import uuid
from datetime import datetime, timezone

from sqlalchemy import DateTime
from sqlalchemy.ext.asyncio import AsyncSession
from sqlmodel import Field, SQLModel, select


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


class EmailConfirmationTokens(SQLModel, table=True):
    __tablename__ = "email_confirmation_tokens"

    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
    user_id: uuid.UUID = Field(index=True, foreign_key="users.id")
    email: str = Field(index=True)
    token_hash: str
    expires_at: datetime = Field(sa_type=DateTime(timezone=True))
    is_used: bool = Field(default=False)
    confirmed_at: datetime | None = Field(default=None, sa_type=DateTime(timezone=True))
    created_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))
    updated_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))

    @staticmethod
    def _as_uuid(record_id: str) -> uuid.UUID | None:
        try:
            return uuid.UUID(str(record_id))
        except ValueError:
            return None

    @classmethod
    async def get_token_by_id(cls, session: AsyncSession, record_id: str):
        uid = cls._as_uuid(record_id)
        if uid is None:
            return None
        result = await session.execute(select(cls).where(cls.id == uid))
        return result.scalars().first()

    @classmethod
    async def get_active_token_by_user(cls, session: AsyncSession, user_id: str):
        """Newest unused token for a user (expiry checked in Python by the service)."""
        uid = cls._as_uuid(user_id)
        if uid is None:
            return None
        statement = (
            select(cls)
            .where(cls.user_id == uid, cls.is_used == False)  # noqa: E712
            .order_by(cls.created_at.desc())
        )
        result = await session.execute(statement)
        return result.scalars().first()

    @classmethod
    async def insert_token(cls, session: AsyncSession, fields: dict):
        row = cls(**fields)
        session.add(row)
        await session.commit()
        return await cls.get_token_by_id(session, row.id)

    @classmethod
    async def mark_confirmed(cls, session: AsyncSession, record_id: str):
        row = await cls.get_token_by_id(session, record_id)
        if not row:
            return None
        row.is_used = True
        row.confirmed_at = _now()
        row.updated_at = _now()
        session.add(row)
        await session.commit()
        await session.refresh(row)
        return row

    @classmethod
    async def mark_used(cls, session: AsyncSession, record_id: str):
        """Retire a token without confirming it — used when the mail send fails."""
        row = await cls.get_token_by_id(session, record_id)
        if not row:
            return None
        row.is_used = True
        row.updated_at = _now()
        session.add(row)
        await session.commit()
        await session.refresh(row)
        return row

    @classmethod
    async def invalidate_tokens_for_user(cls, session: AsyncSession, user_id: str):
        uid = cls._as_uuid(user_id)
        if uid is None:
            return 0
        statement = select(cls).where(cls.user_id == uid, cls.is_used == False)  # noqa: E712
        result = await session.execute(statement)
        rows = result.scalars().all()
        now = _now()
        for row in rows:
            row.is_used = True
            row.updated_at = now
            session.add(row)
        await session.commit()
        return len(rows)