//go:build darwin

package main

import (
	"context"
	"fmt"
	"io/fs"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync/atomic"
	"time"

	tea "github.com/charmbracelet/bubbletea"
)

type dirEntry struct {
	Name       string
	Path       string
	Size       int64
	IsDir      bool
	LastAccess time.Time
}

type fileEntry struct {
	Name string
	Path string
	Size int64
}

type scanResult struct {
	Entries    []dirEntry
	LargeFiles []fileEntry
	TotalSize  int64
}

type cacheEntry struct {
	Entries    []dirEntry
	LargeFiles []fileEntry
	TotalSize  int64
	ModTime    time.Time
	ScanTime   time.Time
}

type historyEntry struct {
	Path          string
	Entries       []dirEntry
	LargeFiles    []fileEntry
	TotalSize     int64
	Selected      int
	EntryOffset   int
	LargeSelected int
	LargeOffset   int
	Dirty         bool
	IsOverview    bool
}

type scanResultMsg struct {
	result scanResult
	err    error
}

type overviewSizeMsg struct {
	Path  string
	Index int
	Size  int64
	Err   error
}

type tickMsg time.Time

type deleteProgressMsg struct {
	done  bool
	err   error
	count int64
	path  string
}

type model struct {
	path                 string
	history              []historyEntry
	entries              []dirEntry
	largeFiles           []fileEntry
	selected             int
	offset               int
	status               string
	totalSize            int64
	scanning             bool
	spinner              int
	filesScanned         *int64
	dirsScanned          *int64
	bytesScanned         *int64
	currentPath          *string
	showLargeFiles       bool
	isOverview           bool
	deleteConfirm        bool
	deleteTarget         *dirEntry
	deleting             bool
	deleteCount          *int64
	cache                map[string]historyEntry
	largeSelected        int
	largeOffset          int
	overviewSizeCache    map[string]int64
	overviewFilesScanned *int64
	overviewDirsScanned  *int64
	overviewBytesScanned *int64
	overviewCurrentPath  *string
	overviewScanning     bool
	overviewScanningSet  map[string]bool // Track which paths are currently being scanned
	width                int             // Terminal width
	height               int             // Terminal height
}

func (m model) inOverviewMode() bool {
	return m.isOverview && m.path == "/"
}

func main() {
	target := os.Getenv("MO_ANALYZE_PATH")
	if target == "" && len(os.Args) > 1 {
		target = os.Args[1]
	}

	var abs string
	var isOverview bool

	if target == "" {
		// Default to overview mode
		isOverview = true
		abs = "/"
	} else {
		var err error
		abs, err = filepath.Abs(target)
		if err != nil {
			fmt.Fprintf(os.Stderr, "cannot resolve %q: %v\n", target, err)
			os.Exit(1)
		}
		isOverview = false
	}

	// Prefetch overview cache in background (non-blocking)
	// Use context with timeout to prevent hanging
	prefetchCtx, prefetchCancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer prefetchCancel()
	go prefetchOverviewCache(prefetchCtx)

	p := tea.NewProgram(newModel(abs, isOverview), tea.WithAltScreen())
	if err := p.Start(); err != nil {
		fmt.Fprintf(os.Stderr, "analyzer error: %v\n", err)
		os.Exit(1)
	}
}

func newModel(path string, isOverview bool) model {
	var filesScanned, dirsScanned, bytesScanned int64
	currentPath := ""
	var overviewFilesScanned, overviewDirsScanned, overviewBytesScanned int64
	overviewCurrentPath := ""

	m := model{
		path:                 path,
		selected:             0,
		status:               "Preparing scan...",
		scanning:             !isOverview,
		filesScanned:         &filesScanned,
		dirsScanned:          &dirsScanned,
		bytesScanned:         &bytesScanned,
		currentPath:          &currentPath,
		showLargeFiles:       false,
		isOverview:           isOverview,
		cache:                make(map[string]historyEntry),
		overviewFilesScanned: &overviewFilesScanned,
		overviewDirsScanned:  &overviewDirsScanned,
		overviewBytesScanned: &overviewBytesScanned,
		overviewCurrentPath:  &overviewCurrentPath,
		overviewSizeCache:    make(map[string]int64),
		overviewScanningSet:  make(map[string]bool),
	}

	// In overview mode, create shortcut entries
	if isOverview {
		m.scanning = false
		m.hydrateOverviewEntries()
		m.selected = 0
		m.offset = 0
		if nextPendingOverviewIndex(m.entries) >= 0 {
			m.overviewScanning = true
			m.status = "Checking system folders..."
		} else {
			m.status = "Ready"
		}
	}

	return m
}

func createOverviewEntries() []dirEntry {
	home := os.Getenv("HOME")
	entries := []dirEntry{}

	if home != "" {
		entries = append(entries,
			dirEntry{Name: "Home (~)", Path: home, IsDir: true, Size: -1},
			dirEntry{Name: "Library (~/Library)", Path: filepath.Join(home, "Library"), IsDir: true, Size: -1},
		)
	}

	entries = append(entries,
		dirEntry{Name: "Applications", Path: "/Applications", IsDir: true, Size: -1},
		dirEntry{Name: "System Library", Path: "/Library", IsDir: true, Size: -1},
	)

	// Add Volumes shortcut only when it contains real mounted folders (e.g., external disks)
	if hasUsefulVolumeMounts("/Volumes") {
		entries = append(entries, dirEntry{Name: "Volumes", Path: "/Volumes", IsDir: true, Size: -1})
	}

	return entries
}

func hasUsefulVolumeMounts(path string) bool {
	entries, err := os.ReadDir(path)
	if err != nil {
		return false
	}

	for _, entry := range entries {
		name := entry.Name()
		// Skip hidden control entries for Spotlight/TimeMachine etc.
		if strings.HasPrefix(name, ".") {
			continue
		}

		info, err := os.Lstat(filepath.Join(path, name))
		if err != nil {
			continue
		}
		if info.Mode()&fs.ModeSymlink != 0 {
			continue // Ignore the synthetic MacintoshHD link
		}
		if info.IsDir() {
			return true
		}
	}
	return false
}

func (m *model) hydrateOverviewEntries() {
	m.entries = createOverviewEntries()
	if m.overviewSizeCache == nil {
		m.overviewSizeCache = make(map[string]int64)
	}
	for i := range m.entries {
		if size, ok := m.overviewSizeCache[m.entries[i].Path]; ok {
			m.entries[i].Size = size
			continue
		}
		if size, err := loadOverviewCachedSize(m.entries[i].Path); err == nil {
			m.entries[i].Size = size
			m.overviewSizeCache[m.entries[i].Path] = size
		}
	}
	m.totalSize = sumKnownEntrySizes(m.entries)
}

func (m *model) scheduleOverviewScans() tea.Cmd {
	if !m.inOverviewMode() {
		return nil
	}

	// Find pending entries (not scanned and not currently scanning)
	var pendingIndices []int
	for i, entry := range m.entries {
		if entry.Size < 0 && !m.overviewScanningSet[entry.Path] {
			pendingIndices = append(pendingIndices, i)
			if len(pendingIndices) >= maxConcurrentOverview {
				break
			}
		}
	}

	// No more work to do
	if len(pendingIndices) == 0 {
		m.overviewScanning = false
		if !hasPendingOverviewEntries(m.entries) {
			m.status = "Ready"
		}
		return nil
	}

	// Mark all as scanning
	var cmds []tea.Cmd
	for _, idx := range pendingIndices {
		entry := m.entries[idx]
		m.overviewScanningSet[entry.Path] = true
		cmd := scanOverviewPathCmd(entry.Path, idx)
		cmds = append(cmds, cmd)
	}

	m.overviewScanning = true
	remaining := 0
	for _, e := range m.entries {
		if e.Size < 0 {
			remaining++
		}
	}
	if len(pendingIndices) > 0 {
		firstEntry := m.entries[pendingIndices[0]]
		if len(pendingIndices) == 1 {
			m.status = fmt.Sprintf("Scanning %s... (%d left)", firstEntry.Name, remaining)
		} else {
			m.status = fmt.Sprintf("Scanning %d directories... (%d left)", len(pendingIndices), remaining)
		}
	}

	cmds = append(cmds, tickCmd())
	return tea.Batch(cmds...)
}

func (m *model) getScanProgress() (files, dirs, bytes int64) {
	if m.filesScanned != nil {
		files = atomic.LoadInt64(m.filesScanned)
	}
	if m.dirsScanned != nil {
		dirs = atomic.LoadInt64(m.dirsScanned)
	}
	if m.bytesScanned != nil {
		bytes = atomic.LoadInt64(m.bytesScanned)
	}
	return
}

func (m model) Init() tea.Cmd {
	if m.inOverviewMode() {
		return m.scheduleOverviewScans()
	}
	return tea.Batch(m.scanCmd(m.path), tickCmd())
}

func (m model) scanCmd(path string) tea.Cmd {
	return func() tea.Msg {
		// Try to load from persistent cache first
		if cached, err := loadCacheFromDisk(path); err == nil {
			result := scanResult{
				Entries:    cached.Entries,
				LargeFiles: cached.LargeFiles,
				TotalSize:  cached.TotalSize,
			}
			return scanResultMsg{result: result, err: nil}
		}

		// Use singleflight to avoid duplicate scans of the same path
		// If multiple goroutines request the same path, only one scan will be performed
		v, err, _ := scanGroup.Do(path, func() (interface{}, error) {
			return scanPathConcurrent(path, m.filesScanned, m.dirsScanned, m.bytesScanned, m.currentPath)
		})

		if err != nil {
			return scanResultMsg{err: err}
		}

		result := v.(scanResult)

		// Save to persistent cache asynchronously with error logging
		go func(p string, r scanResult) {
			if err := saveCacheToDisk(p, r); err != nil {
				// Log error but don't fail the scan
				_ = err // Cache save failure is not critical
			}
		}(path, result)

		return scanResultMsg{result: result, err: nil}
	}
}

func tickCmd() tea.Cmd {
	return tea.Tick(time.Millisecond*80, func(t time.Time) tea.Msg {
		return tickMsg(t)
	})
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.KeyMsg:
		return m.updateKey(msg)
	case tea.WindowSizeMsg:
		m.width = msg.Width
		m.height = msg.Height
		return m, nil
	case deleteProgressMsg:
		if msg.done {
			m.deleting = false
			if msg.err != nil {
				m.status = fmt.Sprintf("Failed to delete: %v", msg.err)
			} else {
				if msg.path != "" {
					m.removePathFromView(msg.path)
					invalidateCache(msg.path)
				}
				invalidateCache(m.path)
				m.status = fmt.Sprintf("Deleted %d items", msg.count)
				// Mark all caches as dirty
				for i := range m.history {
					m.history[i].Dirty = true
				}
				for path := range m.cache {
					entry := m.cache[path]
					entry.Dirty = true
					m.cache[path] = entry
				}
				// Refresh the view
				m.scanning = true
				// Reset scan counters for rescan
				atomic.StoreInt64(m.filesScanned, 0)
				atomic.StoreInt64(m.dirsScanned, 0)
				atomic.StoreInt64(m.bytesScanned, 0)
				if m.currentPath != nil {
					*m.currentPath = ""
				}
				return m, tea.Batch(m.scanCmd(m.path), tickCmd())
			}
		}
		return m, nil
	case scanResultMsg:
		m.scanning = false
		if msg.err != nil {
			m.status = fmt.Sprintf("Scan failed: %v", msg.err)
			return m, nil
		}
		// Filter out 0-byte items for cleaner view
		filteredEntries := make([]dirEntry, 0, len(msg.result.Entries))
		for _, e := range msg.result.Entries {
			if e.Size > 0 {
				filteredEntries = append(filteredEntries, e)
			}
		}
		m.entries = filteredEntries
		m.largeFiles = msg.result.LargeFiles
		m.totalSize = msg.result.TotalSize
		m.status = fmt.Sprintf("Scanned %s", humanizeBytes(m.totalSize))
		m.clampEntrySelection()
		m.clampLargeSelection()
		m.cache[m.path] = cacheSnapshot(m)
		if m.totalSize > 0 {
			if m.overviewSizeCache == nil {
				m.overviewSizeCache = make(map[string]int64)
			}
			m.overviewSizeCache[m.path] = m.totalSize
			go func(path string, size int64) {
				_ = storeOverviewSize(path, size)
			}(m.path, m.totalSize)
		}
		return m, nil
	case overviewSizeMsg:
		// Remove from scanning set
		delete(m.overviewScanningSet, msg.Path)

		if msg.Err == nil {
			if m.overviewSizeCache == nil {
				m.overviewSizeCache = make(map[string]int64)
			}
			m.overviewSizeCache[msg.Path] = msg.Size
		}

		if m.inOverviewMode() {
			// Update entry with result
			for i := range m.entries {
				if m.entries[i].Path == msg.Path {
					if msg.Err == nil {
						m.entries[i].Size = msg.Size
					} else {
						m.entries[i].Size = 0
					}
					break
				}
			}
			m.totalSize = sumKnownEntrySizes(m.entries)

			// Show error briefly if any
			if msg.Err != nil {
				m.status = fmt.Sprintf("Unable to measure %s: %v", displayPath(msg.Path), msg.Err)
			}

			// Schedule next batch of scans
			cmd := m.scheduleOverviewScans()
			return m, cmd
		}
		return m, nil
	case tickMsg:
		// Keep spinner running if scanning or deleting or if there are pending overview items
		hasPending := false
		if m.inOverviewMode() {
			for _, entry := range m.entries {
				if entry.Size < 0 {
					hasPending = true
					break
				}
			}
		}
		if m.scanning || m.deleting || (m.inOverviewMode() && (m.overviewScanning || hasPending)) {
			m.spinner = (m.spinner + 1) % len(spinnerFrames)
			// Update delete progress status
			if m.deleting && m.deleteCount != nil {
				count := atomic.LoadInt64(m.deleteCount)
				if count > 0 {
					m.status = fmt.Sprintf("Deleting... %s items removed", formatNumber(count))
				}
			}
			return m, tickCmd()
		}
		return m, nil
	default:
		return m, nil
	}
}

func (m model) updateKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	// Handle delete confirmation
	if m.deleteConfirm {
		switch msg.String() {
		case "delete", "backspace":
			// Confirm delete - start async deletion
			if m.deleteTarget != nil {
				m.deleteConfirm = false
				m.deleting = true
				var deleteCount int64
				m.deleteCount = &deleteCount
				targetPath := m.deleteTarget.Path
				targetName := m.deleteTarget.Name
				m.deleteTarget = nil
				m.status = fmt.Sprintf("Deleting %s...", targetName)
				return m, tea.Batch(deletePathCmd(targetPath, m.deleteCount), tickCmd())
			}
			m.deleteConfirm = false
			m.deleteTarget = nil
			return m, nil
		case "esc", "q":
			// Cancel delete with ESC or Q
			m.status = "Cancelled"
			m.deleteConfirm = false
			m.deleteTarget = nil
			return m, nil
		default:
			// Ignore other keys - keep showing confirmation
			return m, nil
		}
	}

	switch msg.String() {
	case "q", "ctrl+c":
		return m, tea.Quit
	case "esc":
		if m.showLargeFiles {
			m.showLargeFiles = false
			return m, nil
		}
		return m, tea.Quit
	case "up", "k":
		if m.showLargeFiles {
			if m.largeSelected > 0 {
				m.largeSelected--
				if m.largeSelected < m.largeOffset {
					m.largeOffset = m.largeSelected
				}
			}
		} else if len(m.entries) > 0 && m.selected > 0 {
			m.selected--
			if m.selected < m.offset {
				m.offset = m.selected
			}
		}
	case "down", "j":
		if m.showLargeFiles {
			if m.largeSelected < len(m.largeFiles)-1 {
				m.largeSelected++
				viewport := calculateViewport(m.height, true)
				if m.largeSelected >= m.largeOffset+viewport {
					m.largeOffset = m.largeSelected - viewport + 1
				}
			}
		} else if len(m.entries) > 0 && m.selected < len(m.entries)-1 {
			m.selected++
			viewport := calculateViewport(m.height, false)
			if m.selected >= m.offset+viewport {
				m.offset = m.selected - viewport + 1
			}
		}
	case "enter", "right", "l":
		if m.showLargeFiles {
			return m, nil
		}
		return m.enterSelectedDir()
	case "b", "left", "h":
		if m.showLargeFiles {
			m.showLargeFiles = false
			return m, nil
		}
		if len(m.history) == 0 {
			// Return to overview if at top level
			if !m.inOverviewMode() {
				return m, m.switchToOverviewMode()
			}
			return m, nil
		}
		last := m.history[len(m.history)-1]
		m.history = m.history[:len(m.history)-1]
		m.path = last.Path
		m.selected = last.Selected
		m.offset = last.EntryOffset
		m.largeSelected = last.LargeSelected
		m.largeOffset = last.LargeOffset
		m.isOverview = last.IsOverview
		if last.Dirty {
			// If returning to overview mode, refresh overview entries instead of scanning
			if last.IsOverview {
				m.hydrateOverviewEntries()
				m.totalSize = sumKnownEntrySizes(m.entries)
				m.status = "Ready"
				m.scanning = false
				if nextPendingOverviewIndex(m.entries) >= 0 {
					m.overviewScanning = true
					return m, m.scheduleOverviewScans()
				}
				return m, nil
			}
			m.status = "Scanning..."
			m.scanning = true
			return m, tea.Batch(m.scanCmd(m.path), tickCmd())
		}
		m.entries = last.Entries
		m.largeFiles = last.LargeFiles
		m.totalSize = last.TotalSize
		m.clampEntrySelection()
		m.clampLargeSelection()
		if len(m.entries) == 0 {
			m.selected = 0
		} else if m.selected >= len(m.entries) {
			m.selected = len(m.entries) - 1
		}
		if m.selected < 0 {
			m.selected = 0
		}
		m.status = fmt.Sprintf("Scanned %s", humanizeBytes(m.totalSize))
		m.scanning = false
		return m, nil
	case "r":
		if m.inOverviewMode() {
			// In overview mode, clear cache and re-scan known entries
			m.overviewSizeCache = make(map[string]int64)
			m.overviewScanningSet = make(map[string]bool)
			m.hydrateOverviewEntries() // Reset sizes to pending

			// Reset all entries to pending state for visual feedback
			for i := range m.entries {
				m.entries[i].Size = -1
			}
			m.totalSize = 0

			m.status = "Refreshing..."
			m.overviewScanning = true
			return m, tea.Batch(m.scheduleOverviewScans(), tickCmd())
		}

		// Normal mode: Invalidate cache before rescanning
		invalidateCache(m.path)
		m.status = "Refreshing..."
		m.scanning = true
		// Reset scan counters for refresh
		atomic.StoreInt64(m.filesScanned, 0)
		atomic.StoreInt64(m.dirsScanned, 0)
		atomic.StoreInt64(m.bytesScanned, 0)
		if m.currentPath != nil {
			*m.currentPath = ""
		}
		return m, tea.Batch(m.scanCmd(m.path), tickCmd())
	case "t", "T":
		// Don't allow switching to large files view in overview mode
		if !m.inOverviewMode() {
			m.showLargeFiles = !m.showLargeFiles
			if m.showLargeFiles {
				m.largeSelected = 0
				m.largeOffset = 0
			}
		}
	case "o":
		// Open selected entry
		if m.showLargeFiles {
			if len(m.largeFiles) > 0 {
				selected := m.largeFiles[m.largeSelected]
				go func(path string) {
					ctx, cancel := context.WithTimeout(context.Background(), openCommandTimeout)
					defer cancel()
					_ = exec.CommandContext(ctx, "open", path).Run()
				}(selected.Path)
				m.status = fmt.Sprintf("Opening %s...", selected.Name)
			}
		} else if len(m.entries) > 0 {
			selected := m.entries[m.selected]
			go func(path string) {
				ctx, cancel := context.WithTimeout(context.Background(), openCommandTimeout)
				defer cancel()
				_ = exec.CommandContext(ctx, "open", path).Run()
			}(selected.Path)
			m.status = fmt.Sprintf("Opening %s...", selected.Name)
		}
	case "f", "F":
		// Reveal selected entry in Finder
		if m.showLargeFiles {
			if len(m.largeFiles) > 0 {
				selected := m.largeFiles[m.largeSelected]
				go func(path string) {
					ctx, cancel := context.WithTimeout(context.Background(), openCommandTimeout)
					defer cancel()
					_ = exec.CommandContext(ctx, "open", "-R", path).Run()
				}(selected.Path)
				m.status = fmt.Sprintf("Showing %s in Finder...", selected.Name)
			}
		} else if len(m.entries) > 0 {
			selected := m.entries[m.selected]
			go func(path string) {
				ctx, cancel := context.WithTimeout(context.Background(), openCommandTimeout)
				defer cancel()
				_ = exec.CommandContext(ctx, "open", "-R", path).Run()
			}(selected.Path)
			m.status = fmt.Sprintf("Showing %s in Finder...", selected.Name)
		}
	case "delete", "backspace":
		// Delete selected file or directory
		if m.showLargeFiles {
			if len(m.largeFiles) > 0 {
				selected := m.largeFiles[m.largeSelected]
				m.deleteConfirm = true
				m.deleteTarget = &dirEntry{
					Name:  selected.Name,
					Path:  selected.Path,
					Size:  selected.Size,
					IsDir: false,
				}
			}
		} else if len(m.entries) > 0 && !m.inOverviewMode() {
			selected := m.entries[m.selected]
			m.deleteConfirm = true
			m.deleteTarget = &selected
		}
	}
	return m, nil
}

func (m *model) switchToOverviewMode() tea.Cmd {
	m.isOverview = true
	m.path = "/"
	m.scanning = false
	m.showLargeFiles = false
	m.largeFiles = nil
	m.largeSelected = 0
	m.largeOffset = 0
	m.deleteConfirm = false
	m.deleteTarget = nil
	m.selected = 0
	m.offset = 0
	m.hydrateOverviewEntries()
	cmd := m.scheduleOverviewScans()
	if cmd == nil {
		m.status = "Ready"
		return nil
	}
	// Start tick to animate spinner while scanning
	return tea.Batch(cmd, tickCmd())
}

func (m model) enterSelectedDir() (tea.Model, tea.Cmd) {
	if len(m.entries) == 0 {
		return m, nil
	}
	selected := m.entries[m.selected]
	if selected.IsDir {
		// Always save current state to history (including overview mode)
		m.history = append(m.history, snapshotFromModel(m))
		m.path = selected.Path
		m.selected = 0
		m.offset = 0
		m.status = "Scanning..."
		m.scanning = true
		m.isOverview = false

		// Reset scan counters for new scan
		atomic.StoreInt64(m.filesScanned, 0)
		atomic.StoreInt64(m.dirsScanned, 0)
		atomic.StoreInt64(m.bytesScanned, 0)
		if m.currentPath != nil {
			*m.currentPath = ""
		}

		if cached, ok := m.cache[m.path]; ok && !cached.Dirty {
			m.entries = cloneDirEntries(cached.Entries)
			m.largeFiles = cloneFileEntries(cached.LargeFiles)
			m.totalSize = cached.TotalSize
			m.selected = cached.Selected
			m.offset = cached.EntryOffset
			m.largeSelected = cached.LargeSelected
			m.largeOffset = cached.LargeOffset
			m.clampEntrySelection()
			m.clampLargeSelection()
			m.status = fmt.Sprintf("Cached view for %s", displayPath(m.path))
			m.scanning = false
			return m, nil
		}
		return m, tea.Batch(m.scanCmd(m.path), tickCmd())
	}
	m.status = fmt.Sprintf("File: %s (%s)", selected.Name, humanizeBytes(selected.Size))
	return m, nil
}

func (m *model) clampEntrySelection() {
	if len(m.entries) == 0 {
		m.selected = 0
		m.offset = 0
		return
	}
	if m.selected >= len(m.entries) {
		m.selected = len(m.entries) - 1
	}
	if m.selected < 0 {
		m.selected = 0
	}
	viewport := calculateViewport(m.height, false)
	maxOffset := len(m.entries) - viewport
	if maxOffset < 0 {
		maxOffset = 0
	}
	if m.offset > maxOffset {
		m.offset = maxOffset
	}
	if m.selected < m.offset {
		m.offset = m.selected
	}
	if m.selected >= m.offset+viewport {
		m.offset = m.selected - viewport + 1
	}
}

func (m *model) clampLargeSelection() {
	if len(m.largeFiles) == 0 {
		m.largeSelected = 0
		m.largeOffset = 0
		return
	}
	if m.largeSelected >= len(m.largeFiles) {
		m.largeSelected = len(m.largeFiles) - 1
	}
	if m.largeSelected < 0 {
		m.largeSelected = 0
	}
	viewport := calculateViewport(m.height, true)
	maxOffset := len(m.largeFiles) - viewport
	if maxOffset < 0 {
		maxOffset = 0
	}
	if m.largeOffset > maxOffset {
		m.largeOffset = maxOffset
	}
	if m.largeSelected < m.largeOffset {
		m.largeOffset = m.largeSelected
	}
	if m.largeSelected >= m.largeOffset+viewport {
		m.largeOffset = m.largeSelected - viewport + 1
	}
}

func sumKnownEntrySizes(entries []dirEntry) int64 {
	var total int64
	for _, entry := range entries {
		if entry.Size > 0 {
			total += entry.Size
		}
	}
	return total
}

func nextPendingOverviewIndex(entries []dirEntry) int {
	for i, entry := range entries {
		if entry.Size < 0 {
			return i
		}
	}
	return -1
}

func hasPendingOverviewEntries(entries []dirEntry) bool {
	for _, entry := range entries {
		if entry.Size < 0 {
			return true
		}
	}
	return false
}

func (m *model) removePathFromView(path string) {
	if path == "" {
		return
	}

	var removedSize int64
	for i, entry := range m.entries {
		if entry.Path == path {
			if entry.Size > 0 {
				removedSize = entry.Size
			}
			m.entries = append(m.entries[:i], m.entries[i+1:]...)
			break
		}
	}

	for i := 0; i < len(m.largeFiles); i++ {
		if m.largeFiles[i].Path == path {
			m.largeFiles = append(m.largeFiles[:i], m.largeFiles[i+1:]...)
			break
		}
	}

	if removedSize > 0 {
		if removedSize > m.totalSize {
			m.totalSize = 0
		} else {
			m.totalSize -= removedSize
		}
		m.clampEntrySelection()
	}
	m.clampLargeSelection()
}

func scanOverviewPathCmd(path string, index int) tea.Cmd {
	return func() tea.Msg {
		size, err := measureOverviewSize(path)
		return overviewSizeMsg{
			Path:  path,
			Index: index,
			Size:  size,
			Err:   err,
		}
	}
}