diff --git a/OF DL.Core/Models/Entities/Purchased/ListItem.cs b/OF DL.Core/Models/Entities/Purchased/ListItem.cs
index 45561be..9e21aca 100644
--- a/OF DL.Core/Models/Entities/Purchased/ListItem.cs	
+++ b/OF DL.Core/Models/Entities/Purchased/ListItem.cs	
@@ -17,9 +17,9 @@ public class ListItem
 
     public List<object>? Preview { get; set; }
 
-    public FromUser FromUser { get; set; } = new();
+    public FromUser? FromUser { get; set; }
 
-    public Author Author { get; set; } = new();
+    public Author? Author { get; set; }
 
     public long Id { get; set; }
 
diff --git a/OF DL.Core/Models/Mappers/ArchivedMapper.cs b/OF DL.Core/Models/Mappers/ArchivedMapper.cs
index 2ef0d09..ab722c6 100644
--- a/OF DL.Core/Models/Mappers/ArchivedMapper.cs	
+++ b/OF DL.Core/Models/Mappers/ArchivedMapper.cs	
@@ -28,7 +28,7 @@ public static class ArchivedMapper
         {
             Id = dto.Id,
             PostedAt = dto.PostedAt,
-            Author = MapAuthor(dto.Author),
+            Author = CommonMapper.MapAuthor(dto.Author),
             Text = dto.Text,
             Price = dto.Price,
             IsOpened = dto.IsOpened,
@@ -37,25 +37,8 @@ public static class ArchivedMapper
             Preview = dto.Preview
         };
 
-    private static Entities.Common.Author? MapAuthor(AuthorDto? dto)
-    {
-        if (dto == null)
-        {
-            return null;
-        }
-
-        return new Entities.Common.Author { Id = dto.Id };
-    }
-
-    private static List<Medium>? MapMedia(List<MediumDto>? media)
-    {
-        if (media == null)
-        {
-            return null;
-        }
-
-        return media.Select(MapMedium).ToList();
-    }
+    private static List<Medium>? MapMedia(List<MediumDto>? media) =>
+        media == null ? null : media.Select(MapMedium).ToList();
 
     private static Medium MapMedium(MediumDto dto) =>
         new()
@@ -67,50 +50,7 @@ public static class ArchivedMapper
             Preview = dto.Preview
         };
 
-    private static Entities.Common.Files? MapFiles(FilesDto? dto)
-    {
-        if (dto == null)
-        {
-            return null;
-        }
-
-        return new Entities.Common.Files { Full = MapFull(dto.Full), Drm = MapDrm(dto.Drm) };
-    }
-
-    private static Entities.Common.Full? MapFull(FullDto? dto) =>
-        dto == null ? null : new Entities.Common.Full { Url = dto.Url };
-
-    private static Entities.Common.Drm? MapDrm(DrmDto? dto)
-    {
-        if (dto == null)
-        {
-            return null;
-        }
-
-        return new Entities.Common.Drm
-        {
-            Manifest = MapManifest(dto.Manifest), Signature = MapSignature(dto.Signature)
-        };
-    }
-
-    private static Entities.Common.Manifest? MapManifest(ManifestDto? dto) =>
-        dto == null ? null : new Entities.Common.Manifest { Dash = dto.Dash };
-
-    private static Entities.Common.Signature? MapSignature(SignatureDto? dto) =>
-        dto == null ? null : new Entities.Common.Signature { Dash = MapDash(dto.Dash) };
-
-    private static Entities.Common.Dash? MapDash(DashDto? dto)
-    {
-        if (dto == null)
-        {
-            return null;
-        }
-
-        return new Entities.Common.Dash
-        {
-            CloudFrontPolicy = dto.CloudFrontPolicy,
-            CloudFrontSignature = dto.CloudFrontSignature,
-            CloudFrontKeyPairId = dto.CloudFrontKeyPairId
-        };
-    }
+    private static Entities.Common.Files? MapFiles(FilesDto? dto) => dto == null
+        ? null
+        : new Entities.Common.Files { Full = CommonMapper.MapFull(dto.Full), Drm = CommonMapper.MapDrm(dto.Drm) };
 }
diff --git a/OF DL.Core/Models/Mappers/CommonMapper.cs b/OF DL.Core/Models/Mappers/CommonMapper.cs
new file mode 100644
index 0000000..3312a2f
--- /dev/null
+++ b/OF DL.Core/Models/Mappers/CommonMapper.cs	
@@ -0,0 +1,115 @@
+using OF_DL.Models.Dtos.Common;
+using OF_DL.Models.Entities.Common;
+
+namespace OF_DL.Models.Mappers;
+
+public static class CommonMapper
+{
+    public static Author? MapAuthor(AuthorDto? dto)
+    {
+        if (dto == null || dto.Id == 0)
+        {
+            return null;
+        }
+
+        return new Author { Id = dto.Id };
+    }
+
+    private static Dash? MapDash(DashDto? dto)
+    {
+        if (dto == null || (
+                string.IsNullOrEmpty(dto.CloudFrontPolicy) &&
+                string.IsNullOrEmpty(dto.CloudFrontSignature) &&
+                string.IsNullOrEmpty(dto.CloudFrontKeyPairId)))
+        {
+            return null;
+        }
+
+        return new Dash
+        {
+            CloudFrontPolicy = dto.CloudFrontPolicy,
+            CloudFrontSignature = dto.CloudFrontSignature,
+            CloudFrontKeyPairId = dto.CloudFrontKeyPairId
+        };
+    }
+
+    public static Drm? MapDrm(DrmDto? dto)
+    {
+        if (dto == null || (dto.Manifest == new ManifestDto() && dto.Signature == new SignatureDto()))
+        {
+            return null;
+        }
+
+        return new Drm { Manifest = MapManifest(dto.Manifest), Signature = MapSignature(dto.Signature) };
+    }
+
+    public static Files? MapFiles(FilesDto? dto)
+    {
+        if (dto == null)
+        {
+            return null;
+        }
+
+        Full? full = MapFull(dto.Full);
+        Preview? preview = MapPreview(dto.Preview);
+        Drm? drm = MapDrm(dto.Drm);
+
+        if (full == null && preview == null && drm == null)
+        {
+            return null;
+        }
+
+        return new Files { Full = MapFull(dto.Full), Preview = MapPreview(dto.Preview), Drm = MapDrm(dto.Drm) };
+    }
+
+    public static Full? MapFull(FullDto? dto)
+    {
+        if (dto == null || string.IsNullOrEmpty(dto.Url))
+        {
+            return null;
+        }
+
+        return new Full { Url = dto.Url };
+    }
+
+    public static Manifest? MapManifest(ManifestDto? dto)
+    {
+        if (dto == null || string.IsNullOrEmpty(dto.Dash))
+        {
+            return null;
+        }
+
+        return new Manifest { Dash = dto.Dash };
+    }
+
+    public static Preview? MapPreview(PreviewDto? dto)
+    {
+        if (dto == null || string.IsNullOrEmpty(dto.Url))
+        {
+            return null;
+        }
+
+        return new Preview { Url = dto.Url };
+    }
+
+    public static Signature? MapSignature(SignatureDto? dto)
+    {
+        if (dto == null)
+        {
+            return null;
+        }
+
+        Dash? dash = MapDash(dto.Dash);
+        return dash == null ? null : new Signature { Dash = dash };
+    }
+
+    public static VideoSources? MapVideoSources(VideoSourcesDto? dto)
+    {
+        if (dto == null || (string.IsNullOrEmpty(dto._240) && string.IsNullOrEmpty(dto._720)))
+        {
+            return null;
+        }
+
+        return new VideoSources { _240 = dto._240, _720 = dto._720 };
+    }
+}
diff --git a/OF DL.Core/Models/Mappers/HighlightsMapper.cs b/OF DL.Core/Models/Mappers/HighlightsMapper.cs
index 450ea00..60efa17 100644
--- a/OF DL.Core/Models/Mappers/HighlightsMapper.cs	
+++ b/OF DL.Core/Models/Mappers/HighlightsMapper.cs	
@@ -59,8 +59,6 @@ public static class HighlightsMapper
             Files = MapFiles(dto.Files)
         };
 
-    private static Files? MapFiles(FilesDto? dto) => dto == null ? null : new Files { Full = MapFull(dto.Full) };
-
-    private static Full? MapFull(FullDto? dto) =>
-        dto == null ? null : new Full { Url = dto.Url };
+    private static Files? MapFiles(FilesDto? dto) =>
+        dto == null ? null : new Files { Full = CommonMapper.MapFull(dto.Full) };
 }
diff --git a/OF DL.Core/Models/Mappers/MessagesMapper.cs b/OF DL.Core/Models/Mappers/MessagesMapper.cs
index 52b9a8e..c416ab1 100644
--- a/OF DL.Core/Models/Mappers/MessagesMapper.cs	
+++ b/OF DL.Core/Models/Mappers/MessagesMapper.cs	
@@ -63,35 +63,17 @@ public static class MessagesMapper
     private static List<MessageEntities.Medium>? MapMedia(List<MediumDto>? media) =>
         media?.Select(MapMedium).ToList();
 
-    private static FromUser? MapFromUser(FromUserDto? dto) =>
-        dto?.Id == null ? null : new FromUser { Id = (long)dto.Id };
-
-    private static Files? MapFiles(FilesDto? dto) =>
-        dto == null ? null : new Files { Full = MapFull(dto.Full), Drm = MapDrm(dto.Drm) };
-
-    private static Full? MapFull(FullDto? dto) => dto == null ? null : new Full { Url = dto.Url };
-
-    private static Drm? MapDrm(DrmDto? dto) => dto == null
-        ? null
-        : new Drm { Manifest = MapManifest(dto.Manifest), Signature = MapSignature(dto.Signature) };
-
-    private static Manifest? MapManifest(ManifestDto? dto) => dto == null ? null : new Manifest { Dash = dto.Dash };
-
-    private static Signature? MapSignature(SignatureDto? dto) =>
-        dto == null ? null : new Signature { Dash = MapDash(dto.Dash) };
-
-    private static Dash? MapDash(DashDto? dto)
+    private static FromUser? MapFromUser(FromUserDto? dto)
     {
-        if (dto == null)
+        if (dto?.Id == null || dto.Id == 0)
         {
             return null;
         }
 
-        return new Dash
-        {
-            CloudFrontPolicy = dto.CloudFrontPolicy,
-            CloudFrontSignature = dto.CloudFrontSignature,
-            CloudFrontKeyPairId = dto.CloudFrontKeyPairId
-        };
+        return new FromUser { Id = dto.Id.Value };
     }
+
+    private static Files? MapFiles(FilesDto? dto) => dto == null
+        ? null
+        : new Files { Full = CommonMapper.MapFull(dto.Full), Drm = CommonMapper.MapDrm(dto.Drm) };
 }
diff --git a/OF DL.Core/Models/Mappers/PostMapper.cs b/OF DL.Core/Models/Mappers/PostMapper.cs
index 00c1b8f..1634ce8 100644
--- a/OF DL.Core/Models/Mappers/PostMapper.cs	
+++ b/OF DL.Core/Models/Mappers/PostMapper.cs	
@@ -36,7 +36,7 @@ public static class PostMapper
 
         mapped.Id = dto.Id;
         mapped.PostedAt = dto.PostedAt;
-        mapped.Author = MapSingleAuthor(dto.Author);
+        mapped.Author = CommonMapper.MapAuthor(dto.Author);
         mapped.Text = dto.Text;
         mapped.RawText = dto.RawText;
         mapped.IsOpened = dto.IsOpened;
@@ -53,7 +53,7 @@ public static class PostMapper
         {
             Id = dto.Id,
             PostedAt = dto.PostedAt,
-            Author = MapAuthor(dto.Author),
+            Author = CommonMapper.MapAuthor(dto.Author),
             Text = dto.Text,
             RawText = dto.RawText,
             IsOpened = dto.IsOpened,
@@ -63,12 +63,6 @@ public static class PostMapper
             Preview = dto.Preview
         };
 
-    private static Author? MapAuthor(AuthorDto? dto) =>
-        dto == null ? null : new Author { Id = dto.Id };
-
-    private static Author? MapSingleAuthor(AuthorDto? dto) =>
-        dto == null ? null : new Author { Id = dto.Id };
-
     private static List<Medium>? MapMedia(List<MediumDto>? media) =>
         media?.Select(MapMedium).ToList();
 
@@ -84,39 +78,12 @@ public static class PostMapper
 
     private static Files? MapFiles(FilesDto? dto) => dto == null
         ? null
-        : new Files { Full = MapFull(dto.Full), Preview = MapPreview(dto.Preview), Drm = MapDrm(dto.Drm) };
-
-    private static Full? MapFull(FullDto? dto) =>
-        dto == null || string.IsNullOrEmpty(dto.Url) ? null : new Full { Url = dto.Url };
-
-    private static Preview? MapPreview(PreviewDto? dto) =>
-        dto == null || string.IsNullOrEmpty(dto.Url) ? null : new Preview { Url = dto.Url };
-
-    private static Drm MapDrm(DrmDto? dto) => new()
-    {
-        Manifest = MapManifest(dto?.Manifest), Signature = MapSignature(dto?.Signature)
-    };
-
-    private static Manifest? MapManifest(ManifestDto? dto) =>
-        dto == null ? null : new Manifest { Dash = dto.Dash };
-
-    private static Signature? MapSignature(SignatureDto? dto) =>
-        dto == null ? null : new Signature { Dash = MapDash(dto.Dash) };
-
-    private static Dash? MapDash(DashDto? dto)
-    {
-        if (dto == null)
+        : new Files
         {
-            return null;
-        }
-
-        return new Dash
-        {
-            CloudFrontPolicy = dto.CloudFrontPolicy,
-            CloudFrontSignature = dto.CloudFrontSignature,
-            CloudFrontKeyPairId = dto.CloudFrontKeyPairId
+            Full = CommonMapper.MapFull(dto.Full),
+            Preview = CommonMapper.MapPreview(dto.Preview),
+            Drm = CommonMapper.MapDrm(dto.Drm)
         };
-    }
 
     private static List<Medium>? MapSingleMedia(List<MediumDto>? media) =>
         media?.Select(MapSingleMedium).ToList();
@@ -129,7 +96,7 @@ public static class PostMapper
             CanView = dto.CanView,
             Preview = dto.Preview,
             Files = MapSingleFiles(dto.Files),
-            VideoSources = MapVideoSources(dto.VideoSources)
+            VideoSources = CommonMapper.MapVideoSources(dto.VideoSources)
         };
 
     private static Files? MapSingleFiles(FilesDto? dto)
@@ -141,42 +108,9 @@ public static class PostMapper
 
         return new Files
         {
-            Full = MapSingleFull(dto.Full), Preview = MapSinglePreview(dto.Preview), Drm = MapSingleDrm(dto.Drm)
+            Full = CommonMapper.MapFull(dto.Full),
+            Preview = CommonMapper.MapPreview(dto.Preview),
+            Drm = CommonMapper.MapDrm(dto.Drm)
         };
     }
-
-    private static Full? MapSingleFull(FullDto? dto) =>
-        dto == null || string.IsNullOrEmpty(dto.Url) ? null : new Full { Url = dto.Url };
-
-    private static Preview? MapSinglePreview(PreviewDto? dto) =>
-        dto == null || string.IsNullOrEmpty(dto.Url) ? null : new Preview { Url = dto.Url };
-
-    private static Drm? MapSingleDrm(DrmDto? dto) => dto == null
-        ? null
-        : new Drm { Manifest = MapSingleManifest(dto.Manifest), Signature = MapSingleSignature(dto.Signature) };
-
-    private static Manifest? MapSingleManifest(ManifestDto? dto) =>
-        dto == null ? null : new Manifest { Dash = dto.Dash };
-
-    private static Signature? MapSingleSignature(SignatureDto? dto) =>
-        dto == null ? null : new Signature { Dash = MapSingleDash(dto.Dash) };
-
-    private static Dash? MapSingleDash(DashDto? dto)
-    {
-        if (dto == null)
-        {
-            return null;
-        }
-
-        return new Dash
-        {
-            CloudFrontPolicy = dto.CloudFrontPolicy,
-            CloudFrontSignature = dto.CloudFrontSignature,
-            CloudFrontKeyPairId = dto.CloudFrontKeyPairId
-        };
-    }
-
-    private static VideoSources? MapVideoSources(VideoSourcesDto? dto) => dto == null
-        ? null
-        : new VideoSources { _240 = dto._240, _720 = dto._720 };
 }
diff --git a/OF DL.Core/Models/Mappers/PurchasedMapper.cs b/OF DL.Core/Models/Mappers/PurchasedMapper.cs
index 43b5830..9ace9e5 100644
--- a/OF DL.Core/Models/Mappers/PurchasedMapper.cs	
+++ b/OF DL.Core/Models/Mappers/PurchasedMapper.cs	
@@ -1,5 +1,4 @@
 using OF_DL.Models.Dtos.Purchased;
-using OF_DL.Models.Dtos.Common;
 using MessageDtos = OF_DL.Models.Dtos.Messages;
 using CommonEntities = OF_DL.Models.Entities.Common;
 using MessageEntities = OF_DL.Models.Entities.Messages;
@@ -42,14 +41,18 @@ public static class PurchasedMapper
             Previews = dto.Previews,
             Preview = dto.Preview,
             FromUser = MapFromUser(dto.FromUser),
-            Author = MapAuthor(dto.Author)
+            Author = CommonMapper.MapAuthor(dto.Author)
         };
 
-    private static CommonEntities.FromUser MapFromUser(FromUserDto? dto) =>
-        dto == null ? new CommonEntities.FromUser() : new CommonEntities.FromUser { Id = dto.Id };
+    private static CommonEntities.FromUser? MapFromUser(FromUserDto? dto)
+    {
+        if (dto == null || dto.Id == 0)
+        {
+            return null;
+        }
 
-    private static CommonEntities.Author MapAuthor(AuthorDto? dto) =>
-        dto == null ? new CommonEntities.Author() : new CommonEntities.Author { Id = dto.Id };
+        return new CommonEntities.FromUser { Id = dto.Id };
+    }
 
     private static List<MessageEntities.Medium>? MapMedia(List<MessageDtos.MediumDto>? media) =>
         media?.Select(MessagesMapper.MapMedium).ToList();
diff --git a/OF DL.Core/Models/Mappers/StoriesMapper.cs b/OF DL.Core/Models/Mappers/StoriesMapper.cs
index 4ccdd03..70ef4aa 100644
--- a/OF DL.Core/Models/Mappers/StoriesMapper.cs	
+++ b/OF DL.Core/Models/Mappers/StoriesMapper.cs	
@@ -26,7 +26,6 @@ public static class StoriesMapper
             Files = MapFiles(dto.Files)
         };
 
-    private static Files MapFiles(FilesDto? dto) => new() { Full = MapFull(dto?.Full) };
-
-    private static Full MapFull(FullDto? dto) => new() { Url = dto?.Url };
+    private static Files MapFiles(FilesDto? dto) =>
+        new() { Full = CommonMapper.MapFull(dto?.Full) };
 }
diff --git a/OF DL.Core/Models/Mappers/StreamsMapper.cs b/OF DL.Core/Models/Mappers/StreamsMapper.cs
index 3b3e30d..caa61ee 100644
--- a/OF DL.Core/Models/Mappers/StreamsMapper.cs	
+++ b/OF DL.Core/Models/Mappers/StreamsMapper.cs	
@@ -29,7 +29,7 @@ public static class StreamsMapper
         {
             Id = dto.Id,
             PostedAt = dto.PostedAt,
-            Author = MapAuthor(dto.Author),
+            Author = CommonMapper.MapAuthor(dto.Author),
             Text = dto.Text,
             RawText = dto.RawText,
             Price = dto.Price,
@@ -39,9 +39,6 @@ public static class StreamsMapper
             Preview = dto.Preview
         };
 
-    private static Author? MapAuthor(AuthorDto? dto) =>
-        dto == null ? null : new Author { Id = dto.Id };
-
     private static List<Medium>? MapMedia(List<MediumDto>? media) =>
         media?.Select(MapMedium).ToList();
 
@@ -55,7 +52,7 @@ public static class StreamsMapper
             return null;
         }
 
-        Full? full = MapFull(dto.Full);
+        Full? full = CommonMapper.MapFull(dto.Full);
         Drm? drm = MapDrm(dto.Drm);
 
         if (full == null && drm == null)
@@ -66,43 +63,15 @@ public static class StreamsMapper
         return new Files { Full = full, Drm = drm };
     }
 
-    private static Full? MapFull(FullDto? dto) =>
-        dto == null || string.IsNullOrEmpty(dto.Url) ? null : new Full { Url = dto.Url };
-
     private static Drm? MapDrm(DrmDto? dto)
     {
-        if (dto?.Manifest == null || string.IsNullOrEmpty(dto.Manifest.Dash))
+        Manifest? manifest = CommonMapper.MapManifest(dto?.Manifest);
+        if (manifest == null)
         {
             return null;
         }
 
-        Dash? dash = MapDash(dto.Signature.Dash);
-        if (dash == null)
-        {
-            return null;
-        }
-
-        return new Drm
-        {
-            Manifest = new Manifest { Dash = dto.Manifest.Dash }, Signature = new Signature { Dash = dash }
-        };
-    }
-
-    private static Dash? MapDash(DashDto? dto)
-    {
-        if (dto == null ||
-            string.IsNullOrEmpty(dto.CloudFrontPolicy) ||
-            string.IsNullOrEmpty(dto.CloudFrontSignature) ||
-            string.IsNullOrEmpty(dto.CloudFrontKeyPairId))
-        {
-            return null;
-        }
-
-        return new Dash
-        {
-            CloudFrontPolicy = dto.CloudFrontPolicy,
-            CloudFrontSignature = dto.CloudFrontSignature,
-            CloudFrontKeyPairId = dto.CloudFrontKeyPairId
-        };
+        Signature? signature = CommonMapper.MapSignature(dto?.Signature);
+        return signature == null ? null : new Drm { Manifest = manifest, Signature = signature };
     }
 }
diff --git a/OF DL.Core/Models/Mappers/UserListsMapper.cs b/OF DL.Core/Models/Mappers/UserListsMapper.cs
index 1ff4e32..7f0557a 100644
--- a/OF DL.Core/Models/Mappers/UserListsMapper.cs	
+++ b/OF DL.Core/Models/Mappers/UserListsMapper.cs	
@@ -22,15 +22,8 @@ public static class UserListsMapper
         return mapped;
     }
 
-    public static List<UsersList> FromDto(List<UsersListDto>? dto)
-    {
-        if (dto == null)
-        {
-            return [];
-        }
-
-        return dto.Select(MapUsersList).ToList();
-    }
+    public static List<UsersList> FromDto(List<UsersListDto>? dto) =>
+        dto == null ? [] : dto.Select(MapUsersList).ToList();
 
     private static UserListItem MapListItem(UserListItemDto dto) =>
         new() { Id = dto.Id, Name = dto.Name };