// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build windows

// Package terminal provides support functions for dealing with terminals, as
// commonly found on UNIX systems.
//
// Putting a terminal into raw mode is the most common requirement:
//
// 	oldState, err := terminal.MakeRaw(0)
// 	if err != nil {
// 	        panic(err)
// 	}
// 	defer terminal.Restore(0, oldState)
package terminal

import (
	"os"

	"golang.org/x/sys/windows"
)

type State struct {
	mode uint32
}

// IsTerminal returns whether the given file descriptor is a terminal.
func IsTerminal(fd int) bool {
	var st uint32
	err := windows.GetConsoleMode(windows.Handle(fd), &st)
	return err == nil
}

// MakeRaw put the terminal 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 int) (*State, error) {
	var st uint32
	if err := windows.GetConsoleMode(windows.Handle(fd), &st); err != nil {
		return nil, err
	}
	raw := st &^ (windows.ENABLE_ECHO_INPUT | windows.ENABLE_PROCESSED_INPUT | windows.ENABLE_LINE_INPUT | windows.ENABLE_PROCESSED_OUTPUT)
	if err := windows.SetConsoleMode(windows.Handle(fd), raw); err != nil {
		return nil, err
	}
	return &State{st}, nil
}

// GetState returns the current state of a terminal which may be useful to
// restore the terminal after a signal.
func GetState(fd int) (*State, error) {
	var st uint32
	if err := windows.GetConsoleMode(windows.Handle(fd), &st); err != nil {
		return nil, err
	}
	return &State{st}, nil
}

// Restore restores the terminal connected to the given file descriptor to a
// previous state.
func Restore(fd int, state *State) error {
	return windows.SetConsoleMode(windows.Handle(fd), state.mode)
}

// GetSize returns the visible dimensions of the given terminal.
//
// These dimensions don't include any scrollback buffer height.
func GetSize(fd int) (width, height int, err error) {
	var info windows.ConsoleScreenBufferInfo
	if err := windows.GetConsoleScreenBufferInfo(windows.Handle(fd), &info); err != nil {
		return 0, 0, err
	}
	return int(info.Window.Right - info.Window.Left + 1), int(info.Window.Bottom - info.Window.Top + 1), nil
}

// ReadPassword reads a line of input from a terminal without local echo.  This
// is commonly used for inputting passwords and other sensitive data. The slice
// returned does not include the \n.
func ReadPassword(fd int) ([]byte, error) {
	var st uint32
	if err := windows.GetConsoleMode(windows.Handle(fd), &st); err != nil {
		return nil, err
	}
	old := st

	st &^= (windows.ENABLE_ECHO_INPUT | windows.ENABLE_LINE_INPUT)
	st |= (windows.ENABLE_PROCESSED_OUTPUT | windows.ENABLE_PROCESSED_INPUT)
	if err := windows.SetConsoleMode(windows.Handle(fd), st); err != nil {
		return nil, err
	}

	defer windows.SetConsoleMode(windows.Handle(fd), old)

	var h windows.Handle
	p, _ := windows.GetCurrentProcess()
	if err := windows.DuplicateHandle(p, windows.Handle(fd), p, &h, 0, false, windows.DUPLICATE_SAME_ACCESS); err != nil {
		return nil, err
	}

	f := os.NewFile(uintptr(h), "stdin")
	defer f.Close()
	return readPasswordLine(f)
}
