//go:build windows

package runtime

import (
	"syscall"
	"unsafe"

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

const (
	windowsProcessQueryLimitedInformation = 0x1000
	windowsStillActive                    = 259
)

func processAlivePID(pid int) bool {
	if pid <= 0 {
		return false
	}
	handle, err := windows.OpenProcess(windowsProcessQueryLimitedInformation, false, uint32(pid))
	if err != nil {
		if processSnapshotContainsPID(pid) {
			return true
		}
		return err == syscall.ERROR_ACCESS_DENIED
	}
	defer windows.CloseHandle(handle)
	var exitCode uint32
	if err := windows.GetExitCodeProcess(handle, &exitCode); err == nil {
		return exitCode == windowsStillActive
	}
	return processSnapshotContainsPID(pid)
}

func processSnapshotContainsPID(pid int) bool {
	snapshot, err := windows.CreateToolhelp32Snapshot(windows.TH32CS_SNAPPROCESS, 0)
	if err != nil {
		return false
	}
	defer windows.CloseHandle(snapshot)
	var entry windows.ProcessEntry32
	entry.Size = uint32(unsafe.Sizeof(entry))
	if err := windows.Process32First(snapshot, &entry); err != nil {
		return false
	}
	for {
		if entry.ProcessID == uint32(pid) {
			return true
		}
		if err := windows.Process32Next(snapshot, &entry); err != nil {
			return false
		}
	}
}