import os
import shutil
import uuid
import logging
from datetime import datetime, timezone
from typing import List
from .config import Config

log = logging.getLogger(__name__)


class LocalSessionStorage:
    """Per-request session folder storage with TTL cleanup."""

    def __init__(self, base_dir: str | None = None):
        self.base_dir = base_dir or Config.SESSIONS_DIR
        os.makedirs(self.base_dir, exist_ok=True)

    @staticmethod
    def _now_utc() -> datetime:
        return datetime.now(timezone.utc)

    def _session_path(self, session_id: str) -> str:
        # defensive join to prevent path traversal
        candidate = os.path.realpath(os.path.join(self.base_dir, session_id))
        if not candidate.startswith(os.path.realpath(self.base_dir)):
            raise ValueError("Invalid session path")
        return candidate

    def new_session(self) -> str:
        sid = str(uuid.uuid4())
        path = self._session_path(sid)
        os.makedirs(path, exist_ok=True)
        return sid

    def save_bytes(self, session_id: str, filename: str, content: bytes) -> str:
        path = self._session_path(session_id)
        os.makedirs(path, exist_ok=True)
        safe_name = os.path.basename(filename)
        full = os.path.join(path, safe_name)
        with open(full, 'wb') as f:
            f.write(content)
        return full

    def list_files(self, session_id: str) -> List[str]:
        path = self._session_path(session_id)
        if not os.path.isdir(path):
            return []
        return [os.path.join(path, p) for p in os.listdir(path) if os.path.isfile(os.path.join(path, p))]

    def delete_session(self, session_id: str) -> bool:
        path = self._session_path(session_id)
        if os.path.isdir(path):
            shutil.rmtree(path, ignore_errors=True)
            return True
        return False

    def cleanup_expired(self) -> int:
        """Remove sessions older than TTL; returns count removed."""
        removed = 0
        ttl = Config.SESSION_TTL
        now = self._now_utc()
        for sid in os.listdir(self.base_dir):
            spath = self._session_path(sid)
            try:
                mtime = datetime.fromtimestamp(os.path.getmtime(spath), tz=timezone.utc)
                if now - mtime > ttl:
                    shutil.rmtree(spath, ignore_errors=True)
                    removed += 1
            except Exception as e:
                log.warning(f"cleanup skip {sid}: {e}")
        if removed:
            log.info(f"Session cleanup removed {removed} dirs")
        return removed