"""附件：任务与知识条目共用一张表。

为什么不区分 kind：知识本身就是 `item`（kind=knowledge），附件挂在 `item_id` 上
天然对任务、工单、知识一视同仁；将来要给「工单」加验收材料也不用再建表。

文件本体放磁盘，库里只存元数据与 `storage_key`。这样做的代价是备份要同时备盘，
收益是数据库不会被几十 MB 的文件撑爆、备份与恢复的粒度还能分开。
"""

from __future__ import annotations

import uuid
from datetime import datetime

from sqlalchemy import (
    BigInteger,
    CheckConstraint,
    DateTime,
    ForeignKey,
    Index,
    String,
    func,
)
from sqlalchemy.dialects.postgresql import UUID as PgUUID
from sqlalchemy.orm import Mapped, mapped_column

from app.models import Base

ATTACHMENT_TENANT_TABLES = ("attachment",)


class Attachment(Base):
    __tablename__ = "attachment"
    __table_args__ = (
        CheckConstraint("size_bytes >= 0", name="ck_attachment_size"),
        Index("ix_attachment_ws_item", "workspace_id", "item_id", "created_at"),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
    )
    workspace_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True),
        ForeignKey("workspace.id", ondelete="CASCADE"),
        nullable=False,
    )
    item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True),
        ForeignKey("item.id", ondelete="CASCADE"),
        nullable=False,
    )
    uploader_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="RESTRICT"), nullable=False
    )
    # 原始文件名：只用于展示与下载时的 Content-Disposition，绝不参与磁盘路径
    filename: Mapped[str] = mapped_column(String(255), nullable=False)
    content_type: Mapped[str] = mapped_column(
        String(120), nullable=False, default="application/octet-stream"
    )
    size_bytes: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
    sha256: Mapped[str] = mapped_column(String(64), nullable=False)
    storage_key: Mapped[str] = mapped_column(String(255), nullable=False, unique=True)

    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), nullable=False
    )