Update avatar resolving for users without discriminator

DiscordChatExporter.Core/Discord/Data/Common/ImageCdn.cs

@@ -47,8 +47,8 @@ public static class ImageCdn
             ? $"https://cdn.discordapp.com/avatars/{userId}/{avatarHash}.gif?size={size}"
             : $"https://cdn.discordapp.com/avatars/{userId}/{avatarHash}.png?size={size}";
 
-    public static string GetFallbackUserAvatarUrl(int discriminator) =>
-        $"https://cdn.discordapp.com/embed/avatars/{discriminator % 5}.png";
+    public static string GetFallbackUserAvatarUrl(int index = 0) =>
+        $"https://cdn.discordapp.com/embed/avatars/{index}.png";
 
     public static string GetMemberAvatarUrl(Snowflake guildId, Snowflake userId, string avatarHash, int size = 512) =>
         avatarHash.StartsWith("a_", StringComparison.Ordinal)

DiscordChatExporter.Core/Discord/Data/Guild.cs

@@ -12,7 +12,7 @@ public record Guild(Snowflake Id, string Name, string IconUrl) : IHasId
     public static Guild DirectMessages { get; } = new(
         Snowflake.Zero,
         "Direct Messages",
-        ImageCdn.GetFallbackUserAvatarUrl(0)
+        ImageCdn.GetFallbackUserAvatarUrl()
     );
 
     public static Guild Parse(JsonElement json)
@@ -25,7 +25,7 @@ public record Guild(Snowflake Id, string Name, string IconUrl) : IHasId
                 .GetPropertyOrNull("icon")?
                 .GetNonWhiteSpaceStringOrNull()?
                 .Pipe(h => ImageCdn.GetGuildIconUrl(id, h)) ??
-            ImageCdn.GetFallbackUserAvatarUrl(0);
+            ImageCdn.GetFallbackUserAvatarUrl();
 
         return new Guild(id, name, iconUrl);
     }

DiscordChatExporter.Core/Discord/Data/User.cs

@@ -45,12 +45,14 @@ public partial record User
         var name = json.GetProperty("username").GetNonNullString();
         var displayName = json.GetPropertyOrNull("global_name")?.GetNonWhiteSpaceStringOrNull() ?? name;
 
+        var avatarIndex = discriminator % 5 ?? (int)((id.Value >> 22) % 6);
+
         var avatarUrl =
             json
                 .GetPropertyOrNull("avatar")?
                 .GetNonWhiteSpaceStringOrNull()?
                 .Pipe(h => ImageCdn.GetUserAvatarUrl(id, h)) ??
-            ImageCdn.GetFallbackUserAvatarUrl(discriminator ?? 0);
+            ImageCdn.GetFallbackUserAvatarUrl(avatarIndex);
 
         return new User(id, isBot, discriminator, name, displayName, avatarUrl);
     }