# -*- coding: utf-8 -*-
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# to you under the Apache License, Version 2.0 (the
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from sqlalchemy import Column, Integer, String, Text, func

from airflow.models.base import Base
from airflow.utils.state import State
from airflow.ti_deps.deps.pool_slots_available_dep import STATES_TO_COUNT_AS_RUNNING
from airflow.utils.db import provide_session


class Pool(Base):
    __tablename__ = "slot_pool"

    id = Column(Integer, primary_key=True)
    pool = Column(String(50), unique=True)
    # -1 for infinite
    slots = Column(Integer, default=0)
    description = Column(Text)

    DEFAULT_POOL_NAME = 'default_pool'

    def __repr__(self):
        return self.pool

    @staticmethod
    @provide_session
    def get_pool(pool_name, session=None):
        return session.query(Pool).filter(Pool.pool == pool_name).first()

    @staticmethod
    @provide_session
    def get_default_pool(session=None):
        return Pool.get_pool(Pool.DEFAULT_POOL_NAME, session=session)

    def to_json(self):
        return {
            'id': self.id,
            'pool': self.pool,
            'slots': self.slots,
            'description': self.description,
        }

    @provide_session
    def occupied_slots(self, session):
        """
        Returns the number of slots used by running/queued tasks at the moment.
        """
        from airflow.models.taskinstance import TaskInstance  # Avoid circular import
        return (
            session
            .query(func.count())
            .filter(TaskInstance.pool == self.pool)
            .filter(TaskInstance.state.in_(STATES_TO_COUNT_AS_RUNNING))
            .scalar()
        )

    @provide_session
    def used_slots(self, session):
        """
        Returns the number of slots used by running tasks at the moment.
        """
        from airflow.models.taskinstance import TaskInstance  # Avoid circular import

        running = (
            session
            .query(func.count())
            .filter(TaskInstance.pool == self.pool)
            .filter(TaskInstance.state == State.RUNNING)
            .scalar()
        )
        return running

    @provide_session
    def queued_slots(self, session):
        """
        Returns the number of slots used by queued tasks at the moment.
        """
        from airflow.models.taskinstance import TaskInstance  # Avoid circular import

        return (
            session
            .query(func.count())
            .filter(TaskInstance.pool == self.pool)
            .filter(TaskInstance.state == State.QUEUED)
            .scalar()
        )

    @provide_session
    def open_slots(self, session):
        """
        Returns the number of slots open at the moment
        """
        if self.slots == -1:
            return float('inf')
        else:
            return self.slots - self.occupied_slots(session)
