//go:build windows

package compose

import (
	"context"
	"io"
	"os/exec"
	"path/filepath"
	"strconv"
	"syscall"
	"time"

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

const finalTerminationBound = 2 * time.Second
const processTreeTerminationBound = 2 * time.Second
const createNewProcessGroup = 0x00000200

var windowsSystemDirectory = windows.GetSystemDirectory

func configureProcess(command *exec.Cmd) {
	command.SysProcAttr = &syscall.SysProcAttr{CreationFlags: createNewProcessGroup}
}

func terminateProcess(command *exec.Cmd, done <-chan error) error {
	if command.Process == nil {
		return nil
	}
	return terminateWindowsProcess(
		done,
		func() error { return terminateWindowsProcessTree(command.Process.Pid) },
		command.Process.Kill,
		finalTerminationBound,
	)
}

func terminateWindowsProcessTree(pid int) error {
	ctx, cancel := context.WithTimeout(context.Background(), processTreeTerminationBound)
	defer cancel()
	taskkillPath, err := systemTaskkillPath()
	if err != nil {
		return ErrProcessReap
	}
	command := windowsTreeKillCommand(ctx, taskkillPath, pid)
	command.Stdout = io.Discard
	command.Stderr = io.Discard
	if err := command.Run(); err != nil {
		return ErrProcessReap
	}
	if ctx.Err() != nil {
		return ErrProcessReap
	}
	return nil
}

// systemTaskkillPath resolves taskkill through Windows' protected system-directory API, never PATH.
func systemTaskkillPath() (string, error) {
	systemDirectory, err := windowsSystemDirectory()
	if err != nil {
		return "", ErrProcessReap
	}
	systemDirectory = filepath.Clean(systemDirectory)
	if systemDirectory == "." || !filepath.IsAbs(systemDirectory) {
		return "", ErrProcessReap
	}
	taskkillPath := filepath.Join(systemDirectory, "taskkill.exe")
	if !filepath.IsAbs(taskkillPath) || filepath.Dir(taskkillPath) != systemDirectory {
		return "", ErrProcessReap
	}
	return taskkillPath, nil
}

func windowsTreeKillCommand(ctx context.Context, taskkillPath string, pid int) *exec.Cmd {
	return exec.CommandContext(ctx, taskkillPath, "/PID", strconv.Itoa(pid), "/T", "/F")
}