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

//go:build linux

// Termios ioctl helpers for the debugger — Linux uses TCGETS/TCSETS.
// Kept in a tiny shim so debugcli/debugtui stay platform-neutral.

package hbrt

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

const (
	ioctlGetTermios = syscall.TCGETS
	ioctlSetTermios = syscall.TCSETS
)

var (
	savedTermios syscall.Termios
	termSaved    bool
)

func restoreCooked() {
	fd := int(os.Stdin.Fd())
	var t syscall.Termios
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlGetTermios, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
	if !termSaved {
		savedTermios = t
		termSaved = true
	}
	t.Lflag |= syscall.ICANON | syscall.ECHO
	t.Oflag |= syscall.OPOST
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlSetTermios, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
}

func reenterRaw() {
	fd := int(os.Stdin.Fd())
	var t syscall.Termios
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlGetTermios, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
	t.Lflag &^= syscall.ICANON | syscall.ECHO | syscall.ISIG
	t.Oflag &^= syscall.OPOST
	t.Cc[syscall.VMIN] = 1
	t.Cc[syscall.VTIME] = 0
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlSetTermios, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
}

func termSize() (int, int) {
	type winsize struct {
		Row, Col, Xpixel, Ypixel uint16
	}
	var ws winsize
	_, _, _ = syscall.Syscall(syscall.SYS_IOCTL, uintptr(1),
		uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(&ws)))
	return int(ws.Row), int(ws.Col)
}

// readDebugKey puts stdin into raw mode just long enough to consume
// one keystroke / ANSI escape sequence, then restores the previous
// termios. The cross-platform decoder in debugkey.go turns the bytes
// into a logical key code.
func readDebugKey() int {
	fd := int(os.Stdin.Fd())
	var t syscall.Termios
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlGetTermios, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
	raw := t
	raw.Lflag &^= syscall.ICANON | syscall.ECHO
	raw.Cc[syscall.VMIN] = 1
	raw.Cc[syscall.VTIME] = 0
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlSetTermios, uintptr(unsafe.Pointer(&raw)), 0, 0, 0)
	defer syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlSetTermios, uintptr(unsafe.Pointer(&t)), 0, 0, 0)

	buf := make([]byte, 8)
	n, _ := syscall.Read(fd, buf)
	return decodeDebugKey(buf, n)
}