from typing import TYPE_CHECKING
from sqlalchemy import Column, DateTime, String, ForeignKey, BigInteger
from sqlalchemy.sql import func
from .base import AutoID, Base

if TYPE_CHECKING:
    from .user import User
    from .workspace import Workspace

class LibraryItem(Base, AutoID):
    """工作区共享媒体/文件资源库"""
    __tablename__ = "library_items"

    workspace_id = Column(
        String(Workspace.id_length()),
        ForeignKey("workspaces.id", ondelete="CASCADE"),
        index=True,
    )
    # 自引用外键，支持无限级文件夹嵌套
    parent_id = Column(
        String(AutoID.id_length()),
        ForeignKey("library_items.id", ondelete="CASCADE"),
        nullable=True,
        index=True,
    )

    name = Column(String, nullable=False)
    # 节点类型：'folder' (文件夹) 或 'file' (真实文件)
    item_type = Column(String, default="file", nullable=False)

    # --- 以下为真实文件（item_type='file'）的核心字段 ---
    s3_key = Column(String, nullable=True)         # S3 中的 Object Key
    file_size = Column(BigInteger, nullable=True)  # 文件大小（字节数 Bytes），用于统计容量占用
    mime_type = Column(String, nullable=True)      # 媒体类型，例如 'image/jpeg', 'video/mp4', 'application/pdf'
    
    uploaded_by = Column(
        String(User.id_length()),
        ForeignKey("users.id", ondelete="SET NULL"),
        nullable=True,
    )
    created_at = Column(DateTime(timezone=True), server_default=func.now())