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 Tasks(SQLModel, table=True):
    __tablename__ = "tasks"

    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
    title: str
    status: str = Field(default="open")  # open | done
    priority: str = Field(default="medium")  # high | medium | low
    due_date: datetime | None = Field(default=None, sa_type=DateTime(timezone=True))
    # The assignee is a real users row; views rejects candidate-role accounts.
    assignee_id: uuid.UUID = Field(index=True, foreign_key="users.id")
    # Optional links to the work the task is about. Schema-only for now — the
    # Tasks screen does not surface them yet.
    inbox_id: int | None = Field(default=None, foreign_key="inbox.id")
    job_post_id: uuid.UUID | None = Field(default=None, foreign_key="job_posts.id")
    created_by: uuid.UUID = Field(foreign_key="users.id")
    created_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))
    updated_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_task_by_id(cls, session: AsyncSession, record_id):
        uid = cls._as_uuid(record_id)
        if uid is None:
            return None
        result = await session.execute(
            select(cls).where(cls.id == uid, cls.is_deleted == False)  # noqa: E712
        )
        return result.scalars().first()

    @classmethod
    async def fetch_tasks(
        cls,
        session: AsyncSession,
        *,
        status: str | None = None,
        priority: str | None = None,
        assignee_id: uuid.UUID | None = None,
        top: int | None = None,
        skip: int = 0,
    ):
        statement = select(cls).where(cls.is_deleted == False)  # noqa: E712
        if status:
            statement = statement.where(cls.status == status)
        if priority:
            statement = statement.where(cls.priority == priority)
        if assignee_id is not None:
            statement = statement.where(cls.assignee_id == assignee_id)
        count_statement = select(func.count()).select_from(statement.subquery())
        total = (await session.execute(count_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

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

    @classmethod
    async def update_task(cls, session: AsyncSession, record_id, fields: dict):
        row = await cls.get_task_by_id(session, record_id)
        if not row:
            return None
        for key, value in fields.items():
            setattr(row, key, value)
        row.updated_at = _now()
        session.add(row)
        await session.commit()
        await session.refresh(row)
        return row

    @classmethod
    async def soft_delete_task(cls, session: AsyncSession, record_id):
        row = await cls.get_task_by_id(session, record_id)
        if not row:
            return None
        row.is_deleted = True
        row.updated_at = _now()
        session.add(row)
        await session.commit()
        return row


import users.models as _users_models  # noqa: E402, F401