Vorrania/backend/app/services/stock.py

"""Chargen-Logik: Einlagern erzeugt Lots, Auslagern bucht per FEFO ab."""

from __future__ import annotations

from datetime import date

from sqlalchemy import asc
from sqlalchemy.orm import Session

from ..models import (
    DatePrecision,
    Item,
    Location,
    Lot,
    Movement,
    MovementType,
    Product,
    User,
)
from .conversion import to_base
from .dates import clean_precision, normalize_best_before


class StockError(ValueError):
    """Fachlicher Fehler beim Ein-/Auslagern (z.B. zu wenig Bestand)."""


# ---------------------------------------------------------------------------
# Gegenstände (Non-Food): Menge je Lagerort statt Chargen mit MHD.
#
# Technisch wird dieselbe Lot-Tabelle genutzt – je (Produkt, Lagerort) genau
# eine Zeile mit ``best_before = NULL``. So laufen Bestands-Summe, Bewegungslog
# und Export unverändert weiter; nur MHD/FEFO entfällt. Die Lebensmittel-Logik
# oben (check_in/check_out) bleibt davon unberührt.
# ---------------------------------------------------------------------------

def _object_lot(db: Session, product_id: int, location_id: str | None) -> Lot | None:
    """Die (einzige) Bestandszeile eines Gegenstands an einem Lagerort."""
    query = db.query(Lot).filter(
        Lot.product_id == product_id, Lot.best_before.is_(None)
    )
    if location_id is None:
        query = query.filter(Lot.location_id.is_(None))
    else:
        query = query.filter(Lot.location_id == location_id)
    return query.first()


def object_add(
    db: Session,
    product: Product,
    quantity: float,
    location_id: str | None,
    user: User | None,
    note: str | None = None,
) -> Lot:
    """Erhöht die Menge eines Gegenstands an einem Lagerort."""
    lot = _object_lot(db, product.id, location_id)
    if lot is None:
        lot = Lot(
            product_id=product.id,
            quantity=0.0,
            best_before=None,
            best_before_precision=DatePrecision.day.value,
            location_id=location_id,
        )
        db.add(lot)
        db.flush()
    lot.quantity += quantity
    db.add(
        Movement(
            product_id=product.id,
            lot_id=lot.id,
            user_id=user.id if user else None,
            type=MovementType.in_,
            quantity=quantity,
            unit_used=product.base_unit.value,
            note=note,
            location_id=location_id,
        )
    )
    return lot


def object_remove(
    db: Session,
    product: Product,
    quantity: float,
    location_id: str | None,
    reason: str,
    user: User | None,
    note: str | None = None,
) -> None:
    """Entfernt eine Menge mit Grund (verloren/kaputt/…) aus dem Bestand."""
    lot = _object_lot(db, product.id, location_id)
    have = lot.quantity if lot else 0.0
    if quantity > have + 1e-9:
        raise StockError(
            f"Am Lagerort sind nur {have:g} {product.base_unit.value} vorhanden "
            f"(benötigt {quantity:g})."
        )
    lot.quantity -= quantity
    db.add(
        Movement(
            product_id=product.id,
            lot_id=lot.id,
            user_id=user.id if user else None,
            type=MovementType.out,
            quantity=quantity,
            unit_used=product.base_unit.value,
            note=note,
            location_id=location_id,
            reason=reason,
        )
    )
    if lot.quantity <= 1e-9:
        db.delete(lot)


def object_relocate(
    db: Session,
    product: Product,
    quantity: float,
    from_location_id: str | None,
    to_location_id: str | None,
    user: User | None,
    note: str | None = None,
) -> None:
    """Bucht eine Menge von einem Lagerort zum anderen um (ohne Grund)."""
    if from_location_id == to_location_id:
        raise StockError("Quell- und Ziel-Lagerort sind identisch.")
    src = _object_lot(db, product.id, from_location_id)
    have = src.quantity if src else 0.0
    if quantity > have + 1e-9:
        raise StockError(
            f"Am Quell-Lagerort sind nur {have:g} {product.base_unit.value} "
            f"vorhanden (benötigt {quantity:g})."
        )
    beleg = note or "Umlagerung"
    src.quantity -= quantity
    # Als neutrale Korrektur (adjust) protokollieren, damit Umlagerungen die
    # Ein-/Auslager-Statistiken nicht verfälschen.
    db.add(
        Movement(
            product_id=product.id,
            lot_id=src.id,
            user_id=user.id if user else None,
            type=MovementType.adjust,
            quantity=-quantity,
            unit_used=product.base_unit.value,
            note=beleg,
            location_id=from_location_id,
        )
    )
    if src.quantity <= 1e-9:
        db.delete(src)

    dest = _object_lot(db, product.id, to_location_id)
    if dest is None:
        dest = Lot(
            product_id=product.id,
            quantity=0.0,
            best_before=None,
            best_before_precision=DatePrecision.day.value,
            location_id=to_location_id,
        )
        db.add(dest)
        db.flush()
    dest.quantity += quantity
    db.add(
        Movement(
            product_id=product.id,
            lot_id=dest.id,
            user_id=user.id if user else None,
            type=MovementType.adjust,
            quantity=quantity,
            unit_used=product.base_unit.value,
            note=beleg,
            location_id=to_location_id,
        )
    )


def removal_stats(db: Session, product_id: int) -> dict[str, dict]:
    """Entnahmen je Grund summieren: {reason: {quantity, count}}."""
    rows = (
        db.query(Movement)
        .filter(
            Movement.product_id == product_id,
            Movement.type == MovementType.out,
            Movement.reason.isnot(None),
        )
        .all()
    )
    stats: dict[str, dict] = {}
    for m in rows:
        eintrag = stats.setdefault(m.reason, {"quantity": 0.0, "count": 0})
        eintrag["quantity"] += m.quantity
        eintrag["count"] += 1
    return stats


def current_stock(db: Session, product_id: int) -> float:
    """Bestand eines Produkts (in Basiseinheiten).

    Einzelstück-Produkte zählen die Anzahl ihrer Items, alle anderen summieren
    die Lot-Mengen.
    """
    product = db.get(Product, product_id)
    if product is not None and product.individual:
        return float(db.query(Item).filter(Item.product_id == product_id).count())
    total = (
        db.query(Lot).with_entities(Lot.quantity).filter(Lot.product_id == product_id).all()
    )
    return float(sum(q for (q,) in total))


def location_stock_base(db: Session, product: Product, location_id: str) -> float:
    """Bestand eines Produkts an EINEM Lagerort (in Basiseinheiten).

    Einzelstücke zählen die Items an diesem Ort, sonst werden die Lot-Mengen des
    Ortes summiert.
    """
    if product.individual:
        return float(
            db.query(Item)
            .filter(Item.product_id == product.id, Item.location_id == location_id)
            .count()
        )
    total = (
        db.query(Lot.quantity)
        .filter(Lot.product_id == product.id, Lot.location_id == location_id)
        .all()
    )
    return float(sum(q for (q,) in total))


def descendant_location_ids(db: Session, location_id: str) -> set[str]:
    """Alle Unter-Lagerorte (rekursiv) eines Lagerorts."""
    result: set[str] = set()
    stack = [location_id]
    while stack:
        cur = stack.pop()
        for (lid,) in db.query(Location.id).filter(Location.parent_id == cur).all():
            if lid not in result:
                result.add(lid)
                stack.append(lid)
    return result


def location_subtree_stock_base(db: Session, product: Product, location_id: str) -> float:
    """Bestand an einem Lagerort INKL. aller Unter-Lagerorte (Basiseinheiten).

    So gilt ein Mindestbestand auf „Hedingen" als gedeckt, wenn der Vorrat
    irgendwo darunter liegt (z.B. „Hedingen → Keller").
    """
    ids = {location_id} | descendant_location_ids(db, location_id)
    return float(sum(location_stock_base(db, product, lid) for lid in ids))


def check_in(
    db: Session,
    product: Product,
    quantity: float,
    unit: str,
    best_before: date | None,
    location_id: str | None,
    user: User | None,
    note: str | None = None,
    best_before_precision: str | None = DatePrecision.day.value,
) -> Lot:
    """Legt eine neue Charge an und protokolliert die Bewegung.

    Ist nur Monat/Jahr angegeben, wird das MHD auf den Monatsletzten gelegt;
    die Genauigkeit wird an der Charge vermerkt, damit die Anzeige "09/2026"
    statt "30.09.2026" schreiben kann.
    """
    quantity_base = to_base(db, product, quantity, unit)
    precision = clean_precision(best_before_precision)

    lot = Lot(
        product_id=product.id,
        quantity=quantity_base,
        best_before=normalize_best_before(best_before, precision),
        best_before_precision=precision,
        location_id=location_id,
    )
    db.add(lot)
    db.flush()  # lot.id verfügbar machen

    db.add(
        Movement(
            product_id=product.id,
            lot_id=lot.id,
            user_id=user.id if user else None,
            type=MovementType.in_,
            quantity=quantity_base,
            unit_used=unit,
            note=note,
        )
    )
    return lot


def check_out_lot(
    db: Session,
    product: Product,
    lot: Lot,
    quantity: float,
    unit: str,
    user: User | None,
    note: str | None = None,
) -> list[dict]:
    """Bucht gezielt von EINER Charge ab (manuelle Auswahl statt FEFO)."""
    needed = to_base(db, product, quantity, unit)
    if needed > lot.quantity + 1e-9:
        raise StockError(
            f"Diese Charge hat nur {lot.quantity:g} {product.base_unit.value} "
            f"(benötigt {needed:g})."
        )

    lot.quantity -= needed
    db.add(
        Movement(
            product_id=product.id,
            lot_id=lot.id,
            user_id=user.id if user else None,
            type=MovementType.out,
            quantity=needed,
            unit_used=unit,
            note=note,
        )
    )
    affected = [{"lot_id": lot.id, "quantity": needed}]
    if lot.quantity <= 1e-9:
        db.delete(lot)
    return affected


def _fefo_lots(db: Session, product_id: int) -> list[Lot]:
    """Lots eines Produkts, sortiert nach Ablaufdatum (NULL zuletzt), dann Alter."""
    lots = (
        db.query(Lot)
        .filter(Lot.product_id == product_id, Lot.quantity > 0)
        .order_by(asc(Lot.created_at))
        .all()
    )
    # NULL-best_before ans Ende (nach Datum aufsteigend). In Python sortieren, damit
    # es über SQLite und Postgres identisch funktioniert.
    return sorted(
        lots,
        key=lambda lot: (lot.best_before is None, lot.best_before or date.max, lot.id),
    )


def check_out(
    db: Session,
    product: Product,
    quantity: float,
    unit: str,
    user: User | None,
    note: str | None = None,
) -> list[dict]:
    """Bucht ``quantity`` (in ``unit``) per FEFO von den Chargen ab.

    Gibt die Liste der betroffenen Chargen mit abgebuchter Menge zurück.
    Wirft StockError, wenn der Gesamtbestand nicht ausreicht.
    """
    needed = to_base(db, product, quantity, unit)
    available = current_stock(db, product.id)
    if needed > available + 1e-9:
        raise StockError(
            f"Nicht genug Bestand: benötigt {needed:g}, verfügbar {available:g} "
            f"{product.base_unit.value}"
        )

    affected: list[dict] = []
    remaining = needed
    for lot in _fefo_lots(db, product.id):
        if remaining <= 1e-9:
            break
        take = min(lot.quantity, remaining)
        lot.quantity -= take
        remaining -= take

        db.add(
            Movement(
                product_id=product.id,
                lot_id=lot.id,
                user_id=user.id if user else None,
                type=MovementType.out,
                quantity=take,
                unit_used=unit,
                note=note,
            )
        )
        affected.append({"lot_id": lot.id, "quantity": take})

        # Leere Charge entfernen, damit das "MHD-Array" sauber bleibt.
        if lot.quantity <= 1e-9:
            db.delete(lot)

    return affected