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 HiringCosts(SQLModel, table=True):
    __tablename__ = "hiring_costs"

    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
    job_post_id: uuid.UUID | None = Field(default=None, foreign_key="job_posts.id")
    # Source attribution (REQ-ANL-09): spend tagged to a channel feeds the
    # cost-per-application column of source performance; untagged spend only
    # ever feeds cost-per-hire.
    source_channel_id: int | None = Field(default=None, foreign_key="source_channels.id")
    cost_type: str = Field(default="other")
    amount: float = Field(default=0.0)
    currency: str = Field(default="USD")
    incurred_at: datetime = Field(default_factory=_now, sa_type=DateTime(timezone=True))
    description: str | None = Field(default=None)
    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))

    @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_costs(
        cls,
        session: AsyncSession,
        *,
        job_post_id=None,
        from_date=None,
        to_date=None,
        top: int | None = None,
        skip: int = 0,
    ):
        statement = select(cls)
        if job_post_id is not None:
            uid = cls._as_uuid(job_post_id)
            if uid is not None:
                statement = statement.where(cls.job_post_id == uid)
        if from_date is not None:
            statement = statement.where(cls.incurred_at >= from_date)
        if to_date is not None:
            statement = statement.where(cls.incurred_at < to_date)
        count_statement = select(func.count()).select_from(statement.subquery())
        total = (await session.execute(count_statement)).scalar_one()
        statement = statement.order_by(cls.incurred_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_cost(cls, session: AsyncSession, fields: dict):
        row = cls(**fields)
        session.add(row)
        await session.commit()
        return await cls.get_by_id(session, row.id)

    @classmethod
    def scoped_to_job(cls, statement, department=None, recruiter_id=None):
        if not department and not recruiter_id:
            return statement
        from job.job_post.models import JobPosts
        statement = statement.outerjoin(JobPosts, cls.job_post_id == JobPosts.id)
        if department:
            statement = statement.where(JobPosts.department == department)
        rid = cls._as_uuid(recruiter_id)
        if rid is not None:
            statement = statement.where(JobPosts.has_recruiter(rid))
        return statement

    @classmethod
    async def sum_amount(cls, session: AsyncSession, *, from_date=None, to_date=None,
                         department=None, recruiter_id=None):
        statement = select(func.coalesce(func.sum(cls.amount), 0.0))
        if from_date is not None:
            statement = statement.where(cls.incurred_at >= from_date)
        if to_date is not None:
            statement = statement.where(cls.incurred_at < to_date)
        statement = cls.scoped_to_job(statement, department, recruiter_id)
        result = await session.execute(statement)
        return float(result.scalar_one() or 0.0)

    @classmethod
    async def sum_by_source_channel(
        cls, session: AsyncSession, *, from_date=None, to_date=None,
        department=None, recruiter_id=None,
    ):
        statement = select(
            cls.source_channel_id,
            func.coalesce(func.sum(cls.amount), 0.0),
        ).where(cls.source_channel_id.is_not(None))
        if from_date is not None:
            statement = statement.where(cls.incurred_at >= from_date)
        if to_date is not None:
            statement = statement.where(cls.incurred_at < to_date)
        statement = cls.scoped_to_job(statement, department, recruiter_id)
        statement = statement.group_by(cls.source_channel_id)
        result = await session.execute(statement)
        return {channel_id: float(total or 0.0) for channel_id, total in result.all()}

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