Refactor downloads to use job-specific subdirectories

Organize downloaded files into per-job subdirectories under "downloads" instead of a flat structure. Update DownloadController and VideoService to read, write, and delete files within these job-specific directories. Add helper methods for directory management and improve logging. Update download/delete endpoints and result URLs to reflect the new structure. Clean up empty job directories after file deletion.

TuneRipper.Api/Services/SessionService.cs

@@ -0,0 +1,124 @@
+using System.Collections.Concurrent;
+
+namespace TuneRipper.Api.Services;
+
+public class SessionService : ISessionService
+{
+    private readonly IWebHostEnvironment _environment;
+    private readonly ILogger<SessionService> _logger;
+    private readonly ConcurrentDictionary<string, DateTime> _sessions = new();
+    private readonly Timer _cleanupTimer;
+    
+    // Session expires after 24 hours of inactivity
+    private readonly TimeSpan _sessionTimeout = TimeSpan.FromHours(24);
+
+    public SessionService(IWebHostEnvironment environment, ILogger<SessionService> logger)
+    {
+        _environment = environment;
+        _logger = logger;
+        
+        // Clean up expired sessions every hour
+        _cleanupTimer = new Timer(
+            callback: _ => CleanupExpiredSessions(),
+            state: null,
+            dueTime: TimeSpan.FromHours(1),
+            period: TimeSpan.FromHours(1)
+        );
+    }
+
+    public string CreateSession()
+    {
+        var sessionId = Guid.NewGuid().ToString("N")[..16]; // Use first 16 characters for shorter IDs
+        _sessions[sessionId] = DateTime.UtcNow;
+        
+        // Ensure session directory exists
+        var sessionPath = GetSessionDownloadsPath(sessionId);
+        Directory.CreateDirectory(sessionPath);
+        
+        _logger.LogInformation("Created new session: {SessionId}", sessionId);
+        return sessionId;
+    }
+
+    public string GetOrCreateSession(string? sessionId)
+    {
+        if (!string.IsNullOrWhiteSpace(sessionId) && IsValidSession(sessionId))
+        {
+            // Update last activity time
+            _sessions[sessionId] = DateTime.UtcNow;
+            return sessionId;
+        }
+
+        return CreateSession();
+    }
+
+    public bool IsValidSession(string sessionId)
+    {
+        if (string.IsNullOrWhiteSpace(sessionId))
+            return false;
+
+        if (_sessions.TryGetValue(sessionId, out var lastActivity))
+        {
+            // Check if session has expired
+            if (DateTime.UtcNow - lastActivity > _sessionTimeout)
+            {
+                _sessions.TryRemove(sessionId, out _);
+                return false;
+            }
+            return true;
+        }
+
+        return false;
+    }
+
+    public void CleanupExpiredSessions()
+    {
+        try
+        {
+            var expiredSessions = _sessions
+                .Where(kvp => DateTime.UtcNow - kvp.Value > _sessionTimeout)
+                .Select(kvp => kvp.Key)
+                .ToList();
+
+            foreach (var sessionId in expiredSessions)
+            {
+                if (_sessions.TryRemove(sessionId, out _))
+                {
+                    // Clean up session directory
+                    var sessionPath = GetSessionDownloadsPath(sessionId);
+                    if (Directory.Exists(sessionPath))
+                    {
+                        try
+                        {
+                            Directory.Delete(sessionPath, recursive: true);
+                            _logger.LogInformation("Cleaned up expired session directory: {SessionId}", sessionId);
+                        }
+                        catch (Exception ex)
+                        {
+                            _logger.LogWarning(ex, "Failed to delete expired session directory: {SessionId}", sessionId);
+                        }
+                    }
+                }
+            }
+
+            if (expiredSessions.Count > 0)
+            {
+                _logger.LogInformation("Cleaned up {Count} expired sessions", expiredSessions.Count);
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error during session cleanup");
+        }
+    }
+
+    public string GetSessionDownloadsPath(string sessionId)
+    {
+        var downloadsRoot = Path.Combine(_environment.WebRootPath, "downloads");
+        return Path.Combine(downloadsRoot, sessionId);
+    }
+
+    public void Dispose()
+    {
+        _cleanupTimer?.Dispose();
+    }
+}