// disableNativeConsole turns off native console mode
func disableNativeConsole(state *State) error {
	// Try and restore both in an out before error checking.
	errout := winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode)
	errin := winterm.SetConsoleMode(uintptr(state.inHandle), state.inMode)
	if errout != nil {
		return errout
	}
	if errin != nil {
		return errin
	}
	return nil
}

// enableNativeConsole turns on native console mode
func enableNativeConsole(state State) error {
	if err := winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode|enableVirtualTerminalProcessing); err != nil {
		return err
	}

	if err := winterm.SetConsoleMode(uintptr(state.inHandle), state.inMode|enableVirtualTerminalInput); err != nil {
		winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode) // restore out if we can
		return err
	}

	return nil
}

// probeNativeConsole probes the console to determine if native can be supported,
func probeNativeConsole(state State) error {
	if err := winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode|enableVirtualTerminalProcessing); err != nil {
		return err
	}
	defer winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode)

	if err := winterm.SetConsoleMode(uintptr(state.inHandle), state.inMode|enableVirtualTerminalInput); err != nil {
		return err
	}
	defer winterm.SetConsoleMode(uintptr(state.inHandle), state.inMode)

	return nil
}

// MakeRaw puts the terminal (Windows Console) connected to the given file descriptor into raw
// mode and returns the previous state of the terminal so that it can be restored.
func MakeRaw(fd uintptr) (*State, error) {
	state, err := SaveState(fd)
	if err != nil {
		return nil, err
	}

	// See
	// -- https://msdn.microsoft.com/en-us/library/windows/desktop/ms686033(v=vs.85).aspx
	// -- https://msdn.microsoft.com/en-us/library/windows/desktop/ms683462(v=vs.85).aspx
	mode := state.mode

	// Disable these modes
	mode &^= winterm.ENABLE_ECHO_INPUT
	mode &^= winterm.ENABLE_LINE_INPUT
	mode &^= winterm.ENABLE_MOUSE_INPUT
	mode &^= winterm.ENABLE_WINDOW_INPUT
	mode &^= winterm.ENABLE_PROCESSED_INPUT

	// Enable these modes
	mode |= winterm.ENABLE_EXTENDED_FLAGS
	mode |= winterm.ENABLE_INSERT_MODE
	mode |= winterm.ENABLE_QUICK_EDIT_MODE

	err = winterm.SetConsoleMode(fd, mode)
	if err != nil {
		return nil, err
	}
	return state, nil
}

// enableNativeConsole turns on native console mode
func enableNativeConsole(state State) error {
	// First attempt both enableVirtualTerminalProcessing and disableNewlineAutoReturn
	if err := winterm.SetConsoleMode(uintptr(state.outHandle),
		state.outMode|(enableVirtualTerminalProcessing|disableNewlineAutoReturn)); err != nil {

		// That may fail, so fallback to trying just enableVirtualTerminalProcessing
		if err := winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode|enableVirtualTerminalProcessing); err != nil {
			return err
		}
	}

	if err := winterm.SetConsoleMode(uintptr(state.inHandle), state.inMode|enableVirtualTerminalInput); err != nil {
		winterm.SetConsoleMode(uintptr(state.outHandle), state.outMode) // restore out if we can
		return err
	}

	return nil
}

// SetRawTerminalOutput puts the output of terminal connected to the given file
// descriptor into raw mode. On UNIX, this does nothing and returns nil for the
// state. On Windows, it disables LF -> CRLF translation.
func SetRawTerminalOutput(fd uintptr) (*State, error) {
	state, err := SaveState(fd)
	if err != nil {
		return nil, err
	}

	// Ignore failures, since disableNewlineAutoReturn might not be supported on this
	// version of Windows.
	winterm.SetConsoleMode(fd, state.mode|disableNewlineAutoReturn)
	return state, err
}

// DisableEcho disables echo for the terminal connected to the given file descriptor.
// -- See https://msdn.microsoft.com/en-us/library/windows/desktop/ms683462(v=vs.85).aspx
func DisableEcho(fd uintptr, state *State) error {
	mode := state.inMode
	mode &^= winterm.ENABLE_ECHO_INPUT
	mode |= winterm.ENABLE_PROCESSED_INPUT | winterm.ENABLE_LINE_INPUT
	err := winterm.SetConsoleMode(fd, mode)
	if err != nil {
		return err
	}

	// Register an interrupt handler to catch and restore prior state
	restoreAtInterrupt(fd, state)
	return nil
}

// RestoreTerminal restores the terminal connected to the given file descriptor
// to a previous state.
func RestoreTerminal(fd uintptr, state *State) error {
	return winterm.SetConsoleMode(fd, state.mode)
}

// RestoreTerminal restores the terminal connected to the given file descriptor
// to a previous state.
func RestoreTerminal(fd uintptr, state *State) error {
	if usingNativeConsole {
		return disableNativeConsole(state)
	}
	return winterm.SetConsoleMode(fd, state.outMode)
}

// StdStreams returns the standard streams (stdin, stdout, stedrr).
func StdStreams() (stdIn io.ReadCloser, stdOut, stdErr io.Writer) {
	// Turn on VT handling on all std handles, if possible. This might
	// fail, in which case we will fall back to terminal emulation.
	var emulateStdin, emulateStdout, emulateStderr bool
	fd := os.Stdin.Fd()
	if mode, err := winterm.GetConsoleMode(fd); err == nil {
		// Validate that enableVirtualTerminalInput is supported, but do not set it.
		if err = winterm.SetConsoleMode(fd, mode|enableVirtualTerminalInput); err != nil {
			emulateStdin = true
		} else {
			vtInputSupported = true
		}
		// Unconditionally set the console mode back even on failure because SetConsoleMode
		// remembers invalid bits on input handles.
		winterm.SetConsoleMode(fd, mode)
	}

	fd = os.Stdout.Fd()
	if mode, err := winterm.GetConsoleMode(fd); err == nil {
		// Validate disableNewlineAutoReturn is supported, but do not set it.
		if err = winterm.SetConsoleMode(fd, mode|enableVirtualTerminalProcessing|disableNewlineAutoReturn); err != nil {
			emulateStdout = true
		} else {
			winterm.SetConsoleMode(fd, mode|enableVirtualTerminalProcessing)
		}
	}

	fd = os.Stderr.Fd()
	if mode, err := winterm.GetConsoleMode(fd); err == nil {
		// Validate disableNewlineAutoReturn is supported, but do not set it.
		if err = winterm.SetConsoleMode(fd, mode|enableVirtualTerminalProcessing|disableNewlineAutoReturn); err != nil {
			emulateStderr = true
		} else {
			winterm.SetConsoleMode(fd, mode|enableVirtualTerminalProcessing)
		}
	}

	if os.Getenv("ConEmuANSI") == "ON" {
		// The ConEmu terminal emulates ANSI on output streams well.
		emulateStdin = true
		emulateStdout = false
		emulateStderr = false
	}

	if emulateStdin {
		stdIn = windows.NewAnsiReader(syscall.STD_INPUT_HANDLE)
	} else {
		stdIn = os.Stdin
	}

	if emulateStdout {
		stdOut = windows.NewAnsiWriter(syscall.STD_OUTPUT_HANDLE)
	} else {
		stdOut = os.Stdout
	}

	if emulateStderr {
		stdErr = windows.NewAnsiWriter(syscall.STD_ERROR_HANDLE)
	} else {
		stdErr = os.Stderr
	}

	return
}