"""同一本地数据库的 Windows named mutex。"""

from __future__ import annotations

import ctypes
from ctypes import wintypes
import hashlib
import os
from pathlib import Path

from cmbuyer_client.core.errors import SingleInstanceError


class NamedMutex:
    _ALREADY_EXISTS = 183

    def __init__(self, database_path: Path) -> None:
        if os.name != "nt":
            raise SingleInstanceError("named_mutex_requires_windows")
        canonical = str(database_path.expanduser().resolve()).casefold().encode("utf-8")
        # Global namespace 覆盖同一 Windows 用户的多个交互 session；默认 DACL 不向其他用户泄露句柄。
        name = "Global\\cmbuyer-" + hashlib.sha256(canonical).hexdigest()
        kernel32 = ctypes.WinDLL("kernel32", use_last_error=True)
        kernel32.CreateMutexW.argtypes = (wintypes.LPVOID, wintypes.BOOL, wintypes.LPCWSTR)
        kernel32.CreateMutexW.restype = wintypes.HANDLE
        kernel32.ReleaseMutex.argtypes = (wintypes.HANDLE,)
        kernel32.ReleaseMutex.restype = wintypes.BOOL
        kernel32.CloseHandle.argtypes = (wintypes.HANDLE,)
        kernel32.CloseHandle.restype = wintypes.BOOL
        ctypes.set_last_error(0)
        handle = kernel32.CreateMutexW(None, True, name)
        if not handle:
            raise SingleInstanceError("named_mutex_failed")
        if ctypes.get_last_error() == self._ALREADY_EXISTS:
            kernel32.CloseHandle(handle)
            raise SingleInstanceError("instance_already_running")
        self._kernel32 = kernel32
        self._handle = handle

    def close(self) -> None:
        handle = getattr(self, "_handle", None)
        if handle:
            self._kernel32.ReleaseMutex(handle)
            self._kernel32.CloseHandle(handle)
            self._handle = None

    def __enter__(self) -> "NamedMutex":
        return self

    def __exit__(self, exc_type: object, exc: object, traceback: object) -> None:
        self.close()