"""HF私有临时快照生命周期；创建/回收必须持同目录公共提交锁。"""
from contextlib import contextmanager
import json
import logging
import os
from pathlib import Path
import re
import stat
import uuid


logger=logging.getLogger('ComfyUI-Ranking.DB')


class SnapshotStore:
    MANIFEST='snapshot-owner.json'
    NAME=re.compile(r'\.hf-sync-[0-9a-f]{32}\Z')
    PAYLOAD=re.compile(r'(0|[1-9][0-9]*)\.json\Z')

    def __init__(self,directory):
        self.root=Path(os.path.abspath(directory))

    @staticmethod
    def _check(path,directory=False):
        info=os.lstat(path)
        if (getattr(info,'st_file_attributes',0)&1024
                or not (stat.S_ISDIR(info.st_mode) if directory else stat.S_ISREG(info.st_mode))
                or not info.st_ino):
            raise ValueError('invalid snapshot path')
        return (info.st_dev,info.st_ino)

    def _owner(self,path):
        if path.parent!=self.root or not self.NAME.fullmatch(path.name):
            raise ValueError('unknown snapshot directory')
        self._check(self.root,directory=True)
        directory_id=self._check(path,directory=True)
        marker=path/self.MANIFEST
        marker_id=self._check(marker)
        descriptor=os.open(marker,os.O_RDONLY|getattr(os,'O_NOFOLLOW',0)
            |getattr(os,'O_NONBLOCK',0)|getattr(os,'O_BINARY',0))
        with os.fdopen(descriptor,'rb') as stream:
            info=os.fstat(stream.fileno())
            if not stat.S_ISREG(info.st_mode) or (info.st_dev,info.st_ino)!=marker_id:
                raise ValueError('snapshot owner identity changed')
            data=stream.read(4097)
        if len(data)>4096:raise ValueError('snapshot owner too large')
        owner=json.loads(data)
        if (not isinstance(owner,dict) or set(owner)!={'schema','kind','directory'}
                or type(owner['schema']) is not int or owner['schema']!=1
                or owner['kind']!='ranking-hf-snapshot' or owner['directory']!=path.name):
            raise ValueError('invalid snapshot owner')
        if self._check(path,directory=True)!=directory_id or self._check(marker)!=marker_id:
            raise ValueError('snapshot identity changed')
        return directory_id

    def remove(self,path):
        """只删除验证归属且内容全为普通快照文件的本层目录，不递归删除。"""
        path=Path(path)
        directory_id=self._owner(path)
        entries=[]
        for entry in path.iterdir():
            if len(entries)>=4096:raise ValueError('too many snapshot files')
            if entry.name!=self.MANIFEST and not self.PAYLOAD.fullmatch(entry.name):
                raise ValueError('unknown snapshot content')
            self._check(entry)
            entries.append(entry)
        # 先完整校验，再删除数据，归属记录最后删除，失败可在后续接手。
        for entry in sorted(entries,key=lambda entry:entry.name==self.MANIFEST):
            self._check(self.root,directory=True)
            if self._check(path,directory=True)!=directory_id:
                raise ValueError('snapshot directory changed')
            entry.unlink()
        path.rmdir()

    def cleanup_stale(self):
        self._check(self.root,directory=True)
        removed=retained=0
        for path in self.root.glob('.hf-sync-*'):
            try:self.remove(path);removed+=1
            except FileNotFoundError:
                if path.exists() or path.is_symlink():retained+=1
            except (OSError,ValueError):retained+=1
        return removed,retained

    @contextmanager
    def temporary(self):
        self._check(self.root,directory=True)
        path=self.root/('.hf-sync-'+uuid.uuid4().hex)
        path.mkdir(mode=0o700)
        try:
            with (path/self.MANIFEST).open('xb') as stream:
                data=json.dumps({'schema':1,'kind':'ranking-hf-snapshot','directory':path.name}).encode('utf-8')
                stream.write(data);stream.flush();os.fsync(stream.fileno())
            yield str(path)
        finally:
            try:self.remove(path)
            except FileNotFoundError:
                if path.exists() or path.is_symlink():
                    logger.warning('HF snapshot cleanup unavailable; retained for recovery')
            except (OSError,ValueError):
                logger.warning('HF snapshot cleanup unavailable; retained for recovery')