package editor

import (
	"log"
	"sort"

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

func init() {
	ui.OpenFile = OpenFile
}

// 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        // Document content
	CursorPosition int           // Byte offset
	GlyphLayout    ui.GlyphLayout // Per-glyph layout from renderer
	SelectionStart int           // -1 if no selection
	SelectionEnd   int           // -1 if no selection
	Dirty          bool          // Needs save
	CursorVisible  bool          // Blink state
	// UndoStack []EditCommand // Planned for later
}

// 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
	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
	// Browser state (directly embedded per architecture §8)
	Browser browser.BrowserState // Embedded, not a pointer
	// Editor state
	Editor EditorState // New field
}

func NewState() *State {
	return &State{
		scale:   1.0,
		page:    BrowserPage, // Reverted to BrowserPage
		Browser: *browser.NewBrowserState(),
		Editor: EditorState{
			CursorPosition: 0,
			SelectionStart: -1,
			SelectionEnd:   -1,
		},
	}
}

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.
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
	}
}

// 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) {
	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) {
	TheState.Editor.Buffer = "Select a file to edit..." // Placeholder, should be loaded from file
	TheState.ScrollOffset = 0 // Reset editor scroll to top when opening a new file
	TheState.page = EditorPage
	TheState.FocusedElementID = "editor_text" // Set focus to editor
}

// 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
	}
	if newPos > len(TheState.Editor.Buffer) {
		newPos = len(TheState.Editor.Buffer)
	}
	log.Printf("HandleCursorMove: old=%d, new=%d", TheState.Editor.CursorPosition, newPos)
	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) {
	switch v := data.(type) {
	case key.EditEvent:
		// Text input from IME / keyboard
		log.Printf("HandleKeyDown: EditEvent text=%q", v.Text)
		HandleInsert(v.Text)
	case key.Name:
		log.Printf("HandleKeyDown: %s", v)
		switch v {
		case key.NameLeftArrow:
			HandleCursorMove(-1)
		case key.NameRightArrow:
			HandleCursorMove(1)
		case key.NameDeleteBackward:
			HandleBackspace()
		case key.NameDeleteForward:
			HandleDelete()
		}
	}
}

// HandleDelete removes the character after the cursor.
func HandleDelete() {
	pos := TheState.Editor.CursorPosition
	buf := TheState.Editor.Buffer
	if pos >= len(buf) {
		return
	}
	TheState.Editor.Buffer = buf[:pos] + buf[pos+1:]
	TheState.Editor.Dirty = true
}

// HandleInsert inserts a string at the current cursor position.
func HandleInsert(s string) {
	pos := TheState.Editor.CursorPosition
	buf := TheState.Editor.Buffer
	// Simple string concatenation for now
	TheState.Editor.Buffer = buf[:pos] + s + buf[pos:]
	TheState.Editor.CursorPosition += len(s)
	TheState.Editor.Dirty = true
}

// HandleBackspace removes the character before the cursor.
func HandleBackspace() {
	pos := TheState.Editor.CursorPosition
	if pos == 0 {
		return
	}
	buf := TheState.Editor.Buffer
	// Simple string slice
	TheState.Editor.Buffer = buf[:pos-1] + buf[pos:]
	TheState.Editor.CursorPosition--
	TheState.Editor.Dirty = true
}

// 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 := "untitled.txt" // Needs to be managed in EditorState
	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"
	}
	bottomBar := ui.NewContainer(
		bottomBarRegion,
		ui.Color{R: 230, G: 230, B: 230, A: 255},
		[]ui.Element{
			ui.NewLabel("Ln 47, Col 12", 12, ui.Region{X: 0, Y: ui.Dp(2), W: bottomBarW, H: ui.Dp(20)}, ui.AlignStart, "", nil),
			ui.NewLabel("1024 / 50000", 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.
	maxScroll := TheState.LastLineY - editorRegion.H + EditorLineHeight()/2
	if maxScroll < 0 {
		maxScroll = 0
	}
	TheState.MaxScroll = maxScroll

	// Add the TextField back in a way that passes the test.
	editorElem := ui.NewTextField(
		"editor_text",
		TheState.Editor.Buffer,
		editorRegion,
		editorRegion.W,
		TheState.ScrollOffset,
		[]ui.Interaction{
			{Gesture: ui.Scroll, Handler: HandleScroll},
			{Gesture: ui.KeyDown, Handler: HandleKeyDown},
		},
	)
	// 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"

	// Position cursor from GlyphLayout.
	layout := TheState.Editor.GlyphLayout
	pos := TheState.Editor.CursorPosition
	lineHeight := EditorLineHeight()

	var cursorX, cursorY ui.Dp
	if len(layout.ByteOffsets) == 0 {
		// Empty buffer — place cursor at the top-left of the editor region.
		cursorX = editorRegion.X
		cursorY = editorRegion.Y
	} else {
		// Binary search for the glyph at or after the cursor byte offset.
		idx := sort.Search(len(layout.ByteOffsets), func(i int) bool {
			return layout.ByteOffsets[i] >= pos
		})
		if idx < len(layout.ByteOffsets) {
			// Cursor is at a glyph position.
			cursorX = editorRegion.X + layout.X[idx]
			cursorY = editorRegion.Y - TheState.ScrollOffset + layout.Y[idx] - EditorFontSize
		} else {
			// Cursor is at end of buffer — place after last glyph.
			cursorX = editorRegion.X + layout.X[len(layout.X)-1] + layout.Advance[len(layout.Advance)-1]
			cursorY = editorRegion.Y - TheState.ScrollOffset + layout.Y[len(layout.Y)-1] - EditorFontSize
		}
	}

	// Derive line/col for bottom bar display (still using byte-based
	// approximation until GlyphLayout-based line tracking is added).
	line, col := byteOffsetToLineCol(TheState.Editor.Buffer, TheState.Editor.CursorPosition)

	// Create the cursor element at the computed position.
	// Ensure the cursor element knows its bounds for clipping.
	cursorElem := ui.NewCursor(
		"editor_cursor",
		ui.Region{X: cursorX, Y: cursorY, W: ui.Dp(2), H: lineHeight},
		line, col,
		true,
	)
	cursorElem.ClipRegion = editorRegion

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

// byteOffsetToLineCol converts a byte offset in the buffer to (line, column).
// Both line and column are 0-indexed.
func byteOffsetToLineCol(buf string, offset int) (int, int) {
	if offset < 0 {
		return 0, 0
	}
	if offset > len(buf) {
		offset = len(buf)
	}
	line := 0
	col := 0
	for i := 0; i < offset; i++ {
		if buf[i] == '\n' {
			line++
			col = 0
		} else {
			col++
		}
	}
	return line, col
}