certain/backend/app/models.py

"""SQLAlchemy-Modelle.

Konventionen (wie in der Vorlage): ``Mapped[...] = mapped_column(...)``, Geld als
Ganzzahl in Cent/Rappen, Enums als kurze VARCHAR-Strings (``native_enum=False``,
ohne DB-CHECK) – das hält Alembic auf SQLite einfach.

Phase 0 umfasst nur Benutzer, Sitzungen und Benutzer-Einstellungen. Fachliche
Tabellen (Konten, Kategorien, Transaktionen, Budget …) kommen in späteren Phasen
hinzu und werden dann alle über ``owner_id`` je Benutzer getrennt.
"""

from __future__ import annotations

import enum
# date/time unter Alias, weil es Spalten namens "date"/"time" gibt, die die
# gleichnamigen Typen sonst in den (späten) Annotationen beschatten.
from datetime import date as date_t, datetime, time as time_t, timezone

from sqlalchemy import (
    Boolean,
    Date,
    DateTime,
    Enum as SAEnum,
    ForeignKey,
    Integer,
    Numeric,
    String,
    Text,
    Time,
    UniqueConstraint,
)
from sqlalchemy.orm import Mapped, mapped_column, relationship

from .database import Base


def _now() -> datetime:
    return datetime.now(timezone.utc)


def _enum(enum_cls: type[enum.Enum]):
    """Enum als VARCHAR ohne DB-CHECK – Alembic-freundlich auf SQLite."""
    return SAEnum(enum_cls, native_enum=False, create_constraint=False, length=32)


class Role(str, enum.Enum):
    admin = "admin"
    user = "user"


class AccountType(str, enum.Enum):
    girokonto = "girokonto"
    sparkonto = "sparkonto"
    bargeld = "bargeld"
    kreditkarte = "kreditkarte"
    depot = "depot"
    sonstiges = "sonstiges"


# Kontotypen, deren Ziel-Transfer standardmäßig als budgetierte Ausgabe zählt
# (Sparen/Investment). Andere Transfers sind budgetneutral.
SAVINGS_ACCOUNT_TYPES = {AccountType.sparkonto, AccountType.depot}


class IdentifierKind(str, enum.Enum):
    iban = "iban"
    account_no = "account_no"
    card_no = "card_no"
    text = "text"  # freier Erkennungs-Text im Buchungstext (Zielkonto bei Transfers)


class CategoryKind(str, enum.Enum):
    income = "income"
    expense = "expense"


class TxnType(str, enum.Enum):
    expense = "expense"
    income = "income"
    transfer = "transfer"


class BudgetTreatment(str, enum.Enum):
    budgeted = "budgeted"
    neutral = "neutral"


class AmountMode(str, enum.Enum):
    """Wie der Betrag in der CSV steht."""
    signed = "signed"              # eine Spalte, mit Vorzeichen (− = Ausgabe)
    debit_credit = "debit_credit"  # getrennte Soll-/Haben-Spalten
    abs_expense = "abs_expense"     # Betrag ohne Vorzeichen, immer Ausgabe


class MatchField(str, enum.Enum):
    payee = "payee"
    purpose = "purpose"
    any = "any"  # trifft, wenn das Muster im Empfänger ODER im Zweck vorkommt


class RuleSource(str, enum.Enum):
    learned = "learned"  # automatisch aus bestätigten Zuordnungen gelernt
    manual = "manual"    # vom Nutzer als Schlagwort angelegt


class ImportStatus(str, enum.Enum):
    committed = "committed"
    undone = "undone"


class User(Base):
    __tablename__ = "users"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    username: Mapped[str] = mapped_column(String(64), unique=True, nullable=False)
    password_hash: Mapped[str] = mapped_column(String(255), nullable=False)
    role: Mapped[Role] = mapped_column(_enum(Role), nullable=False, default=Role.user)
    display_name: Mapped[str | None] = mapped_column(String(120), nullable=True)
    is_active: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
    # Vom Admin mit Temporär-Passwort angelegt: beim ersten Login ändern lassen.
    must_change_password: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    # Warum der Wechsel fällig ist: "temp" (Admin-Passwort) oder "policy"
    # (Richtlinie wurde verschärft). Steuert nur den Hinweistext.
    must_change_password_reason: Mapped[str | None] = mapped_column(String(16), nullable=True)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)

    # --- Zwei-Faktor (TOTP) ---
    # Das Secret liegt im Klartext. Verschlüsseln brächte hier nichts: der
    # Schlüssel läge auf derselben Maschine wie die Datenbank. Wer die DB-Datei
    # hat, hätte dann auch den Schlüssel. Schutz kommt aus Dateirechten.
    totp_secret: Mapped[str | None] = mapped_column(String(64), nullable=True)
    totp_enabled: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    totp_confirmed_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    # Zuletzt verbrauchtes 30-Sekunden-Zeitfenster – verhindert, dass derselbe
    # Code innerhalb seiner Gültigkeit ein zweites Mal benutzt wird.
    totp_last_step: Mapped[int | None] = mapped_column(Integer, nullable=True)

    sessions: Mapped[list[Session]] = relationship(
        back_populates="user", cascade="all, delete-orphan"
    )
    settings: Mapped[list[UserSetting]] = relationship(
        back_populates="user", cascade="all, delete-orphan"
    )
    recovery_codes: Mapped[list[RecoveryCode]] = relationship(
        back_populates="user", cascade="all, delete-orphan"
    )


class Session(Base):
    """Server-seitige Sitzung. Im Cookie liegt nur das Klartext-Token, hier der Hash."""

    __tablename__ = "sessions"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    user_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    token_hash: Mapped[str] = mapped_column(String(64), unique=True, nullable=False, index=True)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
    expires_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
    last_seen_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    user_agent: Mapped[str | None] = mapped_column(String(255), nullable=True)
    # Passwort stimmt, der zweite Faktor fehlt noch. Solche Sitzungen gelten
    # nirgends als angemeldet (siehe services/sessions.validate) und laufen
    # nach wenigen Minuten ab.
    pending_2fa: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    failed_2fa: Mapped[int] = mapped_column(Integer, nullable=False, default=0)

    user: Mapped[User] = relationship(back_populates="sessions")


class RecoveryCode(Base):
    """Einmal-Wiederherstellungscode für den Fall eines verlorenen Authenticators.

    Gespeichert wird nur der SHA-256-Hash. Bewusst nicht Argon2: die Codes sind
    zufällig und hochentrop, und pro Prüfung stünden bis zu zehn Kandidaten an.
    """

    __tablename__ = "recovery_codes"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    user_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    code_hash: Mapped[str] = mapped_column(String(64), nullable=False, index=True)
    used_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)

    user: Mapped[User] = relationship(back_populates="recovery_codes")


class AppSetting(Base):
    """Globale, vom Admin gepflegte Einstellungen – im Gegensatz zu
    ``user_settings`` bewusst ohne ``owner_id``. Beherbergt heute die
    Passwortrichtlinie (siehe ``services/policy``)."""

    __tablename__ = "app_settings"

    key: Mapped[str] = mapped_column(String(64), primary_key=True)
    value: Mapped[str | None] = mapped_column(String(255), nullable=True)


class UserSetting(Base):
    """Freie Schlüssel-Wert-Einstellungen je Benutzer.

    Bekannte Schlüssel: ``base_currency`` (EUR|CHF), ``budget_start_day`` (int),
    ``locale`` (de|en), ``theme`` (system|light|dark), ``date_format``.
    """

    __tablename__ = "user_settings"

    user_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), primary_key=True
    )
    key: Mapped[str] = mapped_column(String(64), primary_key=True)
    value: Mapped[str | None] = mapped_column(String(255), nullable=True)

    user: Mapped[User] = relationship(back_populates="settings")


# ---------------------------------------------------------------------------
# Phase 1: Konten, Kategorien, Transaktionen, Wechselkurse
# Alle fachlichen Tabellen tragen owner_id und werden nur owner-gescoped gelesen.
# ---------------------------------------------------------------------------


class Account(Base):
    __tablename__ = "accounts"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    name: Mapped[str] = mapped_column(String(120), nullable=False)
    type: Mapped[AccountType] = mapped_column(_enum(AccountType), nullable=False, default=AccountType.girokonto)
    currency: Mapped[str] = mapped_column(String(3), nullable=False, default="EUR")
    icon: Mapped[str] = mapped_column(String(40), nullable=False, default="wallet")
    color: Mapped[str] = mapped_column(String(9), nullable=False, default="#3f51b5")
    opening_balance_cents: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    opening_date: Mapped[date_t | None] = mapped_column(Date, nullable=True)
    is_archived: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    position: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now, onupdate=_now)

    identifiers: Mapped[list[AccountIdentifier]] = relationship(
        back_populates="account", cascade="all, delete-orphan"
    )


class AccountIdentifier(Base):
    """Erkennungsmerkmal eines Kontos (IBAN/Kontonummer/Kartennummer) für die
    Transfer-Erkennung beim Import. ``value_norm`` ist die normalisierte Form."""

    __tablename__ = "account_identifiers"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    account_id: Mapped[int] = mapped_column(
        ForeignKey("accounts.id", ondelete="CASCADE"), nullable=False, index=True
    )
    kind: Mapped[IdentifierKind] = mapped_column(_enum(IdentifierKind), nullable=False, default=IdentifierKind.iban)
    value: Mapped[str] = mapped_column(String(64), nullable=False)
    value_norm: Mapped[str] = mapped_column(String(64), nullable=False, index=True)

    account: Mapped[Account] = relationship(back_populates="identifiers")

    __table_args__ = (
        UniqueConstraint("account_id", "kind", "value_norm", name="uq_ident_account_kind_value"),
    )


class CategoryGroup(Base):
    __tablename__ = "category_groups"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    name: Mapped[str] = mapped_column(String(120), nullable=False)
    kind: Mapped[CategoryKind] = mapped_column(_enum(CategoryKind), nullable=False, default=CategoryKind.expense)
    icon: Mapped[str] = mapped_column(String(40), nullable=False, default="list")
    color: Mapped[str] = mapped_column(String(9), nullable=False, default="#6b7480")
    position: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    is_builtin: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)

    categories: Mapped[list[Category]] = relationship(
        back_populates="group", cascade="all, delete-orphan"
    )


class Category(Base):
    __tablename__ = "categories"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    group_id: Mapped[int] = mapped_column(
        ForeignKey("category_groups.id", ondelete="CASCADE"), nullable=False, index=True
    )
    name: Mapped[str] = mapped_column(String(120), nullable=False)
    type: Mapped[CategoryKind] = mapped_column(_enum(CategoryKind), nullable=False, default=CategoryKind.expense)
    icon: Mapped[str] = mapped_column(String(40), nullable=False, default="more-horizontal")
    color: Mapped[str] = mapped_column(String(9), nullable=False, default="#6b7480")
    position: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    is_builtin: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    is_archived: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)

    group: Mapped[CategoryGroup] = relationship(back_populates="categories")


class Transaction(Base):
    __tablename__ = "transactions"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    type: Mapped[TxnType] = mapped_column(_enum(TxnType), nullable=False)
    date: Mapped[date_t] = mapped_column(Date, nullable=False, index=True)
    time: Mapped[time_t | None] = mapped_column(Time, nullable=True)

    account_id: Mapped[int] = mapped_column(
        ForeignKey("accounts.id", ondelete="CASCADE"), nullable=False, index=True
    )
    to_account_id: Mapped[int | None] = mapped_column(
        ForeignKey("accounts.id", ondelete="CASCADE"), nullable=True, index=True
    )

    # Betrag in Kontowährung (bei Transfers: abgebuchter Betrag vom Quellkonto).
    amount_cents: Mapped[int] = mapped_column(Integer, nullable=False)
    # Nur bei währungsübergreifenden Transfers: gutgeschriebener Betrag am Zielkonto.
    to_amount_cents: Mapped[int | None] = mapped_column(Integer, nullable=True)
    # Manuell gesetzter Kurs (Kontowährung je 1 EUR); überschreibt den EZB-Kurs.
    fx_rate: Mapped[float | None] = mapped_column(Numeric(18, 8), nullable=True)
    # Eingefrorener EUR-Wert von amount_cents zum Buchungsdatum (Pivot für Budget/Dashboard).
    amount_eur_cents: Mapped[int] = mapped_column(Integer, nullable=False, default=0)

    category_id: Mapped[int | None] = mapped_column(
        ForeignKey("categories.id", ondelete="SET NULL"), nullable=True, index=True
    )
    # Übersteuert die Standard-Regel für Sparen/Depot-Transfers (budgeted|neutral).
    budget_treatment: Mapped[BudgetTreatment | None] = mapped_column(_enum(BudgetTreatment), nullable=True)
    # Kategorie, gegen die ein budgetierter Transfer zählt (Sparen/Investment).
    budget_category_id: Mapped[int | None] = mapped_column(
        ForeignKey("categories.id", ondelete="SET NULL"), nullable=True
    )

    payee: Mapped[str | None] = mapped_column(String(255), nullable=True)
    description: Mapped[str | None] = mapped_column(String(255), nullable=True)
    notes: Mapped[str | None] = mapped_column(Text, nullable=True)

    # Import (Phase 4): Herkunft für Undo und Duplikaterkennung.
    import_batch_id: Mapped[int | None] = mapped_column(
        ForeignKey("import_batches.id", ondelete="SET NULL"), nullable=True, index=True
    )
    import_hash: Mapped[str | None] = mapped_column(String(64), nullable=True, index=True)

    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now, onupdate=_now)


class ExchangeRate(Base):
    """EZB-Referenzkurs: wie viele Einheiten der Währung ein Euro wert war.

    EUR ist implizit 1.0 (keine Zeile). In der Praxis nur CHF. Nicht owner-gescoped
    (öffentliche Referenzdaten)."""

    __tablename__ = "exchange_rates"

    date: Mapped[date_t] = mapped_column(Date, primary_key=True)
    currency: Mapped[str] = mapped_column(String(3), primary_key=True)
    rate_per_eur: Mapped[float] = mapped_column(Numeric(18, 8), nullable=False)
    source: Mapped[str] = mapped_column(String(16), nullable=False, default="ecb")


# ---------------------------------------------------------------------------
# Phase 2: Budget (ein Standard-Budget als Vorlage + Monats-Overrides)
# Planned-Beträge sind in der Hauptwährung des Nutzers.
# ---------------------------------------------------------------------------


class BudgetTemplateLine(Base):
    """Standard-Budget je Kategorie (die editierbare Vorlage)."""

    __tablename__ = "budget_template_lines"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    category_id: Mapped[int] = mapped_column(
        ForeignKey("categories.id", ondelete="CASCADE"), nullable=False
    )
    planned_cents: Mapped[int] = mapped_column(Integer, nullable=False, default=0)

    __table_args__ = (
        UniqueConstraint("owner_id", "category_id", name="uq_tpl_owner_category"),
    )


class PlannedIncomeLine(Base):
    """Geplante Einnahme (z. B. Gehalt) mit optionaler Kategorie und Zielkonto."""

    __tablename__ = "planned_income_lines"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    label: Mapped[str] = mapped_column(String(120), nullable=False)
    category_id: Mapped[int | None] = mapped_column(
        ForeignKey("categories.id", ondelete="SET NULL"), nullable=True
    )
    target_account_id: Mapped[int | None] = mapped_column(
        ForeignKey("accounts.id", ondelete="SET NULL"), nullable=True
    )
    planned_cents: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    position: Mapped[int] = mapped_column(Integer, nullable=False, default=0)


class BudgetPeriod(Base):
    """Ein Budget-Monat. Existiert erst, sobald der Monat angepasst wurde."""

    __tablename__ = "budget_periods"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    label: Mapped[str] = mapped_column(String(7), nullable=False)  # YYYY-MM (End-/Hauptmonat)
    customized: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)

    lines: Mapped[list[BudgetPeriodLine]] = relationship(
        back_populates="period", cascade="all, delete-orphan"
    )

    __table_args__ = (
        UniqueConstraint("owner_id", "label", name="uq_period_owner_label"),
    )


class BudgetPeriodLine(Base):
    """Monatsspezifischer Budget-Wert (Snapshot-on-Customize)."""

    __tablename__ = "budget_period_lines"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    budget_period_id: Mapped[int] = mapped_column(
        ForeignKey("budget_periods.id", ondelete="CASCADE"), nullable=False, index=True
    )
    category_id: Mapped[int] = mapped_column(
        ForeignKey("categories.id", ondelete="CASCADE"), nullable=False
    )
    planned_cents: Mapped[int] = mapped_column(Integer, nullable=False, default=0)

    period: Mapped[BudgetPeriod] = relationship(back_populates="lines")

    __table_args__ = (
        UniqueConstraint("budget_period_id", "category_id", name="uq_periodline_period_category"),
    )


# ---------------------------------------------------------------------------
# Phase 3: Dashboard-Layout (frei anordbare Karten, JSON, je Benutzer)
# ---------------------------------------------------------------------------


class DashboardLayout(Base):
    __tablename__ = "dashboard_layouts"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, unique=True, index=True
    )
    # JSON-Array: [{i, type, x, y, w, h, props}]
    layout: Mapped[str] = mapped_column(Text, nullable=False, default="[]")
    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now, onupdate=_now)


# ---------------------------------------------------------------------------
# Phase 4: CSV-Import (Templates, Batches für Undo, lernende Kategorie-Regeln)
# ---------------------------------------------------------------------------


class ImportTemplate(Base):
    __tablename__ = "import_templates"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    name: Mapped[str] = mapped_column(String(120), nullable=False)
    delimiter: Mapped[str] = mapped_column(String(2), nullable=False, default=";")
    decimal_sep: Mapped[str] = mapped_column(String(1), nullable=False, default=",")
    date_format: Mapped[str] = mapped_column(String(32), nullable=False, default="%d.%m.%Y")
    encoding: Mapped[str] = mapped_column(String(16), nullable=False, default="utf-8")
    has_header: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
    skip_rows: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    amount_mode: Mapped[AmountMode] = mapped_column(_enum(AmountMode), nullable=False, default=AmountMode.signed)
    # JSON: Feld -> 0-basierter Spaltenindex (oder null). Felder: date, time,
    # amount, debit, credit, currency, payee, purpose, counterparty_iban.
    column_map: Mapped[str] = mapped_column(Text, nullable=False, default="{}")
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)


class ImportBatch(Base):
    __tablename__ = "import_batches"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    account_id: Mapped[int] = mapped_column(
        ForeignKey("accounts.id", ondelete="CASCADE"), nullable=False
    )
    template_id: Mapped[int | None] = mapped_column(
        ForeignKey("import_templates.id", ondelete="SET NULL"), nullable=True
    )
    filename: Mapped[str] = mapped_column(String(255), nullable=False, default="")
    row_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    imported_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    status: Mapped[ImportStatus] = mapped_column(_enum(ImportStatus), nullable=False, default=ImportStatus.committed)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)


class CategorizationRule(Base):
    """Regel: Empfänger/Zweck enthält Muster -> Kategorie.

    Zwei Quellen (``source``): ``learned`` wird beim Import automatisch aus
    bestätigten Zuordnungen gelernt; ``manual`` legt der Nutzer als Schlagwort je
    Kategorie an. ``applied_count``/``overridden_count`` zählen, wie oft die Regel
    zutraf und wie oft ihr Vorschlag wegkorrigiert wurde – daraus wird ein
    manuelles Schlagwort ggf. als „stimmt vielleicht nicht" markiert."""

    __tablename__ = "categorization_rules"

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    owner_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    match_field: Mapped[MatchField] = mapped_column(_enum(MatchField), nullable=False, default=MatchField.payee)
    pattern: Mapped[str] = mapped_column(String(255), nullable=False)  # normalisiert (lowercase)
    category_id: Mapped[int | None] = mapped_column(
        ForeignKey("categories.id", ondelete="CASCADE"), nullable=True
    )
    # Optionale Zusatzbedingung: Regel greift nur bei genau diesem (absoluten) Betrag.
    amount_cents: Mapped[int | None] = mapped_column(Integer, nullable=True)
    # Wenn True: passende Buchung wird zum Transfer (category_id bleibt leer).
    is_transfer: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    # Optionales festes Zielkonto für Transfer-Regeln. Ohne -> Zielkonto wird aus
    # dem Buchungstext (Konto-Erkennungs-Texte) erraten.
    target_account_id: Mapped[int | None] = mapped_column(
        ForeignKey("accounts.id", ondelete="SET NULL"), nullable=True
    )
    # Art der Regel: "expense" | "income" | "transfer". Erlaubt, dasselbe Wort je
    # einmal für eine Ausgabe- UND eine Einnahme-Kategorie zu verwenden (das
    # Matching filtert ohnehin nach Buchungsart).
    kind: Mapped[str] = mapped_column(String(16), nullable=False, default="expense")
    source: Mapped[RuleSource] = mapped_column(_enum(RuleSource), nullable=False, default=RuleSource.learned)
    priority: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    hits: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    applied_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    overridden_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    # „Behalten, nicht mehr fragen" – unterdrückt das Flaggen trotz Korrekturen.
    confirmed: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)

    __table_args__ = (
        # Der Betrag gehört dazu: dasselbe Wort darf mehrere Preise haben
        # („sv = 5.00" und „sv = 7.50"), ohne Betrag ist es der Auffang.
        UniqueConstraint("owner_id", "match_field", "pattern", "kind", "amount_cents",
                         name="uq_rule_owner_field_pattern_kind_amount"),
    )