fix(analyze): reuse recent cache and refresh stale results

cmd/analyze/analyze_test.go

@@ -415,6 +415,221 @@ func TestLoadCacheExpiresWhenDirectoryChanges(t *testing.T) {
 	}
 }
 
+func TestLoadCacheReusesRecentEntryAfterDirectoryChanges(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+
+	target := filepath.Join(home, "recent-change-target")
+	if err := os.MkdirAll(target, 0o755); err != nil {
+		t.Fatalf("create target: %v", err)
+	}
+
+	result := scanResult{TotalSize: 5, TotalFiles: 1}
+	if err := saveCacheToDisk(target, result); err != nil {
+		t.Fatalf("saveCacheToDisk: %v", err)
+	}
+
+	cachePath, err := getCachePath(target)
+	if err != nil {
+		t.Fatalf("getCachePath: %v", err)
+	}
+
+	file, err := os.Open(cachePath)
+	if err != nil {
+		t.Fatalf("open cache: %v", err)
+	}
+	var entry cacheEntry
+	if err := gob.NewDecoder(file).Decode(&entry); err != nil {
+		t.Fatalf("decode cache: %v", err)
+	}
+	_ = file.Close()
+
+	// Make cache entry look recently scanned, but older than mod time grace.
+	entry.ModTime = time.Now().Add(-2 * time.Hour)
+	entry.ScanTime = time.Now().Add(-1 * time.Hour)
+
+	tmp := cachePath + ".tmp"
+	f, err := os.Create(tmp)
+	if err != nil {
+		t.Fatalf("create tmp cache: %v", err)
+	}
+	if err := gob.NewEncoder(f).Encode(&entry); err != nil {
+		t.Fatalf("encode tmp cache: %v", err)
+	}
+	_ = f.Close()
+	if err := os.Rename(tmp, cachePath); err != nil {
+		t.Fatalf("rename tmp cache: %v", err)
+	}
+
+	if err := os.Chtimes(target, time.Now(), time.Now()); err != nil {
+		t.Fatalf("chtimes target: %v", err)
+	}
+
+	if _, err := loadCacheFromDisk(target); err != nil {
+		t.Fatalf("expected recent cache to be reused, got error: %v", err)
+	}
+}
+
+func TestLoadCacheExpiresWhenModifiedAndReuseWindowPassed(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+
+	target := filepath.Join(home, "reuse-window-target")
+	if err := os.MkdirAll(target, 0o755); err != nil {
+		t.Fatalf("create target: %v", err)
+	}
+
+	result := scanResult{TotalSize: 5, TotalFiles: 1}
+	if err := saveCacheToDisk(target, result); err != nil {
+		t.Fatalf("saveCacheToDisk: %v", err)
+	}
+
+	cachePath, err := getCachePath(target)
+	if err != nil {
+		t.Fatalf("getCachePath: %v", err)
+	}
+
+	file, err := os.Open(cachePath)
+	if err != nil {
+		t.Fatalf("open cache: %v", err)
+	}
+	var entry cacheEntry
+	if err := gob.NewDecoder(file).Decode(&entry); err != nil {
+		t.Fatalf("decode cache: %v", err)
+	}
+	_ = file.Close()
+
+	// Within overall 7-day TTL but beyond reuse window.
+	entry.ModTime = time.Now().Add(-48 * time.Hour)
+	entry.ScanTime = time.Now().Add(-(cacheReuseWindow + time.Hour))
+
+	tmp := cachePath + ".tmp"
+	f, err := os.Create(tmp)
+	if err != nil {
+		t.Fatalf("create tmp cache: %v", err)
+	}
+	if err := gob.NewEncoder(f).Encode(&entry); err != nil {
+		t.Fatalf("encode tmp cache: %v", err)
+	}
+	_ = f.Close()
+	if err := os.Rename(tmp, cachePath); err != nil {
+		t.Fatalf("rename tmp cache: %v", err)
+	}
+
+	if err := os.Chtimes(target, time.Now(), time.Now()); err != nil {
+		t.Fatalf("chtimes target: %v", err)
+	}
+
+	if _, err := loadCacheFromDisk(target); err == nil {
+		t.Fatalf("expected cache load to fail after reuse window passes")
+	}
+}
+
+func TestLoadStaleCacheFromDiskAllowsRecentExpiredCache(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+
+	target := filepath.Join(home, "stale-cache-target")
+	if err := os.MkdirAll(target, 0o755); err != nil {
+		t.Fatalf("create target: %v", err)
+	}
+
+	result := scanResult{TotalSize: 7, TotalFiles: 2}
+	if err := saveCacheToDisk(target, result); err != nil {
+		t.Fatalf("saveCacheToDisk: %v", err)
+	}
+
+	cachePath, err := getCachePath(target)
+	if err != nil {
+		t.Fatalf("getCachePath: %v", err)
+	}
+	file, err := os.Open(cachePath)
+	if err != nil {
+		t.Fatalf("open cache: %v", err)
+	}
+	var entry cacheEntry
+	if err := gob.NewDecoder(file).Decode(&entry); err != nil {
+		t.Fatalf("decode cache: %v", err)
+	}
+	_ = file.Close()
+
+	// Expired for normal cache validation but still inside stale fallback window.
+	entry.ModTime = time.Now().Add(-48 * time.Hour)
+	entry.ScanTime = time.Now().Add(-48 * time.Hour)
+
+	tmp := cachePath + ".tmp"
+	f, err := os.Create(tmp)
+	if err != nil {
+		t.Fatalf("create tmp cache: %v", err)
+	}
+	if err := gob.NewEncoder(f).Encode(&entry); err != nil {
+		t.Fatalf("encode tmp cache: %v", err)
+	}
+	_ = f.Close()
+	if err := os.Rename(tmp, cachePath); err != nil {
+		t.Fatalf("rename tmp cache: %v", err)
+	}
+
+	if err := os.Chtimes(target, time.Now(), time.Now()); err != nil {
+		t.Fatalf("chtimes target: %v", err)
+	}
+
+	if _, err := loadCacheFromDisk(target); err == nil {
+		t.Fatalf("expected normal cache load to fail")
+	}
+	if _, err := loadStaleCacheFromDisk(target); err != nil {
+		t.Fatalf("expected stale cache load to succeed, got error: %v", err)
+	}
+}
+
+func TestLoadStaleCacheFromDiskExpiresByStaleTTL(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+
+	target := filepath.Join(home, "stale-cache-expired-target")
+	if err := os.MkdirAll(target, 0o755); err != nil {
+		t.Fatalf("create target: %v", err)
+	}
+
+	result := scanResult{TotalSize: 9, TotalFiles: 3}
+	if err := saveCacheToDisk(target, result); err != nil {
+		t.Fatalf("saveCacheToDisk: %v", err)
+	}
+
+	cachePath, err := getCachePath(target)
+	if err != nil {
+		t.Fatalf("getCachePath: %v", err)
+	}
+	file, err := os.Open(cachePath)
+	if err != nil {
+		t.Fatalf("open cache: %v", err)
+	}
+	var entry cacheEntry
+	if err := gob.NewDecoder(file).Decode(&entry); err != nil {
+		t.Fatalf("decode cache: %v", err)
+	}
+	_ = file.Close()
+
+	entry.ScanTime = time.Now().Add(-(staleCacheTTL + time.Hour))
+
+	tmp := cachePath + ".tmp"
+	f, err := os.Create(tmp)
+	if err != nil {
+		t.Fatalf("create tmp cache: %v", err)
+	}
+	if err := gob.NewEncoder(f).Encode(&entry); err != nil {
+		t.Fatalf("encode tmp cache: %v", err)
+	}
+	_ = f.Close()
+	if err := os.Rename(tmp, cachePath); err != nil {
+		t.Fatalf("rename tmp cache: %v", err)
+	}
+
+	if _, err := loadStaleCacheFromDisk(target); err == nil {
+		t.Fatalf("expected stale cache load to fail after stale TTL")
+	}
+}
+
 func TestScanPathPermissionError(t *testing.T) {
 	root := t.TempDir()
 	lockedDir := filepath.Join(root, "locked")

cmd/analyze/cache.go

@@ -182,7 +182,7 @@ func getCachePath(path string) (string, error) {
 	return filepath.Join(cacheDir, filename), nil
 }
 
-func loadCacheFromDisk(path string) (*cacheEntry, error) {
+func loadRawCacheFromDisk(path string) (*cacheEntry, error) {
 	cachePath, err := getCachePath(path)
 	if err != nil {
 		return nil, err
@@ -200,23 +200,56 @@ func loadCacheFromDisk(path string) (*cacheEntry, error) {
 		return nil, err
 	}
 
+	return &entry, nil
+}
+
+func loadCacheFromDisk(path string) (*cacheEntry, error) {
+	entry, err := loadRawCacheFromDisk(path)
+	if err != nil {
+		return nil, err
+	}
+
 	info, err := os.Stat(path)
 	if err != nil {
 		return nil, err
 	}
 
-	if info.ModTime().After(entry.ModTime) {
-		// Allow grace window.
-		if cacheModTimeGrace <= 0 || info.ModTime().Sub(entry.ModTime) > cacheModTimeGrace {
-			return nil, fmt.Errorf("cache expired: directory modified")
-		}
-	}
-
-	if time.Since(entry.ScanTime) > 7*24*time.Hour {
+	scanAge := time.Since(entry.ScanTime)
+	if scanAge > 7*24*time.Hour {
 		return nil, fmt.Errorf("cache expired: too old")
 	}
 
-	return &entry, nil
+	if info.ModTime().After(entry.ModTime) {
+		// Allow grace window.
+		if cacheModTimeGrace <= 0 || info.ModTime().Sub(entry.ModTime) > cacheModTimeGrace {
+			// Directory mod time is noisy on macOS; reuse recent cache to avoid
+			// frequent full rescans while still forcing refresh for older entries.
+			if cacheReuseWindow <= 0 || scanAge > cacheReuseWindow {
+				return nil, fmt.Errorf("cache expired: directory modified")
+			}
+		}
+	}
+
+	return entry, nil
+}
+
+// loadStaleCacheFromDisk loads cache without strict freshness checks.
+// It is used for fast first paint before triggering a background refresh.
+func loadStaleCacheFromDisk(path string) (*cacheEntry, error) {
+	entry, err := loadRawCacheFromDisk(path)
+	if err != nil {
+		return nil, err
+	}
+
+	if _, err := os.Stat(path); err != nil {
+		return nil, err
+	}
+
+	if time.Since(entry.ScanTime) > staleCacheTTL {
+		return nil, fmt.Errorf("stale cache expired")
+	}
+
+	return entry, nil
 }
 
 func saveCacheToDisk(path string, result scanResult) error {

cmd/analyze/constants.go

@@ -16,6 +16,8 @@ const (
 	maxConcurrentOverview  = 8
 	batchUpdateSize        = 100
 	cacheModTimeGrace      = 30 * time.Minute
+	cacheReuseWindow       = 24 * time.Hour
+	staleCacheTTL          = 3 * 24 * time.Hour
 
 	// Worker pool limits.
 	minWorkers         = 16

cmd/analyze/main.go

@@ -63,8 +63,10 @@ type historyEntry struct {
 }
 
 type scanResultMsg struct {
+	path   string
 	result scanResult
 	err    error
+	stale  bool
 }
 
 type overviewSizeMsg struct {
@@ -369,9 +371,19 @@ func (m model) scanCmd(path string) tea.Cmd {
 				Entries:    cached.Entries,
 				LargeFiles: cached.LargeFiles,
 				TotalSize:  cached.TotalSize,
-				TotalFiles: 0, // Cache doesn't store file count currently, minor UI limitation
+				TotalFiles: cached.TotalFiles,
 			}
-			return scanResultMsg{result: result, err: nil}
+			return scanResultMsg{path: path, result: result, err: nil}
+		}
+
+		if stale, err := loadStaleCacheFromDisk(path); err == nil {
+			result := scanResult{
+				Entries:    stale.Entries,
+				LargeFiles: stale.LargeFiles,
+				TotalSize:  stale.TotalSize,
+				TotalFiles: stale.TotalFiles,
+			}
+			return scanResultMsg{path: path, result: result, err: nil, stale: true}
 		}
 
 		v, err, _ := scanGroup.Do(path, func() (any, error) {
@@ -379,7 +391,7 @@ func (m model) scanCmd(path string) tea.Cmd {
 		})
 
 		if err != nil {
-			return scanResultMsg{err: err}
+			return scanResultMsg{path: path, err: err}
 		}
 
 		result := v.(scanResult)
@@ -390,7 +402,28 @@ func (m model) scanCmd(path string) tea.Cmd {
 			}
 		}(path, result)
 
-		return scanResultMsg{result: result, err: nil}
+		return scanResultMsg{path: path, result: result, err: nil}
+	}
+}
+
+func (m model) scanFreshCmd(path string) tea.Cmd {
+	return func() tea.Msg {
+		v, err, _ := scanGroup.Do(path, func() (any, error) {
+			return scanPathConcurrent(path, m.filesScanned, m.dirsScanned, m.bytesScanned, m.currentPath)
+		})
+
+		if err != nil {
+			return scanResultMsg{path: path, err: err}
+		}
+
+		result := v.(scanResult)
+		go func(p string, r scanResult) {
+			if err := saveCacheToDisk(p, r); err != nil {
+				_ = err
+			}
+		}(path, result)
+
+		return scanResultMsg{path: path, result: result}
 	}
 }
 
@@ -442,6 +475,9 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		}
 		return m, nil
 	case scanResultMsg:
+		if msg.path != "" && msg.path != m.path {
+			return m, nil
+		}
 		m.scanning = false
 		if msg.err != nil {
 			m.status = fmt.Sprintf("Scan failed: %v", msg.err)
@@ -457,7 +493,6 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.largeFiles = msg.result.LargeFiles
 		m.totalSize = msg.result.TotalSize
 		m.totalFiles = msg.result.TotalFiles
-		m.status = fmt.Sprintf("Scanned %s", humanizeBytes(m.totalSize))
 		m.clampEntrySelection()
 		m.clampLargeSelection()
 		m.cache[m.path] = cacheSnapshot(m)
@@ -470,6 +505,23 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 				_ = storeOverviewSize(path, size)
 			}(m.path, m.totalSize)
 		}
+
+		if msg.stale {
+			m.status = fmt.Sprintf("Loaded cached data for %s, refreshing...", displayPath(m.path))
+			m.scanning = true
+			if m.totalFiles > 0 {
+				m.lastTotalFiles = m.totalFiles
+			}
+			atomic.StoreInt64(m.filesScanned, 0)
+			atomic.StoreInt64(m.dirsScanned, 0)
+			atomic.StoreInt64(m.bytesScanned, 0)
+			if m.currentPath != nil {
+				m.currentPath.Store("")
+			}
+			return m, tea.Batch(m.scanFreshCmd(m.path), tickCmd())
+		}
+
+		m.status = fmt.Sprintf("Scanned %s", humanizeBytes(m.totalSize))
 		return m, nil
 	case overviewSizeMsg:
 		delete(m.overviewScanningSet, msg.Path)