优化

internal/service/cache_cleanup.go

@@ -4,8 +4,11 @@
 package service
 
 import (
+	"errors"
 	"os"
 	"path/filepath"
+	"sort"
+	"strings"
 	"time"
 )
 
@@ -42,3 +45,97 @@ func walkAndPrune(root string, cutoff time.Time) error {
 	}
 	return nil
 }
+
+// PruneImageCacheResult holds stats from an image cache prune operation.
+type PruneImageCacheResult struct {
+	TotalFilesBefore int
+	TotalBytesBefore int64
+	DeletedFiles     int
+	FreedBytes       int64
+	RemainingBytes   int64
+}
+
+type imageCacheFileEntry struct {
+	path    string
+	size    int64
+	modTime time.Time
+}
+
+// PruneImageCache scans imagesDir for cached image files. If the total disk usage
+// exceeds maxSizeBytes, it removes files starting from the oldest (by ModTime)
+// until disk usage falls to or below targetSizeBytes (80% of maxSizeBytes).
+//
+// In-flight temporary files (*.tmp) are skipped to avoid corrupting concurrent writes.
+// Empty subdirectories left behind are best-effort removed.
+func PruneImageCache(imagesDir string, maxSizeBytes int64) (PruneImageCacheResult, error) {
+	var result PruneImageCacheResult
+	if imagesDir == "" || maxSizeBytes <= 0 {
+		return result, nil
+	}
+	if _, err := os.Stat(imagesDir); err != nil {
+		return result, nil
+	}
+
+	var (
+		dirs    []string
+		entries []imageCacheFileEntry
+	)
+
+	_ = filepath.Walk(imagesDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return nil
+		}
+		if info.IsDir() {
+			if path != imagesDir {
+				dirs = append(dirs, path)
+			}
+			return nil
+		}
+		// Skip temporary files created during image download.
+		name := info.Name()
+		if strings.HasSuffix(name, ".tmp") || strings.HasPrefix(name, "img-") && strings.Contains(name, ".tmp") {
+			return nil
+		}
+		size := info.Size()
+		result.TotalFilesBefore++
+		result.TotalBytesBefore += size
+		entries = append(entries, imageCacheFileEntry{
+			path:    path,
+			size:    size,
+			modTime: info.ModTime(),
+		})
+		return nil
+	})
+
+	result.RemainingBytes = result.TotalBytesBefore
+	if result.TotalBytesBefore <= maxSizeBytes {
+		return result, nil
+	}
+
+	// High/Low watermark: prune down to 80% of max size to leave headroom
+	// and prevent disk thrashing on consecutive writes.
+	targetSizeBytes := maxSizeBytes * 80 / 100
+
+	sort.Slice(entries, func(i, j int) bool {
+		return entries[i].modTime.Before(entries[j].modTime)
+	})
+
+	for _, entry := range entries {
+		if result.RemainingBytes <= targetSizeBytes {
+			break
+		}
+		if err := os.Remove(entry.path); err == nil || errors.Is(err, os.ErrNotExist) {
+			result.DeletedFiles++
+			result.FreedBytes += entry.size
+			result.RemainingBytes -= entry.size
+		}
+	}
+
+	// Clean up emptied subdirectories from deepest to shallowest.
+	for i := len(dirs) - 1; i >= 0; i-- {
+		_ = os.Remove(dirs[i])
+	}
+
+	return result, nil
+}
+