Added an additional check to Manga volume/chapter parser to handle duplicate volume/chapter markers in the file:

"Series - Vol 1 Ch 2.5 - Vol 2 Omakes"

This will now be parsed correctly as Volume 1 Chapter 2.5.

API.Tests/Parsing/MangaParsingTests.cs

@@ -1,4 +1,5 @@
 using API.Entities.Enums;
+using API.Services.Tasks.Scanner.Parser;
 using Xunit;
 
 namespace API.Tests.Parsing;
@@ -17,7 +18,7 @@ public class MangaParsingTests
     [InlineData("v001", "1")]
     [InlineData("Vol 1", "1")]
     [InlineData("vol_356-1", "356")] // Mangapy syntax
-    [InlineData("No Volume", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("No Volume", Parser.LooseLeafVolume)]
     [InlineData("U12 (Under 12) Vol. 0001 Ch. 0001 - Reiwa Scans (gb)", "1")]
     [InlineData("[Suihei Kiki]_Kasumi_Otoko_no_Ko_[Taruby]_v1.1.zip", "1.1")]
     [InlineData("Tonikaku Cawaii [Volume 11].cbz", "11")]
@@ -32,18 +33,18 @@ public class MangaParsingTests
     [InlineData("Dorohedoro v01 (2010) (Digital) (LostNerevarine-Empire).cbz", "1")]
     [InlineData("Dorohedoro v11 (2013) (Digital) (LostNerevarine-Empire).cbz", "11")]
     [InlineData("Yumekui_Merry_v01_c01[Bakayarou-Kuu].rar", "1")]
-    [InlineData("Yumekui-Merry_DKThias_Chapter11v2.zip", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("Yumekui-Merry_DKThias_Chapter11v2.zip", Parser.LooseLeafVolume)]
     [InlineData("Itoshi no Karin - c001-006x1 (v01) [Renzokusei Scans]", "1")]
-    [InlineData("Kedouin Makoto - Corpse Party Musume, Chapter 12", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("Kedouin Makoto - Corpse Party Musume, Chapter 12", Parser.LooseLeafVolume)]
     [InlineData("VanDread-v01-c001[MD].zip", "1")]
     [InlineData("Ichiban_Ushiro_no_Daimaou_v04_ch27_[VISCANS].zip", "4")]
     [InlineData("Mob Psycho 100 v02 (2019) (Digital) (Shizu).cbz", "2")]
     [InlineData("Kodomo no Jikan vol. 1.cbz", "1")]
     [InlineData("Kodomo no Jikan vol. 10.cbz", "10")]
-    [InlineData("Kedouin Makoto - Corpse Party Musume, Chapter 12 [Dametrans][v2]", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("Kedouin Makoto - Corpse Party Musume, Chapter 12 [Dametrans][v2]", Parser.LooseLeafVolume)]
     [InlineData("Vagabond_v03", "3")]
     [InlineData("Mujaki No Rakune Volume 10.cbz", "10")]
-    [InlineData("Umineko no Naku Koro ni - Episode 3 - Banquet of the Golden Witch #02.cbz", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("Umineko no Naku Koro ni - Episode 3 - Banquet of the Golden Witch #02.cbz", Parser.LooseLeafVolume)]
     [InlineData("Volume 12 - Janken Boy is Coming!.cbz", "12")]
     [InlineData("[dmntsf.net] One Piece - Digital Colored Comics Vol. 20 Ch. 177 - 30 Million vs 81 Million.cbz", "20")]
     [InlineData("Gantz.V26.cbz", "26")]
@@ -52,7 +53,7 @@ public class MangaParsingTests
     [InlineData("NEEDLESS_Vol.4_-_Simeon_6_v2_[SugoiSugoi].rar", "4")]
     [InlineData("Okusama wa Shougakusei c003 (v01) [bokuwaNEET]", "1")]
     [InlineData("Sword Art Online Vol 10 - Alicization Running [Yen Press] [LuCaZ] {r2}.epub", "10")]
-    [InlineData("Noblesse - Episode 406 (52 Pages).7z", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("Noblesse - Episode 406 (52 Pages).7z", Parser.LooseLeafVolume)]
     [InlineData("X-Men v1 #201 (September 2007).cbz", "1")]
     [InlineData("Hentai Ouji to Warawanai Neko. - Vol. 06 Ch. 034.5", "6")]
     [InlineData("The 100 Girlfriends Who Really, Really, Really, Really, Really Love You - Vol. 03 Ch. 023.5 - Volume 3 Extras.cbz", "3")]
@@ -64,7 +65,7 @@ public class MangaParsingTests
     [InlineData("スライム倒して300年、知らないうちにレベルMAXになってました 1-3巻", "1-3")]
     [InlineData("Dance in the Vampire Bund {Special Edition} v03.5 (2019) (Digital) (KG Manga)", "3.5")]
     [InlineData("Kebab Том 1 Глава 3", "1")]
-    [InlineData("Манга Глава 2", API.Services.Tasks.Scanner.Parser.Parser.LooseLeafVolume)]
+    [InlineData("Манга Глава 2", Parser.LooseLeafVolume)]
     [InlineData("Манга Тома 1-4", "1-4")]
     [InlineData("Манга Том 1-4", "1-4")]
     [InlineData("조선왕조실톡 106화", "106")]
@@ -72,13 +73,54 @@ public class MangaParsingTests
     [InlineData("몰?루 아카이브 7.5권", "7.5")]
     [InlineData("63권#200", "63")]
     [InlineData("시즌34삽화2", "34")]
+    [InlineData("시즌3-4삽화2", "3-4")]
     [InlineData("Accel World Chapter 001 Volume 002", "2")]
     [InlineData("Accel World Volume 2", "2")]
     [InlineData("Nagasarete Airantou - Vol. 30 Ch. 187.5 - Vol.31 Omake", "30")]
     [InlineData("Zom 100 - Bucket List of the Dead v01",  "1")]
     public void ParseVolumeTest(string filename, string expected)
     {
-        Assert.Equal(expected, API.Services.Tasks.Scanner.Parser.Parser.ParseVolume(filename, LibraryType.Manga));
+        Assert.Equal(expected, Parser.ParseVolume(filename, LibraryType.Manga));
+    }
+
+    [Theory]
+    [InlineData("One Piece - Vol 2 Ch 1.1 - Volume 4 Omakes", "2")]
+    [InlineData("Attack on Titan - Vol. 5 Ch. 20 - Vol.10 Special", "5")]
+    [InlineData("Naruto - Volume 1 Chapter 1 - Volume 2 Preview", "1")]
+    [InlineData("My Hero Academia - Vol 15 - Vol 20 Extras", "15")]
+
+    // Edge cases for duplicate detection
+    [InlineData("Series - Vol 1 - Not Vol but Voldemort", "1")] // Should not trigger false positive
+    [InlineData("Volume Wars - Vol 1 vs Vol 2", "1")] // Series name contains "Volume"
+    [InlineData("Vol 3 - The Volume Chronicles - Vol 5", "3")] // Multiple volume references
+
+    // Thai Volume tests
+    [InlineData("เล่ม 5 - Chapter 1", "5")]
+    [InlineData("เล่มที่ 12 Test", "12")]
+
+    // Chinese Volume tests
+    [InlineData("幽游白书完全版 第03卷 天下", "3")]
+    [InlineData("阿衰online 第1册", "1")]
+    [InlineData("卷5 Test", "5")]
+    [InlineData("册10 Test", "10")]
+
+    // Korean Volume tests
+    [InlineData("제5권 Test", "5")]
+    [InlineData("10화 Test", "10")]
+    [InlineData("시즌3 Test", "3")]
+    [InlineData("5시즌 Test", Parser.LooseLeafVolume)]
+
+    // Japanese Volume tests
+    [InlineData("Test 5巻", "5")]
+    [InlineData("Series 10-15巻", "10-15")]
+
+    // Russian Volume tests
+    [InlineData("Том 5 Test", "5")]
+    [InlineData("Тома 10 Test", "10")]
+    [InlineData("5 Том Test", "5")]
+    public void ParseDuplicateVolumeTest(string filename, string expected)
+    {
+        Assert.Equal(expected, Parser.ParseVolume(filename, LibraryType.Manga));
     }
 
     [Theory]
@@ -208,19 +250,19 @@ public class MangaParsingTests
     [InlineData("Zom 100 - Bucket List of the Dead v01",  "Zom 100 - Bucket List of the Dead")]
     public void ParseSeriesTest(string filename, string expected)
     {
-        Assert.Equal(expected, API.Services.Tasks.Scanner.Parser.Parser.ParseSeries(filename, LibraryType.Manga));
+        Assert.Equal(expected, Parser.ParseSeries(filename, LibraryType.Manga));
     }
 
     [Theory]
     [InlineData("Killing Bites Vol. 0001 Ch. 0001 - Galactica Scanlations (gb)", "1")]
     [InlineData("My Girlfriend Is Shobitch v01 - ch. 09 - pg. 008.png", "9")]
     [InlineData("Historys Strongest Disciple Kenichi_v11_c90-98.zip", "90-98")]
-    [InlineData("B_Gata_H_Kei_v01[SlowManga&OverloadScans]", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("B_Gata_H_Kei_v01[SlowManga&OverloadScans]", Parser.DefaultChapter)]
-    [InlineData("BTOOOM! v01 (2013) (Digital) (Shadowcat-Empire)", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("BTOOOM! v01 (2013) (Digital) (Shadowcat-Empire)", Parser.DefaultChapter)]
     [InlineData("Gokukoku no Brynhildr - c001-008 (v01) [TrinityBAKumA]", "1-8")]
-    [InlineData("Dance in the Vampire Bund v16-17 (Digital) (NiceDragon)", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Dance in the Vampire Bund v16-17 (Digital) (NiceDragon)", Parser.DefaultChapter)]
     [InlineData("c001", "1")]
-    [InlineData("[Suihei Kiki]_Kasumi_Otoko_no_Ko_[Taruby]_v1.12.zip", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("[Suihei Kiki]_Kasumi_Otoko_no_Ko_[Taruby]_v1.12.zip", Parser.DefaultChapter)]
     [InlineData("Adding volume 1 with File: Ana Satsujin Vol. 1 Ch. 5 - Manga Box (gb).cbz", "5")]
     [InlineData("Hinowa ga CRUSH! 018 (2019) (Digital) (LuCaZ).cbz", "18")]
     [InlineData("Cynthia The Mission - c000-006 (v06) [Desudesu&Brolen].zip", "0-6")]
@@ -243,7 +285,7 @@ public class MangaParsingTests
     [InlineData("Itoshi no Karin - c001-006x1 (v01) [Renzokusei Scans]", "1-6")]
     [InlineData("APOSIMZ 040 (2020) (Digital) (danke-Empire).cbz", "40")]
     [InlineData("Kedouin Makoto - Corpse Party Musume, Chapter 12", "12")]
-    [InlineData("Vol 1", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Vol 1", Parser.DefaultChapter)]
     [InlineData("VanDread-v01-c001[MD].zip", "1")]
     [InlineData("Goblin Slayer Side Story - Year One 025.5", "25.5")]
     [InlineData("Kedouin Makoto - Corpse Party Musume, Chapter 01", "1")]
@@ -255,10 +297,10 @@ public class MangaParsingTests
     [InlineData("Fullmetal Alchemist chapters 101-108.cbz", "101-108")]
     [InlineData("Umineko no Naku Koro ni - Episode 3 - Banquet of the Golden Witch #02.cbz", "2")]
     [InlineData("To Love Ru v09 Uncensored (Ch.071-079).cbz", "71-79")]
-    [InlineData("Corpse Party -The Anthology- Sachikos game of love Hysteric Birthday 2U Extra Chapter.rar", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Corpse Party -The Anthology- Sachikos game of love Hysteric Birthday 2U Extra Chapter.rar", Parser.DefaultChapter)]
     [InlineData("Beelzebub_153b_RHS.zip", "153.5")]
     [InlineData("Beelzebub_150-153b_RHS.zip", "150-153.5")]
-    [InlineData("Transferred to another world magical swordsman v1.1", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Transferred to another world magical swordsman v1.1", Parser.DefaultChapter)]
     [InlineData("Kiss x Sis - Ch.15 - The Angst of a 15 Year Old Boy.cbz", "15")]
     [InlineData("Kiss x Sis - Ch.12 - 1 , 2 , 3P!.cbz", "12")]
     [InlineData("Umineko no Naku Koro ni - Episode 1 - Legend of the Golden Witch #1", "1")]
@@ -277,21 +319,21 @@ public class MangaParsingTests
     [InlineData("Kimi no Koto ga Daidaidaidaidaisuki na 100-nin no Kanojo Chapter 1-10", "1-10")]
     [InlineData("Deku_&_Bakugo_-_Rising_v1_c1.1.cbz", "1.1")]
     [InlineData("Chapter 63 - The Promise Made for 520 Cenz.cbr", "63")]
-    [InlineData("Harrison, Kim - The Good, The Bad, and the Undead - Hollows Vol 2.5.epub", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Harrison, Kim - The Good, The Bad, and the Undead - Hollows Vol 2.5.epub", Parser.DefaultChapter)]
     [InlineData("Kaiju No. 8 036 (2021) (Digital)", "36")]
-    [InlineData("Samurai Jack Vol. 01 - The threads of Time", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Samurai Jack Vol. 01 - The threads of Time", Parser.DefaultChapter)]
     [InlineData("【TFO汉化&Petit汉化】迷你偶像漫画第25话", "25")]
     [InlineData("자유록 13회#2", "13")]
     [InlineData("이세계에서 고아원을 열었지만, 어째서인지 아무도 독립하려 하지 않는다 38-1화 ", "38")]
     [InlineData("[ハレム]ナナとカオル ～高校生のSMごっこ～　第10話", "10")]
-    [InlineData("Dance in the Vampire Bund {Special Edition} v03.5 (2019) (Digital) (KG Manga)", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Dance in the Vampire Bund {Special Edition} v03.5 (2019) (Digital) (KG Manga)", Parser.DefaultChapter)]
     [InlineData("Kebab Том 1 Глава 3", "3")]
     [InlineData("Манга Глава 2", "2")]
     [InlineData("Манга 2 Глава", "2")]
     [InlineData("Манга Том 1 2 Глава", "2")]
     [InlineData("Accel World Chapter 001 Volume 002", "1")]
     [InlineData("Bleach 001-003", "1-3")]
-    [InlineData("Accel World Volume 2", API.Services.Tasks.Scanner.Parser.Parser.DefaultChapter)]
+    [InlineData("Accel World Volume 2", Parser.DefaultChapter)]
     [InlineData("Historys Strongest Disciple Kenichi_v11_c90-98", "90-98")]
     [InlineData("Historys Strongest Disciple Kenichi c01-c04", "1-4")]
     [InlineData("Adabana c00-02", "0-2")]
@@ -301,7 +343,36 @@ public class MangaParsingTests
     [InlineData("Monster #8 Ch. 001", "1")]
     public void ParseChaptersTest(string filename, string expected)
     {
-        Assert.Equal(expected, API.Services.Tasks.Scanner.Parser.Parser.ParseChapter(filename, LibraryType.Manga));
+        Assert.Equal(expected, Parser.ParseChapter(filename, LibraryType.Manga));
+    }
+
+    /// <summary>
+    /// Handles edge case testing around duplicate numbers in the filename
+    /// </summary>
+    [Theory]
+    [InlineData("Manga Title - Ch.1 - The 22 beers", "1")]
+    public void ParseExtraNumberChaptersTest(string filename, string expected)
+    {
+        Assert.Equal(expected, Parser.ParseChapter(filename, LibraryType.Manga));
+    }
+
+    [Theory]
+    [InlineData("Manga Title - Ch.1 Part.A - Ch.2 Omake", "1")]
+    [InlineData("Another Series - Chapter 10 Something - Chapter 15 Extra", "10")]
+    [InlineData("Test_Ch_3_Content_Ch_7_Bonus", "3")]
+    [InlineData("One Piece - Ch 5 Part 1 - Chapter 10 Omakes", "5")]
+    [InlineData("Attack on Titan - Chapter 20 Content - Ch 25 Special", "20")]
+    [InlineData("Naruto - Ch. 1 Story - Ch. 5 Preview", "1")]
+    [InlineData("My Hero Academia - Chapter 15 - Chapter 20 Extras", "15")]
+    [InlineData("Series Name - c2 Content - c5 Bonus", "2")]
+    [InlineData("Test Series - c1 Part1 - Chapter 3 Extra", "1")]
+    [InlineData("Another Test - Chapter 7 - c10 Omake", "7")]
+    [InlineData("Series - Ch 1 - Not Ch but Chaos", "1")]
+    [InlineData("Chapter Wars - Ch 1 vs Ch 2", "1")]
+    [InlineData("Ch 3 - The Chapter Chronicles - Ch 5", "3")]
+    public void ParseDuplicateChapterTest(string filename, string expected)
+    {
+        Assert.Equal(expected, Parser.ParseChapter(filename, LibraryType.Manga));
     }
 
 
@@ -318,7 +389,7 @@ public class MangaParsingTests
     [InlineData("Love Hina Omnibus v05 (2015) (Digital-HD) (Asgard-Empire).cbz", "Omnibus")]
     public void ParseEditionTest(string input, string expected)
     {
-        Assert.Equal(expected, API.Services.Tasks.Scanner.Parser.Parser.ParseEdition(input));
+        Assert.Equal(expected, Parser.ParseEdition(input));
     }
     [Theory]
     [InlineData("Beelzebub Special OneShot - Minna no Kochikame x Beelzebub (2016) [Mangastream].cbz", false)]
@@ -339,7 +410,7 @@ public class MangaParsingTests
     [InlineData("Hajime no Ippo - Artbook", false)]
     public void IsMangaSpecialTest(string input, bool expected)
     {
-        Assert.Equal(expected, API.Services.Tasks.Scanner.Parser.Parser.IsSpecial(input, LibraryType.Manga));
+        Assert.Equal(expected, Parser.IsSpecial(input, LibraryType.Manga));
     }
 
     [Theory]
@@ -348,7 +419,7 @@ public class MangaParsingTests
     [InlineData("image.txt", MangaFormat.Unknown)]
     public void ParseFormatTest(string inputFile, MangaFormat expected)
     {
-        Assert.Equal(expected, API.Services.Tasks.Scanner.Parser.Parser.ParseFormat(inputFile));
+        Assert.Equal(expected, Parser.ParseFormat(inputFile));
     }
 
 

API/Services/Tasks/Scanner/Parser/Parser.cs

@@ -117,6 +117,36 @@ public static partial class Parser
     private static readonly Regex SpecialTokenRegex = new(@"SP\d+",
         MatchOptions, RegexTimeout);
 
+    /// <summary>
+    /// An additional check to avoid situations like "One Piece - Vol 4 ch 2 - vol 6 omakes"
+    /// </summary>
+    private static readonly Regex DuplicateVolumeRegex = new Regex(
+        @"(?i)(vol\.?|volume|v)(\s|_)*\d+.*?(vol\.?|volume|v)(\s|_)*\d+",
+        MatchOptions, RegexTimeout);
+
+    private static readonly Regex DuplicateChapterRegex = new Regex(
+        @"(?i)(ch\.?|chapter|c)(\s|_)*\d+.*?(ch\.?|chapter|c)(\s|_)*\d+",
+        MatchOptions, RegexTimeout);
+
+    // Regex to detect range patterns that should NOT be treated as duplicates (History's Strongest c1-c4)
+    private static readonly Regex VolumeRangeRegex = new Regex(
+        @"(vol\.?|v)(\s|_)?\d+(\.\d+)?-(vol\.?|v)(\s|_)?\d+(\.\d+)?",
+        MatchOptions, RegexTimeout);
+
+    private static readonly Regex ChapterRangeRegex = new Regex(
+        @"(ch\.?|c)(\s|_)?\d+(\.\d+)?-(ch\.?|c)(\s|_)?\d+(\.\d+)?",
+        MatchOptions, RegexTimeout);
+
+    // Regex to find volume number after a volume marker
+    private static readonly Regex VolumeNumberRegex = new Regex(
+        @"(vol\.?|volume|v)(\s|_)*(?<Volume>\d+(\.\d+)?(-\d+(\.\d+)?)?)",
+        MatchOptions, RegexTimeout);
+
+    // Regex to find chapter number after a chapter marker
+    private static readonly Regex ChapterNumberRegex = new Regex(
+        @"(ch\.?|chapter|c)(\s|_)*(?<Chapter>\d+(\.\d+)?(-\d+(\.\d+)?)?)",
+        MatchOptions, RegexTimeout);
+
 
     private static readonly Regex[] MangaVolumeRegex =
     [
@@ -171,7 +201,7 @@ public static partial class Parser
             MatchOptions, RegexTimeout),
         // Korean Season: 시즌n -> Season n,
         new Regex(
-            @"시즌(?<Volume>\d+\-?\d+)",
+            @"시즌(?<Volume>\d+(\-\d+)?)",
             MatchOptions, RegexTimeout),
         // Korean Season: 시즌n -> Season n, n시즌 -> season n
         new Regex(
@@ -741,6 +771,8 @@ public static partial class Parser
 
     public static string ParseMangaVolume(string filename)
     {
+        filename = RemoveDuplicateVolumeIfExists(filename);
+
         foreach (var regex in MangaVolumeRegex)
         {
             var matches = regex.Matches(filename);
@@ -841,6 +873,8 @@ public static partial class Parser
 
     private static string ParseMangaChapter(string filename)
     {
+        filename = RemoveDuplicateChapterIfExists(filename);
+
         foreach (var regex in MangaChapterRegex)
         {
             var matches = regex.Matches(filename);
@@ -1185,6 +1219,75 @@ public static partial class Parser
         return filename;
     }
 
+    /// <summary>
+    /// Checks for a duplicate volume marker and removes it
+    /// </summary>
+    /// <param name="filename"></param>
+    /// <returns></returns>
+    private static string RemoveDuplicateVolumeIfExists(string filename)
+    {
+        // First check if this contains a volume range pattern - if so, don't process as duplicate (v1-v2, edge case)
+        if (VolumeRangeRegex.IsMatch(filename))
+            return filename;
+
+        var duplicateMatch = DuplicateVolumeRegex.Match(filename);
+        if (!duplicateMatch.Success) return filename;
+
+        // Find the start position of the first volume marker
+        var firstVolumeStart = duplicateMatch.Groups[1].Index;
+
+        // Find the volume number after the first marker
+        var volumeNumberMatch = VolumeNumberRegex.Match(filename, firstVolumeStart);
+        if (!volumeNumberMatch.Success) return filename;
+
+        var volumeNumberEnd = volumeNumberMatch.Index + volumeNumberMatch.Length;
+
+        // Find the second volume marker after the first volume number
+        var secondVolumeMatch = VolumeNumberRegex.Match(filename, volumeNumberEnd);
+        if (secondVolumeMatch.Success)
+        {
+            // Truncate the filename at the second volume marker
+            return filename.Substring(0, secondVolumeMatch.Index).TrimEnd(' ', '-', '_');
+        }
+
+        return filename;
+    }
+
+    /// <summary>
+    /// Removes duplicate chapter markers from filename, keeping only the first occurrence
+    /// </summary>
+    /// <param name="filename">Original filename</param>
+    /// <returns>Processed filename with duplicate chapter markers removed</returns>
+    public static string RemoveDuplicateChapterIfExists(string filename)
+    {
+        // First check if this contains a chapter range pattern - if so, don't process as duplicate (c1-c2, edge case)
+        if (ChapterRangeRegex.IsMatch(filename))
+            return filename;
+
+        var duplicateMatch = DuplicateChapterRegex.Match(filename);
+        if (!duplicateMatch.Success) return filename;
+
+        // Find the start position of the first chapter marker
+        var firstChapterStart = duplicateMatch.Groups[1].Index;
+
+        // Find the chapter number after the first marker
+        var chapterNumberMatch = ChapterNumberRegex.Match(filename, firstChapterStart);
+        if (!chapterNumberMatch.Success) return filename;
+
+        var chapterNumberEnd = chapterNumberMatch.Index + chapterNumberMatch.Length;
+
+        // Find the second chapter marker after the first chapter number
+        var secondChapterMatch = ChapterNumberRegex.Match(filename, chapterNumberEnd);
+        if (secondChapterMatch.Success)
+        {
+            // Truncate the filename at the second chapter marker
+            return filename.Substring(0, secondChapterMatch.Index).TrimEnd(' ', '-', '_');
+        }
+
+        return filename;
+    }
+
+
     [GeneratedRegex(SupportedExtensions)]
     private static partial Regex SupportedExtensionsRegex();
     [GeneratedRegex(@"\d-{1}\d")]