"""Single-instance lock for up/stop."""

from __future__ import annotations

import os
import sys
from types import TracebackType

from gpu_rent.errors import GpuRentError
from gpu_rent.paths import lock_path


def _pid_alive(pid: int) -> bool:
    if pid <= 0:
        return False
    if sys.platform == "win32":
        import ctypes

        handle = ctypes.windll.kernel32.OpenProcess(0x100000, False, pid)
        if handle:
            ctypes.windll.kernel32.CloseHandle(handle)
            return True
        return False
    try:
        os.kill(pid, 0)
        return True
    except OSError:
        return False


class SessionLock:
    def __enter__(self) -> SessionLock:
        path = lock_path()
        path.parent.mkdir(parents=True, exist_ok=True)
        if path.is_file():
            try:
                old = int(path.read_text(encoding="utf-8").strip() or "0")
            except ValueError:
                old = 0
            if _pid_alive(old) and old != os.getpid():
                raise GpuRentError(
                    f"gpu-rent уже работает (pid {old}, {path}). Дождись окончания up/stop."
                )
        path.write_text(str(os.getpid()), encoding="utf-8")
        self._path = path
        self._pid = os.getpid()
        return self

    def __exit__(
        self,
        exc_type: type[BaseException] | None,
        exc: BaseException | None,
        tb: TracebackType | None,
    ) -> None:
        try:
            if self._path.is_file() and self._path.read_text(encoding="utf-8").strip() == str(self._pid):
                self._path.unlink()
        except OSError:
            pass