Extract release group from trailing (...) metadata

Amazon/streaming rips like:
  Helluva Boss (2020) - S01E01 - Murder Family (1080p AMZN WEB-DL x265 Celdra)
tuck the release group in as the last word of the closing metadata
block instead of a "-Group" suffix or its own brackets. That trailing
word is now promoted to a [Group] prefix and stripped from the
parentheses, e.g.:
  [Celdra] Helluva Boss (2020) - S01E01 - Murder Family (1080p AMZN WEB-DL x265)

Only fires when the rest of the block already looks like quality
metadata (resolution/source/codec/etc.), so unrelated parentheticals
like "(2020)" or "(Dual Audio)" are left untouched.

Futonizer.csproj

@@ -9,8 +9,8 @@
     <ImplicitUsings>enable</ImplicitUsings>
     <AssemblyName>Futonizer</AssemblyName>
     <RootNamespace>Futonizer</RootNamespace>
-    <Version>1.0.7</Version>
+    <Version>1.0.8</Version>
-    <FileVersion>1.0.7.0</FileVersion>
+    <FileVersion>1.0.8.0</FileVersion>
     <ApplicationIcon>Assets\app.ico</ApplicationIcon>
   </PropertyGroup>
 

Services/FileNameHelper.cs

@@ -20,6 +20,13 @@ public static class FileNameHelper
     private static readonly Regex FileSuffixTagRegex =
         new(@"-([A-Za-z][A-Za-z0-9]{2,20})$", RegexOptions.Compiled);
 
+    // Trailing parenthesised metadata block ending in the release group as its
+    // last word, e.g. "... (1080p AMZN WEB-DL x265 Celdra)" → group="Celdra".
+    // Common on Amazon/streaming rips that don't set the group off with a
+    // "-" or its own brackets.
+    private static readonly Regex TrailingParenGroupRegex =
+        new(@"\(([^()]*)\)$", RegexOptions.Compiled);
+
     // Prefix release tag:  "[KAA] Show Name"  →  tag = "KAA"
     private static readonly Regex PrefixTagRegex =
         new(@"^\[(.+?)\]", RegexOptions.Compiled);
@@ -45,7 +52,8 @@ public static class FileNameHelper
         new(@"^(BD|BluRay|Blu-Ray|WEB|WEB-DL|WEBRip|HDTV|AMZN|NF|DSNP|HULU|MAX)$",RegexOptions.IgnoreCase | RegexOptions.Compiled), // sources
         new(@"^(Remux|Encode)$",                                                   RegexOptions.IgnoreCase | RegexOptions.Compiled), // processing
         new(@"^(HEVC|AVC|x264|x265|H\.?264|H\.?265|VP9)$",                        RegexOptions.IgnoreCase | RegexOptions.Compiled), // video codecs
-        new(@"^(FLAC|AAC|DTS|TrueHD|Atmos|AC3|EAC3|Opus|MP3)$",                  RegexOptions.IgnoreCase | RegexOptions.Compiled), // audio codecs
+        new(@"^(FLAC|AAC|DTS(-HD)?|TrueHD|Atmos|E?AC3|DDP?|Opus|MP3)(\d(\.\d)?)?$", RegexOptions.IgnoreCase | RegexOptions.Compiled), // audio codecs (+ optional channel suffix, e.g. DDP5.1)
+        new(@"^\d\.\d$",                                                           RegexOptions.Compiled),                           // bare channel count, e.g. 5.1
         new(@"^(HDR|SDR|10bit|8bit|HDR10|DV|DoVi)$",                              RegexOptions.IgnoreCase | RegexOptions.Compiled), // HDR / bit-depth
     ];
 
@@ -56,8 +64,10 @@ public static class FileNameHelper
     /// (in order):
     /// <list type="number">
     ///   <item>Filename suffix tag extraction — a trailing <c>-GroupName</c> on
-    ///         the filename stem is stripped and promoted to a bracket prefix.
+    ///         the filename stem, or a release group tucked in as the last word
-    ///         Takes priority over any folder-derived tag.</item>
+    ///         of a trailing <c>(...)</c> metadata block (e.g. Amazon rips like
+    ///         <c>(1080p AMZN WEB-DL x265 Celdra)</c>), is stripped and promoted
+    ///         to a bracket prefix. Takes priority over any folder-derived tag.</item>
     ///   <item>Show-name injection — if the (now tag-free) filename starts with
     ///         an episode code (e.g. S01E01) the show name is derived from the
     ///         parent folder and prepended.</item>
@@ -85,6 +95,31 @@ public static class FileNameHelper
             stemNoExt = stemNoExt[..fileSuffixMatch.Index];
             fileName  = stemNoExt + ext;
         }
+        else
+        {
+            // 1b. Extract a release group tucked in as the last word of a
+            //     trailing "(...)" metadata block, e.g.
+            //     "... (1080p AMZN WEB-DL x265 Celdra)" → tag="Celdra",
+            //     stem="... (1080p AMZN WEB-DL x265)".
+            var parenMatch = TrailingParenGroupRegex.Match(stemNoExt);
+            if (parenMatch.Success)
+            {
+                string parenContent = parenMatch.Groups[1].Value;
+                var words = parenContent.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+                // Only treat the last word as a release group if the rest of the
+                // block is recognisable quality/source/codec metadata — this
+                // avoids misfiring on unrelated parentheticals like "(2020)" or
+                // "(Dual Audio)" that don't carry a group name.
+                if (words.Length >= 2 && !IsMetadataToken(words[^1]) && words[..^1].Any(IsMetadataToken))
+                {
+                    fileTag = words[^1];
+                    string remaining = string.Join(" ", words[..^1]);
+                    string beforeParen = stemNoExt[..parenMatch.Index].TrimEnd();
+                    stemNoExt = string.IsNullOrEmpty(remaining) ? beforeParen : $"{beforeParen} ({remaining})";
+                    fileName = stemNoExt + ext;
+                }
+            }
+        }
 
         // 2. Determine the release tag: filename suffix > folder tag.
         string? tag = fileTag;