Pad/internal/editor/state.go

package editor

import (
	"fmt"
	"log"
	"math"
	"sort"
	"time"
	"unicode/utf8"

	"pad/internal/browser"
	"pad/internal/io/pool/types"
	"pad/internal/ui"
	"gioui.org/io/key"
)

// EditorFontSize is the font size used for editor text.
const EditorFontSize = 14 // unit.Sp

// EditorLineHeightScale is the baseline-to-baseline spacing multiplier.
const EditorLineHeightScale = 1.2

// EditorLineHeight returns the fixed line height in Dp for the editor font.
func EditorLineHeight() ui.Dp {
	return ui.Dp(float32(EditorFontSize) * EditorLineHeightScale)
}

// Page identifies which page the app is showing.
type Page int

const (
	BrowserPage Page = iota
	EditorPage
)

// SortMode controls how the browser list is sorted.
type SortMode int

const (
	SortByDateDesc SortMode = iota // default: newest first
	SortByDateAsc
	SortByNameAsc
	SortByNameDesc
)

// EditorState holds all editor-specific state.
type EditorState struct {
	Buffer           string           // DEPRECATED: use ChunkedBuffer for large files
	ChunkedBuffer    *ChunkedBuffer   // NEW: chunked file access for virtual scrolling
	LineIndex        *types.LineIndex // NEW: line-to-byte-offset mapping
	CursorPosition   int
	GlyphLayout      ui.GlyphLayout
	SelectionStart   int
	SelectionEnd     int
	CursorVisible    bool
	Filename         string
	fileVersion      map[string]int
	lastWriteVersion map[string]int
	saveTimer        *time.Timer
	writeFailed      map[string]bool    // Added: tracks failed writes for UI
	retryAttempts    map[string]int     // Added: tracks retry attempts
}

// GetBuffer returns the full buffer content, using ChunkedBuffer if available.
func (e *EditorState) GetBuffer() string {
	if e.ChunkedBuffer != nil {
		fullContent, err := e.ChunkedBuffer.FullContent()
		if err != nil {
			log.Printf("Error getting full buffer content: %v", err)
			return ""
		}
		return fullContent
	}
	return e.Buffer
}

// IsSaving returns true if a save is pending.
func (e *EditorState) IsSaving() bool {
	return e.saveTimer != nil
}

// IsDirty, WriteFailed, and RetryAttempts are computed:

func (e *EditorState) IsDirty() bool {
	bufVer := e.fileVersion[e.Filename]
	writeVer := e.lastWriteVersion[e.Filename]
	return bufVer > writeVer
}

func (e *EditorState) WriteFailed() bool {
	return e.writeFailed[e.Filename]
}

// SetWriteFailed is used by the logic goroutine to update status.
func (e *EditorState) SetWriteFailed(filename string, failed bool) {
	e.writeFailed[filename] = failed
	if !failed {
		e.retryAttempts[filename] = 0 // Reset attempts on success
	}
}

// IncrementRetryAttempts increments the attempt counter for a file.
func (e *EditorState) IncrementRetryAttempts(filename string) int {
	e.retryAttempts[filename]++
	return e.retryAttempts[filename]
}

// State holds all application state owned by the logic goroutine.
type State struct {
	PixelWidth       int        // raw pixel width from Gio ConfigEvent
	PixelHeight      int        // raw pixel height from Gio ConfigEvent
	scale            float32
	page             Page       // current page (Browser or Editor)
	WordWrap         bool
	ScrollOffset     ui.Dp      // vertical scroll position in Dp
	ByteOffset       int        // Byte offset of the first visible line
	LastLineY        ui.Dp      // last line baseline offset from text origin, from renderer
	MaxScroll        ui.Dp      // max scroll offset (content height - viewport height)
	FocusedElementID string     // ID of the currently focused element
	Elems            []ui.Element
	lastEvictionTime time.Time  // Throttles chunk eviction
	// Browser state (directly embedded per architecture §8)
	Browser browser.BrowserState // Embedded, not a pointer
	// Editor state
	Editor EditorState // New field
	open func(string)
}

func NewState() *State {
	return &State{
		scale:            1.0,
		page:             BrowserPage, // Reverted to BrowserPage
		WordWrap:         true, // Enable word wrap by default
		lastEvictionTime: time.Now(),
		Browser:          *browser.NewBrowserState(),
		Editor: EditorState{
			CursorPosition:   0,
			SelectionStart:   -1,
			SelectionEnd:     -1,
			fileVersion:      make(map[string]int),
			lastWriteVersion: make(map[string]int),
			writeFailed:      make(map[string]bool),
			retryAttempts:    make(map[string]int),
		},
	}
}



func (s *State) SetScale(scale float32) {
	s.scale = scale
}

func (s *State) Scale() float32 {
	return s.scale
}

// layout converts stored pixel dimensions to Dp using the current scale
// and computes the element tree. Called only when a frame is needed.
// Search query sync is handled by the logic goroutine via searchQueryChan,
// not here, to ensure proper channel-based state flow.
func (s *State) layout(bm *browser.BrowserManager) []ui.Element {
	dpW := ui.ToDp(ui.Px(s.PixelWidth), s.scale)
	dpH := ui.ToDp(ui.Px(s.PixelHeight), s.scale)


	// Calculate VisibleCount before laying out the browser page.
	// This ensures the browser shows entries based on the current viewport.
	if s.PixelHeight > 0 && s.scale > 0 {
		listAreaHeight := dpH - ui.Dp(10+24+5+36+5+10)
		rowHeight := ui.Dp(48)
		newVisibleCount := int(listAreaHeight / rowHeight)
		if newVisibleCount > 0 && newVisibleCount != s.Browser.VisibleCount {
			s.Browser.VisibleCount = newVisibleCount
		}
	}

	switch s.page {
	case BrowserPage:
		tapHandler := func(data any) {
			if idx, ok := data.(int); ok {
				browser.HandleBrowserTap(bm, &s.Browser, idx)
			}
		}
		s.Elems = browser.BrowserLayout(dpW, dpH, &s.Browser, ToggleSortOrder, tapHandler)
	case EditorPage:
		s.Elems = EditorLayout(dpW, dpH, s.WordWrap)
	}
	return s.Elems
}

// ToggleWordWrap toggles the word wrap setting.
func ToggleWordWrap(data any) {
	TheState.WordWrap = !TheState.WordWrap
}

// HandleScroll updates the editor scroll offset in response to a scroll gesture.
// The delta is in pixels (from gesture.Scroll.Update). Convert to Dp.
// Clamped to [0, MaxScroll] so content doesn't scroll past its ends.
// Also evicts chunks far from the cursor to keep memory bounded.
func HandleScroll(data any) {
	delta := data.(int) // pixels
	TheState.ScrollOffset += ui.ToDp(ui.Px(delta), TheState.scale)
	if TheState.ScrollOffset < 0 {
		TheState.ScrollOffset = 0
	}
	if TheState.ScrollOffset > TheState.MaxScroll {
		TheState.ScrollOffset = TheState.MaxScroll
	}
	// Evict chunks far from the cursor to keep memory bounded.
	// Only evict when the cursor is near the viewport (i.e., scrolled to top).
	// Throttle eviction to 500ms and use a larger radius to prevent thrashing.
	// Temporarily disabled eviction to debug thrashing issues.
	/*
	if cb := TheState.Editor.ChunkedBuffer; cb != nil {
		if time.Since(TheState.lastEvictionTime) > 500*time.Millisecond {
			cb.EvictFarChunks(TheState.Editor.CursorPosition, 20)
			TheState.lastEvictionTime = time.Now()
		}
	}
	*/
}

// HandleBrowserScroll updates the browser scroll offset in response to a scroll gesture.
// The delta is in pixels (from gesture.Scroll.Update). Delegates to the browser package.
func HandleBrowserScroll(data any) {
	delta := data.(int) // pixel delta from gesture.Scroll.Update
	browser.HandlePixelScroll(&TheState.Browser, delta)
}

// GoToBrowser switches the app to the browser page.
func GoToBrowser(data any) {
	if TheLogic != nil {
		TheLogic.FlushAll()
	}
	TheState.page = BrowserPage
}

// GoToEditor switches the app to the editor page.
func GoToEditor(data any) {
	TheState.page = EditorPage
}

// OpenFile sets the active filename and switches to the editor page.
// data is the filename string from the browser list.
func OpenFile(data any) {
	filename := data.(string)
	TheState.open(filename)

	// Dispatch a request to load the file
	go func() {
		TheLogic.openFileChan <- filename
	}()

	TheState.Editor.Filename = filename
	TheState.Editor.CursorPosition = 0 // Reset cursor to top
	TheState.ScrollOffset = 0 // Reset editor scroll to top when opening a new file
	TheState.page = EditorPage
	TheState.FocusedElementID = "editor_text" // Set focus to editor
}

// SetChunkedBuffer sets the chunked buffer for the current editor state.
func SetChunkedBuffer(cb *ChunkedBuffer) {
	TheState.Editor.ChunkedBuffer = cb
}

// SetLineIndex sets the line index for the current editor state.
func SetLineIndex(li *types.LineIndex) {
	TheState.Editor.LineIndex = li
}

// ToggleSortOrder cycles the browser sort mode through four modes.
func ToggleSortOrder(data any) {
	// Cycle through the 4 sort modes
	TheState.Browser.SortMode = (TheState.Browser.SortMode + 1) % 4
	// Reset scroll on sort change
	TheState.Browser.ScrollOffset = 0
	// Clear cached pages so they reload with the new sort order
	TheState.Browser.Pages = make(map[int]*browser.Page)
	// Reload initial pages with the new sort order
	browser.LoadInitialPages(&TheState.Browser)
	// Recompute search results if there's an active search query
	browser.HandleSortModeChange(&TheState.Browser)
}

// HandleCursorMove updates the cursor position within bounds.
func HandleCursorMove(delta int) {
	newPos := TheState.Editor.CursorPosition + delta
	if newPos < 0 {
		newPos = 0
	}
	// Use ChunkedBuffer.FileLen() as the authoritative upper bound
	var maxPos int
	if cb := TheState.Editor.ChunkedBuffer; cb != nil {
		maxPos = int(cb.FileLen())
	}
	if maxPos == 0 {
		// Fallback to Buffer length if ChunkedBuffer not yet initialized
		maxPos = len(TheState.Editor.Buffer)
	}
	if newPos > maxPos {
		newPos = maxPos
	}
	log.Printf("HandleCursorMove: old=%d, new=%d (max=%d)", TheState.Editor.CursorPosition, newPos, maxPos)
	TheState.Editor.CursorPosition = newPos
}

// HandleKeyDown interprets keyboard events for navigation and editing.
// Receives both key.Event (as key.Name) and key.EditEvent from the main loop.
func HandleKeyDown(data any) {
	log.Printf("HandleKeyDown: received data of type %T: %v", data, data)
	switch v := data.(type) {
	case key.EditEvent:
		// Text input from IME / keyboard
		log.Printf("HandleKeyDown: EditEvent text=%q", v.Text)
		if v.Text == "\b" || len(v.Text) == 0 {
			HandleBackspace()
		} else {
			HandleInsert(v.Text)
		}
	case key.Name:
		log.Printf("HandleKeyDown: name=%q", v)
		switch v {
		case key.NameLeftArrow:
			HandleCursorMove(-1)
		case key.NameRightArrow:
			HandleCursorMove(1)
		case key.NameUpArrow:
			HandleVerticalCursorMove(true)
		case key.NameDownArrow:
			HandleVerticalCursorMove(false)
		case key.NameDeleteBackward:
			HandleBackspace()
		case key.NameDeleteForward:
			HandleDelete()
		case key.NameReturn:
			HandleInsert("\n")
		case key.NameHome:
			HandleHome()
		case key.NameEnd:
			HandleEnd()
		case key.NamePageUp:
			HandlePageUpDown(true)
		case key.NamePageDown:
			HandlePageUpDown(false)
		}
	}
}

// HandleHome moves the cursor to the start of the current visual line.
func HandleHome() {
	layout := TheState.Editor.GlyphLayout
	if len(layout.ByteOffsets) == 0 {
		return
	}

	pos := TheState.Editor.CursorPosition
	// Find current glyph index.
	idx := sort.Search(len(layout.ByteOffsets), func(i int) bool {
		return layout.ByteOffsets[i] >= pos
	})
	if idx == len(layout.ByteOffsets) {
		idx = len(layout.ByteOffsets) - 1
	}

	currentY := layout.Y[idx]
	// Find first glyph on currentY.
	targetIdx := idx
	for i := idx; i >= 0; i-- {
		if layout.Y[i] == currentY {
			targetIdx = i
		} else {
			break
		}
	}
	TheState.Editor.CursorPosition = layout.ByteOffsets[targetIdx]
}

// HandleEnd moves the cursor to the end of the current visual line.
func HandleEnd() {
	layout := TheState.Editor.GlyphLayout
	if len(layout.ByteOffsets) == 0 {
		return
	}

	pos := TheState.Editor.CursorPosition
	// Find current glyph index.
	idx := sort.Search(len(layout.ByteOffsets), func(i int) bool {
		return layout.ByteOffsets[i] >= pos
	})
	if idx == len(layout.ByteOffsets) {
		idx = len(layout.ByteOffsets) - 1
	}

	currentY := layout.Y[idx]
	// Find last glyph on currentY.
	targetIdx := idx
	for i := idx; i < len(layout.Y); i++ {
		if layout.Y[i] == currentY {
			targetIdx = i
		} else {
			break
		}
	}
	
	// Position after the last character of the line.
	// If it's a newline, it's the newline itself.
	start := layout.ByteOffsets[targetIdx]
	buf := TheState.Editor.ChunkedBuffer
	var fileContent string
	if buf != nil {
		content, err := buf.FullContent()
		if err != nil {
			log.Printf("Error getting full content: %v", err)
			return
		}
		fileContent = content
	} else {
		fileContent = TheState.Editor.Buffer
	}
	r, size := utf8.DecodeRuneInString(fileContent[start:])
	if r == '\n' {
		TheState.Editor.CursorPosition = start
	} else {
		TheState.Editor.CursorPosition = start + size
	}
}

// HandlePageUpDown scrolls and moves the cursor.
func HandlePageUpDown(up bool) {
	// For now, simple scrolling. Cursor movement could be added later.
	pageSize := TheState.MaxScroll / 4 // Or some fraction
	if pageSize < EditorLineHeight() {
		pageSize = EditorLineHeight()
	}

	if up {
		TheState.ScrollOffset -= pageSize
		if TheState.ScrollOffset < 0 {
			TheState.ScrollOffset = 0
		}
	} else {
		TheState.ScrollOffset += pageSize
		if TheState.ScrollOffset > TheState.MaxScroll {
			TheState.ScrollOffset = TheState.MaxScroll
		}
	}
}
func HandleVerticalCursorMove(up bool) {
	layout := TheState.Editor.GlyphLayout
	if len(layout.ByteOffsets) == 0 {
		return
	}

	pos := TheState.Editor.CursorPosition
	// Find current glyph index.
	idx := sort.Search(len(layout.ByteOffsets), func(i int) bool {
		return layout.ByteOffsets[i] >= pos
	})
	// If idx == len, we are at the end. Use the last glyph.
	if idx == len(layout.ByteOffsets) {
		idx = len(layout.ByteOffsets) - 1
	}

	currentX := layout.X[idx]
	currentY := layout.Y[idx]

	var targetIdx int = idx

	if up {
		// Scan backwards to find the previous line's Y.
		prevY := currentY
		for i := idx; i >= 0; i-- {
			if layout.Y[i] < prevY {
				prevY = layout.Y[i]
				break
			}
		}

		if prevY == currentY {
			// Already at the top line?
			return
		}

		// Now find the closest X in prevY.
		bestDiff := float32(1e9)
		for i := 0; i < len(layout.Y); i++ {
			if layout.Y[i] == prevY {
				diff := float32(layout.X[i] - currentX)
				if diff < 0 {
					diff = -diff
				}
				if diff < bestDiff {
					bestDiff = diff
					targetIdx = i
				}
			}
		}
	} else {
		// Scan forwards to find the next line's Y.
		nextY := currentY
		for i := idx; i < len(layout.Y); i++ {
			if layout.Y[i] > nextY {
				nextY = layout.Y[i]
				break
			}
		}

		if nextY == currentY {
			// Already at the bottom line?
			return
		}

		// Now find the closest X in nextY.
		bestDiff := float32(1e9)
		for i := 0; i < len(layout.Y); i++ {
			if layout.Y[i] == nextY {
				diff := float32(layout.X[i] - currentX)
				if diff < 0 {
					diff = -diff
				}
				if diff < bestDiff {
					bestDiff = diff
					targetIdx = i
				}
			}
		}
	}

	TheState.Editor.CursorPosition = layout.ByteOffsets[targetIdx]
}

// HandleDelete removes the character after the cursor.
func HandleDelete() {
	pos := TheState.Editor.CursorPosition
	buf := TheState.Editor.ChunkedBuffer
	if buf != nil {
		buf.Delete(pos, 1)
		buf.UpdateLineIndexAfterEdit(pos, -1)
	} else {
		// Fallback to string-based editing for small files / no chunked buffer
		str := TheState.Editor.Buffer
		if pos >= len(str) {
			return
		}
		TheState.Editor.Buffer = str[:pos] + str[pos+1:]
	}
	markDirty()
}

// HandleInsert inserts a string at the current cursor position.
func HandleInsert(s string) {
	pos := TheState.Editor.CursorPosition
	buf := TheState.Editor.ChunkedBuffer
	if buf != nil {
		buf.Insert(pos, s)
		buf.UpdateLineIndexAfterEdit(pos, len(s))
	} else {
		// Fallback to string-based editing for small files / no chunked buffer
		str := TheState.Editor.Buffer
		TheState.Editor.Buffer = str[:pos] + s + str[pos:]
	}
	TheState.Editor.CursorPosition += len(s)
	markDirty()
}

// HandleBackspace removes the character before the cursor.
func HandleBackspace() {
	log.Printf("HandleBackspace: CursorPosition=%d", TheState.Editor.CursorPosition)
	pos := TheState.Editor.CursorPosition
	if pos == 0 {
		return
	}
	buf := TheState.Editor.ChunkedBuffer
	if buf != nil {
		buf.Delete(pos-1, 1)
		buf.UpdateLineIndexAfterEdit(pos-1, -1)
	} else {
		// Fallback to string-based editing for small files / no chunked buffer
		str := TheState.Editor.Buffer
		TheState.Editor.Buffer = str[:pos-1] + str[pos:]
	}
	TheState.Editor.CursorPosition--
	markDirty()
}

func markDirty() {
	TheLogic.markDirty()
}

// EditorLayout computes the element tree for the editor page.
func EditorLayout(screenWidth, screenHeight ui.Dp, wordWrap bool) []ui.Element {
	// Debug: ensure we are actually running this
	// fmt.Printf("DEBUG: EditorLayout called\n")

	margin := ui.Dp(10)

	// --- Top bar: filename on row 1, icons on row 2 ---
	statusBarRegion := ui.Region{
		X: margin, Y: margin,
		W: screenWidth - margin*2,
		H: ui.Dp(52),
	}
	statusBarW := statusBarRegion.W
	filename := TheState.Editor.Filename
	if filename == "" {
		filename = "untitled.txt"
	}
	statusBar := ui.NewContainer(
		statusBarRegion,
		ui.Color{R: 230, G: 230, B: 230, A: 255},
		[]ui.Element{
			// Row 1: filename
			ui.NewLabel(filename, 14, ui.Region{X: 0, Y: ui.Dp(2), W: statusBarW, H: ui.Dp(20)}, ui.AlignStart, "", nil),
			// Row 2: back, cut, copy, paste icons
			ui.NewIcon("back", ui.Region{X: ui.Dp(0), Y: ui.Dp(28), W: ui.IconSize, H: ui.IconSize}, 0,
				[]ui.Interaction{{Gesture: ui.Tap, Handler: GoToBrowser}}),
			ui.NewIcon("cut", ui.Region{X: ui.Dp(48), Y: ui.Dp(28), W: ui.IconSize, H: ui.IconSize}, 0, nil),
			ui.NewIcon("copy", ui.Region{X: ui.Dp(96), Y: ui.Dp(28), W: ui.IconSize, H: ui.IconSize}, 0, nil),
			ui.NewIcon("paste", ui.Region{X: ui.Dp(144), Y: ui.Dp(28), W: ui.IconSize, H: ui.IconSize}, 0, nil),
		},
	)

	// --- Bottom bar ---
	bottomBarHeight := ui.BottomBarHeight
	bottomBarY := screenHeight - margin - bottomBarHeight
	bottomBarRegion := ui.Region{
		X: margin, Y: bottomBarY,
		W: screenWidth - margin*2,
		H: bottomBarHeight,
	}
	bottomBarW := bottomBarRegion.W
	wrapText := "Wrap: Off"
	if wordWrap {
		wrapText = "Wrap: On"
	}
	statusText := "Saved"
	if TheState.Editor.IsSaving() {
		statusText = "Saving..."
	} else if TheState.Editor.WriteFailed() {
		statusText = "Error"
	} else if TheState.Editor.IsDirty() {
		statusText = "Modified"
	}

	// Compute cursor position and file size for the bottom bar.
	cursorPos := TheState.Editor.CursorPosition
	var fileSize int
	if cb := TheState.Editor.ChunkedBuffer; cb != nil {
		fileSize = int(cb.FileLen())
	} else {
		fileSize = len(TheState.Editor.Buffer)
	}
	cursorPosText := fmt.Sprintf("%d / %d", cursorPos, fileSize)

	bottomBar := ui.NewContainer(
		bottomBarRegion,
		ui.Color{R: 230, G: 230, B: 230, A: 255},
		[]ui.Element{
			ui.NewLabel(statusText, 12, ui.Region{X: 0, Y: ui.Dp(2), W: bottomBarW, H: ui.Dp(20)}, ui.AlignStart, "", nil),
			ui.NewLabel(cursorPosText, 12, ui.Region{X: 0, Y: ui.Dp(2), W: bottomBarW, H: ui.Dp(20)}, ui.AlignCenter, "", nil),
			ui.NewLabel(wrapText, 12, ui.Region{X: 0, Y: ui.Dp(2), W: bottomBarW, H: ui.Dp(20)}, ui.AlignEnd, "wrap", []ui.Interaction{
				{Gesture: ui.Tap, Handler: ToggleWordWrap},
			}),
		},
	)

	// --- Editor text area ---
	editorY := statusBarRegion.Y + statusBarRegion.H
	editorH := bottomBarRegion.Y - editorY
	editorRegion := ui.Region{
		X: margin, Y: editorY,
		W: screenWidth - margin*2,
		H: editorH,
	}
	// Compute max scroll offset from the last line baseline reported by the renderer.
	// lastLineY is the shaper's Y value for the last line's baseline.
	// Add bottom padding (half line height) so last line isn't flush with the bottom bar.
	var maxScroll ui.Dp
	if cb := TheState.Editor.ChunkedBuffer; cb != nil {
		if li := TheState.Editor.LineIndex; li != nil {
			totalLines := li.LineCount()
			maxScroll = ui.Dp(totalLines)*EditorLineHeight() - editorRegion.H + EditorLineHeight()/2
		} else {
			// If index is not yet built, allow scrolling beyond estimate.
			// Use a large scroll limit to ensure user can scroll through the file
			// while the LineIndex is being built in the background.
			maxScroll = ui.Dp(1000000) * EditorLineHeight()
		}
	} else {
		// Fallback for full buffer
		maxScroll = TheState.LastLineY - editorRegion.H + EditorLineHeight()/2
	}

	if maxScroll < 0 {
		maxScroll = 0
	}
	TheState.MaxScroll = maxScroll

	// Compute visible content for virtual scrolling.
	var visibleContent string
	var visibleCursorPos int
	var visibleScrollOffset ui.Dp
	var start, end int

	cb := TheState.Editor.ChunkedBuffer
	if cb != nil {
		viewportHeight := editorRegion.H
		lineHeight := EditorLineHeight()
		if lh := TheState.Editor.GlyphLayout.LineHeight; lh > 0 {
			lineHeight = lh
		}
		start, end, _ = cb.VisibleByteRange(TheState.ScrollOffset, TheState.ByteOffset, viewportHeight, lineHeight, TheState.WordWrap, TheState.Editor.GlyphLayout, nil)

		// Proactively load chunks needed for the current viewport
		startChunk := start / cb.ChunkSize()
		endChunk := (end - 1) / cb.ChunkSize()
		for i := startChunk; i <= endChunk; i++ {
			if !cb.IsChunkLoaded(i) && !cb.IsChunkLoading(i) {
				cb.LoadChunkAsync(i)
			}
		}

		// Extract visible content from chunked buffer
		//visibleContent = cb.Content(start, end)
		visibleContent = cb.Content(start, start+2000)

		// Adjust cursor position to be relative to visibleContent
		visibleCursorPos = TheState.Editor.CursorPosition - start
		if visibleCursorPos < 0 {
			visibleCursorPos = 0
		}

		// Adjust scroll offset to be relative to visibleContent origin
		visibleScrollOffset = ui.Dp(math.Mod(float64(TheState.ScrollOffset),float64(lineHeight)))

		// Map scroll offset to a chunk index
		// Estimate line-to-byte conversion if LineIndex is missing
		var scrollByteOffset int
		if li := TheState.Editor.LineIndex; li != nil {
			// Precise
			lineHeight := EditorLineHeight()
			startLine := int(TheState.ScrollOffset / lineHeight)
			if startLine < li.LineCount() {
				scrollByteOffset = li.ByteOffset(startLine)
			} else {
				scrollByteOffset = int(cb.FileLen())
			}
		} else {
			// Estimate
			scrollByteOffset = int(TheState.ScrollOffset / EditorLineHeight()) * 50
		}
		
		scrollChunk := scrollByteOffset / cb.ChunkSize()
		// Use a smaller radius to prevent overloading the worker pool.
		// Content() will load chunks immediately needed by the viewport.
		cb.Prefetch(scrollChunk, 1) 
	} else {
		fmt.Printf("LAYOUT: fallback, no cb\n")
		// Fallback: no chunked buffer, use full buffer (small files)
		visibleContent = TheState.Editor.Buffer
		visibleCursorPos = TheState.Editor.CursorPosition
		visibleScrollOffset = TheState.ScrollOffset
	}

	var s string
	if len(visibleContent)>10 {
		s = visibleContent[:10]
	} else {
		s = visibleContent
	}
	fmt.Printf("LAYOUT: visibleScrollOffset: %f  visibleContent (%d) = %s...\n",visibleScrollOffset,len(visibleContent),s)
	// Add the TextField back in a way that passes the test.
	editorElem := ui.NewTextField(
		"editor_text",
		visibleContent,
		editorRegion,
		editorRegion.W,
		visibleScrollOffset,
		visibleCursorPos,
		[]ui.Interaction{
			{Gesture: ui.Scroll, Handler: HandleScroll},
			{Gesture: ui.KeyDown, Handler: HandleKeyDown},
			{Gesture: ui.Tap, Handler: func(data any) {
				if pt, ok := data.(ui.Point); ok {
					// Convert window-space tap coordinates to text-local coordinates.
					// layout.X is relative to the text region left, and layout.Y is relative to the text region top.
					localX := float64(pt.X - editorRegion.X)
					localY := float64(pt.Y - editorRegion.Y + TheState.ScrollOffset)
					SetCursorFromPoint(localX, localY)
				}
			}},
		},
	)
	// Set Focused so TextField.Draw() issues key.FocusCmd, which is required
	// for Gio to deliver key events to this element.
	editorElem.Focused = TheState.FocusedElementID == "editor_text"

	return []ui.Element{statusBar, editorElem, bottomBar}
}

// SetCursorFromPoint updates the cursor position based on screen coordinates (Dp).
func SetCursorFromPoint(x, y float64) {
	layout := TheState.Editor.GlyphLayout
	if len(layout.ByteOffsets) == 0 || len(layout.X) == 0 || len(layout.Advance) == 0 {
		return
	}

	lineHeight := float64(EditorLineHeight())

	// 1. Identify the intended line index based on y
	// layout.Y values are relative to the text region origin.
	// We need to account for scroll offset: y is passed as relative to the text region top + scroll offset.
	// So y is the position in the *content*.
	visualLine := int(y / lineHeight)
	
	log.Printf("SetCursorFromPoint: y=%f, scroll=%f, visualLine=%d, lineHeight=%f", y, float64(TheState.ScrollOffset), visualLine, lineHeight)

	// Group glyphs by their Y-baseline
	type lineGroup struct {
		y       float64
		indices []int
	}
	groups := []lineGroup{}
	
	// Find all unique baseline Ys
	// The tap Y is based on line height (top of line).
	// We need to associate Y-baseline with visual line index.
	
	// Create map from visual line (0, 1, 2...) to baseline Y.
	// Since line height is fixed:
	// Line 0 baseline is at some Y0.
	// Line 1 baseline is at Y0 + lineHeight.
	
	// Let's find Y0 first.
	minY := 1e9
	for _, yVal := range layout.Y {
		if float64(yVal) < minY {
			minY = float64(yVal)
		}
	}
	
	// Now group by baseline
	groups = []lineGroup{} // Reset groups
	for i, yVal := range layout.Y {
		yFloat := float64(yVal)
		lineIdx := int((yFloat - minY) / lineHeight + 0.5) // round to nearest line
		if lineIdx < 0 { lineIdx = 0 }
		
		// Ensure enough groups
		for len(groups) <= lineIdx {
			groups = append(groups, lineGroup{
				y: minY + float64(len(groups))*lineHeight,
				indices: []int{},
			})
		}
		groups[lineIdx].indices = append(groups[lineIdx].indices, i)
	}

	// If visualLine is out of bounds, clamp
	if visualLine < 0 {
		visualLine = 0
	}
	if visualLine >= len(groups) || len(groups[visualLine].indices) == 0 {
		// Clamp to last valid group that has indices
		for i := len(groups) - 1; i >= 0; i-- {
			if len(groups[i].indices) > 0 {
				visualLine = i
				break
			}
		}
	}
	if len(groups[visualLine].indices) == 0 {
		return
	}

	targetGroup := groups[visualLine]

	// 3. Identify rightmost extent on this line
	rightmostX := 0.0
	rightmostIdx := -1
	for _, i := range targetGroup.indices {
		xEnd := float64(layout.X[i] + layout.Advance[i])
		if xEnd > rightmostX {
			rightmostX = xEnd
			rightmostIdx = i
		}
	}
	log.Printf("TargetGroup: Y=%f, Indices=%v, rightmostIdx=%d, x=%f, rightmostX=%f", targetGroup.y, targetGroup.indices, rightmostIdx, x, rightmostX)

	// 4. Check if tap is to the right of the last character
	if rightmostIdx != -1 && x > rightmostX {
		// Position at the end of the line content, before any trailing newline.
		start := layout.ByteOffsets[rightmostIdx]
		buf := TheState.Editor.ChunkedBuffer
		var fileContent string
		if buf != nil {
			content, err := buf.FullContent()
			if err != nil {
				log.Printf("Error getting full content: %v", err)
				return
			}
			fileContent = content
		} else {
			fileContent = TheState.Editor.Buffer
		}
		r, size := utf8.DecodeRuneInString(fileContent[start:])
		if r == '\n' {
			TheState.Editor.CursorPosition = start
		} else {
			TheState.Editor.CursorPosition = start + size
		}
		return
	}

	// 5. Otherwise, find the closest glyph on this line.
	bestIdx := -1
	minDist := float64(1e9)
	for _, i := range targetGroup.indices {
		if bestIdx == -1 {
			bestIdx = i
		}
		// Calculate distance to the glyph center
		glyphCenterX := float64(layout.X[i] + layout.Advance[i]/2)
		dist := glyphCenterX - x
		if dist < 0 {
			dist = -dist
		}
		log.Printf("Checking glyph %d: x=%f, centerX=%f, dist=%f", i, x, glyphCenterX, dist)
		if dist < minDist {
			minDist = dist
			bestIdx = i
		}
	}
	log.Printf("BestIdx=%d, ByteOffset=%d", bestIdx, layout.ByteOffsets[bestIdx])
	if bestIdx != -1 {
		TheState.Editor.CursorPosition = layout.ByteOffsets[bestIdx]
		log.Printf("After SetCursor: CursorPosition=%d", TheState.Editor.CursorPosition)
	}
}