five/hbrt/termios_windows.go

// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

//go:build windows

// Windows console equivalent of the Unix termios helpers. Rather than
// dealing with ReadConsoleInput's VK_* keycodes we turn on
// ENABLE_VIRTUAL_TERMINAL_INPUT / PROCESSING on modern Windows (10+),
// which makes the console speak ANSI — same byte stream the Unix path
// sees. Everything above this file stays platform-neutral.

package hbrt

import (
	"os"
	"syscall"
	"unsafe"
)

const (
	enableProcessedInput       = 0x0001
	enableLineInput            = 0x0002
	enableEchoInput            = 0x0004
	enableVirtualTerminalInput = 0x0200

	enableProcessedOutput          = 0x0001
	enableVirtualTerminalProcessing = 0x0004
)

var (
	kernel32                       = syscall.NewLazyDLL("kernel32.dll")
	procGetConsoleMode             = kernel32.NewProc("GetConsoleMode")
	procSetConsoleMode             = kernel32.NewProc("SetConsoleMode")
	procGetConsoleScreenBufferInfo = kernel32.NewProc("GetConsoleScreenBufferInfo")
)

type smallRect struct {
	Left, Top, Right, Bottom int16
}

type consoleScreenBufferInfo struct {
	Size              struct{ X, Y int16 }
	CursorPosition    struct{ X, Y int16 }
	Attributes        uint16
	Window            smallRect
	MaximumWindowSize struct{ X, Y int16 }
}

func getConsoleMode(h syscall.Handle) (uint32, bool) {
	var mode uint32
	r, _, _ := procGetConsoleMode.Call(uintptr(h), uintptr(unsafe.Pointer(&mode)))
	return mode, r != 0
}

func setConsoleMode(h syscall.Handle, mode uint32) {
	_, _, _ = procSetConsoleMode.Call(uintptr(h), uintptr(mode))
}

// Remember the input mode at program start so we can restore it.
var (
	savedInMode  uint32
	savedOutMode uint32
	termSaved    bool
)

func restoreCooked() {
	hIn := syscall.Handle(os.Stdin.Fd())
	hOut := syscall.Handle(os.Stdout.Fd())
	if !termSaved {
		if m, ok := getConsoleMode(hIn); ok {
			savedInMode = m
		}
		if m, ok := getConsoleMode(hOut); ok {
			savedOutMode = m
		}
		termSaved = true
	}
	// Cooked: line input + echo, plus VT so our ANSI rendering still works.
	inMode := (savedInMode | enableProcessedInput | enableLineInput | enableEchoInput | enableVirtualTerminalInput)
	setConsoleMode(hIn, inMode)
	outMode := savedOutMode | enableProcessedOutput | enableVirtualTerminalProcessing
	setConsoleMode(hOut, outMode)
}

func reenterRaw() {
	hIn := syscall.Handle(os.Stdin.Fd())
	hOut := syscall.Handle(os.Stdout.Fd())
	// Raw: no line input, no echo, but keep VT so F-keys arrive as
	// ESC[15~ etc. and our ANSI writes still render.
	inMode := (savedInMode &^ (enableLineInput | enableEchoInput | enableProcessedInput)) | enableVirtualTerminalInput
	setConsoleMode(hIn, inMode)
	outMode := savedOutMode | enableProcessedOutput | enableVirtualTerminalProcessing
	setConsoleMode(hOut, outMode)
}

func termSize() (int, int) {
	hOut := syscall.Handle(os.Stdout.Fd())
	var info consoleScreenBufferInfo
	r, _, _ := procGetConsoleScreenBufferInfo.Call(uintptr(hOut), uintptr(unsafe.Pointer(&info)))
	if r == 0 {
		return 24, 80
	}
	cols := int(info.Window.Right - info.Window.Left + 1)
	rows := int(info.Window.Bottom - info.Window.Top + 1)
	return rows, cols
}

// readDebugKey reads a single key with raw console mode. VT input is
// enabled so F-keys / arrows arrive as the same ANSI escape sequences
// the Unix build expects, and decodeDebugKey classifies them.
func readDebugKey() int {
	hIn := syscall.Handle(os.Stdin.Fd())
	var before uint32
	if m, ok := getConsoleMode(hIn); ok {
		before = m
	}
	rawMode := (before &^ (enableLineInput | enableEchoInput | enableProcessedInput)) | enableVirtualTerminalInput
	setConsoleMode(hIn, rawMode)
	defer setConsoleMode(hIn, before)

	buf := make([]byte, 8)
	n, _ := os.Stdin.Read(buf)
	return decodeDebugKey(buf, n)
}