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 JobAssignments(SQLModel, table=True):
    __tablename__ = "job_assignments"

    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
    job_post_id: uuid.UUID = Field(index=True, foreign_key="job_posts.id")
    user_id: uuid.UUID = Field(foreign_key="users.id")
    assignment_role: str = Field(default="primary_recruiter")
    valid_from: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))
    valid_to: datetime | None = Field(default=None, sa_type=DateTime(timezone=True))
    assigned_by: uuid.UUID = Field(foreign_key="users.id")
    created_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))

    @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):
        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 fetch_by_job(
        cls,
        session: AsyncSession,
        job_post_id,
        *,
        current_only: bool = True,
        assignment_role: str | None = None,
    ):
        uid = cls._as_uuid(job_post_id)
        if uid is None:
            return []
        statement = select(cls).where(cls.job_post_id == uid)
        if current_only:
            statement = statement.where(cls.valid_to.is_(None))
        if assignment_role:
            statement = statement.where(cls.assignment_role == assignment_role)
        statement = statement.order_by(cls.valid_from.desc())
        result = await session.execute(statement)
        return list(result.scalars().all())

    @classmethod
    async def close_current(cls, session: AsyncSession, job_post_id, assignment_role):
        """End every open interval of this role on the job. Returns how many closed."""
        uid = cls._as_uuid(job_post_id)
        if uid is None or not assignment_role:
            return 0
        statement = select(cls).where(
            cls.job_post_id == uid,
            cls.assignment_role == assignment_role,
            cls.valid_to.is_(None),
        )
        result = await session.execute(statement)
        rows = list(result.scalars().all())
        if not rows:
            return 0
        now = _now()
        for row in rows:
            row.valid_to = now
            session.add(row)
        await session.commit()
        return len(rows)

    @classmethod
    async def insert_assignment(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 count_open_reqs_by_user(cls, session: AsyncSession, user_id):
        uid = cls._as_uuid(user_id)
        if uid is None:
            return 0
        statement = (
            select(func.count())
            .select_from(cls)
            .where(cls.user_id == uid, cls.valid_to.is_(None))
        )
        result = await session.execute(statement)
        return result.scalar_one()

    @classmethod
    async def count_open_reqs_by_users(cls, session: AsyncSession, user_ids):
        """Open requisitions per user: current assignments joined to open job_posts."""
        from job.job_post.enums import RequisitionStatus
        from job.job_post.models import JobPosts

        uids = [u for u in (user_ids or []) if u]
        if not uids:
            return {}
        statement = (
            select(cls.user_id, func.count())
            .select_from(cls)
            .join(JobPosts, JobPosts.id == cls.job_post_id)
            .where(
                cls.user_id.in_(uids),
                cls.valid_to.is_(None),
                JobPosts.requisition_status == RequisitionStatus.OPEN.value,
                JobPosts.is_deleted == False,  # noqa: E712
            )
            .group_by(cls.user_id)
        )
        result = await session.execute(statement)
        return {uid: int(n or 0) for uid, n in result.all()}


class ApplicationAssignments(SQLModel, table=True):
    __tablename__ = "application_assignments"

    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
    inbox_id: int = Field(index=True, foreign_key="inbox.id")
    user_id: uuid.UUID = Field(foreign_key="users.id")
    assignment_role: str = Field(default="primary_recruiter")
    valid_from: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))
    valid_to: datetime | None = Field(default=None, sa_type=DateTime(timezone=True))
    assigned_by: uuid.UUID = Field(foreign_key="users.id")
    created_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))

    @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):
        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 fetch_by_inbox(cls, session: AsyncSession, inbox_id: int, *, current_only: bool = True):
        statement = select(cls).where(cls.inbox_id == int(inbox_id))
        if current_only:
            statement = statement.where(cls.valid_to.is_(None))
        statement = statement.order_by(cls.valid_from.desc())
        result = await session.execute(statement)
        return list(result.scalars().all())

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

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