"""分片上传会话 ORM：支撑断点续传。对齐 server 的 UploadSession 形态（SQLite 版）。"""

from __future__ import annotations

import json
from datetime import datetime, timezone
from typing import Any

from sqlalchemy import DateTime, ForeignKey, Integer, String, Text, TypeDecorator
from sqlalchemy.orm import Mapped, mapped_column

from ..database import Base


def _now() -> datetime:
    return datetime.now(timezone.utc)


class _IntList(TypeDecorator):
    """把 list[int] 存成 JSON 字符串。SQLite 没有 ARRAY 类型。"""

    impl = Text
    cache_ok = True

    def process_bind_param(self, value: Any, dialect) -> str | None:
        return json.dumps(value) if value is not None else None

    def process_result_value(self, value: Any, dialect) -> list[int]:
        return json.loads(value) if value else []


class UploadSession(Base):
    __tablename__ = "upload_session"

    upload_id: Mapped[str] = mapped_column(String(64), primary_key=True)
    filename: Mapped[str] = mapped_column(String(512), nullable=False)
    size_bytes: Mapped[int] = mapped_column(Integer, nullable=False)
    chunk_size: Mapped[int] = mapped_column(Integer, nullable=False)
    total_chunks: Mapped[int] = mapped_column(Integer, nullable=False)
    uploaded_chunks: Mapped[list[int]] = mapped_column(_IntList, default=list)
    # pending → completed（complete 成功）| abandoned（reaper 清理）
    status: Mapped[str] = mapped_column(String(32), nullable=False, default="pending")
    # 拼接完成后的视频相对 upload_dir 路径
    final_path: Mapped[str | None] = mapped_column(String(1024), nullable=True)
    # complete 后关联的 Task.id（直接引用，避免反向查找 source_path）
    task_id: Mapped[int | None] = mapped_column(ForeignKey("task.id"), nullable=True)

    created_at: Mapped[datetime] = mapped_column(DateTime, default=_now)
    updated_at: Mapped[datetime] = mapped_column(DateTime, default=_now, onupdate=_now)