From 6ea903ebb9f4cc5494f7cd9a386d7576b1cd6904 Mon Sep 17 00:00:00 2001
From: ChronosX88 <chronosx88@gmail.com>
Date: Sun, 7 Mar 2021 23:12:25 +0300
Subject: [PATCH] Implement linking event to previous in chat room when saving
 event

---
 .../Storage/EventStorageManager.cs            | 19 +++++++++++++++++--
 .../ChatSubsystem/Storage/Models/Event.cs     |  2 +-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/ZirconiumPlugins/ChatSubsystem/Storage/EventStorageManager.cs b/src/ZirconiumPlugins/ChatSubsystem/Storage/EventStorageManager.cs
index e1642cf..a94f0c6 100644
--- a/src/ZirconiumPlugins/ChatSubsystem/Storage/EventStorageManager.cs
+++ b/src/ZirconiumPlugins/ChatSubsystem/Storage/EventStorageManager.cs
@@ -43,8 +43,23 @@ namespace ChatSubsystem.Storage
                 await events.InsertOneAsync(e);
                 return;
             }
-            // TODO link to previous events in the room
-            res.PrevID = res.Id;
+            e.PrevID = res.Id;
+            
+            connectToField = (FieldDefinition<Event, EntityID>)"PrevEvents";
+            var opts = new AggregateGraphLookupOptions<Event, Event, EventWithChildren>()
+            {
+                RestrictSearchWithMatch = "{ ChatId: "+e.ChatId+" }"
+            };
+            res = await events.Aggregate()
+                .GraphLookup(events, connectFromField, connectToField, startWith, @as, opts)
+                .Match("{ Children: { $size: 0 } }").FirstOrDefaultAsync();
+            if (res == null)
+            {
+                await events.InsertOneAsync(e);
+                return;
+            }
+            
+            e.PrevEvent = res.EventID;
             await events.InsertOneAsync(e);
         }
 
diff --git a/src/ZirconiumPlugins/ChatSubsystem/Storage/Models/Event.cs b/src/ZirconiumPlugins/ChatSubsystem/Storage/Models/Event.cs
index ef25d7c..32fe214 100644
--- a/src/ZirconiumPlugins/ChatSubsystem/Storage/Models/Event.cs
+++ b/src/ZirconiumPlugins/ChatSubsystem/Storage/Models/Event.cs
@@ -13,7 +13,7 @@ namespace ChatSubsystem.Storage.Models
         public EntityID ChatId { get; set; }
         public string Type { get; set; }
         public long Timestamp { get; set; }
-        public EntityID[] PrevEvents { get; set; }
+        public EntityID PrevEvent { get; set; }
         public ObjectId PrevID { get; set; }
         public EntityID OriginServer { get; set; }
         public EventContent Content { get; set; }