import os
import sys
import tempfile
from pathlib import Path

class SingleInstance:
    def __init__(self, app_name="PCM_Report"):
        self.lockfile = Path(tempfile.gettempdir()) / f"{app_name}.lock"
        self.fp = None
        
    def __enter__(self):
        try:
            if self.lockfile.exists():
                # 尝试读取PID，检查进程是否还在运行
                try:
                    pid = int(self.lockfile.read_text().strip())
                    # 检查进程是否存在
                    if sys.platform == "win32":
                        import ctypes
                        kernel32 = ctypes.windll.kernel32
                        PROCESS_QUERY_INFORMATION = 0x0400
                        handle = kernel32.OpenProcess(PROCESS_QUERY_INFORMATION, 0, pid)
                        if handle:
                            kernel32.CloseHandle(handle)
                            return False  # 进程存在，不允许启动
                    else:
                        os.kill(pid, 0)  # Unix系统检查
                        return False
                except (ValueError, ProcessLookupError, OSError):
                    # 进程不存在，删除旧锁文件
                    self.lockfile.unlink(missing_ok=True)
            
            # 创建锁文件
            self.lockfile.write_text(str(os.getpid()))
            return True
        except Exception:
            return False
    
    def __exit__(self, *args):
        try:
            if self.lockfile.exists():
                self.lockfile.unlink()
        except Exception:
            pass