"""UploadSession 的 DAO。"""

from __future__ import annotations

from datetime import datetime, timedelta

from sqlalchemy import select
from sqlalchemy.orm import Session

from ..models.upload_session import UploadSession


class UploadSessionDAO:
    def __init__(self, db: Session) -> None:
        self.db = db

    def create(self, session: UploadSession) -> UploadSession:
        self.db.add(session)
        self.db.commit()
        self.db.refresh(session)
        return session

    def get_by_upload_id(self, upload_id: str) -> UploadSession | None:
        stmt = (
            select(UploadSession)
            .where(UploadSession.upload_id == upload_id)
            .limit(1)
        )
        return self.db.scalars(stmt).first()

    def mark_uploaded(self, session: UploadSession, chunks: list[int]) -> UploadSession:
        """更新已上传分片集合（整体替换，避免并发追加丢失）。"""
        session.uploaded_chunks = sorted(set(chunks))
        self.db.commit()
        self.db.refresh(session)
        return session

    def mark_completed(self, session: UploadSession, file_id: int) -> UploadSession:
        session.file_id = file_id
        session.status = "completed"
        self.db.commit()
        self.db.refresh(session)
        return session

    def list_stale(self, ttl_seconds: int) -> list[UploadSession]:
        """返回 pending 且 updated_at 早于 cutoff 的会话（被放弃的上传）。"""
        cutoff = datetime.now() - timedelta(seconds=ttl_seconds)
        stmt = (
            select(UploadSession)
            .where(UploadSession.status == "pending")
            .where(UploadSession.updated_at < cutoff)
        )
        return list(self.db.scalars(stmt).all())

    def delete(self, session: UploadSession) -> None:
        self.db.delete(session)
        self.db.commit()