import uuid
from datetime import datetime, timezone

from sqlalchemy import DateTime, func
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)


class Notifications(SQLModel, table=True):
    __tablename__ = "notifications"

    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
    user_id: uuid.UUID = Field(index=True, foreign_key="users.id")
    kind: str
    title: str
    body: str | None = Field(default=None)
    link_path: str | None = Field(default=None)
    inbox_id: int | None = Field(default=None)
    job_post_id: uuid.UUID | None = Field(default=None)
    is_read: bool = Field(default=False, index=True)
    created_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))
    is_deleted: bool = Field(default=False)

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

    @classmethod
    async def get_by_id(cls, session: AsyncSession, record_id, *, user_id=None):
        uid = cls._as_uuid(record_id)
        if uid is None:
            return None
        statement = select(cls).where(cls.id == uid, cls.is_deleted == False)  # noqa: E712
        if user_id is not None:
            statement = statement.where(cls.user_id == user_id)
        result = await session.execute(statement)
        return result.scalars().first()

    @classmethod
    async def fetch_notifications(
        cls,
        session: AsyncSession,
        *,
        user_id,
        unread_only: bool = False,
        top: int | None = None,
        skip: int = 0,
    ):
        statement = select(cls).where(
            cls.user_id == user_id,
            cls.is_deleted == False,  # noqa: E712
            cls.title != "ATS score ready",
        )
        if unread_only:
            statement = statement.where(cls.is_read == False)  # noqa: E712
        count_statement = select(func.count()).select_from(statement.subquery())
        total = (await session.execute(count_statement)).scalar_one()
        unread_statement = select(func.count()).select_from(cls).where(
            cls.user_id == user_id,
            cls.is_deleted == False,  # noqa: E712
            cls.is_read == False,  # noqa: E712
            cls.title != "ATS score ready",
        )
        unread = (await session.execute(unread_statement)).scalar_one()
        statement = statement.order_by(cls.created_at.desc())
        if skip:
            statement = statement.offset(skip)
        if top is not None:
            statement = statement.limit(top)
        result = await session.execute(statement)
        return list(result.scalars().all()), total, unread

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

    @classmethod
    async def insert_many(cls, session: AsyncSession, payloads, *, commit: bool = True):
        """One row per payload. `commit=False` rides the caller's transaction."""
        rows = []
        for fields in payloads or []:
            uid = cls._as_uuid(fields.get("user_id"))
            if uid is None or not fields.get("kind") or not fields.get("title"):
                continue
            job_id = cls._as_uuid(fields.get("job_post_id")) if fields.get("job_post_id") else None
            row = cls(
                user_id=uid,
                kind=fields["kind"],
                title=fields["title"],
                body=fields.get("body"),
                link_path=fields.get("link_path"),
                inbox_id=fields.get("inbox_id"),
                job_post_id=job_id,
            )
            session.add(row)
            rows.append(row)
        if commit and rows:
            await session.commit()
        return rows

    @classmethod
    async def mark_read(cls, session: AsyncSession, record_id, *, user_id):
        row = await cls.get_by_id(session, record_id, user_id=user_id)
        if not row:
            return None
        row.is_read = True
        session.add(row)
        await session.commit()
        await session.refresh(row)
        return row

    @classmethod
    async def mark_all_read(cls, session: AsyncSession, user_id):
        statement = select(cls).where(
            cls.user_id == user_id,
            cls.is_deleted == False,  # noqa: E712
            cls.is_read == False,  # noqa: E712
        )
        result = await session.execute(statement)
        rows = list(result.scalars().all())
        for row in rows:
            row.is_read = True
            session.add(row)
        await session.commit()
        return len(rows)

    @classmethod
    async def soft_delete_notification(cls, session: AsyncSession, record_id, *, user_id):
        row = await cls.get_by_id(session, record_id, user_id=user_id)
        if not row:
            return None
        row.is_deleted = True
        session.add(row)
        await session.commit()
        return row