five/hbrtl/rawtty.go

// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// Raw terminal for Five. Uses /dev/tty opened fresh each ReadKey call.
package hbrtl

import (
	"os"
	"syscall"
	"unsafe"
)

var (
	origTermios syscall.Termios
	rawModeOn   bool
	stdinFd     int
)

// InitRawTerminal sets raw mode on stdin.
func InitRawTerminal() {
	if rawModeOn {
		return
	}
	stdinFd = int(os.Stdin.Fd())

	// Save original
	_, _, e := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(stdinFd), 0x5401, uintptr(unsafe.Pointer(&origTermios)), 0, 0, 0)
	if e != 0 {
		return
	}

	// Set raw on stdin
	raw := origTermios
	raw.Lflag &^= syscall.ICANON | syscall.ECHO | syscall.ISIG
	raw.Oflag &^= syscall.OPOST
	raw.Cc[syscall.VMIN] = 1
	raw.Cc[syscall.VTIME] = 0
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(stdinFd), 0x5402, uintptr(unsafe.Pointer(&raw)), 0, 0, 0)

	rawModeOn = true
}

// RestoreTerminal restores original terminal.
func RestoreTerminal() {
	if !rawModeOn {
		return
	}
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(stdinFd), 0x5402, uintptr(unsafe.Pointer(&origTermios)), 0, 0, 0)
	rawModeOn = false
}

// IsRawMode returns true if raw mode is active.
func IsRawMode() bool {
	return rawModeOn
}

// ReadKey reads one key. Opens /dev/tty fresh each time to avoid buffered data.
func ReadKey() int {
	if !rawModeOn {
		InitRawTerminal()
	}
	os.Stdout.Sync()

	// Open /dev/tty fresh — no stale data possible
	fd, err := syscall.Open("/dev/tty", syscall.O_RDONLY, 0)
	if err != nil {
		return 27 // ESC
	}
	defer syscall.Close(fd)

	// Set this fd to raw too
	var t syscall.Termios
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5401, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
	t.Lflag &^= syscall.ICANON | syscall.ECHO | syscall.ISIG
	t.Cc[syscall.VMIN] = 1
	t.Cc[syscall.VTIME] = 0
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5402, uintptr(unsafe.Pointer(&t)), 0, 0, 0)

	// Flush input buffer (TCFLSH = 0x540B, TCIFLUSH = 0)
	syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), 0x540B, 0)

	buf := make([]byte, 1)
	n, e := syscall.Read(fd, buf)
	if e != nil || n == 0 {
		return 27
	}
	b := buf[0]

	if b == 27 { // ESC — bare ESC or sequence?
		// Short timeout to check for sequence
		var t2 syscall.Termios
		syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5401, uintptr(unsafe.Pointer(&t2)), 0, 0, 0)
		t2.Cc[syscall.VMIN] = 0
		t2.Cc[syscall.VTIME] = 1 // 100ms
		syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5402, uintptr(unsafe.Pointer(&t2)), 0, 0, 0)

		n2, _ := syscall.Read(fd, buf)
		if n2 == 0 {
			return 27 // bare ESC
		}
		if buf[0] == '[' {
			n3, _ := syscall.Read(fd, buf)
			if n3 == 0 {
				return 27
			}
			switch buf[0] {
			case 'A':
				return 'A'
			case 'B':
				return 'B'
			case 'C':
				return 'C'
			case 'D':
				return 'D'
			case '5':
				syscall.Read(fd, buf)
				return '5'
			case '6':
				syscall.Read(fd, buf)
				return '6'
			case 'H':
				return 'H'
			case 'F':
				return 'F'
			default:
				return 27
			}
		}
		return 27
	}

	return int(b)
}