from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy import func
from sqlalchemy.orm import Session

from ..database import get_db
from ..deps import get_current_user, require_admin
from ..models import Group, Product, Unit, User
from ..schemas import UnitCreate, UnitOut, UnitUpdate

router = APIRouter(prefix="/units", tags=["units"])


@router.get("", response_model=list[UnitOut])
def list_units(
    db: Session = Depends(get_db), _: User = Depends(get_current_user)
) -> list[Unit]:
    return db.query(Unit).order_by(Unit.kind, Unit.factor).all()


@router.post("", response_model=UnitOut, status_code=status.HTTP_201_CREATED)
def create_unit(
    payload: UnitCreate,
    db: Session = Depends(get_db),
    _: User = Depends(require_admin),
) -> Unit:
    exists = db.query(Unit).filter(func.lower(Unit.name) == payload.name.lower()).first()
    if exists:
        raise HTTPException(status.HTTP_409_CONFLICT, "Einheit existiert bereits")
    unit = Unit(name=payload.name, kind=payload.kind, factor=payload.factor, is_builtin=False)
    db.add(unit)
    db.commit()
    db.refresh(unit)
    return unit


@router.patch("/{unit_id}", response_model=UnitOut)
def update_unit(
    unit_id: int,
    payload: UnitUpdate,
    db: Session = Depends(get_db),
    _: User = Depends(require_admin),
) -> Unit:
    """Umbenennen – auch bei eingebauten Einheiten, wie bei den Gebinden.
    Produkte und Gruppen verweisen ueber die ID und bleiben unberuehrt."""
    unit = db.get(Unit, unit_id)
    if unit is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Einheit nicht gefunden")

    name = payload.name.strip()
    doppelt = (
        db.query(Unit)
        .filter(func.lower(Unit.name) == name.lower(), Unit.id != unit_id)
        .first()
    )
    if doppelt is not None:
        raise HTTPException(status.HTTP_409_CONFLICT, "Einheit existiert bereits")

    unit.name = name
    db.commit()
    db.refresh(unit)
    return unit


@router.delete("/{unit_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_unit(
    unit_id: int,
    db: Session = Depends(get_db),
    _: User = Depends(require_admin),
) -> None:
    unit = db.get(Unit, unit_id)
    if unit is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Einheit nicht gefunden")
    if unit.is_builtin:
        raise HTTPException(status.HTTP_400_BAD_REQUEST, "Eingebaute Einheiten können nicht gelöscht werden")
    in_use = (
        db.query(Product).filter(Product.display_unit_id == unit_id).first()
        or db.query(Group).filter(Group.min_stock_unit_id == unit_id).first()
    )
    if in_use:
        raise HTTPException(
            status.HTTP_409_CONFLICT, "Einheit wird noch von Produkten/Gruppen verwendet"
        )
    db.delete(unit)
    db.commit()