term.go

// +build !windows

// Package term provides provides structures and helper functions to work with
// terminal (state, sizes).
package term

import (
	"errors"
	"io"
	"os"
	"os/signal"
	"syscall"
	"unsafe"
)

var (
	// ErrInvalidState is returned if the state of the terminal is invalid.
	ErrInvalidState = errors.New("Invalid terminal state")
)

// State represents the state of the terminal.
type State struct {
	termios Termios
}

// Winsize represents the size of the terminal window.
type Winsize struct {
	Height uint16
	Width  uint16
	x      uint16
	y      uint16
}

// StdStreams returns the standard streams (stdin, stdout, stedrr).
func StdStreams() (stdIn io.ReadCloser, stdOut, stdErr io.Writer) {
	return os.Stdin, os.Stdout, os.Stderr
}

// GetFdInfo returns the file descriptor for an os.File and indicates whether the file represents a terminal.
func GetFdInfo(in interface{}) (uintptr, bool) {
	var inFd uintptr
	var isTerminalIn bool
	if file, ok := in.(*os.File); ok {
		inFd = file.Fd()
		isTerminalIn = IsTerminal(inFd)
	}
	return inFd, isTerminalIn
}

// GetWinsize returns the window size based on the specified file descriptor.
func GetWinsize(fd uintptr) (*Winsize, error) {
	ws := &Winsize{}
	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(ws)))
	// Skip errno = 0
	if err == 0 {
		return ws, nil
	}
	return ws, err
}

// SetWinsize tries to set the specified window size for the specified file descriptor.
func SetWinsize(fd uintptr, ws *Winsize) error {
	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, uintptr(syscall.TIOCSWINSZ), uintptr(unsafe.Pointer(ws)))
	// Skip errno = 0
	if err == 0 {
		return nil
	}
	return err
}

// IsTerminal returns true if the given file descriptor is a terminal.
func IsTerminal(fd uintptr) bool {
	var termios Termios
	return tcget(fd, &termios) == 0
}

// RestoreTerminal restores the terminal connected to the given file descriptor
// to a previous state.
func RestoreTerminal(fd uintptr, state *State) error {
	if state == nil {
		return ErrInvalidState
	}
	if err := tcset(fd, &state.termios); err != 0 {
		return err
	}
	return nil
}

// SaveState saves the state of the terminal connected to the given file descriptor.
func SaveState(fd uintptr) (*State, error) {
	var oldState State
	if err := tcget(fd, &oldState.termios); err != 0 {
		return nil, err
	}

	return &oldState, nil
}

// DisableEcho applies the specified state to the terminal connected to the file
// descriptor, with echo disabled.
func DisableEcho(fd uintptr, state *State) error {
	newState := state.termios
	newState.Lflag &^= syscall.ECHO

	if err := tcset(fd, &newState); err != 0 {
		return err
	}
	handleInterrupt(fd, state)
	return nil
}

// SetRawTerminal puts the terminal connected to the given file descriptor into
// raw mode and returns the previous state.
func SetRawTerminal(fd uintptr) (*State, error) {
	oldState, err := MakeRaw(fd)
	if err != nil {
		return nil, err
	}
	handleInterrupt(fd, oldState)
	return oldState, err
}

func handleInterrupt(fd uintptr, state *State) {
	sigchan := make(chan os.Signal, 1)
	signal.Notify(sigchan, os.Interrupt)

	go func() {
		_ = <-sigchan
		RestoreTerminal(fd, state)
		os.Exit(0)
	}()
}