"""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
from datetime import datetime, timezone

from sqlalchemy import (
    Boolean,
    DateTime,
    Enum as SAEnum,
    ForeignKey,
    Integer,
    String,
)
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 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)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)

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

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


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")