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tea.go
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// Package tea provides a framework for building rich terminal user interfaces
// based on the paradigms of The Elm Architecture. It's well-suited for simple
// and complex terminal applications, either inline, full-window, or a mix of
// both. It's been battle-tested in several large projects and is
// production-ready.
//
// A tutorial is available at https://github.com/charmbracelet/bubbletea/tree/master/tutorials
//
// Example programs can be found at https://github.com/charmbracelet/bubbletea/tree/master/examples
package tea
import (
"context"
"fmt"
"io"
"os"
"os/signal"
"runtime/debug"
"sync"
"syscall"
"time"
"github.com/containerd/console"
isatty "github.com/mattn/go-isatty"
"github.com/muesli/cancelreader"
te "github.com/muesli/termenv"
"golang.org/x/term"
)
// Msg contain data from the result of a IO operation. Msgs trigger the update
// function and, henceforth, the UI.
type Msg interface{}
// Model contains the program's state as well as its core functions.
type Model interface {
// Init is the first function that will be called. It returns an optional
// initial command. To not perform an initial command return nil.
Init() Cmd
// Update is called when a message is received. Use it to inspect messages
// and, in response, update the model and/or send a command.
Update(Msg) (Model, Cmd)
// View renders the program's UI, which is just a string. The view is
// rendered after every Update.
View() string
}
// Cmd is an IO operation that returns a message when it's complete. If it's
// nil it's considered a no-op. Use it for things like HTTP requests, timers,
// saving and loading from disk, and so on.
//
// Note that there's almost never a reason to use a command to send a message
// to another part of your program. That can almost always be done in the
// update function.
type Cmd func() Msg
// Options to customize the program during its initialization. These are
// generally set with ProgramOptions.
//
// The options here are treated as bits.
type startupOptions byte
func (s startupOptions) has(option startupOptions) bool {
return s&option != 0
}
const (
withAltScreen startupOptions = 1 << iota
withMouseCellMotion
withMouseAllMotion
withInputTTY
withCustomInput
withANSICompressor
)
// Program is a terminal user interface.
type Program struct {
initialModel Model
// Configuration options that will set as the program is initializing,
// treated as bits. These options can be set via various ProgramOptions.
startupOptions startupOptions
ctx context.Context
mtx *sync.Mutex
msgs chan Msg
errs chan error
readLoopDone chan struct{}
output io.Writer // where to send output. this will usually be os.Stdout.
input io.Reader // this will usually be os.Stdin.
cancelReader cancelreader.CancelReader
renderer renderer
altScreenActive bool
altScreenWasActive bool // was the altscreen active before releasing the terminal?
// CatchPanics is incredibly useful for restoring the terminal to a usable
// state after a panic occurs. When this is set, Bubble Tea will recover
// from panics, print the stack trace, and disable raw mode. This feature
// is on by default.
CatchPanics bool
ignoreSignals bool
killc chan bool
console console.Console
// Stores the original reference to stdin for cases where input is not a
// TTY on windows and we've automatically opened CONIN$ to receive input.
// When the program exits this will be restored.
//
// Lint ignore note: the linter will find false positive on unix systems
// as this value only comes into play on Windows, hence the ignore comment
// below.
windowsStdin *os.File //nolint:golint,structcheck,unused
}
// Batch performs a bunch of commands concurrently with no ordering guarantees
// about the results. Use a Batch to return several commands.
//
// Example:
//
// func (m model) Init() Cmd {
// return tea.Batch(someCommand, someOtherCommand)
// }
//
func Batch(cmds ...Cmd) Cmd {
var validCmds []Cmd
for _, c := range cmds {
if c == nil {
continue
}
validCmds = append(validCmds, c)
}
if len(validCmds) == 0 {
return nil
}
return func() Msg {
return batchMsg(validCmds)
}
}
// batchMsg is the internal message used to perform a bunch of commands. You
// can send a batchMsg with Batch.
type batchMsg []Cmd
// Quit is a special command that tells the Bubble Tea program to exit.
func Quit() Msg {
return quitMsg{}
}
// quitMsg in an internal message signals that the program should quit. You can
// send a quitMsg with Quit.
type quitMsg struct{}
// EnterAltScreen is a special command that tells the Bubble Tea program to
// enter the alternate screen buffer.
//
// Because commands run asynchronously, this command should not be used in your
// model's Init function. To initialize your program with the altscreen enabled
// use the WithAltScreen ProgramOption instead.
func EnterAltScreen() Msg {
return enterAltScreenMsg{}
}
// enterAltScreenMsg in an internal message signals that the program should
// enter alternate screen buffer. You can send a enterAltScreenMsg with
// EnterAltScreen.
type enterAltScreenMsg struct{}
// ExitAltScreen is a special command that tells the Bubble Tea program to exit
// the alternate screen buffer. This command should be used to exit the
// alternate screen buffer while the program is running.
//
// Note that the alternate screen buffer will be automatically exited when the
// program quits.
func ExitAltScreen() Msg {
return exitAltScreenMsg{}
}
// exitAltScreenMsg in an internal message signals that the program should exit
// alternate screen buffer. You can send a exitAltScreenMsg with ExitAltScreen.
type exitAltScreenMsg struct{}
// EnableMouseCellMotion is a special command that enables mouse click,
// release, and wheel events. Mouse movement events are also captured if
// a mouse button is pressed (i.e., drag events).
//
// Because commands run asynchronously, this command should not be used in your
// model's Init function. Use the WithMouseCellMotion ProgramOption instead.
func EnableMouseCellMotion() Msg {
return enableMouseCellMotionMsg{}
}
// enableMouseCellMotionMsg is a special command that signals to start
// listening for "cell motion" type mouse events (ESC[?1002l). To send an
// enableMouseCellMotionMsg, use the EnableMouseCellMotion command.
type enableMouseCellMotionMsg struct{}
// EnableMouseAllMotion is a special command that enables mouse click, release,
// wheel, and motion events, which are delivered regardless of whether a mouse
// button is pressed, effectively enabling support for hover interactions.
//
// Many modern terminals support this, but not all. If in doubt, use
// EnableMouseCellMotion instead.
//
// Because commands run asynchronously, this command should not be used in your
// model's Init function. Use the WithMouseAllMotion ProgramOption instead.
func EnableMouseAllMotion() Msg {
return enableMouseAllMotionMsg{}
}
// enableMouseAllMotionMsg is a special command that signals to start listening
// for "all motion" type mouse events (ESC[?1003l). To send an
// enableMouseAllMotionMsg, use the EnableMouseAllMotion command.
type enableMouseAllMotionMsg struct{}
// DisableMouse is a special command that stops listening for mouse events.
func DisableMouse() Msg {
return disableMouseMsg{}
}
// disableMouseMsg is an internal message that that signals to stop listening
// for mouse events. To send a disableMouseMsg, use the DisableMouse command.
type disableMouseMsg struct{}
// WindowSizeMsg is used to report the terminal size. It's sent to Update once
// initially and then on every terminal resize. Note that Windows does not
// have support for reporting when resizes occur as it does not support the
// SIGWINCH signal.
type WindowSizeMsg struct {
Width int
Height int
}
// HideCursor is a special command for manually instructing Bubble Tea to hide
// the cursor. In some rare cases, certain operations will cause the terminal
// to show the cursor, which is normally hidden for the duration of a Bubble
// Tea program's lifetime. You will most likely not need to use this command.
func HideCursor() Msg {
return hideCursorMsg{}
}
// hideCursorMsg is an internal command used to hide the cursor. You can send
// this message with HideCursor.
type hideCursorMsg struct{}
// NewProgram creates a new Program.
func NewProgram(model Model, opts ...ProgramOption) *Program {
p := &Program{
mtx: &sync.Mutex{},
initialModel: model,
output: os.Stdout,
input: os.Stdin,
msgs: make(chan Msg),
CatchPanics: true,
killc: make(chan bool, 1),
}
// Apply all options to the program.
for _, opt := range opts {
opt(p)
}
return p
}
// StartReturningModel initializes the program. Returns the final model.
func (p *Program) StartReturningModel() (Model, error) {
cmds := make(chan Cmd)
p.errs = make(chan error)
// Channels for managing goroutine lifecycles.
var (
sigintLoopDone = make(chan struct{})
cmdLoopDone = make(chan struct{})
resizeLoopDone = make(chan struct{})
initSignalDone = make(chan struct{})
waitForGoroutines = func(withReadLoop bool) {
if withReadLoop {
select {
case <-p.readLoopDone:
case <-time.After(500 * time.Millisecond):
// The read loop hangs, which means the input
// cancelReader's cancel function has returned true even
// though it was not able to cancel the read.
}
}
<-cmdLoopDone
<-resizeLoopDone
<-sigintLoopDone
<-initSignalDone
}
)
var cancelContext context.CancelFunc
p.ctx, cancelContext = context.WithCancel(context.Background())
defer cancelContext()
switch {
case p.startupOptions.has(withInputTTY):
// Open a new TTY, by request
f, err := openInputTTY()
if err != nil {
return p.initialModel, err
}
defer f.Close() // nolint:errcheck
p.input = f
case !p.startupOptions.has(withCustomInput):
// If the user hasn't set a custom input, and input's not a terminal,
// open a TTY so we can capture input as normal. This will allow things
// to "just work" in cases where data was piped or redirected into this
// application.
f, isFile := p.input.(*os.File)
if !isFile {
break
}
if isatty.IsTerminal(f.Fd()) {
break
}
f, err := openInputTTY()
if err != nil {
return p.initialModel, err
}
defer f.Close() // nolint:errcheck
p.input = f
}
// Listen for SIGINT. Note that in most cases ^C will not send an
// interrupt because the terminal will be in raw mode and thus capture
// that keystroke and send it along to Program.Update. If input is not a
// TTY, however, ^C will be caught here.
go func() {
sig := make(chan os.Signal, 1)
signal.Notify(sig, syscall.SIGINT)
defer func() {
signal.Stop(sig)
close(sigintLoopDone)
}()
for {
select {
case <-p.ctx.Done():
return
case <-sig:
if !p.ignoreSignals {
p.msgs <- quitMsg{}
return
}
}
}
}()
if p.CatchPanics {
defer func() {
if r := recover(); r != nil {
p.shutdown(true)
fmt.Printf("Caught panic:\n\n%s\n\nRestoring terminal...\n\n", r)
debug.PrintStack()
return
}
}()
}
// Check if output is a TTY before entering raw mode, hiding the cursor and
// so on.
if err := p.initTerminal(); err != nil {
return p.initialModel, err
}
// If no renderer is set use the standard one.
if p.renderer == nil {
p.renderer = newRenderer(p.output, p.mtx, p.startupOptions.has(withANSICompressor))
}
// Honor program startup options.
if p.startupOptions&withAltScreen != 0 {
p.EnterAltScreen()
}
if p.startupOptions&withMouseCellMotion != 0 {
p.EnableMouseCellMotion()
} else if p.startupOptions&withMouseAllMotion != 0 {
p.EnableMouseAllMotion()
}
// Initialize the program.
model := p.initialModel
if initCmd := model.Init(); initCmd != nil {
go func() {
defer close(initSignalDone)
select {
case cmds <- initCmd:
case <-p.ctx.Done():
}
}()
} else {
close(initSignalDone)
}
// Start the renderer.
p.renderer.start()
p.renderer.setAltScreen(p.altScreenActive)
// Render the initial view.
p.renderer.write(model.View())
// Subscribe to user input.
if p.input != nil {
if err := p.initCancelReader(); err != nil {
return model, err
}
} else {
defer close(p.readLoopDone)
}
defer p.cancelReader.Close() // nolint:errcheck
if f, ok := p.output.(*os.File); ok && isatty.IsTerminal(f.Fd()) {
// Get the initial terminal size and send it to the program.
go func() {
w, h, err := term.GetSize(int(f.Fd()))
if err != nil {
p.errs <- err
}
select {
case <-p.ctx.Done():
case p.msgs <- WindowSizeMsg{w, h}:
}
}()
// Listen for window resizes.
go listenForResize(p.ctx, f, p.msgs, p.errs, resizeLoopDone)
} else {
close(resizeLoopDone)
}
// Process commands.
go func() {
defer close(cmdLoopDone)
for {
select {
case <-p.ctx.Done():
return
case cmd := <-cmds:
if cmd == nil {
continue
}
// Don't wait on these goroutines, otherwise the shutdown
// latency would get too large as a Cmd can run for some time
// (e.g. tick commands that sleep for half a second). It's not
// possible to cancel them so we'll have to leak the goroutine
// until Cmd returns.
go func() {
select {
case p.msgs <- cmd():
case <-p.ctx.Done():
}
}()
}
}
}()
// Handle updates and draw.
for {
select {
case <-p.killc:
return nil, nil
case err := <-p.errs:
cancelContext()
waitForGoroutines(p.cancelReader.Cancel())
p.shutdown(false)
return model, err
case msg := <-p.msgs:
// Handle special internal messages.
switch msg := msg.(type) {
case quitMsg:
cancelContext()
waitForGoroutines(p.cancelReader.Cancel())
p.shutdown(false)
return model, nil
case batchMsg:
for _, cmd := range msg {
cmds <- cmd
}
continue
case WindowSizeMsg:
p.mtx.Lock()
p.renderer.repaint()
p.mtx.Unlock()
case enterAltScreenMsg:
p.EnterAltScreen()
case exitAltScreenMsg:
p.ExitAltScreen()
case enableMouseCellMotionMsg:
p.EnableMouseCellMotion()
case enableMouseAllMotionMsg:
p.EnableMouseAllMotion()
case disableMouseMsg:
p.DisableMouseCellMotion()
p.DisableMouseAllMotion()
case hideCursorMsg:
hideCursor(p.output)
case execMsg:
// NB: this blocks.
p.exec(msg.cmd, msg.fn)
}
// Process internal messages for the renderer.
if r, ok := p.renderer.(*standardRenderer); ok {
r.handleMessages(msg)
}
var cmd Cmd
model, cmd = model.Update(msg) // run update
cmds <- cmd // process command (if any)
p.renderer.write(model.View()) // send view to renderer
}
}
}
// Start initializes the program. Ignores the final model.
func (p *Program) Start() error {
_, err := p.StartReturningModel()
return err
}
// Send sends a message to the main update function, effectively allowing
// messages to be injected from outside the program for interoperability
// purposes.
//
// If the program is not running this this will be a no-op, so it's safe to
// send messages if the program is unstarted, or has exited.
func (p *Program) Send(msg Msg) {
p.msgs <- msg
}
// Quit is a convenience function for quitting Bubble Tea programs. Use it
// when you need to shut down a Bubble Tea program from the outside.
//
// If you wish to quit from within a Bubble Tea program use the Quit command.
//
// If the program is not running this will be a no-op, so it's safe to call
// if the program is unstarted or has already exited.
func (p *Program) Quit() {
p.Send(Quit())
}
// Kill stops the program immediately and restores the former terminal state.
// The final render that you would normally see when quitting will be skipped.
func (p *Program) Kill() {
p.killc <- true
p.shutdown(true)
}
// shutdown performs operations to free up resources and restore the terminal
// to its original state.
func (p *Program) shutdown(kill bool) {
if p.renderer != nil {
if kill {
p.renderer.kill()
} else {
p.renderer.stop()
}
}
p.ExitAltScreen()
p.DisableMouseCellMotion()
p.DisableMouseAllMotion()
_ = p.restoreTerminalState()
}
// EnterAltScreen enters the alternate screen buffer, which consumes the entire
// terminal window. ExitAltScreen will return the terminal to its former state.
//
// Deprecated: Use the WithAltScreen ProgramOption instead.
func (p *Program) EnterAltScreen() {
p.mtx.Lock()
defer p.mtx.Unlock()
if p.altScreenActive {
return
}
enterAltScreen(p.output)
p.altScreenActive = true
if p.renderer != nil {
p.renderer.setAltScreen(p.altScreenActive)
}
}
// ExitAltScreen exits the alternate screen buffer.
//
// Deprecated: The altscreen will exited automatically when the program exits.
func (p *Program) ExitAltScreen() {
p.mtx.Lock()
defer p.mtx.Unlock()
if !p.altScreenActive {
return
}
exitAltScreen(p.output)
p.altScreenActive = false
if p.renderer != nil {
p.renderer.setAltScreen(p.altScreenActive)
}
}
// EnableMouseCellMotion enables mouse click, release, wheel and motion events
// if a mouse button is pressed (i.e., drag events).
//
// Deprecated: Use the WithMouseCellMotion ProgramOption instead.
func (p *Program) EnableMouseCellMotion() {
p.mtx.Lock()
defer p.mtx.Unlock()
fmt.Fprintf(p.output, te.CSI+te.EnableMouseCellMotionSeq)
}
// DisableMouseCellMotion disables Mouse Cell Motion tracking. This will be
// called automatically when exiting a Bubble Tea program.
//
// Deprecated: The mouse will automatically be disabled when the program exits.
func (p *Program) DisableMouseCellMotion() {
p.mtx.Lock()
defer p.mtx.Unlock()
fmt.Fprintf(p.output, te.CSI+te.DisableMouseCellMotionSeq)
}
// EnableMouseAllMotion enables mouse click, release, wheel and motion events,
// regardless of whether a mouse button is pressed. Many modern terminals
// support this, but not all.
//
// Deprecated: Use the WithMouseAllMotion ProgramOption instead.
func (p *Program) EnableMouseAllMotion() {
p.mtx.Lock()
defer p.mtx.Unlock()
fmt.Fprintf(p.output, te.CSI+te.EnableMouseAllMotionSeq)
}
// DisableMouseAllMotion disables All Motion mouse tracking. This will be
// called automatically when exiting a Bubble Tea program.
//
// Deprecated: The mouse will automatically be disabled when the program exits.
func (p *Program) DisableMouseAllMotion() {
p.mtx.Lock()
defer p.mtx.Unlock()
fmt.Fprintf(p.output, te.CSI+te.DisableMouseAllMotionSeq)
}
// ReleaseTerminal restores the original terminal state and cancels the input
// reader. You can return control to the Program with RestoreTerminal.
func (p *Program) ReleaseTerminal() error {
p.ignoreSignals = true
p.cancelInput()
p.altScreenWasActive = p.altScreenActive
if p.altScreenActive {
p.ExitAltScreen()
time.Sleep(time.Millisecond * 10) // give the terminal a moment to catch up
}
return p.restoreTerminalState()
}
// RestoreTerminal reinitializes the Program's input reader, restores the
// terminal to the former state when the program was running, and repaints.
// Use it to reinitialize a Program after running ReleaseTerminal.
func (p *Program) RestoreTerminal() error {
p.ignoreSignals = false
if err := p.initTerminal(); err != nil {
return err
}
if err := p.initCancelReader(); err != nil {
return err
}
if p.altScreenWasActive {
p.EnterAltScreen()
}
go p.Send(repaintMsg{})
return nil
}
// Println prints above the Program. This output is unmanaged by the program
// and will persist across renders by the Program.
//
// If the altscreen is active no output will be printed.
func (p *Program) Println(args ...interface{}) {
p.msgs <- printLineMessage{
messageBody: fmt.Sprint(args...),
}
}
// Printf prints above the Program. It takes a format template followed by
// values similar to fmt.Printf. This output is unmanaged by the program and
// will persist across renders by the Program.
//
// Unlike fmt.Printf (but similar to log.Printf) the message will be print on
// its own line.
//
// If the altscreen is active no output will be printed.
func (p *Program) Printf(template string, args ...interface{}) {
p.msgs <- printLineMessage{
messageBody: fmt.Sprintf(template, args...),
}
}