Change FileProgress callback to channel-based progress

Replace callback-based progress reporting in Builder.AddFile with
channel-based FileHashProgress for consistency with EnumerateStatus
and ScanStatus patterns. Update scanner.go to use the new channel API.

internal/scanner/scanner.go

@@ -32,11 +32,12 @@ type EnumerateStatus struct {
 
 // ScanStatus contains progress information for the scan phase.
 type ScanStatus struct {
-	TotalFiles   int64   // Total number of files to scan
-	ScannedFiles int64   // Number of files scanned so far
-	TotalBytes   int64   // Total bytes to read (sum of all file sizes)
-	ScannedBytes int64   // Bytes read so far
-	BytesPerSec  float64 // Current throughput rate
+	TotalFiles   int64         // Total number of files to scan
+	ScannedFiles int64         // Number of files scanned so far
+	TotalBytes   int64         // Total bytes to read (sum of all file sizes)
+	ScannedBytes int64         // Bytes read so far
+	BytesPerSec  float64       // Current throughput rate
+	ETA          time.Duration // Estimated time to completion
 }
 
 // Options configures scanner behavior.
@@ -177,6 +178,31 @@ func (s *Scanner) enumerateFileWithInfo(filePath string, basePath string, info f
 	// Compute absolute path for file reading
 	absPath := filepath.Join(basePath, cleanPath)
 
+	// Handle symlinks
+	if info.Mode()&fs.ModeSymlink != 0 {
+		if !s.options.FollowSymLinks {
+			// Skip symlinks when not following them
+			return nil
+		}
+		// Resolve symlink to get real file info
+		realPath, err := filepath.EvalSymlinks(absPath)
+		if err != nil {
+			// Skip broken symlinks
+			return nil
+		}
+		realInfo, err := s.fs.Stat(realPath)
+		if err != nil {
+			return nil
+		}
+		// Skip if symlink points to a directory
+		if realInfo.IsDir() {
+			return nil
+		}
+		// Use resolved path for reading, but keep original path in manifest
+		absPath = realPath
+		info = realInfo
+	}
+
 	entry := &FileEntry{
 		Path:    cleanPath,
 		AbsPath: absPath,
@@ -270,34 +296,58 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 			return err
 		}
 
-		// Add to manifest with progress callback
+		// Create progress channel for this file
+		var fileProgress chan mfer.FileHashProgress
+		var wg sync.WaitGroup
+		if progress != nil {
+			fileProgress = make(chan mfer.FileHashProgress, 1)
+			wg.Add(1)
+			go func(baseScannedBytes int64) {
+				defer wg.Done()
+				for p := range fileProgress {
+					// Send progress at most once per second
+					now := time.Now()
+					if now.Sub(lastProgressTime) >= time.Second {
+						elapsed := now.Sub(startTime).Seconds()
+						currentBytes := baseScannedBytes + p.BytesRead
+						var rate float64
+						var eta time.Duration
+						if elapsed > 0 && currentBytes > 0 {
+							rate = float64(currentBytes) / elapsed
+							remainingBytes := totalBytes - currentBytes
+							if rate > 0 {
+								eta = time.Duration(float64(remainingBytes)/rate) * time.Second
+							}
+						}
+						sendScanStatus(progress, ScanStatus{
+							TotalFiles:   totalFiles,
+							ScannedFiles: scannedFiles,
+							TotalBytes:   totalBytes,
+							ScannedBytes: currentBytes,
+							BytesPerSec:  rate,
+							ETA:          eta,
+						})
+						lastProgressTime = now
+					}
+				}
+			}(scannedBytes)
+		}
+
+		// Add to manifest with progress channel
 		bytesRead, err := builder.AddFile(
 			entry.Path,
 			entry.Size,
 			entry.Mtime,
 			f,
-			func(fileBytes int64) {
-				// Send progress at most once per second
-				now := time.Now()
-				if progress != nil && now.Sub(lastProgressTime) >= time.Second {
-					elapsed := now.Sub(startTime).Seconds()
-					currentBytes := scannedBytes + fileBytes
-					var rate float64
-					if elapsed > 0 {
-						rate = float64(currentBytes) / elapsed
-					}
-					sendScanStatus(progress, ScanStatus{
-						TotalFiles:   totalFiles,
-						ScannedFiles: scannedFiles,
-						TotalBytes:   totalBytes,
-						ScannedBytes: currentBytes,
-						BytesPerSec:  rate,
-					})
-					lastProgressTime = now
-				}
-			},
+			fileProgress,
 		)
-		f.Close()
+		_ = f.Close()
+
+		// Close channel and wait for goroutine to finish
+		if fileProgress != nil {
+			close(fileProgress)
+			wg.Wait()
+		}
 
 		if err != nil {
 			return err
@@ -307,7 +357,7 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 		scannedBytes += bytesRead
 	}
 
-	// Send final progress
+	// Send final progress (ETA is 0 at completion)
 	if progress != nil {
 		elapsed := time.Since(startTime).Seconds()
 		var rate float64
@@ -320,6 +370,7 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 			TotalBytes:   totalBytes,
 			ScannedBytes: scannedBytes,
 			BytesPerSec:  rate,
+			ETA:          0,
 		})
 	}