package term

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

type Termios struct {
	Iflag  uintptr
	Oflag  uintptr
	Cflag  uintptr
	Lflag  uintptr
	Cc     [20]byte
	Ispeed uintptr
	Ospeed uintptr
}

const (
	// Input flags
	inpck  = 0x010
	istrip = 0x020
	icrnl  = 0x100
	ixon   = 0x200

	// Output flags
	opost = 0x1

	// Control flags
	cs8 = 0x300

	// Local flags
	icanon = 0x100
	iexten = 0x400
)

const (
	HUPCL   = 0x4000
	ICANON  = 0x100
	ICRNL   = 0x100
	IEXTEN  = 0x400
	BRKINT  = 0x2
	CFLUSH  = 0xf
	CLOCAL  = 0x8000
	CREAD   = 0x800
	CS5     = 0x0
	CS6     = 0x100
	CS7     = 0x200
	CS8     = 0x300
	CSIZE   = 0x300
	CSTART  = 0x11
	CSTATUS = 0x14
	CSTOP   = 0x13
	CSTOPB  = 0x400
	CSUSP   = 0x1a
	IGNBRK  = 0x1
	IGNCR   = 0x80
	IGNPAR  = 0x4
	IMAXBEL = 0x2000
	INLCR   = 0x40
	INPCK   = 0x10
	ISIG    = 0x80
	ISTRIP  = 0x20
	IUTF8   = 0x4000
	IXANY   = 0x800
	IXOFF   = 0x400
	IXON    = 0x200
	NOFLSH  = 0x80000000
	OCRNL   = 0x10
	OFDEL   = 0x20000
	OFILL   = 0x80
	ONLCR   = 0x2
	ONLRET  = 0x40
	ONOCR   = 0x20
	ONOEOT  = 0x8
	OPOST   = 0x1
	RENB    = 0x1000
	PARMRK  = 0x8
	PARODD  = 0x2000

	TOSTOP   = 0x400000
	VDISCARD = 0xf
	VDSUSP   = 0xb
	VEOF     = 0x0
	VEOL     = 0x1
	VEOL2    = 0x2
	VERASE   = 0x3
	VINTR    = 0x8
	VKILL    = 0x5
	VLNEXT   = 0xe
	VMIN     = 0x10
	VQUIT    = 0x9
	VREPRINT = 0x6
	VSTART   = 0xc
	VSTATUS  = 0x12
	VSTOP    = 0xd
	VSUSP    = 0xa
	VT0      = 0x0
	VT1      = 0x10000
	VTDLY    = 0x10000
	VTIME    = 0x11
	ECHO     = 0x00000008

	PENDIN = 0x20000000
)

type State struct {
	termios Termios
}

type Winsize struct {
	Width  uint16
	Height uint16
	x      uint16
	y      uint16
}

func GetWinsize(fd uintptr) (*Winsize, error) {
	ws := &Winsize{}
	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(ws)))
	return ws, err
}

func SetWinsize(fd uintptr, ws *Winsize) error {
	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, uintptr(syscall.TIOCSWINSZ), uintptr(unsafe.Pointer(ws)))
	return err
}

// IsTerminal returns true if the given file descriptor is a terminal.
func IsTerminal(fd int) bool {
	var termios Termios
	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), uintptr(getTermios), uintptr(unsafe.Pointer(&termios)))
	return err == 0
}

// Restore restores the terminal connected to the given file descriptor to a
// previous state.
func Restore(fd int, state *State) error {
	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), uintptr(setTermios), uintptr(unsafe.Pointer(&state.termios)))
	return err
}

func SetRawTerminal() (*State, error) {
	oldState, err := MakeRaw(int(os.Stdin.Fd()))
	if err != nil {
		return nil, err
	}
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	go func() {
		_ = <-c
		Restore(int(os.Stdin.Fd()), oldState)
		os.Exit(0)
	}()
	return oldState, err
}

func RestoreTerminal(state *State) {
	Restore(int(os.Stdin.Fd()), state)
}