"""分片上传会话实体。

一个会话对应一次「分片上传 + 拼接入库」流程：客户端创建会话拿到 upload_id，
逐片上传，最后 complete 触发服务端拼接、算 sha256、去重并落 DB。
"""

from __future__ import annotations

from datetime import datetime

from sqlalchemy import BigInteger, DateTime, JSON, String, func
from sqlalchemy.orm import Mapped, mapped_column

from ..database import Base


class UploadSession(Base):
    __tablename__ = "upload_session"

    id: Mapped[int] = mapped_column(BigInteger, primary_key=True, autoincrement=True)
    # 客户端持有的会话标识（uuid4().hex），服务端生成，防伪造路径
    upload_id: Mapped[str] = mapped_column(String(64), nullable=False, unique=True, index=True)
    filename: Mapped[str] = mapped_column(String(512), nullable=False)
    size_bytes: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
    chunk_size: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
    total_chunks: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
    # 已上传分片下标数组，例如 [0, 1, 3]；JSON 列
    uploaded_chunks: Mapped[list] = mapped_column(JSON, nullable=False, default=list)
    # complete 成功后指向 UploadedFile.id；失败/未完成时为 None
    file_id: Mapped[int | None] = mapped_column(BigInteger, nullable=True, default=None)
    # pending / completed
    status: Mapped[str] = mapped_column(String(32), nullable=False, default="pending")
    created_at: Mapped[datetime] = mapped_column(
        DateTime, server_default=func.now(), nullable=False
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime, server_default=func.now(), onupdate=func.now(), nullable=False
    )

    def __repr__(self) -> str:  # pragma: no cover
        return (
            f"<UploadSession upload_id={self.upload_id!r} "
            f"file={self.filename!r} status={self.status}>"
        )