// +build windows

package termstatus

import (
	"io"
	"syscall"
	"unsafe"

	"golang.org/x/crypto/ssh/terminal"
)

// clearCurrentLine removes all characters from the current line and resets the
// cursor position to the first column.
func clearCurrentLine(wr io.Writer, fd uintptr) func(io.Writer, uintptr) {
	// easy case, the terminal is cmd or psh, without redirection
	if isWindowsTerminal(fd) {
		return windowsClearCurrentLine
	}

	// check if the output file type is a pipe (0x0003)
	if getFileType(fd) != fileTypePipe {
		// return empty func, update state is not possible on this terminal
		return func(io.Writer, uintptr) {}
	}

	// assume we're running in mintty/cygwin
	return posixClearCurrentLine
}

// moveCursorUp moves the cursor to the line n lines above the current one.
func moveCursorUp(wr io.Writer, fd uintptr) func(io.Writer, uintptr, int) {
	// easy case, the terminal is cmd or psh, without redirection
	if isWindowsTerminal(fd) {
		return windowsMoveCursorUp
	}

	// check if the output file type is a pipe (0x0003)
	if getFileType(fd) != fileTypePipe {
		// return empty func, update state is not possible on this terminal
		return func(io.Writer, uintptr, int) {}
	}

	// assume we're running in mintty/cygwin
	return posixMoveCursorUp
}

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

var (
	procGetConsoleScreenBufferInfo = kernel32.NewProc("GetConsoleScreenBufferInfo")
	procSetConsoleCursorPosition   = kernel32.NewProc("SetConsoleCursorPosition")
	procFillConsoleOutputCharacter = kernel32.NewProc("FillConsoleOutputCharacterW")
	procFillConsoleOutputAttribute = kernel32.NewProc("FillConsoleOutputAttribute")
	procGetFileType                = kernel32.NewProc("GetFileType")
)

type (
	short int16
	word  uint16
	dword uint32

	coord struct {
		x short
		y short
	}
	smallRect struct {
		left   short
		top    short
		right  short
		bottom short
	}
	consoleScreenBufferInfo struct {
		size              coord
		cursorPosition    coord
		attributes        word
		window            smallRect
		maximumWindowSize coord
	}
)

// windowsClearCurrentLine removes all characters from the current line and
// resets the cursor position to the first column.
func windowsClearCurrentLine(wr io.Writer, fd uintptr) {
	var info consoleScreenBufferInfo
	procGetConsoleScreenBufferInfo.Call(fd, uintptr(unsafe.Pointer(&info)))

	// clear the line
	cursor := coord{
		x: info.window.left,
		y: info.cursorPosition.y,
	}
	var count, w dword
	count = dword(info.size.x)
	procFillConsoleOutputAttribute.Call(fd, uintptr(info.attributes), uintptr(count), *(*uintptr)(unsafe.Pointer(&cursor)), uintptr(unsafe.Pointer(&w)))
	procFillConsoleOutputCharacter.Call(fd, uintptr(' '), uintptr(count), *(*uintptr)(unsafe.Pointer(&cursor)), uintptr(unsafe.Pointer(&w)))
}

// windowsMoveCursorUp moves the cursor to the line n lines above the current one.
func windowsMoveCursorUp(wr io.Writer, fd uintptr, n int) {
	var info consoleScreenBufferInfo
	procGetConsoleScreenBufferInfo.Call(fd, uintptr(unsafe.Pointer(&info)))

	// move cursor up by n lines and to the first column
	info.cursorPosition.y -= short(n)
	info.cursorPosition.x = 0
	procSetConsoleCursorPosition.Call(fd, uintptr(*(*int32)(unsafe.Pointer(&info.cursorPosition))))
}

// isWindowsTerminal return true if the file descriptor is a windows terminal (cmd, psh).
func isWindowsTerminal(fd uintptr) bool {
	return terminal.IsTerminal(int(fd))
}

const fileTypePipe = 0x0003

// getFileType returns the file type for the given fd.
// https://msdn.microsoft.com/de-de/library/windows/desktop/aa364960(v=vs.85).aspx
func getFileType(fd uintptr) int {
	r, _, e := syscall.Syscall(procGetFileType.Addr(), 1, fd, 0, 0)
	if e != 0 {
		return 0
	}
	return int(r)
}

// canUpdateStatus returns true if status lines can be printed, the process
// output is not redirected to a file or pipe.
func canUpdateStatus(fd uintptr) bool {
	// easy case, the terminal is cmd or psh, without redirection
	if isWindowsTerminal(fd) {
		return true
	}

	// check if the output file type is a pipe (0x0003)
	if getFileType(fd) != fileTypePipe {
		return false
	}

	// assume we're running in mintty/cygwin
	return true
}