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"""This module defines dep for pool slots availability."""

from __future__ import annotations

from sqlalchemy import select

from airflow.configuration import conf
from airflow.ti_deps.deps.base_ti_dep import BaseTIDep
from airflow.utils.session import provide_session


class PoolSlotsAvailableDep(BaseTIDep):
    """Dep for pool slots availability."""

    NAME = "Pool Slots Available"
    IGNORABLE = True

    @provide_session
    def _get_dep_statuses(self, ti, dep_context=None, *, session):
        """
        Determine if the pool task instance is in has available slots.

        :param ti: the task instance to get the dependency status for
        :param session: database session
        :param dep_context: the context for which this dependency should be evaluated for
        :return: True if there are available slots in the pool.
        """
        from airflow.models.dag import DagModel
        from airflow.models.pool import Pool  # To avoid a circular dependency

        pool_name = ti.pool

        # Controlled by UNIQUE key in slot_pool table, only (at most) one result can be returned.
        pool: Pool | None = session.scalar(select(Pool).where(Pool.pool == pool_name))
        if pool is None:
            yield self._failing_status(
                reason=f"Tasks using non-existent pool '{pool_name}' will not be scheduled"
            )
            return

        # Check team compatibility
        if pool.team_name:
            if not conf.getboolean("core", "multi_team"):
                raise ValueError(
                    "Multi-team mode is not configured in the Airflow environment but the pool the task is using belongs to a team"
                )

            dag_team_name = DagModel.get_team_name(ti.dag_id, session=session)
            if dag_team_name != pool.team_name:
                yield self._failing_status(
                    reason=f"Pool '{pool_name}' is assigned to team '{pool.team_name}' "
                    f"but task's DAG belongs to team '{dag_team_name or 'None'}'"
                )
                return

        open_slots = pool.open_slots(session=session)
        if ti.state in pool.get_occupied_states():
            open_slots += ti.pool_slots

        if open_slots <= (ti.pool_slots - 1):
            yield self._failing_status(
                reason=f"Not scheduling since there are {open_slots} open slots in pool {pool_name} "
                f"and require {ti.pool_slots} pool slots"
            )
        else:
            yield self._passing_status(
                reason=f"There are enough open slots in {pool_name} to execute the task",
            )
