationGroup(notifications: $0)!
         }
     }