lazygit/pkg/gocui/gui.go

// Copyright 2014 The gocui Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gocui

import (
	standardErrors "errors"
	"runtime"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/gdamore/tcell/v3"
	"github.com/go-errors/errors"
	"github.com/jesseduffield/generics/set"
	"github.com/petermattis/goid"
	"github.com/rivo/uniseg"
	"github.com/samber/lo"
)

// OutputMode represents an output mode, which determines how colors
// are used.
type OutputMode int

const DOUBLE_CLICK_THRESHOLD = 500 * time.Millisecond

var (
	// ErrNoSuchKeybind is returned when the keybinding being parsed does not exist.
	ErrNoSuchKeybind = standardErrors.New("no such keybind")

	// ErrUnknownView allows to assert if a View must be initialized.
	ErrUnknownView = standardErrors.New("unknown view")

	// ErrQuit is used to decide if the MainLoop finished successfully.
	ErrQuit = standardErrors.New("quit")

	// ErrKeybindingNotHandled is returned when a keybinding is not handled, so that the key can be dispatched further
	ErrKeybindingNotHandled = standardErrors.New("keybinding not handled")

	// ErrLoopExited is returned by OnUIThreadAndWait when MainLoop has already
	// returned. Nothing dequeues user events after that, so the callback it was
	// asked to run on the main goroutine never will be.
	ErrLoopExited = standardErrors.New("main loop exited")
)

const (
	// OutputNormal provides 8-colors terminal mode.
	OutputNormal OutputMode = iota

	// Output256 provides 256-colors terminal mode.
	Output256

	// Output216 provides 216 ansi color terminal mode.
	Output216

	// OutputGrayscale provides greyscale terminal mode.
	OutputGrayscale

	// OutputTrue provides 24bit color terminal mode.
	// This mode is recommended even if your terminal doesn't support
	// such mode. The colors are represented exactly as you
	// write them (no clamping or truncating). `tcell` should take care
	// of what your terminal can do.
	OutputTrue
)

type tabClickHandler func(int) error

type tabClickBinding struct {
	viewName string
	handler  tabClickHandler
}

// TODO: would be good to define inbound and outbound click handlers e.g.
// clicking on a file is an inbound thing where we don't care what context you're
// in when it happens, whereas clicking on the main view from the files view is an
// outbound click with a specific handler. But this requires more thinking about
// where handlers should live.
type ViewMouseBinding struct {
	// the view that is clicked
	ViewName string

	// the view that has focus when the click occurs.
	FocusedView string

	Handler func(ViewMouseBindingOpts) error

	Modifier Modifier

	// must be a mouse key
	Key KeyName
}

type ViewMouseBindingOpts struct {
	X int // i.e. origin x + cursor x
	Y int // i.e. origin y + cursor y

	Key KeyName // which button was clicked (will be one of the Mouse* constants)

	IsDoubleClick bool // true if this is a double click
}

type GuiMutexes struct {
	ViewsMutex sync.Mutex
}

type replayedEvents struct {
	Keys        chan *TcellKeyEventWrapper
	Resizes     chan *TcellResizeEventWrapper
	MouseEvents chan *TcellMouseEventWrapper
	FocusEvents chan *TcellFocusEventWrapper
}

type RecordingConfig struct {
	Speed  float64
	Leeway int
}

type clickInfo struct {
	x        int
	y        int
	key      KeyName
	viewName string
	time     time.Time
}

// Gui represents the whole User Interface, including the views, layouts
// and keybindings.
type Gui struct {
	RecordingConfig
	// replayedEvents is for passing simulated input events, for the purposes
	// of testing. Events must be submitted through the Replay* methods, which
	// attach a task to each event; pushing into the channels directly would
	// bypass the busy-tracking that integration tests rely on.
	replayedEvents replayedEvents
	playRecording  bool

	tabClickBindings         []*tabClickBinding
	viewMouseBindings        []*ViewMouseBinding
	lastClick                *clickInfo
	gEvents                  chan GocuiEvent
	userEvents               *userEventQueue
	views                    []*View
	currentView              *View
	managers                 []Manager
	keybindings              []*keybinding
	focusHandler             func(bool) error
	openHyperlink            func(string, string) error
	onSelectSearchResultFunc func(*View, int)
	renderSearchStatusFunc   func(*View, int, int)
	maxX, maxY               int
	outputMode               OutputMode
	stop                     chan struct{}
	// loopExited is closed when MainLoop returns, so callers (e.g. the
	// integration-test harness) can wait for the event loop to actually finish
	// rather than polling or sleeping a fixed interval.
	loopExited chan struct{}

	// BgColor and FgColor allow to configure the background and foreground
	// colors of the GUI.
	BgColor, FgColor, FrameColor Attribute

	// SelBgColor and SelFgColor allow to configure the background and
	// foreground colors of the frame of the current view.
	SelBgColor, SelFgColor, SelFrameColor Attribute

	// If Highlight is true, Sel{Bg,Fg}Colors will be used to draw the
	// frame of the current view.
	Highlight bool

	// If ShowListFooter is true then show list footer (i.e. the part that says we're at item 5 out of 10)
	ShowListFooter bool

	// If Cursor is true then the cursor is enabled.
	Cursor bool

	// If Mouse is true then mouse events will be enabled.
	Mouse bool

	IsPasting bool

	// If InputEsc is true, when ESC sequence is in the buffer and it doesn't
	// match any known sequence, ESC means KeyEsc.
	InputEsc bool

	// SupportOverlaps is true when we allow for view edges to overlap with other
	// view edges
	SupportOverlaps bool

	Mutexes GuiMutexes

	OnSearchEscape func() error

	SearchEscapeKeys    []Key
	NextSearchMatchKeys []Key
	PrevSearchMatchKeys []Key

	ErrorHandler func(error) error

	ShouldHandleMouseEvent func(view *View, key KeyName) bool

	screen         tcell.Screen
	suspendedMutex sync.Mutex
	suspended      bool

	taskManager *TaskManager

	// The task of the event currently being processed on the main goroutine, if
	// any. Only touched from the main goroutine (in processEvent). It's excluded
	// from the Busy() check so that an event handler asking "is anything else
	// busy?" doesn't count itself.
	currentTask Task

	lastHoverView        *View
	mouseCapture         *View
	mouseGestureCanceled bool

	// uiThreadID is the goroutine id of the main event loop, recorded when
	// MainLoop starts. IsUIThread compares against it. Written once, read from
	// worker goroutines, so it's atomic.
	uiThreadID atomic.Int64

	// focused says whether the terminal we're running in has focus, as far as
	// its focus reports tell us (see IsFocused). Written by the event loop,
	// readable from anywhere, so it's atomic.
	focused atomic.Bool

	// blockInputCount, when greater than zero, withholds keyboard input from
	// the handlers: key events are buffered into bufferedKeyEvents and replayed
	// once the count drops back to zero, while mouse clicks and hover are
	// dropped outright. It's a counter so blocking can nest. Both fields are
	// only touched on the UI thread. See BeginBlockingEvents.
	blockInputCount   int
	bufferedKeyEvents []GocuiEvent
}

type NewGuiOpts struct {
	OutputMode      OutputMode
	SupportOverlaps bool
	PlayRecording   bool
	Headless        bool
	// only applicable when Headless is true
	Width int
	// only applicable when Headless is true
	Height int

	RuneReplacements map[rune]string
}

// NewGui returns a new Gui object with a given output mode.
func NewGui(opts NewGuiOpts) (*Gui, error) {
	g := &Gui{}

	var err error
	if opts.Headless {
		err = g.tcellInitSimulation(opts.Width, opts.Height)
	} else {
		err = g.tcellInit(runeReplacements)
	}
	if err != nil {
		return nil, err
	}

	if opts.Headless || runtime.GOOS == "windows" {
		g.maxX, g.maxY = g.screen.Size()
	} else {
		// TODO: find out if we actually need this bespoke logic for linux
		g.maxX, g.maxY, err = g.getTermWindowSize()
		if err != nil {
			return nil, err
		}
	}

	g.outputMode = opts.OutputMode

	g.stop = make(chan struct{})
	g.loopExited = make(chan struct{})

	g.gEvents = make(chan GocuiEvent, 20)
	g.userEvents = newUserEventQueue()
	g.taskManager = newTaskManager()

	if opts.PlayRecording {
		g.replayedEvents = replayedEvents{
			Keys:        make(chan *TcellKeyEventWrapper),
			Resizes:     make(chan *TcellResizeEventWrapper),
			MouseEvents: make(chan *TcellMouseEventWrapper),
			FocusEvents: make(chan *TcellFocusEventWrapper),
		}
	}

	g.BgColor, g.FgColor, g.FrameColor = ColorDefault, ColorDefault, ColorDefault
	g.SelBgColor, g.SelFgColor, g.SelFrameColor = ColorDefault, ColorDefault, ColorDefault

	// SupportOverlaps is true when we allow for view edges to overlap with other
	// view edges
	g.SupportOverlaps = opts.SupportOverlaps

	// default keys for when searching strings in a view
	g.SearchEscapeKeys = []Key{NewKeyName(KeyEsc)}
	g.NextSearchMatchKeys = []Key{NewKeyRune('n')}
	g.PrevSearchMatchKeys = []Key{NewKeyRune('N')}

	g.playRecording = opts.PlayRecording

	// Record the UI thread here, at construction. This assumes NewGui is called
	// on the same goroutine that will run MainLoop, which holds for all our
	// callers -- and it means IsUIThread is already correct for the UI work that
	// runs during startup, before we reach MainLoop.
	g.uiThreadID.Store(goid.Get())

	// Assume we start out focused: a terminal that supports focus reports sends
	// one for the state it is already in when we turn reporting on in MainLoop,
	// and passing that on as a change would have the app react to a change that
	// never happened.
	g.focused.Store(true)

	return g, nil
}

func (g *Gui) NewTask() *TaskImpl {
	return g.taskManager.NewTask(false)
}

// NewBackgroundTask creates a task that is tracked for idle detection but does
// not count towards the program being busy for repo-switch safety. See
// TaskImpl.background.
func (g *Gui) NewBackgroundTask() *TaskImpl {
	return g.taskManager.NewTask(true)
}

// ReplayKeyEvent simulates a key press, as if the user had typed it. It's used
// by integration tests. The event carries a task, so that the program counts
// as busy from before the event is submitted until the main loop has fully
// processed it; the test driver relies on this when it waits for the program
// to go idle after submitting an event. (If the task were only created once
// the main loop picks the event up, there would be a window in which the event
// is still in flight but nothing counts as busy.)
func (g *Gui) ReplayKeyEvent(ev *TcellKeyEventWrapper) {
	ev.task = g.NewTask()
	g.replayedEvents.Keys <- ev
}

// ReplayMouseEvent is like ReplayKeyEvent, but for mouse events.
func (g *Gui) ReplayMouseEvent(ev *TcellMouseEventWrapper) {
	ev.task = g.NewTask()
	g.replayedEvents.MouseEvents <- ev
}

// ReplayFocusEvent is like ReplayKeyEvent, but for focus events.
func (g *Gui) ReplayFocusEvent(ev *TcellFocusEventWrapper) {
	ev.task = g.NewTask()
	g.replayedEvents.FocusEvents <- ev
}

// Busy reports whether any foreground work is in flight, ignoring the event
// currently being processed on the main goroutine (see currentTask). Background
// routines (auto-fetch etc.) don't count. It's used to decide whether it's safe
// to switch repos. Must be called on the main goroutine.
func (g *Gui) Busy() bool {
	return g.taskManager.hasBusyForegroundTaskExcept(g.currentTask)
}

// WaitUntilIdle blocks until the program is idle (no busy tasks). This is
// useful for integration tests which want to wait for the program to finish
// processing before taking the next step in the test.
func (g *Gui) WaitUntilIdle() {
	g.taskManager.WaitUntilIdle()
}

// Close finalizes the library. It should be called after a successful
// initialization and when gocui is not needed anymore.
func (g *Gui) Close() {
	close(g.stop)
	Screen.Fini()
}

// LoopExited returns a channel that is closed once MainLoop has returned.
func (g *Gui) LoopExited() <-chan struct{} {
	return g.loopExited
}

// Size returns the terminal's size.
func (g *Gui) Size() (x, y int) {
	return g.maxX, g.maxY
}

// SetRune writes a rune at the given point, relative to the top-left
// corner of the terminal. It checks if the position is valid and applies
// the given colors.
// Should only be used if you know that the given rune is not part of a grapheme cluster.
func (g *Gui) SetRune(x, y int, ch rune, fgColor, bgColor Attribute) error {
	if x < 0 || y < 0 || x >= g.maxX || y >= g.maxY {
		// swallowing error because it's not that big of a deal
		return nil
	}
	tcellSetCell(x, y, string(ch), fgColor, bgColor, g.outputMode)
	return nil
}

// SetView creates a new view with its top-left corner at (x0, y0)
// and the bottom-right one at (x1, y1). If a view with the same name
// already exists, its dimensions are updated; otherwise, the error
// ErrUnknownView is returned, which allows to assert if the View must
// be initialized. It checks if the position is valid.
func (g *Gui) SetView(name string, x0, y0, x1, y1 int, overlaps byte) (*View, error) {
	if name == "" {
		return nil, errors.New("invalid name")
	}

	if v, err := g.View(name); err == nil {
		sizeChanged := v.x0 != x0 || v.x1 != x1 || v.y0 != y0 || v.y1 != y1

		v.x0 = x0
		v.y0 = y0
		v.x1 = x1
		v.y1 = y1

		if sizeChanged {
			v.ClearViewLines()

			if v.Editable {
				cursorX, cursorY := v.TextArea.GetCursorXY()
				newViewCursorX, newOriginX := updatedCursorAndOrigin(0, v.InnerWidth(), cursorX)
				newViewCursorY, newOriginY := updatedCursorAndOrigin(0, v.InnerHeight(), cursorY)

				v.SetCursor(newViewCursorX, newViewCursorY)
				v.SetOrigin(newOriginX, newOriginY)
			}
		}

		return v, nil
	}

	g.Mutexes.ViewsMutex.Lock()

	v := NewView(name, x0, y0, x1, y1, g.outputMode)
	v.BgColor, v.FgColor = g.BgColor, g.FgColor
	v.SelBgColor, v.SelFgColor = g.SelBgColor, g.SelFgColor
	v.Overlaps = overlaps
	g.views = append(g.views, v)

	v.setOnSelectResult(g.onSelectSearchItem)
	v.setRenderSearchStatus(g.renderSearchStatus)

	g.Mutexes.ViewsMutex.Unlock()

	return v, errors.Wrap(ErrUnknownView, 0)
}

func (g *Gui) onSelectSearchItem(v *View, selectedLineIdx int) {
	if g.onSelectSearchResultFunc != nil {
		g.onSelectSearchResultFunc(v, selectedLineIdx)
	}
}

func (g *Gui) renderSearchStatus(v *View, selected int, total int) {
	if g.renderSearchStatusFunc != nil {
		g.renderSearchStatusFunc(v, selected, total)
	}
}

// SetViewBeneath sets a view stacked beneath another view
func (g *Gui) SetViewBeneath(name string, aboveViewName string, height int) (*View, error) {
	aboveView, err := g.View(aboveViewName)
	if err != nil {
		return nil, err
	}

	viewTop := aboveView.y1 + 1
	return g.SetView(name, aboveView.x0, viewTop, aboveView.x1, viewTop+height-1, 0)
}

// SetViewOnTop sets the given view on top of the existing ones.
func (g *Gui) SetViewOnTop(name string) (*View, error) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	for i, v := range g.views {
		if v.name == name {
			s := append(g.views[:i], g.views[i+1:]...)
			g.views = append(s, v)
			return v, nil
		}
	}
	return nil, errors.Wrap(ErrUnknownView, 0)
}

// SetViewOnBottom sets the given view on bottom of the existing ones.
func (g *Gui) SetViewOnBottom(name string) (*View, error) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	for i, v := range g.views {
		if v.name == name {
			s := append(g.views[:i], g.views[i+1:]...)
			g.views = append([]*View{v}, s...)
			return v, nil
		}
	}
	return nil, errors.Wrap(ErrUnknownView, 0)
}

func (g *Gui) SetViewOnTopOf(toMove string, other string) error {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	if toMove == other {
		return nil
	}

	// need to find the two current positions and then move toMove before other in the list.
	toMoveIndex := -1
	otherIndex := -1

	for i, v := range g.views {
		if v.name == toMove {
			toMoveIndex = i
		}

		if v.name == other {
			otherIndex = i
		}
	}

	if toMoveIndex == -1 || otherIndex == -1 {
		return errors.Wrap(ErrUnknownView, 0)
	}

	// already on top
	if toMoveIndex > otherIndex {
		return nil
	}

	// need to actually do it the other way around. Last is highest
	viewToMove := g.views[toMoveIndex]

	g.views = append(g.views[:toMoveIndex], g.views[toMoveIndex+1:]...)
	g.views = append(g.views[:otherIndex], append([]*View{viewToMove}, g.views[otherIndex:]...)...)
	return nil
}

// replaces the content in toView with the content in fromView
func (g *Gui) CopyContent(fromView *View, toView *View) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	toView.CopyContent(fromView)
}

// Views returns all the views in the GUI.
func (g *Gui) Views() []*View {
	return g.views
}

// View returns a pointer to the view with the given name, or error
// ErrUnknownView if a view with that name does not exist.
func (g *Gui) View(name string) (*View, error) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	for _, v := range g.views {
		if v.name == name {
			return v, nil
		}
	}
	return nil, errors.Wrap(ErrUnknownView, 0)
}

// VisibleViewByPosition returns a pointer to a view matching the given position, or
// error ErrUnknownView if a view in that position does not exist.
func (g *Gui) VisibleViewByPosition(x, y int) (*View, error) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	// traverse views in reverse order checking top views first
	for i := len(g.views); i > 0; i-- {
		v := g.views[i-1]

		if !v.Visible {
			continue
		}

		frameOffset := 0
		if v.Frame {
			frameOffset = 1
		}
		if x > v.x0-frameOffset && x < v.x1+frameOffset && y > v.y0-frameOffset && y < v.y1+frameOffset {
			return v, nil
		}
	}
	return nil, errors.Wrap(ErrUnknownView, 0)
}

// ViewPosition returns the coordinates of the view with the given name, or
// error ErrUnknownView if a view with that name does not exist.
func (g *Gui) ViewPosition(name string) (x0, y0, x1, y1 int, err error) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	for _, v := range g.views {
		if v.name == name {
			return v.x0, v.y0, v.x1, v.y1, nil
		}
	}
	return 0, 0, 0, 0, errors.Wrap(ErrUnknownView, 0)
}

// DeleteView deletes a view by name.
func (g *Gui) DeleteView(name string) error {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	for i, v := range g.views {
		if v.name == name {
			if g.mouseCapture == v {
				g.CancelMouseCapture()
			}
			if g.lastHoverView == v {
				g.lastHoverView = nil
			}
			g.views = append(g.views[:i], g.views[i+1:]...)
			return nil
		}
	}
	return errors.Wrap(ErrUnknownView, 0)
}

// SetCurrentView gives the focus to a given view.
func (g *Gui) SetCurrentView(name string) (*View, error) {
	g.Mutexes.ViewsMutex.Lock()
	defer g.Mutexes.ViewsMutex.Unlock()

	for _, v := range g.views {
		if v.name == name {
			g.currentView = v
			return v, nil
		}
	}
	return nil, errors.Wrap(ErrUnknownView, 0)
}

// CurrentView returns the currently focused view, or nil if no view
// owns the focus.
func (g *Gui) CurrentView() *View {
	return g.currentView
}

// SetKeybinding creates a new keybinding. If viewname equals to ""
// (empty string) then the keybinding will apply to all views. key must
// be a rune or a Key.
func (g *Gui) SetKeybinding(viewname string, key Key, handler func(*Gui, *View) error) {
	kb := newKeybinding(viewname, key, handler)
	g.keybindings = append(g.keybindings, kb)
}

// DeleteKeybindings deletes all keybindings of view.
func (g *Gui) DeleteAllKeybindings() {
	g.keybindings = []*keybinding{}
	g.tabClickBindings = []*tabClickBinding{}
	g.viewMouseBindings = []*ViewMouseBinding{}
}

// DeleteKeybindings deletes all keybindings of view.
func (g *Gui) DeleteViewKeybindings(viewname string) {
	var s []*keybinding
	for _, kb := range g.keybindings {
		if kb.viewName != viewname {
			s = append(s, kb)
		}
	}
	g.keybindings = s
}

// SetTabClickBinding sets a binding for a tab click event
func (g *Gui) SetTabClickBinding(viewName string, handler tabClickHandler) error {
	g.tabClickBindings = append(g.tabClickBindings, &tabClickBinding{
		viewName: viewName,
		handler:  handler,
	})

	return nil
}

func (g *Gui) SetViewClickBinding(binding *ViewMouseBinding) error {
	g.viewMouseBindings = append(g.viewMouseBindings, binding)

	return nil
}

// captureMouse routes subsequent mouse events to view until the mouse button is
// released or CancelMouseCapture is called.
func (g *Gui) captureMouse(view *View) {
	g.mouseCapture = view
	g.mouseGestureCanceled = false
}

func (g *Gui) releaseMouseCapture() {
	g.mouseCapture = nil
}

// CancelMouseCapture releases capture and ignores the rest of the physical
// gesture until the mouse button is released.
func (g *Gui) CancelMouseCapture() {
	g.releaseMouseCapture()
	g.mouseGestureCanceled = true
}

func (g *Gui) SetFocusHandler(handler func(bool) error) {
	g.focusHandler = handler
}

func (g *Gui) SetOpenHyperlinkFunc(openHyperlinkFunc func(string, string) error) {
	g.openHyperlink = openHyperlinkFunc
}

func (g *Gui) SetOnSelectSearchResultFunc(onSelectSearchResultFunc func(*View, int)) {
	g.onSelectSearchResultFunc = onSelectSearchResultFunc
}

func (g *Gui) SetRenderSearchStatusFunc(renderSearchStatusFunc func(*View, int, int)) {
	g.renderSearchStatusFunc = renderSearchStatusFunc
}

// SetUpdateQueueHighWaterMarkHandler registers a diagnostic callback invoked
// with the new depth whenever the queue of pending Update callbacks reaches a
// new maximum. It may be called from any goroutine.
func (g *Gui) SetUpdateQueueHighWaterMarkHandler(f func(depth int)) {
	g.userEvents.setHighWaterMarkHandler(f)
}

// userEvent represents an event triggered by the user.
type userEvent struct {
	f    func(*Gui) error
	task Task
	// Signals that this event only modifies view content (e.g. SetContent).
	// When all events in a batch are contentOnly, processEvent
	// can skip the expensive layout() call in flush().
	contentOnly bool
}

// userEventQueue is an unbounded, order-preserving FIFO of work enqueued by
// Update and friends for the main loop to run.
//
// It's unbounded (rather than a fixed-size channel) because producers must
// never block or lose work. Update can be called from the UI goroutine itself,
// where a blocking send would deadlock against the loop that drains the queue;
// and it can be called from arbitrary worker goroutines that may enqueue faster
// than the loop drains. That happens while the loop is stalled — suspended for
// a subprocess (the editor runs on the UI thread), or hung in a long handler —
// and also when a long-running worker operation emits a steady stream of
// updates that outpaces the loop (e.g. the waiting-status spinner ticks while a
// large directory is toggled into a custom patch). A fixed channel forces a
// choice between blocking (deadlock), dropping or reordering, and panicking on
// overflow; an unbounded queue avoids all three while preserving FIFO order.
//
// enqueue appends under the mutex and rings the doorbell; the main loop selects
// on the doorbell to wake, then drains the slice to empty. The doorbell is
// buffered(1) and rung with a non-blocking send, so it's a coalescing "work
// pending" flag rather than a per-event signal: a burst of appends leaves at
// most one token, and the loop drains everything the token represents on a
// single wake. A token left over after a drain (because the drain happened to
// empty the slice after the ring) just causes one harmless empty wake.
type userEventQueue struct {
	mutex    sync.Mutex
	events   []userEvent
	doorbell chan struct{}

	// highWaterMark is the deepest the queue has ever been, and
	// onHighWaterMark (if set) is called with the new depth each time that
	// record is broken. Purely diagnostic: it lets us see how deep the queue
	// gets in practice (see SetUpdateQueueHighWaterMarkHandler).
	highWaterMark   int
	onHighWaterMark func(int)
}

func newUserEventQueue() *userEventQueue {
	return &userEventQueue{doorbell: make(chan struct{}, 1)}
}

// enqueue appends an event and wakes the main loop. It never blocks.
func (q *userEventQueue) enqueue(ev userEvent) {
	q.mutex.Lock()
	q.events = append(q.events, ev)
	newHighWaterMark := 0
	if len(q.events) > q.highWaterMark {
		q.highWaterMark = len(q.events)
		newHighWaterMark = q.highWaterMark
	}
	onHighWaterMark := q.onHighWaterMark
	q.mutex.Unlock()

	// Report outside the lock: the handler does I/O (logging) and must not
	// stall other producers or the draining loop.
	if newHighWaterMark > 0 && onHighWaterMark != nil {
		onHighWaterMark(newHighWaterMark)
	}

	select {
	case q.doorbell <- struct{}{}:
	default:
	}
}

func (q *userEventQueue) setHighWaterMarkHandler(f func(int)) {
	q.mutex.Lock()
	q.onHighWaterMark = f
	q.mutex.Unlock()
}

// dequeue pops the oldest event, reporting false when the queue is empty.
func (q *userEventQueue) dequeue() (userEvent, bool) {
	q.mutex.Lock()
	defer q.mutex.Unlock()

	if len(q.events) == 0 {
		return userEvent{}, false
	}
	ev := q.events[0]
	if len(q.events) == 1 {
		// Release the backing array whenever the queue drains, so a one-off
		// burst doesn't pin its peak size for the rest of the session.
		q.events = nil
	} else {
		q.events[0] = userEvent{}
		q.events = q.events[1:]
	}
	return ev, true
}

// Update enqueues f for the UI loop to run on its next iteration. Multiple
// Update calls from the same goroutine arrive in source order (the queue is
// FIFO). The enqueue never blocks and never drops work; see userEventQueue for
// why the queue is unbounded.
func (g *Gui) Update(f func(*Gui) error) {
	g.update(f, false)
}

// Like Update, but the enqueued work is a background routine (or triggered by
// one), so it doesn't count towards the program being busy for repo-switch
// safety. See TaskImpl.background.
func (g *Gui) UpdateBackground(f func(*Gui) error) {
	g.update(f, true)
}

func (g *Gui) update(f func(*Gui) error, background bool) {
	task := g.taskManager.NewTask(background)
	g.userEvents.enqueue(userEvent{f: f, task: task})
}

// Like Update, but signals that the callback only modifies content.
func (g *Gui) UpdateContentOnly(f func(*Gui) error) {
	g.updateContentOnly(f, false)
}

// Like UpdateContentOnly, but for background work (see UpdateBackground).
func (g *Gui) UpdateContentOnlyBackground(f func(*Gui) error) {
	g.updateContentOnly(f, true)
}

func (g *Gui) updateContentOnly(f func(*Gui) error, background bool) {
	task := g.taskManager.NewTask(background)
	g.userEvents.enqueue(userEvent{f: f, task: task, contentOnly: true})
}

// IsUIThread reports whether the caller is running on the main event-loop
// goroutine (the one running MainLoop). It calls goid.Get, so use it only for
// debug assertions, not to drive production control flow.
func (g *Gui) IsUIThread() bool {
	return goid.Get() == g.uiThreadID.Load()
}

// BeginBlockingEvents starts withholding keyboard input from the handlers, so a
// long-running operation can't be disrupted by keys the user presses while it
// runs. Keys are buffered and replayed once EndBlockingEvents balances this
// call; mouse clicks and hover are dropped for the duration. Scrolling,
// resizing, focus changes and all rendering keep working throughout. It's a
// counter, so blocking nests; every call must be paired with EndBlockingEvents.
//
// Must be called on the UI thread. Callers arrange this by beginning the block
// synchronously from the keybinding handler, before dispatching the operation
// to a worker — beginning it from the worker would race the next queued
// keypress, which is exactly the input we mean to withhold.
func (g *Gui) BeginBlockingEvents() {
	g.blockInputCount++
}

// EndBlockingEvents balances a BeginBlockingEvents call. When the last nested
// block ends, the keys buffered while blocked are replayed in order through the
// normal dispatch path, so they act on the now-current context (a key whose
// binding no longer exists is simply ignored, just as if it had been pressed
// now). Must be called on the UI thread.
func (g *Gui) EndBlockingEvents() error {
	g.blockInputCount--
	if g.blockInputCount > 0 {
		return nil
	}

	buffered := g.bufferedKeyEvents
	g.bufferedKeyEvents = nil
	for i := range buffered {
		if err := g.handleEvent(&buffered[i]); err != nil {
			return err
		}
	}
	return nil
}

// OnUIThreadAndWait runs f on the main event-loop goroutine and blocks the
// caller until f has run. Use it to read UI-thread-owned state (the model,
// contexts) from a worker without racing the UI thread.
//
// The error it returns is the wait's own, never f's: it reports that f was not
// run at all, which happens when the main loop has exited (ErrLoopExited). f
// doesn't report an error because what callers want on the UI thread — reading
// and mutating state — doesn't fail.
//
// It must be called from a worker goroutine, never from the UI thread itself:
// the UI thread would block waiting for a callback only it can run, which
// deadlocks. Callers arrange this by construction (see the refresh helper's
// RefreshFromWorker); a debug-only assertion there guards against getting it
// wrong.
func (g *Gui) OnUIThreadAndWait(f func()) error {
	return g.onUIThreadAndWait(f, false)
}

// Like OnUIThreadAndWait, but the enqueued work belongs to a background routine,
// so it doesn't count towards the program being busy (see UpdateBackground).
func (g *Gui) OnUIThreadAndWaitBackground(f func()) error {
	return g.onUIThreadAndWait(f, true)
}

func (g *Gui) onUIThreadAndWait(f func(), background bool) error {
	enqueue := g.Update
	if background {
		enqueue = g.UpdateBackground
	}

	ran := make(chan struct{})
	enqueue(func(*Gui) error {
		f()
		close(ran)
		return nil
	})

	select {
	case <-ran:
		return nil
	case <-g.loopExited:
		// The queue we just enqueued onto is no longer being served, so waiting
		// on `ran` here would mean waiting for the rest of the process's life.
		return ErrLoopExited
	}
}

// Calls a function in a goroutine. Handles panics gracefully and tracks
// number of background tasks.
// Always use this when you want to spawn a goroutine and you want lazygit to
// consider itself 'busy` as it runs the code. Don't use for long-running
// background goroutines where you wouldn't want lazygit to be considered busy
// (i.e. when you wouldn't want a loader to be shown to the user)
func (g *Gui) OnWorker(f func(Task) error) {
	g.onWorker(f, false)
}

// Like OnWorker, but for a background routine (or work triggered by one), so it
// doesn't count towards the program being busy for repo-switch safety. See
// TaskImpl.background.
func (g *Gui) OnWorkerBackground(f func(Task) error) {
	g.onWorker(f, true)
}

func (g *Gui) onWorker(f func(Task) error, background bool) {
	task := g.taskManager.NewTask(background)
	go func() {
		g.onWorkerAux(f, task)
		task.Done()
	}()
}

func (g *Gui) onWorkerAux(f func(Task) error, task Task) {
	panicking := true
	defer func() {
		if panicking && Screen != nil {
			Screen.Fini()
		}
	}()

	err := f(task)

	panicking = false

	if err != nil {
		g.Update(func(g *Gui) error {
			return err
		})
	}
}

// A Manager is in charge of GUI's layout and can be used to build widgets.
type Manager interface {
	// Layout is called every time the GUI is redrawn, it must contain the
	// base views and its initializations.
	Layout(*Gui) error
}

// The ManagerFunc type is an adapter to allow the use of ordinary functions as
// Managers. If f is a function with the appropriate signature, ManagerFunc(f)
// is an Manager object that calls f.
type ManagerFunc func(*Gui) error

// Layout calls f(g)
func (f ManagerFunc) Layout(g *Gui) error {
	return f(g)
}

// SetManager sets the given GUI managers. It deletes all views and
// keybindings.
func (g *Gui) SetManager(managers ...Manager) {
	g.managers = managers
	g.currentView = nil
	g.views = nil
	g.keybindings = nil
	g.tabClickBindings = nil

	go func() { g.gEvents <- GocuiEvent{Type: eventResize} }()
}

// SetManagerFunc sets the given manager function. It deletes all views and
// keybindings.
func (g *Gui) SetManagerFunc(manager func(*Gui) error) {
	g.SetManager(ManagerFunc(manager))
}

// MainLoop runs the main loop until an error is returned. A successful
// finish should return ErrQuit.
func (g *Gui) MainLoop() error {
	defer close(g.loopExited)

	go func() {
		for {
			select {
			case <-g.stop:
				return
			default:
				g.gEvents <- g.pollEvent()
			}
		}
	}()

	Screen.EnableFocus()
	Screen.EnablePaste()

	previousEnableMouse := false
	for {
		if g.Mouse != previousEnableMouse {
			if g.Mouse {
				Screen.EnableMouse()
			} else {
				Screen.DisableMouse()
			}

			previousEnableMouse = g.Mouse
		}

		err := g.processEvent()
		if err != nil {
			return err
		}
	}
}

func (g *Gui) handleError(err error) error {
	if err != nil && !standardErrors.Is(err, ErrQuit) && g.ErrorHandler != nil {
		return g.ErrorHandler(err)
	}

	return err
}

func (g *Gui) processEvent() error {
	contentOnly := false

	// currentTask is the task of the event we're about to handle; recording it
	// lets Busy() ignore it, so a handler asking "is anything else busy?" (the
	// repo-switch guard does) doesn't count itself. Handlers of the remaining
	// events drained below run with currentTask still set to this primary event;
	// that's fine because the only Busy() callers are keybinding handlers, which
	// are always the primary event here.
	select {
	case ev := <-g.gEvents:
		// Replayed test events already carry their task (see ReplayKeyEvent);
		// organic events get theirs here.
		task := ev.task
		if task == nil {
			task = g.NewTask()
		}
		g.currentTask = task
		defer func() { g.currentTask = nil; task.Done() }()

		if err := g.handleError(g.handleEvent(&ev)); err != nil {
			return err
		}
	case <-g.userEvents.doorbell:
		ev, ok := g.userEvents.dequeue()
		if !ok {
			// A leftover doorbell token whose events were already drained by a
			// previous iteration's processRemainingEvents: nothing to run and
			// nothing new to render.
			return nil
		}
		contentOnly = ev.contentOnly
		g.currentTask = ev.task
		defer func() { g.currentTask = nil; ev.task.Done() }()

		if err := g.handleError(ev.f(g)); err != nil {
			return err
		}
	}

	remainingContentOnly, err := g.processRemainingEvents()
	if err != nil {
		return err
	}
	contentOnly = contentOnly && remainingContentOnly

	if contentOnly {
		return g.flushContentOnly(g.views)
	}
	return g.flush()
}

// processRemainingEvents handles the remaining events in the events pool.
// Returns true if all processed events were content-only.
func (g *Gui) processRemainingEvents() (bool, error) {
	contentOnly := true
	for {
		select {
		case ev := <-g.gEvents:
			contentOnly = false
			err := g.handleError(g.handleEvent(&ev))
			if ev.task != nil {
				ev.task.Done()
			}
			if err != nil {
				return false, err
			}
		default:
			// No gui event is pending; drain a queued user event instead.
			// gui events take priority so input stays responsive, but they're
			// bounded (buffer of 20), so this can't starve the user-event queue.
			ev, ok := g.userEvents.dequeue()
			if !ok {
				return contentOnly, nil
			}
			contentOnly = ev.contentOnly && contentOnly
			err := g.handleError(ev.f(g))
			ev.task.Done()
			if err != nil {
				return false, err
			}
		}
	}
}

// handleEvent handles an event, based on its type (key-press, error,
// etc.)
func (g *Gui) handleEvent(ev *GocuiEvent) error {
	if g.blockInputCount > 0 && eventWithheldWhileBlocking(ev) {
		if ev.Type == eventKey {
			// Buffer keys so they replay against fresh state on unblock.
			g.bufferedKeyEvents = append(g.bufferedKeyEvents, *ev)
		}
		// Mouse clicks and hover fall through to here without being buffered:
		// replaying them once the operation has changed the layout underneath
		// them would target the wrong thing, so we drop them outright.
		return nil
	}

	switch ev.Type {
	case eventKey, eventMouse, eventMouseMove:
		return g.onKey(ev)
	case eventError:
		return ev.Err
	case eventResize:
		g.onResize()
		return nil
	case eventFocus:
		return g.onFocus(ev)
	case eventPaste:
		g.IsPasting = ev.Start
		return nil
	default:
		return nil
	}
}

// eventWithheldWhileBlocking reports whether an event must not reach the
// handlers while input is blocked (see BeginBlockingEvents). Key events are
// withheld (buffered for replay); mouse clicks and hover are withheld (dropped).
// Everything else — mouse scrolling, resize, focus, paste, errors — flows
// through as usual.
func eventWithheldWhileBlocking(ev *GocuiEvent) bool {
	switch ev.Type {
	case eventKey:
		return true
	case eventMouse:
		return !IsMouseScrollKey(ev.Key.KeyName())
	case eventMouseMove:
		return true
	default:
		return false
	}
}

func (g *Gui) onResize() {
	// not sure if we actually need this
	// g.screen.Sync()
}

// drawFrameEdges draws the horizontal and vertical edges of a view.
func (g *Gui) drawFrameEdges(v *View, fgColor, bgColor Attribute) error {
	runeH, runeV := '─', '│'
	if len(v.FrameRunes) >= 2 {
		runeH, runeV = v.FrameRunes[0], v.FrameRunes[1]
	}

	for x := v.x0 + 1; x < v.x1 && x < g.maxX; x++ {
		if x < 0 {
			continue
		}
		if v.y0 > -1 && v.y0 < g.maxY {
			if err := g.SetRune(x, v.y0, runeH, fgColor, bgColor); err != nil {
				return err
			}
		}
		if v.y1 > -1 && v.y1 < g.maxY {
			if err := g.SetRune(x, v.y1, runeH, fgColor, bgColor); err != nil {
				return err
			}
		}
	}

	showScrollbar, realScrollbarStart, realScrollbarEnd := calcRealScrollbarStartEnd(v)
	for y := v.y0 + 1; y < v.y1 && y < g.maxY; y++ {
		if y < 0 {
			continue
		}
		if v.x0 > -1 && v.x0 < g.maxX {
			if err := g.SetRune(v.x0, y, runeV, fgColor, bgColor); err != nil {
				return err
			}
		}
		if v.x1 > -1 && v.x1 < g.maxX {
			runeToPrint := calcScrollbarRune(showScrollbar, realScrollbarStart, realScrollbarEnd, y, runeV)

			if err := g.SetRune(v.x1, y, runeToPrint, fgColor, bgColor); err != nil {
				return err
			}
		}
	}
	return nil
}

func calcScrollbarRune(
	showScrollbar bool, scrollbarStart int, scrollbarEnd int, position int, runeV rune,
) rune {
	if showScrollbar && (position >= scrollbarStart && position <= scrollbarEnd) {
		return '▐'
	}

	return runeV
}

func calcRealScrollbarStartEnd(v *View) (bool, int, int) {
	height := v.InnerHeight()
	fullHeight := v.scrollbarContentHeight() - v.scrollMargin()

	if v.CanScrollPastBottom {
		fullHeight += height
	}

	if height < 2 || height >= fullHeight {
		return false, 0, 0
	}

	originY := v.OriginY()
	scrollbarStart, scrollbarHeight := calcScrollbar(fullHeight, height, originY, height-1)
	top := v.y0 + 1
	realScrollbarStart := top + scrollbarStart
	realScrollbarEnd := realScrollbarStart + scrollbarHeight

	return true, realScrollbarStart, realScrollbarEnd
}

func cornerRune(index byte) rune {
	return []rune{' ', '│', '│', '│', '─', '┘', '┐', '┤', '─', '└', '┌', '├', '├', '┴', '┬', '┼'}[index]
}

// cornerCustomRune returns rune from `v.FrameRunes` slice. If the length of slice is less than 11
// all the missing runes will be translated to the default `cornerRune()`
func cornerCustomRune(v *View, index byte) rune {
	// Translate `cornerRune()` index
	//  0    1    2    3    4    5    6    7    8    9    10   11   12   13   14   15
	// ' ', '│', '│', '│', '─', '┘', '┐', '┤', '─', '└', '┌', '├', '├', '┴', '┬', '┼'
	// into `FrameRunes` index
	//  0    1    2    3    4    5    6    7    8    9    10
	// '─', '│', '┌', '┐', '└', '┘', '├', '┤', '┬', '┴', '┼'
	switch index {
	case 1, 2, 3:
		return v.FrameRunes[1]
	case 4, 8:
		return v.FrameRunes[0]
	case 5:
		return v.FrameRunes[5]
	case 6:
		return v.FrameRunes[3]
	case 7:
		if len(v.FrameRunes) < 8 {
			break
		}
		return v.FrameRunes[7]
	case 9:
		return v.FrameRunes[4]
	case 10:
		return v.FrameRunes[2]
	case 11, 12:
		if len(v.FrameRunes) < 7 {
			break
		}
		return v.FrameRunes[6]
	case 13:
		if len(v.FrameRunes) < 10 {
			break
		}
		return v.FrameRunes[9]
	case 14:
		if len(v.FrameRunes) < 9 {
			break
		}
		return v.FrameRunes[8]
	case 15:
		if len(v.FrameRunes) < 11 {
			break
		}
		return v.FrameRunes[10]
	default:
		return ' ' // cornerRune(0)
	}
	return cornerRune(index)
}

func corner(v *View, directions byte) rune {
	index := v.Overlaps | directions
	if len(v.FrameRunes) >= 6 {
		return cornerCustomRune(v, index)
	}
	return cornerRune(index)
}

// drawFrameCorners draws the corners of the view.
func (g *Gui) drawFrameCorners(v *View, fgColor, bgColor Attribute) error {
	if v.y0 == v.y1 {
		if !g.SupportOverlaps && v.x0 >= 0 && v.x1 >= 0 && v.y0 >= 0 && v.x0 < g.maxX && v.x1 < g.maxX && v.y0 < g.maxY {
			if err := g.SetRune(v.x0, v.y0, '╶', fgColor, bgColor); err != nil {
				return err
			}
			if err := g.SetRune(v.x1, v.y0, '╴', fgColor, bgColor); err != nil {
				return err
			}
		}
		return nil
	}

	runeTL, runeTR, runeBL, runeBR := '┌', '┐', '└', '┘'
	if len(v.FrameRunes) >= 6 {
		runeTL, runeTR, runeBL, runeBR = v.FrameRunes[2], v.FrameRunes[3], v.FrameRunes[4], v.FrameRunes[5]
	}
	if g.SupportOverlaps {
		runeTL = corner(v, BOTTOM|RIGHT)
		runeTR = corner(v, BOTTOM|LEFT)
		runeBL = corner(v, TOP|RIGHT)
		runeBR = corner(v, TOP|LEFT)
	}

	corners := []struct {
		x, y int
		ch   rune
	}{{v.x0, v.y0, runeTL}, {v.x1, v.y0, runeTR}, {v.x0, v.y1, runeBL}, {v.x1, v.y1, runeBR}}

	for _, c := range corners {
		if c.x >= 0 && c.y >= 0 && c.x < g.maxX && c.y < g.maxY {
			if err := g.SetRune(c.x, c.y, c.ch, fgColor, bgColor); err != nil {
				return err
			}
		}
	}
	return nil
}

// drawTitle draws the title of the view.
func (g *Gui) drawTitle(v *View, fgColor, bgColor Attribute) error {
	if v.y0 < 0 || v.y0 >= g.maxY {
		return nil
	}

	tabs := v.Tabs
	prefix := v.TitlePrefix
	if prefix != "" {
		if len(v.FrameRunes) > 0 {
			prefix += string(v.FrameRunes[0])
		} else {
			prefix += "─"
		}
	}
	separator := " - "
	charIndex := 0
	currentTabStart := -1
	currentTabEnd := -1
	if len(tabs) == 0 {
		tabs = []string{v.Title}
	} else {
		for i, tab := range tabs {
			if i == v.TabIndex {
				currentTabStart = charIndex
				currentTabEnd = charIndex + len(tab)
				break
			}
			charIndex += len(tab)
			if i < len(tabs)-1 {
				charIndex += len(separator)
			}
		}
	}

	str := strings.Join(tabs, separator)

	x := v.x0 + 2
	for _, ch := range prefix {
		if err := g.SetRune(x, v.y0, ch, fgColor, bgColor); err != nil {
			return err
		}
		x += uniseg.StringWidth(string(ch))
	}
	for i, ch := range str {
		if x < 0 {
			continue
		} else if x > v.x1-2 || x >= g.maxX {
			break
		}
		currentFgColor := fgColor
		currentBgColor := bgColor
		// if you are the current view and you have multiple tabs, de-highlight the non-selected tabs
		if v == g.currentView && len(v.Tabs) > 0 {
			currentFgColor = v.FgColor
			currentBgColor = v.BgColor
		}

		if i >= currentTabStart && i <= currentTabEnd && g.IsFocused() {
			currentFgColor = v.SelFgColor
			if v != g.currentView {
				currentFgColor &= ^AttrBold
			}
		}
		if err := g.SetRune(x, v.y0, ch, currentFgColor, currentBgColor); err != nil {
			return err
		}
		x += uniseg.StringWidth(string(ch))
	}
	return nil
}

// drawSubtitle draws the subtitle of the view.
func (g *Gui) drawSubtitle(v *View, fgColor, bgColor Attribute) error {
	if v.y0 < 0 || v.y0 >= g.maxY {
		return nil
	}

	start := v.x1 - 5 - uniseg.StringWidth(v.Subtitle)
	if start < v.x0 {
		return nil
	}
	x := start
	for _, ch := range v.Subtitle {
		if x >= v.x1 {
			break
		}
		if err := g.SetRune(x, v.y0, ch, fgColor, bgColor); err != nil {
			return err
		}
		x += uniseg.StringWidth(string(ch))
	}
	return nil
}

// drawListFooter draws the footer of a list view, showing something like '1 of 10'
func (g *Gui) drawListFooter(v *View, fgColor, bgColor Attribute) error {
	if len(v.buf.lines) == 0 {
		return nil
	}

	message := v.Footer

	if v.y1 < 0 || v.y1 >= g.maxY {
		return nil
	}

	start := v.x1 - 1 - uniseg.StringWidth(message)
	if start < v.x0 {
		return nil
	}
	x := start
	for _, ch := range message {
		if x >= v.x1 {
			break
		}
		if err := g.SetRune(x, v.y1, ch, fgColor, bgColor); err != nil {
			return err
		}
		x += uniseg.StringWidth(string(ch))
	}
	return nil
}

// flush updates the gui, re-drawing frames and buffers.
func (g *Gui) flush() error {
	// The screen must not be touched while suspended (see Suspend).
	if g.isSuspended() {
		return nil
	}

	// pretty sure we don't need this, but keeping it here in case we get weird visual artifacts
	// g.clear(g.FgColor, g.BgColor)

	maxX, maxY := Screen.Size()
	// if GUI's size has changed, we need to redraw all views
	if maxX != g.maxX || maxY != g.maxY {
		for _, v := range g.views {
			v.ClearViewLines()
		}
	}
	g.maxX, g.maxY = maxX, maxY

	for _, m := range g.managers {
		if err := m.Layout(g); err != nil {
			return err
		}
	}
	for _, v := range g.views {
		if err := g.draw(v); err != nil {
			return err
		}
	}

	Screen.Show()
	return nil
}

// Redraws only tainted views and skips the layout pass.
// tcell's cell-level dirty tracking ensures only
// actually-changed cells are emitted to the terminal.
// Will also redraw any views that overlap tainted views
func (g *Gui) flushContentOnly(views []*View) error {
	// The screen must not be touched while suspended (see Suspend).
	if g.isSuspended() {
		return nil
	}

	for _, v := range viewsToRedrawContentOnly(views) {
		if err := g.draw(v); err != nil {
			return err
		}
	}

	Screen.Show()
	return nil
}

func viewsToRedrawContentOnly(views []*View) []*View {
	redrawIndexes := set.New[int]()

	for i, v := range views {
		if !v.IsTainted() && !redrawIndexes.Includes(i) {
			continue
		}

		redrawIndexes.Add(i)

		for j, above := range views[i+1:] {
			aboveIndex := i + 1 + j
			if !redrawIndexes.Includes(aboveIndex) && rectsOverlap(v, above) {
				redrawIndexes.Add(aboveIndex)
			}
		}
	}

	return lo.FilterMap(views, func(view *View, i int) (*View, bool) {
		return view, redrawIndexes.Includes(i)
	})
}

// Reports whether two views' rectangles share at least one cell.
func rectsOverlap(a, b *View) bool {
	ax0, ay0, ax1, ay1 := a.Dimensions()
	bx0, by0, bx1, by1 := b.Dimensions()
	return ax0 <= bx1 && ax1 >= bx0 && ay0 <= by1 && ay1 >= by0
}

func (g *Gui) ForceLayoutAndRedraw() error {
	return g.flush()
}

// Redraws only tainted views outside of the normal main
// loop, without a layout pass. Useful during longer operations that block the
// main thread, e.g. to update a spinner in a status view.
func (g *Gui) ForceFlushViewsContentOnly(views []*View) error {
	return g.flushContentOnly(views)
}

// draw manages the cursor and calls the draw function of a view.
func (g *Gui) draw(v *View) error {
	if !v.Visible || v.y1 < v.y0 || v.x1 < v.x0 {
		return nil
	}

	if g.Cursor {
		if curview := g.currentView; curview != nil {
			vMaxX, vMaxY := curview.InnerSize()
			if curview.cx >= 0 && curview.cx < vMaxX && curview.cy >= 0 && curview.cy < vMaxY {
				cx, cy := curview.x0+curview.cx+1, curview.y0+curview.cy+1
				Screen.ShowCursor(cx, cy)
			} else {
				Screen.HideCursor()
			}
		}
	} else {
		Screen.HideCursor()
	}

	v.draw(g.IsFocused())

	if v.Frame {
		var fgColor, bgColor, frameColor Attribute
		if g.Highlight && v == g.currentView && g.IsFocused() {
			fgColor = g.SelFgColor
			bgColor = g.SelBgColor
			frameColor = g.SelFrameColor
		} else {
			bgColor = g.BgColor
			if v.TitleColor != ColorDefault {
				fgColor = v.TitleColor
			} else {
				fgColor = g.FgColor
			}
			if v.FrameColor != ColorDefault {
				frameColor = v.FrameColor
			} else {
				frameColor = g.FrameColor
			}
		}

		if err := g.drawFrameEdges(v, frameColor, bgColor); err != nil {
			return err
		}
		if err := g.drawFrameCorners(v, frameColor, bgColor); err != nil {
			return err
		}
		if v.Title != "" || len(v.Tabs) > 0 {
			if err := g.drawTitle(v, fgColor, bgColor); err != nil {
				return err
			}
		}
		if v.Subtitle != "" {
			if err := g.drawSubtitle(v, fgColor, bgColor); err != nil {
				return err
			}
		}
		if v.Footer != "" && g.ShowListFooter {
			if err := g.drawListFooter(v, fgColor, bgColor); err != nil {
				return err
			}
		}
	}

	return nil
}

// onKey manages key-press events. A keybinding handler is called when
// a key-press or mouse event satisfies a configured keybinding. Furthermore,
// currentView's internal buffer is modified if currentView.Editable is true.
func (g *Gui) onKey(ev *GocuiEvent) error {
	switch ev.Type {
	case eventKey:

		// newlines. I actually don't quite understand why, because from reading
		// When pasting text in Ghostty, it sends us '\r' (which is delivered as
		// ctrl-j by tcell) instead of '\n' for newlines. I actually don't quite
		// understand why, because from reading Ghostty's source code (e.g.
		// https://github.com/ghostty-org/ghostty/commit/010338354a0) it does
		// this conversion only for non-bracketed paste mode, but I'm seeing it
		// in bracketed paste mode. Whatever I'm missing here, converting '\r'
		// back to '\n' fixes pasting multi-line text from Ghostty, and doesn't
		// seem harmful for other terminal emulators.
		if g.IsPasting && ev.Key.Equals(NewKeyStrMod("j", ModCtrl)) {
			ev.Key = NewKeyName(KeyEnter)
		}

		err := g.execKeybindings(g.currentView, ev)
		if err != nil {
			return err
		}

	case eventMouse:
		mx, my := ev.MouseX, ev.MouseY
		if g.mouseGestureCanceled {
			if ev.Key.KeyName() == MouseRelease {
				g.mouseGestureCanceled = false
			}
			return nil
		}
		// While the mouse is captured, all mouse events go to the view that
		// was under the pointer when the button was pressed, even if the
		// pointer has since left it; this is what lets drag gestures keep
		// acting on the view they started in.
		v := g.mouseCapture
		if v == nil {
			var err error
			v, err = g.VisibleViewByPosition(mx, my)
			if err != nil {
				break
			}
		}
		if ev.Key.KeyName() == MouseRelease {
			g.releaseMouseCapture()
		}

		// newCx and newCy are relative to the view port, i.e. to the visible area of the view
		newCx := mx - v.x0 - 1
		newCy := my - v.y0 - 1
		// newX and newY are relative to the view's content, independent of its scroll position
		newX := newCx + v.ox
		newY := newCy + v.oy
		// if view is editable don't go further than the furthest character for that line
		if v.Editable {
			if newY < 0 {
				newY = 0
				newCy = -v.oy
			} else if newY >= len(v.buf.lines) {
				newY = len(v.buf.lines) - 1
				newCy = newY - v.oy
			}

			visibleLineWidth := 0
			for _, c := range v.buf.lines[newY].cells {
				visibleLineWidth += c.width
			}
			if visibleLineWidth < newX {
				newX = visibleLineWidth
				newCx = visibleLineWidth - v.ox
			}
		}

		if ev.Key.KeyName() == MouseLeft && (ev.Key.Mod()&ModMotion) == 0 && !v.Editable && g.openHyperlink != nil {
			if link := v.hyperlinkAt(newX, newY); link != "" {
				return g.openHyperlink(link, v.name)
			}
		}

		if g.ShouldHandleMouseEvent != nil {
			if !g.ShouldHandleMouseEvent(v, ev.Key.KeyName()) {
				// Give clients a chance to reject clicks, for example clicks in inactive views
				// when a modal panel is open.
				break
			}
		}
		if ev.Key.KeyName() == MouseLeft && ev.Key.Mod()&ModMotion == 0 {
			g.captureMouse(v)
		}

		if !IsMouseScrollKey(ev.Key.KeyName()) && ev.Key.KeyName() != MouseRelease {
			cursorX, cursorY := newCx, newCy
			// A captured drag can report positions outside the view; keep the
			// view cursor inside its bounds in that case. Handlers still get
			// the unclamped position through the binding opts.
			if g.mouseCapture != nil {
				cursorX = max(0, min(cursorX, v.InnerWidth()-1))
				cursorY = max(0, min(cursorY, v.InnerHeight()-1))
			}
			v.SetCursor(cursorX, cursorY)
			if v.Editable {
				v.TextArea.SetCursor2D(newX, newY)

				// SetCursor2D might have adjusted the text area's cursor to the
				// left to move left from a soft line break, so we need to
				// update the view's cursor to match the text area's cursor.
				cX, _ := v.TextArea.GetCursorXY()
				v.SetCursorX(cX)
			}
		}

		// Only an actual click may activate tabs; a captured drag that
		// crosses the tab row must not switch tabs.
		if ev.Key.KeyName() == MouseLeft && ev.Key.Mod()&ModMotion == 0 && v.Frame && my == v.y0 {
			if len(v.Tabs) > 0 {
				tabIndex := v.GetClickedTabIndex(mx - v.x0)

				if tabIndex >= 0 {
					for _, binding := range g.tabClickBindings {
						if binding.viewName == v.Name() {
							return binding.handler(tabIndex)
						}
					}
				}
			}
		}

		if IsMouseKey(ev.Key) {
			isDoubleClick := g.recordClickInfo(newX, newY, ev.Key.KeyName(), v)
			opts := ViewMouseBindingOpts{X: newX, Y: newY, Key: ev.Key.KeyName(), IsDoubleClick: isDoubleClick}
			matched, err := g.execMouseKeybindings(v, ev, opts)
			if err != nil {
				return err
			}
			if matched {
				return nil
			}
		}

		if err := g.execKeybindings(v, ev); err != nil {
			return err
		}

	case eventMouseMove:
		mx, my := ev.MouseX, ev.MouseY
		v, err := g.VisibleViewByPosition(mx, my)
		if err != nil {
			break
		}
		if g.lastHoverView != nil && g.lastHoverView != v {
			g.lastHoverView.lastHoverPosition = nil
			g.lastHoverView.hoveredHyperlink = nil
		}
		g.lastHoverView = v
		v.onMouseMove(mx, my)

	default:
	}

	return nil
}

// remember the information for this click, and return true if it was a double click
func (g *Gui) recordClickInfo(x, y int, key KeyName, v *View) bool {
	if IsMouseScrollKey(key) {
		g.lastClick = nil
		return false
	}
	// A release ends a gesture but is not a click of its own; it must leave
	// the click info of the press that started it alone, or no double click
	// could ever be detected.
	if key == MouseRelease {
		return false
	}

	clickInfo := &clickInfo{
		x:        x,
		y:        y,
		key:      key,
		viewName: v.Name(),
		time:     time.Now(),
	}

	isDoubleClick := g.lastClick != nil &&
		clickInfo.x == g.lastClick.x &&
		clickInfo.y == g.lastClick.y &&
		clickInfo.key == g.lastClick.key &&
		clickInfo.viewName == g.lastClick.viewName &&
		clickInfo.time.Before(g.lastClick.time.Add(DOUBLE_CLICK_THRESHOLD))

	g.lastClick = clickInfo
	return isDoubleClick
}

func (g *Gui) execMouseKeybindings(view *View, ev *GocuiEvent, opts ViewMouseBindingOpts) (bool, error) {
	isMatch := func(binding *ViewMouseBinding) bool {
		return binding.ViewName == view.Name() &&
			ev.Key.KeyName() == binding.Key &&
			ev.Key.Mod() == binding.Modifier
	}

	// first pass looks for ones that match the focused view
	for _, binding := range g.viewMouseBindings {
		if isMatch(binding) && binding.FocusedView != "" && binding.FocusedView == g.currentView.Name() {
			if err := binding.Handler(opts); !errors.Is(err, ErrKeybindingNotHandled) {
				return true, err
			}
		}
	}

	for _, binding := range g.viewMouseBindings {
		if isMatch(binding) && binding.FocusedView == "" {
			return true, binding.Handler(opts)
		}
	}

	return false, nil
}

func IsMouseKey(key Key) bool {
	switch key.KeyName() {
	case
		MouseLeft,
		MouseRight,
		MouseMiddle,
		MouseRelease,
		MouseWheelUp,
		MouseWheelDown,
		MouseWheelLeft,
		MouseWheelRight:
		return true
	default:
		return false
	}
}

func IsMouseScrollKey(keyName KeyName) bool {
	switch keyName {
	case
		MouseWheelUp,
		MouseWheelDown,
		MouseWheelLeft,
		MouseWheelRight:
		return true
	default:
		return false
	}
}

// execKeybindings executes the keybinding handlers that match the passed view
// and event.
func (g *Gui) execKeybindings(v *View, ev *GocuiEvent) error {
	var globalKb *keybinding
	var matchingParentViewKb *keybinding

	if g.IsPasting && v != nil && !v.Editable {
		return nil
	}

	// if we're searching, and we've hit n/N/Esc, we ignore the default keybinding
	if v != nil && v.IsSearching() {
		if lo.SomeBy(g.NextSearchMatchKeys, func(k Key) bool { return ev.Key.Equals(k) }) {
			return v.gotoNextMatch()
		} else if lo.SomeBy(g.PrevSearchMatchKeys, func(k Key) bool { return ev.Key.Equals(k) }) {
			return v.gotoPreviousMatch()
		} else if lo.SomeBy(g.SearchEscapeKeys, func(k Key) bool { return ev.Key.Equals(k) }) {
			v.searcher.clearSearch()
			if g.OnSearchEscape != nil {
				if err := g.OnSearchEscape(); err != nil {
					return err
				}
			}
			return nil
		}
	}

	var err error

	for _, kb := range g.keybindings {
		if kb.handler == nil {
			continue
		}
		if !kb.matchKeypress(ev.Key) {
			continue
		}
		if g.matchView(v, kb) {
			err = g.execKeybinding(v, kb)
			if !errors.Is(err, ErrKeybindingNotHandled) {
				return err
			}

			matchingParentViewKb = nil
			break
		}
		if v != nil && g.matchView(v.ParentView, kb) {
			matchingParentViewKb = kb
		}
		if globalKb == nil && kb.viewName == "" {
			globalKb = kb
		}
	}
	if matchingParentViewKb != nil {
		err = g.execKeybinding(v.ParentView, matchingParentViewKb)
		if !errors.Is(err, ErrKeybindingNotHandled) {
			return err
		}
	}

	if g.currentView != nil && g.currentView.Editable && g.currentView.Editor != nil {
		matched := g.currentView.Editor.Edit(g.currentView, ev.Key)
		if matched {
			return nil
		}
	}

	if globalKb != nil {
		err = g.execKeybinding(v, globalKb)
	}
	return err
}

// execKeybinding executes a given keybinding
func (g *Gui) execKeybinding(v *View, kb *keybinding) error {
	if err := kb.handler(g, v); err != nil {
		return err
	}
	return nil
}

// IsFocused reports whether the terminal we're running in has focus. Terminals
// that don't report focus at all leave this true for good.
func (g *Gui) IsFocused() bool {
	return g.focused.Load()
}

func (g *Gui) onFocus(ev *GocuiEvent) error {
	// Terminals report their focus state when we turn focus reporting on, and
	// some report it again when their window is activated, so only pass on the
	// reports that actually change it.
	if ev.Focused == g.focused.Load() {
		return nil
	}
	g.focused.Store(ev.Focused)

	if g.focusHandler != nil {
		return g.focusHandler(ev.Focused)
	}

	return nil
}

// While g.suspended is true, nothing must be drawn to the screen: tcell
// releases the screen's cell buffer when disengaging, and drawing to a
// disengaged screen spins forever inside tcell while holding the screen lock,
// which then blocks Resume (and with it all further input) forever. For the
// flag to guarantee that, it must only ever be false while the screen is
// engaged: Suspend sets it before disengaging, and Resume clears it only
// after re-engaging.

func (g *Gui) Suspend() error {
	g.suspendedMutex.Lock()
	defer g.suspendedMutex.Unlock()

	if g.suspended {
		return errors.New("Already suspended")
	}

	g.suspended = true

	if err := g.screen.Suspend(); err != nil {
		g.suspended = false
		return err
	}

	return nil
}

func (g *Gui) Resume() error {
	g.suspendedMutex.Lock()
	defer g.suspendedMutex.Unlock()

	if !g.suspended {
		return errors.New("Cannot resume because we are not suspended")
	}

	if err := g.screen.Resume(); err != nil {
		return err
	}

	g.suspended = false

	// Schedule a redraw of the whole screen. Nothing else guarantees one:
	// flushes are skipped while suspended, and after re-engaging the screen
	// the terminal shows nothing until we draw again.
	go func() { g.gEvents <- GocuiEvent{Type: eventResize} }()

	return nil
}

func (g *Gui) isSuspended() bool {
	g.suspendedMutex.Lock()
	defer g.suspendedMutex.Unlock()

	return g.suspended
}

// matchView returns if the keybinding matches the current view (and the view's context)
func (g *Gui) matchView(v *View, kb *keybinding) bool {
	// if the user is typing in a field, ignore char keys
	if v == nil {
		return false
	}
	if v.Editable && kb.key.Str() != "" && kb.key.Mod() == 0 {
		return false
	}
	if kb.viewName != v.name {
		return false
	}
	return true
}

// returns a string representation of the current state of the gui, character-for-character
func (g *Gui) Snapshot() string {
	if g.screen == nil {
		return "<no screen rendered>"
	}

	width, height := g.screen.Size()

	builder := &strings.Builder{}

	for y := range height {
		for x := 0; x < width; x++ {
			char, _, charWidth := g.screen.Get(x, y)
			if charWidth == 0 {
				continue
			}
			builder.WriteString(char)
			if charWidth > 1 {
				x += charWidth - 1
			}
		}
		builder.WriteRune('\n')
	}

	return builder.String()
}

func (g *Gui) SetEditKeybindings(moveWordLeft, moveWordRight, backspaceWord, forwardDeleteWord []Key) {
	moveWordLeftKeybinding = moveWordLeft
	moveWordRightKeybinding = moveWordRight
	backspaceWordKeybinding = backspaceWord
	forwardDeleteWordKeybinding = forwardDeleteWord
}