from datetime import datetime

from sqlalchemy.orm import Session

from app.models.finished_goods import FinishedGoodsLocation
from app.schemas.location import LocationRequest


class DuplicateLocationError(Exception):
    """总排号已存在货位记录。"""

    def __init__(self, location_code: str, registered_at: str):
        self.location_code = location_code
        self.registered_at = registered_at


class AlreadyOffShelfError(Exception):
    """总排号已下架至转运区域。"""

    def __init__(self, location_code: str, registered_at: str):
        self.location_code = location_code
        self.registered_at = registered_at


def _is_transit_location(location_code: str) -> bool:
    return location_code.startswith("TRANS-")


def register_location(db: Session, req: LocationRequest) -> FinishedGoodsLocation:
    existing = (
        db.query(FinishedGoodsLocation)
        .filter(FinishedGoodsLocation.zongpai_no == req.zongpai_no)
        .first()
    )
    if existing:
        if _is_transit_location(existing.location_code):
            raise AlreadyOffShelfError(
                location_code=existing.location_code,
                registered_at=existing.created_at.isoformat(),
            )

        if _is_transit_location(req.location_code):
            previous_location = existing.location_code
            existing.location_code = req.location_code
            existing.created_at = datetime.now()
            db.commit()
            db.refresh(existing)
            existing.previous_location = previous_location
            return existing

        raise DuplicateLocationError(
            location_code=existing.location_code,
            registered_at=existing.created_at.isoformat(),
        )

    record = FinishedGoodsLocation(
        zongpai_no=req.zongpai_no,
        location_code=req.location_code,
    )
    db.add(record)
    db.commit()
    db.refresh(record)
    return record