refactor: extract PathHelper to Services/Common for reusability

Moved PathHelper from DeezerDownloadService to Services/Common/ to:
- Remove awkward dependency of Qobuz on Deezer namespace
- Make path utilities reusable by all services
- Improve code organization and clarify dependencies

Updated imports in DeezerDownloadService, QobuzDownloadService,
BaseDownloadService, and DeezerDownloadServiceTests.

octo-fiesta.Tests/DeezerDownloadServiceTests.cs

@@ -1,6 +1,7 @@
 using octo_fiesta.Services;
 using octo_fiesta.Services.Deezer;
 using octo_fiesta.Services.Local;
+using octo_fiesta.Services.Common;
 using octo_fiesta.Models.Domain;
 using octo_fiesta.Models.Settings;
 using octo_fiesta.Models.Download;

octo-fiesta/Services/Common/BaseDownloadService.cs

@@ -4,7 +4,6 @@ using octo_fiesta.Models.Download;
 using octo_fiesta.Models.Search;
 using octo_fiesta.Models.Subsonic;
 using octo_fiesta.Services.Local;
-using octo_fiesta.Services.Deezer;
 using TagLib;
 using IOFile = System.IO.File;
 

octo-fiesta/Services/Common/PathHelper.cs

@@ -0,0 +1,125 @@
+using IOFile = System.IO.File;
+
+namespace octo_fiesta.Services.Common;
+
+/// <summary>
+/// Helper class for path building and sanitization.
+/// Provides utilities for creating safe file and folder paths for downloaded music files.
+/// </summary>
+public static class PathHelper
+{
+    /// <summary>
+    /// Builds the output path for a downloaded track following the Artist/Album/Track structure.
+    /// </summary>
+    /// <param name="downloadPath">Base download directory path.</param>
+    /// <param name="artist">Artist name (will be sanitized).</param>
+    /// <param name="album">Album name (will be sanitized).</param>
+    /// <param name="title">Track title (will be sanitized).</param>
+    /// <param name="trackNumber">Optional track number for prefix.</param>
+    /// <param name="extension">File extension (e.g., ".flac", ".mp3").</param>
+    /// <returns>Full path for the track file.</returns>
+    public static string BuildTrackPath(string downloadPath, string artist, string album, string title, int? trackNumber, string extension)
+    {
+        var safeArtist = SanitizeFolderName(artist);
+        var safeAlbum = SanitizeFolderName(album);
+        var safeTitle = SanitizeFileName(title);
+        
+        var artistFolder = Path.Combine(downloadPath, safeArtist);
+        var albumFolder = Path.Combine(artistFolder, safeAlbum);
+        
+        var trackPrefix = trackNumber.HasValue ? $"{trackNumber:D2} - " : "";
+        var fileName = $"{trackPrefix}{safeTitle}{extension}";
+        
+        return Path.Combine(albumFolder, fileName);
+    }
+
+    /// <summary>
+    /// Sanitizes a file name by removing invalid characters.
+    /// </summary>
+    /// <param name="fileName">Original file name.</param>
+    /// <returns>Sanitized file name safe for all file systems.</returns>
+    public static string SanitizeFileName(string fileName)
+    {
+        if (string.IsNullOrWhiteSpace(fileName))
+        {
+            return "Unknown";
+        }
+        
+        var invalidChars = Path.GetInvalidFileNameChars();
+        var sanitized = new string(fileName
+            .Select(c => invalidChars.Contains(c) ? '_' : c)
+            .ToArray());
+        
+        if (sanitized.Length > 100)
+        {
+            sanitized = sanitized[..100];
+        }
+        
+        return sanitized.Trim();
+    }
+
+    /// <summary>
+    /// Sanitizes a folder name by removing invalid path characters.
+    /// </summary>
+    /// <param name="folderName">Original folder name.</param>
+    /// <returns>Sanitized folder name safe for all file systems.</returns>
+    public static string SanitizeFolderName(string folderName)
+    {
+        if (string.IsNullOrWhiteSpace(folderName))
+        {
+            return "Unknown";
+        }
+        
+        var invalidChars = Path.GetInvalidFileNameChars()
+            .Concat(Path.GetInvalidPathChars())
+            .Distinct()
+            .ToArray();
+            
+        var sanitized = new string(folderName
+            .Select(c => invalidChars.Contains(c) ? '_' : c)
+            .ToArray());
+        
+        // Remove leading/trailing dots and spaces (Windows folder restrictions)
+        sanitized = sanitized.Trim().TrimEnd('.');
+        
+        if (sanitized.Length > 100)
+        {
+            sanitized = sanitized[..100].TrimEnd('.');
+        }
+        
+        // Ensure we have a valid name
+        if (string.IsNullOrWhiteSpace(sanitized))
+        {
+            return "Unknown";
+        }
+        
+        return sanitized;
+    }
+
+    /// <summary>
+    /// Resolves a unique file path by appending a counter if the file already exists.
+    /// </summary>
+    /// <param name="basePath">Desired file path.</param>
+    /// <returns>Unique file path that does not exist yet.</returns>
+    public static string ResolveUniquePath(string basePath)
+    {
+        if (!IOFile.Exists(basePath))
+        {
+            return basePath;
+        }
+        
+        var directory = Path.GetDirectoryName(basePath)!;
+        var extension = Path.GetExtension(basePath);
+        var fileNameWithoutExt = Path.GetFileNameWithoutExtension(basePath);
+        
+        var counter = 1;
+        string uniquePath;
+        do
+        {
+            uniquePath = Path.Combine(directory, $"{fileNameWithoutExt} ({counter}){extension}");
+            counter++;
+        } while (IOFile.Exists(uniquePath));
+        
+        return uniquePath;
+    }
+}

octo-fiesta/Services/Deezer/DeezerDownloadService.cs

@@ -523,112 +523,3 @@ public class DeezerDownloadService : BaseDownloadService
         public string Artist { get; set; } = string.Empty;
     }
 }
-
-/// <summary>
-/// Helper class for path building and sanitization.
-/// Extracted for testability.
-/// </summary>
-public static class PathHelper
-{
-    /// <summary>
-    /// Builds the output path for a downloaded track following the Artist/Album/Track structure.
-    /// </summary>
-    public static string BuildTrackPath(string downloadPath, string artist, string album, string title, int? trackNumber, string extension)
-    {
-        var safeArtist = SanitizeFolderName(artist);
-        var safeAlbum = SanitizeFolderName(album);
-        var safeTitle = SanitizeFileName(title);
-        
-        var artistFolder = Path.Combine(downloadPath, safeArtist);
-        var albumFolder = Path.Combine(artistFolder, safeAlbum);
-        
-        var trackPrefix = trackNumber.HasValue ? $"{trackNumber:D2} - " : "";
-        var fileName = $"{trackPrefix}{safeTitle}{extension}";
-        
-        return Path.Combine(albumFolder, fileName);
-    }
-
-    /// <summary>
-    /// Sanitizes a file name by removing invalid characters.
-    /// </summary>
-    public static string SanitizeFileName(string fileName)
-    {
-        if (string.IsNullOrWhiteSpace(fileName))
-        {
-            return "Unknown";
-        }
-        
-        var invalidChars = Path.GetInvalidFileNameChars();
-        var sanitized = new string(fileName
-            .Select(c => invalidChars.Contains(c) ? '_' : c)
-            .ToArray());
-        
-        if (sanitized.Length > 100)
-        {
-            sanitized = sanitized[..100];
-        }
-        
-        return sanitized.Trim();
-    }
-
-    /// <summary>
-    /// Sanitizes a folder name by removing invalid path characters.
-    /// </summary>
-    public static string SanitizeFolderName(string folderName)
-    {
-        if (string.IsNullOrWhiteSpace(folderName))
-        {
-            return "Unknown";
-        }
-        
-        var invalidChars = Path.GetInvalidFileNameChars()
-            .Concat(Path.GetInvalidPathChars())
-            .Distinct()
-            .ToArray();
-            
-        var sanitized = new string(folderName
-            .Select(c => invalidChars.Contains(c) ? '_' : c)
-            .ToArray());
-        
-        // Remove leading/trailing dots and spaces (Windows folder restrictions)
-        sanitized = sanitized.Trim().TrimEnd('.');
-        
-        if (sanitized.Length > 100)
-        {
-            sanitized = sanitized[..100].TrimEnd('.');
-        }
-        
-        // Ensure we have a valid name
-        if (string.IsNullOrWhiteSpace(sanitized))
-        {
-            return "Unknown";
-        }
-        
-        return sanitized;
-    }
-
-    /// <summary>
-    /// Resolves a unique file path by appending a counter if the file already exists.
-    /// </summary>
-    public static string ResolveUniquePath(string basePath)
-    {
-        if (!IOFile.Exists(basePath))
-        {
-            return basePath;
-        }
-        
-        var directory = Path.GetDirectoryName(basePath)!;
-        var extension = Path.GetExtension(basePath);
-        var fileNameWithoutExt = Path.GetFileNameWithoutExtension(basePath);
-        
-        var counter = 1;
-        string uniquePath;
-        do
-        {
-            uniquePath = Path.Combine(directory, $"{fileNameWithoutExt} ({counter}){extension}");
-            counter++;
-        } while (IOFile.Exists(uniquePath));
-        
-        return uniquePath;
-    }
-}

octo-fiesta/Services/Qobuz/QobuzDownloadService.cs

@@ -8,7 +8,6 @@ using octo_fiesta.Models.Search;
 using octo_fiesta.Models.Subsonic;
 using octo_fiesta.Services.Local;
 using octo_fiesta.Services.Common;
-using octo_fiesta.Services.Deezer;
 using Microsoft.Extensions.Options;
 using IOFile = System.IO.File;