Recognize trailing [tag] on folder, guard metadata tags

Folders that carry their release tag as a bracket at the end
(rather than a -TAG suffix or [TAG] prefix), e.g.:
  Gravity Falls 2012  Season 2 Complete + EXTRAS 720p BluRay x264 [i_c]
now have that tag ([i_c]) prepended to the episode filename.

Also fixes a real bug where a title's own hyphenated word (e.g.
"Scary-oke") could be mistaken for a "-GroupName" suffix; the word
before the dash must now itself look like quality/source/codec
metadata for that pattern to fire.

Every tag-extraction path (file dash-suffix, file trailing-parens
group, folder dash-suffix, folder bracket-suffix, folder bracket-
prefix) now also refuses to promote something that's obviously a
metadata token itself (e.g. WEB, 1080p, HDR, WEBRip) to a release
tag.

Services/FileNameHelper.cs

@@ -14,11 +14,21 @@ public static class FileNameHelper
     private static readonly Regex FolderSuffixTagRegex =
         new(@"-([A-Z][A-Z0-9]{1,7})$", RegexOptions.Compiled);
 
+    // Folder suffix bracket release tag:  "Show Name ... x264 [i_c]"  →  tag = "i_c"
+    // A bracketed tag at the very end of the folder name (as opposed to
+    // PrefixTagRegex, which matches one at the start).
+    private static readonly Regex FolderSuffixBracketTagRegex =
+        new(@"\[([^\[\]]+)\]$", RegexOptions.Compiled);
+
     // File suffix release tag:  "…HEVC-DemiHuman"  →  tag = "DemiHuman"
     // Mixed case, 3-21 chars (no dots/spaces), at end of filename stem.
-    // Min 3 chars avoids false-positives like "-v2" or "-HD".
+    // Min 3 chars avoids false-positives like "-v2" or "-HD". The word
+    // immediately preceding the dash must itself be recognisable quality/
+    // source/codec metadata (checked by the caller via IsMetadataToken), so
+    // an ordinary hyphenated title word (e.g. "Scary-oke") is never mistaken
+    // for a "-GroupName" suffix.
     private static readonly Regex FileSuffixTagRegex =
-        new(@"-([A-Za-z][A-Za-z0-9]{2,20})$", RegexOptions.Compiled);
+        new(@"(?:^|[\s.])([A-Za-z0-9]+)-([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".
@@ -86,13 +96,18 @@ public static class FileNameHelper
         string folderName  = string.IsNullOrEmpty(folder) ? "" : (Path.GetFileName(folder) ?? "");
 
         // 1. Extract in-filename suffix tag and remove it from the stem.
-        //    e.g. "...HEVC-DemiHuman" → tag="DemiHuman", stem="...HEVC"
+        //    e.g. "...x264-DemiHuman" → tag="DemiHuman", stem="...x264"
+        //    Only fires when the word right before the dash is itself a
+        //    recognised metadata token (codec/source/etc.), so ordinary
+        //    hyphenated title words are left alone.
         string? fileTag = null;
         var fileSuffixMatch = FileSuffixTagRegex.Match(stemNoExt);
-        if (fileSuffixMatch.Success)
+        if (fileSuffixMatch.Success
+            && IsMetadataToken(fileSuffixMatch.Groups[1].Value)
+            && !IsMetadataToken(fileSuffixMatch.Groups[2].Value))
         {
-            fileTag  = fileSuffixMatch.Groups[1].Value;
-            stemNoExt = stemNoExt[..fileSuffixMatch.Index];
+            fileTag  = fileSuffixMatch.Groups[2].Value;
+            stemNoExt = stemNoExt[..(fileSuffixMatch.Groups[2].Index - 1)];
             fileName  = stemNoExt + ext;
         }
         else
@@ -169,17 +184,24 @@ public static class FileNameHelper
     }
 
     /// <summary>
-    /// Extracts the release tag string (without brackets) from a folder name.
-    /// Suffix pattern (<c>-TAG</c>) takes priority over prefix pattern
-    /// (<c>[TAG]</c>).  Returns <c>null</c> when neither is present.
+    /// Extracts the release tag string (without brackets) from a folder name,
+    /// checking (in priority order): a dash suffix (<c>-TAG</c>), a bracketed
+    /// suffix (<c>[tag]</c> at the end), then a bracketed prefix (<c>[tag]</c>
+    /// at the start). Returns <c>null</c> when none are present.
     /// </summary>
     public static string? ExtractReleaseTag(string folderName)
     {
         var suffixMatch = FolderSuffixTagRegex.Match(folderName);
-        if (suffixMatch.Success) return suffixMatch.Groups[1].Value;
+        if (suffixMatch.Success && !IsMetadataToken(suffixMatch.Groups[1].Value))
+            return suffixMatch.Groups[1].Value;
+
+        var bracketSuffixMatch = FolderSuffixBracketTagRegex.Match(folderName);
+        if (bracketSuffixMatch.Success && !IsMetadataBracket(bracketSuffixMatch.Groups[1].Value))
+            return bracketSuffixMatch.Groups[1].Value;
 
         var prefixMatch = PrefixTagRegex.Match(folderName);
-        if (prefixMatch.Success) return prefixMatch.Groups[1].Value;
+        if (prefixMatch.Success && !IsMetadataBracket(prefixMatch.Groups[1].Value))
+            return prefixMatch.Groups[1].Value;
 
         return null;
     }
@@ -198,6 +220,7 @@ public static class FileNameHelper
     {
         // Strip release tags first.
         string name = FolderSuffixTagRegex.Replace(folderName, "").Trim();
+        name = FolderSuffixBracketTagRegex.Replace(name, "").Trim();
         name = PrefixTagRegex.Replace(name, "").Trim();
 
         // Nothing left, or what remains immediately starts with a bracket — no show name.
@@ -226,4 +249,16 @@ public static class FileNameHelper
             if (pattern.IsMatch(token)) return true;
         return false;
     }
+
+    /// <summary>
+    /// True when every word inside a bracketed block is recognisable quality/
+    /// source/codec metadata (e.g. "[HEVC]", "[1080p-FLAC]"), meaning it's
+    /// just another metadata tag rather than an actual release group name
+    /// (e.g. "[i_c]").
+    /// </summary>
+    private static bool IsMetadataBracket(string content)
+    {
+        var parts = content.Split(new[] { ' ', '-' }, StringSplitOptions.RemoveEmptyEntries);
+        return parts.Length > 0 && parts.All(IsMetadataToken);
+    }
 }