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

from ..crud import product_tracking, resolve_product
from ..database import get_db
from ..deps import get_current_user
from ..models import CategoryTracking, Location, Lot, Movement, MovementType, Product, User
from ..schemas import (
    BatchCheckInRequest,
    BatchCheckInResponse,
    BulkLotLocation,
    CheckInRequest,
    CheckInResponse,
    CheckOutRequest,
    CheckOutResponse,
    LotOut,
    LotRow,
    LotSplit,
    LotUpdate,
    RelocateRequest,
    RemoveRequest,
    StockActionResponse,
)
from ..services.conversion import ConversionError, display_unit_info
from ..services.dates import clean_precision, normalize_best_before
from ..services.stock import (
    StockError,
    check_in,
    check_out,
    check_out_lot,
    consolidate_lot_group,
    current_stock,
    object_add,
    object_relocate,
    object_remove,
)

router = APIRouter(tags=["stock"])

OBJECT = CategoryTracking.object.value


@router.post("/stock/checkin", response_model=CheckInResponse)
def stock_checkin(
    payload: CheckInRequest,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> CheckInResponse:
    product = resolve_product(db, payload.product_id, payload.barcode)
    if product_tracking(db, product) == OBJECT:
        # Gegenstände: Menge am Lagerort erhöhen, kein MHD, keine Charge-Auswahl.
        lot = object_add(
            db,
            product=product,
            quantity=payload.quantity,
            location_id=payload.location_id,
            user=user,
            note=payload.note,
        )
        db.commit()
        db.refresh(lot)
        return CheckInResponse(
            lot=LotOut.model_validate(lot), product_stock=current_stock(db, product.id)
        )
    try:
        lot = check_in(
            db,
            product=product,
            quantity=payload.quantity,
            unit=payload.unit,
            best_before=payload.best_before,
            best_before_precision=payload.best_before_precision.value,
            location_id=payload.location_id,
            user=user,
            note=payload.note,
        )
    except ConversionError as exc:
        raise HTTPException(status.HTTP_400_BAD_REQUEST, str(exc)) from exc
    db.commit()
    db.refresh(lot)
    return CheckInResponse(
        lot=LotOut.model_validate(lot), product_stock=current_stock(db, product.id)
    )


@router.post("/stock/checkin/batch", response_model=BatchCheckInResponse)
def stock_checkin_batch(
    payload: BatchCheckInRequest,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> BatchCheckInResponse:
    """Mehrere Chargen desselben Produkts in einem Vorgang einlagern.

    Jede Zeile erzeugt eine eigene Charge mit eigener Menge und eigenem MHD –
    z.B. 5 Gläser mit unterschiedlichen Mindesthaltbarkeitsdaten.
    """
    product = resolve_product(db, payload.product_id, payload.barcode)
    lots: list[Lot] = []
    try:
        for line in payload.lines:
            lots.append(
                check_in(
                    db,
                    product=product,
                    quantity=line.quantity,
                    unit=payload.unit,
                    best_before=line.best_before,
                    best_before_precision=line.best_before_precision.value,
                    location_id=line.location_id,
                    user=user,
                    note=payload.note,
                )
            )
    except ConversionError as exc:
        db.rollback()
        raise HTTPException(status.HTTP_400_BAD_REQUEST, str(exc)) from exc
    db.commit()
    for lot in lots:
        db.refresh(lot)
    return BatchCheckInResponse(
        lots=[LotOut.model_validate(lot) for lot in lots],
        product_stock=current_stock(db, product.id),
    )


@router.post("/stock/checkout", response_model=CheckOutResponse)
def stock_checkout(
    payload: CheckOutRequest,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> CheckOutResponse:
    product = resolve_product(db, payload.product_id, payload.barcode)
    if product_tracking(db, product) == OBJECT:
        raise HTTPException(
            status.HTTP_400_BAD_REQUEST,
            "Gegenstände werden über „Entfernen“ (mit Grund) oder „Umlagern“ gebucht, "
            "nicht ausgecheckt.",
        )
    try:
        if payload.lot_id is not None:
            lot = db.get(Lot, payload.lot_id)
            if lot is None or lot.product_id != product.id:
                raise HTTPException(
                    status.HTTP_404_NOT_FOUND, "Charge gehört nicht zu diesem Produkt"
                )
            affected = check_out_lot(
                db,
                product=product,
                lot=lot,
                quantity=payload.quantity,
                unit=payload.unit,
                user=user,
                note=payload.note,
            )
        else:
            affected = check_out(
                db,
                product=product,
                quantity=payload.quantity,
                unit=payload.unit,
                user=user,
                note=payload.note,
            )
    except ConversionError as exc:
        raise HTTPException(status.HTTP_400_BAD_REQUEST, str(exc)) from exc
    except StockError as exc:
        raise HTTPException(status.HTTP_409_CONFLICT, str(exc)) from exc
    db.commit()
    return CheckOutResponse(
        affected_lots=affected, product_stock=current_stock(db, product.id)
    )


@router.post("/stock/relocate", response_model=StockActionResponse)
def stock_relocate(
    payload: RelocateRequest,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> StockActionResponse:
    """Gegenstands-Menge von einem Lagerort zum anderen umbuchen (ohne Grund)."""
    product = resolve_product(db, payload.product_id, payload.barcode)
    if product_tracking(db, product) != OBJECT:
        raise HTTPException(
            status.HTTP_400_BAD_REQUEST, "Umlagern gibt es nur für Gegenstände."
        )
    try:
        object_relocate(
            db,
            product=product,
            quantity=payload.quantity,
            from_location_id=payload.from_location_id,
            to_location_id=payload.to_location_id,
            user=user,
            note=payload.note,
        )
    except StockError as exc:
        raise HTTPException(status.HTTP_409_CONFLICT, str(exc)) from exc
    db.commit()
    return StockActionResponse(product_stock=current_stock(db, product.id))


@router.post("/stock/remove", response_model=StockActionResponse)
def stock_remove(
    payload: RemoveRequest,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> StockActionResponse:
    """Gegenstands-Menge mit Pflicht-Grund aus dem Bestand entfernen."""
    product = resolve_product(db, payload.product_id, payload.barcode)
    if product_tracking(db, product) != OBJECT:
        raise HTTPException(
            status.HTTP_400_BAD_REQUEST,
            "Entfernen mit Grund gibt es nur für Gegenstände.",
        )
    try:
        object_remove(
            db,
            product=product,
            quantity=payload.quantity,
            location_id=payload.location_id,
            reason=payload.reason.value,
            user=user,
            note=payload.note,
        )
    except StockError as exc:
        raise HTTPException(status.HTTP_409_CONFLICT, str(exc)) from exc
    db.commit()
    return StockActionResponse(product_stock=current_stock(db, product.id))


@router.get("/lots", response_model=list[LotOut])
def list_lots(
    product_id: int | None = None,
    db: Session = Depends(get_db),
    _: User = Depends(get_current_user),
) -> list[Lot]:
    query = db.query(Lot)
    if product_id is not None:
        query = query.filter(Lot.product_id == product_id)
    return query.order_by(Lot.best_before.is_(None), Lot.best_before).all()


@router.get("/lots/rows", response_model=list[LotRow])
def list_all_lots(
    db: Session = Depends(get_db),
    _: User = Depends(get_current_user),
) -> list[LotRow]:
    """Chargen der Charge-Artikel (Lebensmittel + Verbrauchsgegenstand) über alle
    Artikel – für die übergreifende Chargenliste. „Menge je Lagerort" und
    Einzelstücke gehören nicht hierher und werden übersprungen. Der Artikel wird
    eager geladen (kein N+1)."""
    lots = (
        db.query(Lot)
        .options(joinedload(Lot.product).joinedload(Product.category))
        .order_by(Lot.created_at.desc())
        .all()
    )
    rows: list[LotRow] = []
    for lot in lots:
        p = lot.product
        tracking = product_tracking(db, p)
        # Nur Charge-Artikel: Lebensmittel (food) oder Verbrauchsgegenstand (bulk).
        food_like = tracking != CategoryTracking.object.value or bool(p.bulk)
        if not food_like:
            continue
        name, factor = display_unit_info(p)
        rows.append(LotRow(
            id=lot.id, product_id=p.id, product_name=p.name, product_brand=p.brand,
            tracking=CategoryTracking(tracking),
            quantity=lot.quantity, base_unit=p.base_unit,
            package_size=p.package_size, package_label=p.package_label,
            unit_name=name, unit_factor=factor,
            best_before=lot.best_before, best_before_precision=lot.best_before_precision,
            location_id=lot.location_id, created_at=lot.created_at,
        ))
    return rows


@router.post("/lots/bulk-location", response_model=int)
def bulk_lot_location(
    payload: BulkLotLocation,
    db: Session = Depends(get_db),
    _: User = Depends(get_current_user),
) -> int:
    """Lagerort mehrerer Chargen auf einmal setzen (oder mit null leeren). Reine
    Ortsangabe – kein Umbuchen mit Bewegung. Gibt die Anzahl geänderter Zeilen."""
    if not payload.lot_ids:
        return 0
    if payload.location_id is not None and db.get(Location, payload.location_id) is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Lagerort nicht gefunden")
    n = (
        db.query(Lot)
        .filter(Lot.id.in_(payload.lot_ids))
        .update({Lot.location_id: payload.location_id}, synchronize_session=False)
    )
    db.flush()
    # Am Zielort entstandene Dubletten (gleicher Artikel + MHD) zusammenfassen.
    gruppen = (
        db.query(Lot.product_id, Lot.best_before, Lot.best_before_precision)
        .filter(Lot.id.in_(payload.lot_ids))
        .distinct()
        .all()
    )
    for product_id, best_before, precision in gruppen:
        consolidate_lot_group(db, product_id, best_before, precision, payload.location_id)
    db.commit()
    return n


@router.post("/lots/{lot_id}/split", response_model=LotOut)
def split_lot(
    lot_id: int,
    payload: LotSplit,
    db: Session = Depends(get_db),
    _: User = Depends(get_current_user),
) -> Lot:
    """Charge aufteilen: `quantity` (Basiseinheiten) abzweigen und als neue Charge
    mit gleichem MHD an einen anderen Lagerort legen. Der Rest bleibt in der alten
    Charge. Reine Umbuchung wie das Setzen des Lagerorts – kein Bewegungseintrag,
    der Gesamtbestand ändert sich nicht. Gibt die neu entstandene Charge zurück."""
    lot = db.get(Lot, lot_id)
    if lot is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Charge nicht gefunden")
    # Nur echt weniger als die Gesamtmenge lässt sich abteilen – die ganze Menge
    # zu verschieben ist Sache des Lagerort-Feldes, nicht des Aufteilens.
    if payload.quantity >= lot.quantity - 1e-9:
        raise HTTPException(
            status.HTTP_400_BAD_REQUEST,
            "So viel enthält die Charge nicht – zum kompletten Umlagern das "
            "Lagerort-Feld nutzen.",
        )
    if (payload.location_id or None) == (lot.location_id or None):
        raise HTTPException(
            status.HTTP_400_BAD_REQUEST,
            "Bitte einen anderen Lagerort als den aktuellen wählen.",
        )
    if payload.location_id is not None and db.get(Location, payload.location_id) is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Lagerort nicht gefunden")

    lot.quantity -= payload.quantity
    neu = Lot(
        product_id=lot.product_id,
        quantity=payload.quantity,
        best_before=lot.best_before,
        best_before_precision=lot.best_before_precision,
        location_id=payload.location_id,
    )
    db.add(neu)
    db.flush()
    # Liegt am Zielort schon eine Charge mit gleichem MHD, verschmelzen beide.
    survivor = consolidate_lot_group(
        db, lot.product_id, neu.best_before, neu.best_before_precision, payload.location_id
    )
    db.commit()
    db.refresh(survivor)
    return survivor


@router.patch("/lots/{lot_id}", response_model=LotOut)
def update_lot(
    lot_id: int,
    payload: LotUpdate,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> Lot:
    """Korrigiert eine Charge (Menge in Basiseinheiten, MHD, Lagerort)."""
    lot = db.get(Lot, lot_id)
    if lot is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Charge nicht gefunden")

    data = payload.model_dump(exclude_unset=True)

    # MHD und Genauigkeit hängen zusammen: Wird eines von beiden angefasst, muss
    # der gespeicherte Tag neu bestimmt werden (Monatsangabe = Monatsletzter).
    if "best_before" in data or "best_before_precision" in data:
        precision = (
            clean_precision(data["best_before_precision"])
            if "best_before_precision" in data
            else lot.best_before_precision
        )
        best_before = data["best_before"] if "best_before" in data else lot.best_before
        data["best_before"] = normalize_best_before(best_before, precision)
        data["best_before_precision"] = precision

    old_quantity = lot.quantity
    for field, value in data.items():
        setattr(lot, field, value)

    delta = lot.quantity - old_quantity
    if abs(delta) > 1e-9:
        db.add(
            Movement(
                product_id=lot.product_id,
                lot_id=lot.id,
                user_id=user.id,
                type=MovementType.adjust,
                quantity=delta,
                unit_used="base",
                note="Charge korrigiert",
            )
        )
    db.flush()
    # Ist die Charge durch die Änderung (Lagerort/MHD) zur Dublette einer anderen
    # geworden, werden beide zusammengefasst.
    survivor = consolidate_lot_group(
        db, lot.product_id, lot.best_before, lot.best_before_precision, lot.location_id
    )
    db.commit()
    db.refresh(survivor)
    return survivor


@router.delete("/lots/{lot_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_lot(
    lot_id: int,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
) -> None:
    """Entfernt eine Charge komplett aus dem Bestand."""
    lot = db.get(Lot, lot_id)
    if lot is None:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Charge nicht gefunden")
    db.add(
        Movement(
            product_id=lot.product_id,
            lot_id=None,
            user_id=user.id,
            type=MovementType.adjust,
            quantity=-lot.quantity,
            unit_used="base",
            note="Charge gelöscht",
        )
    )
    db.delete(lot)
    db.commit()