Fixing single threads for API threading strategy.

Wino.Core.Domain/Interfaces/IThreadingStrategy.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using Wino.Core.Domain.Entities;
+using Wino.Core.Domain.Models.Folders;
 using Wino.Core.Domain.Models.MailItem;
 
 namespace Wino.Core.Domain.Interfaces
@@ -12,7 +13,7 @@ namespace Wino.Core.Domain.Interfaces
         /// </summary>
         /// <param name="items">Original mails.</param>
         /// <returns>Original mails with thread mails.</returns>
-        Task<List<IMailItem>> ThreadItemsAsync(List<MailCopy> items);
+        Task<List<IMailItem>> ThreadItemsAsync(List<MailCopy> items, IMailItemFolder threadingForFolder);
         bool ShouldThreadWithItem(IMailItem originalItem, IMailItem targetItem);
     }
 }

Wino.Core.Domain/Models/MailItem/ThreadMailItem.cs

@@ -14,19 +14,19 @@ namespace Wino.Core.Domain.Models.MailItem
         public IMailItem LatestMailItem => ThreadItems.LastOrDefault();
         public IMailItem FirstMailItem => ThreadItems.FirstOrDefault();
 
-        public void AddThreadItem(IMailItem item)
+        public bool AddThreadItem(IMailItem item)
         {
-            if (item == null) return;
+            if (item == null) return false;
 
             if (ThreadItems.Any(a => a.Id == item.Id))
             {
-                return;
+                return false;
             }
 
             if (item != null && item.IsDraft)
             {
                 ThreadItems.Insert(0, item);
-                return;
+                return true;
             }
 
             var insertItem = ThreadItems.FirstOrDefault(a => !a.IsDraft && a.CreationDate < item.CreationDate);
@@ -39,6 +39,8 @@ namespace Wino.Core.Domain.Models.MailItem
 
                 ThreadItems.Insert(index, item);
             }
+
+            return true;
         }
 
         public IEnumerable<Guid> GetContainingIds() => ThreadItems?.Select(a => a.UniqueId) ?? default;

Wino.Core/Integration/Threading/APIThreadingStrategy.cs

@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using Wino.Core.Domain.Entities;
 using Wino.Core.Domain.Enums;
 using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain.Models.Folders;
 using Wino.Core.Domain.Models.MailItem;
 using Wino.Core.Services;
 
@@ -27,7 +28,7 @@ namespace Wino.Core.Integration.Threading
         }
 
         ///<inheritdoc/>
-        public async Task<List<IMailItem>> ThreadItemsAsync(List<MailCopy> items)
+        public async Task<List<IMailItem>> ThreadItemsAsync(List<MailCopy> items, IMailItemFolder threadingForFolder)
         {
             var assignedAccount = items[0].AssignedAccount;
 
@@ -62,11 +63,43 @@ namespace Wino.Core.Integration.Threading
                     }
 
                     var thread = new ThreadMailItem();
+
                     foreach (var childThreadItem in threadItem)
                     {
-                        thread.AddThreadItem(childThreadItem);
+                        if (thread.ThreadItems.Any(a => a.Id == childThreadItem.Id))
+                        {
+                            // Mail already exist in the thread.
+                            // There should be only 1 instance of the mail in the thread.
+                            // Make sure we add the correct one.
+
+                            // Add the one with threading folder.
+                            var threadingFolderItem = threadItem.FirstOrDefault(a => a.Id == childThreadItem.Id && a.FolderId == threadingForFolder.Id);
+
+                            if (threadingFolderItem == null) continue;
+
+                            // Remove the existing one.
+                            thread.ThreadItems.Remove(thread.ThreadItems.First(a => a.Id == childThreadItem.Id));
+
+                            // Add the correct one for listing.
+                            thread.AddThreadItem(threadingFolderItem);
+                        }
+                        else
+                        {
+                            thread.AddThreadItem(childThreadItem);
+                        }
+                    }
+
+                    if (thread.ThreadItems.Count > 1)
+                    {
+                        resultList.Add(thread);
+                    }
+                    else
+                    {
+                        // Don't make threads if the thread has only one item.
+                        // Gmail has may have multiple assignments for the same item.
+
+                        resultList.Add(thread.ThreadItems.First());
                     }
-                    resultList.Add(thread);
                 }
             }
 

Wino.Core/Integration/Threading/ImapThreadStrategy.cs

@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using SqlKata;
 using Wino.Core.Domain.Entities;
 using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain.Models.Folders;
 using Wino.Core.Domain.Models.MailItem;
 using Wino.Core.Extensions;
 using Wino.Core.Services;
@@ -58,7 +59,7 @@ namespace Wino.Core.Integration.Threading
             return _databaseService.Connection.FindWithQueryAsync<MailCopy>(query.GetRawQuery());
         }
 
-        public async Task<List<IMailItem>> ThreadItemsAsync(List<MailCopy> items)
+        public async Task<List<IMailItem>> ThreadItemsAsync(List<MailCopy> items, IMailItemFolder threadingForFolder)
         {
             var threads = new List<ThreadMailItem>();
 

Wino.Core/Services/MailService.cs

@@ -241,7 +241,7 @@ namespace Wino.Core.Services
 
                 // Only thread items from Draft and Sent folders must present here.
                 // Otherwise this strategy will fetch the items that are in Deleted folder as well.
-                var accountThreadedItems = await threadingStrategy.ThreadItemsAsync([.. group]);
+                var accountThreadedItems = await threadingStrategy.ThreadItemsAsync([.. group], options.Folders.First());
 
                 // Populate threaded items with folder and account assignments.
                 // Almost everything already should be in cache from initial population.