# services/shape_loader.py
"""按 task_id 从持久化存储重建 OCC 几何形状。

任务完成后 TopoDS_Shape 不驻留内存/Redis（原生内存与体积原因），
需要几何的端点（倒扣检测、按需重导出等）通过 STP 原件重建：
PG(object_key) -> RustFS 下载 -> 临时文件 -> OCC 单线程 executor 解析。
"""
import tempfile
from pathlib import Path
from typing import Optional

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from shared.models.database import ProcessingTask, STPFile
from shared.utils.logger import get_logger

logger = get_logger(__name__)


class ShapeLoader:
    """任务几何重建器"""

    def __init__(self):
        from moldinsight.core.stp_parser import STPParser
        from moldinsight.services.processing_service import processing_service

        self._parser = STPParser()
        self._processing = processing_service

    async def load_shape_for_task(
        self, db_session: AsyncSession, task_id: str
    ) -> Optional["object"]:
        """重建任务的产品几何。任务不存在或 STP 原件不可用时返回 None。"""
        result = await db_session.execute(
            select(ProcessingTask, STPFile)
            .join(STPFile, ProcessingTask.stp_file_id == STPFile.id)
            .where(ProcessingTask.task_id == task_id)
        )
        row = result.first()
        if not row:
            logger.warning(f"几何重建失败：任务不存在 {task_id}")
            return None

        _, stp_file = row
        if not stp_file.object_key:
            logger.warning(f"几何重建失败：任务缺少 object_key {task_id}")
            return None

        from moldinsight.storage.rustfs_storage import rustfs_manager

        try:
            data = await rustfs_manager.download_file(
                file_type="stp_files", object_key=stp_file.object_key
            )
        except Exception as exc:
            logger.error(f"几何重建失败：STP 原件下载失败 {task_id}: {exc}")
            return None

        with tempfile.NamedTemporaryFile(suffix=".stp", delete=False) as tmp:
            tmp.write(data)
            tmp_path = Path(tmp.name)

        try:
            shape = await self._processing.run_occ(
                self._parser.load_step_file, tmp_path
            )
            return shape
        except Exception as exc:
            logger.error(f"几何重建失败：STP 解析失败 {task_id}: {exc}")
            return None
        finally:
            try:
                tmp_path.unlink(missing_ok=True)
            except Exception:
                pass


# 惰性单例：__init__ 会实例化 STPParser 并校验 OCC 可用性，
# 延迟到首次真实使用，避免模块导入期失败拖垮路由加载
_shape_loader: Optional[ShapeLoader] = None


def get_shape_loader() -> ShapeLoader:
    global _shape_loader
    if _shape_loader is None:
        _shape_loader = ShapeLoader()
    return _shape_loader