package isatty

import (

	"errors"

	"strings"

	"syscall"

	"unicode/utf16"

	"unsafe"

)

const (

	objectNameInfo uintptr = 1

	fileNameInfo           = 2

	fileTypePipe           = 3

)

var (

	kernel32                         = syscall.NewLazyDLL("kernel32.dll")

	ntdll                            = syscall.NewLazyDLL("ntdll.dll")

	procGetConsoleMode               = kernel32.NewProc("GetConsoleMode")

	procGetFileInformationByHandleEx = kernel32.NewProc("GetFileInformationByHandleEx")

	procGetFileType                  = kernel32.NewProc("GetFileType")

	procNtQueryObject                = ntdll.NewProc("NtQueryObject")

)

func init() {

	// Check if GetFileInformationByHandleEx is available.

	if procGetFileInformationByHandleEx.Find() != nil {

		procGetFileInformationByHandleEx = nil

	}

}

// IsTerminal return true if the file descriptor is terminal.

func IsTerminal(fd uintptr) bool {

	var st uint32

	r, _, e := syscall.Syscall(procGetConsoleMode.Addr(), 2, fd, uintptr(unsafe.Pointer(&st)), 0)

	return r != 0 && e == 0

}

// Check pipe name is used for cygwin/msys2 pty.

// Cygwin/MSYS2 PTY has a name like:

//   \{cygwin,msys}-XXXXXXXXXXXXXXXX-ptyN-{from,to}-master

func isCygwinPipeName(name string) bool {

	token := strings.Split(name, "-")

	if len(token) < 5 {

		return false

	}

	if token[0] != `\msys` &&

		token[0] != `\cygwin` &&

		token[0] != `\Device\NamedPipe\msys` &&

		token[0] != `\Device\NamedPipe\cygwin` {

		return false

	}

	if token[1] == "" {

		return false

	}

	if !strings.HasPrefix(token[2], "pty") {

		return false

	}

	if token[3] != `from` && token[3] != `to` {

		return false

	}

	if token[4] != "master" {

		return false

	}

	return true

}

// getFileNameByHandle use the undocomented ntdll NtQueryObject to get file full name from file handler

// guys are using Windows XP, this is a workaround for those guys, it will also work on system from

// Windows vista to 10

// see https://stackoverflow.com/a/18792477 for details

func getFileNameByHandle(fd uintptr) (string, error) {

	if procNtQueryObject == nil {

		return "", errors.New("ntdll.dll: NtQueryObject not supported")

	}

	var buf [4 + syscall.MAX_PATH]uint16

	var result int

	r, _, e := syscall.Syscall6(procNtQueryObject.Addr(), 5,

		fd, objectNameInfo, uintptr(unsafe.Pointer(&buf)), uintptr(2*len(buf)), uintptr(unsafe.Pointer(&result)), 0)

	if r != 0 {

		return "", e

	}

	return string(utf16.Decode(buf[4 : 4+buf[0]/2])), nil

}

// IsCygwinTerminal() return true if the file descriptor is a cygwin or msys2

// terminal.

func IsCygwinTerminal(fd uintptr) bool {

	if procGetFileInformationByHandleEx == nil {

		name, err := getFileNameByHandle(fd)

		if err != nil {

			return false

		}

		return isCygwinPipeName(name)

	}

	// Cygwin/msys's pty is a pipe.

	ft, _, e := syscall.Syscall(procGetFileType.Addr(), 1, fd, 0, 0)

	if ft != fileTypePipe || e != 0 {

		return false

	}

	var buf [2 + syscall.MAX_PATH]uint16

	r, _, e := syscall.Syscall6(procGetFileInformationByHandleEx.Addr(),

		4, fd, fileNameInfo, uintptr(unsafe.Pointer(&buf)),

		uintptr(len(buf)*2), 0, 0)

	if r == 0 || e != 0 {

		return false

	}

	l := *(*uint32)(unsafe.Pointer(&buf))

	return isCygwinPipeName(string(utf16.Decode(buf[2 : 2+l/2])))

}