'per_page' and 'offset' can't be used.
	 *
	 * @param array $query Query parameters.
	 *
	 * @return int|null
	 */
	public function query_action( $query ) {
		$query['per_page'] = 1;
		$query['offset']   = 0;
		$results           = $this->query_actions( $query );

		if ( empty( $results ) ) {
			return null;
		} else {
			return (int) $results[0];
		}
	}

	/**
	 * Get a count of all actions in the store, grouped by status
	 *
	 * @return array
	 */
	abstract public function action_counts();

	/**
	 * Get additional action counts.
	 *
	 * - add past-due actions
	 *
	 * @return array
	 */
	public function extra_action_counts() {
		$extra_actions = array();

		$pastdue_action_counts = ( int ) $this->query_actions( array(
			'status' => self::STATUS_PENDING,
			'date'   => as_get_datetime_object(),
		), 'count' );

		if ( $pastdue_action_counts ) {
			$extra_actions['past-due'] = $pastdue_action_counts;
		}

		/**
		 * Allows 3rd party code to add extra action counts (used in filters in the list table).
		 *
		 * @since 3.5.0
		 * @param $extra_actions array Array with format action_count_identifier => action count.
		 */
		return apply_filters( 'action_scheduler_extra_action_counts', $extra_actions );
	}

	/**
	 * @param string $action_id
	 */
	abstract public function cancel_action( $action_id );

	/**
	 * @param string $action_id
	 */
	abstract public function delete_action( $action_id );

	/**
	 * @param string $action_id
	 *
	 * @return DateTime The date the action is schedule to run, or the date that it ran.
	 */
	abstract public function get_date( $action_id );


	/**
	 * @param int      $max_actions
	 * @param DateTime $before_date Claim only actions schedule before the given date. Defaults to now.
	 * @param array    $hooks       Claim only actions with a hook or hooks.
	 * @param string   $group       Claim only actions in the given group.
	 *
	 * @return ActionScheduler_ActionClaim
	 */
	abstract public function stake_claim( $max_actions = 10, DateTime $before_date = null, $hooks = array(), $group = '' );

	/**
	 * @return int
	 */
	abstract public function get_claim_count();

	/**
	 * @param ActionScheduler_ActionClaim $claim
	 */
	abstract public function release_claim( ActionScheduler_ActionClaim $claim );

	/**
	 * @param string $action_id
	 */
	abstract public function unclaim_action( $action_id );

	/**
	 * @param string $action_id
	 */
	abstract public function mark_failure( $action_id );

	/**
	 * @param string $action_id
	 */
	abstract public function log_execution( $action_id );

	/**
	 * @param string $action_id
	 */
	abstract public function mark_complete( $action_id );

	/**
	 * @param string $action_id
	 *
	 * @return string
	 */
	abstract public function get_status( $action_id );

	/**
	 * @param string $action_id
	 * @return mixed
	 */
	abstract public function get_claim_id( $action_id );

	/**
	 * @param string $claim_id
	 * @return array
	 */
	abstract public function find_actions_by_claim_id( $claim_id );

	/**
	 * @param string $comparison_operator
	 * @return string
	 */
	protected function validate_sql_comparator( $comparison_operator ) {
		if ( in_array( $comparison_operator, array('!=', '>', '>=', '<', '<=', '=') ) ) {
			return $comparison_operator;
		}
		return '=';
	}

	/**
	 * Get the time MySQL formated date/time string for an action's (next) scheduled date.
	 *
	 * @param ActionScheduler_Action $action
	 * @param DateTime $scheduled_date (optional)
	 * @return string
	 */
	protected function get_scheduled_date_string( ActionScheduler_Action $action, DateTime $scheduled_date = NULL ) {
		$next = null === $scheduled_date ? $action->get_schedule()->get_date() : $scheduled_date;
		if ( ! $next ) {
			$next = date_create();
		}
		$next->setTimezone( new DateTimeZone( 'UTC' ) );

		return $next->format( 'Y-m-d H:i:s' );
	}

	/**
	 * Get the time MySQL formated date/time string for an action's (next) scheduled date.
	 *
	 * @param ActionScheduler_Action $action
	 * @param DateTime $scheduled_date (optional)
	 * @return string
	 */
	protected function get_scheduled_date_string_local( ActionScheduler_Action $action, DateTime $scheduled_date = NULL ) {
		$next = null === $scheduled_date ? $action->get_schedule()->get_date() : $scheduled_date;
		if ( ! $next ) {
			$next = date_create();
		}

		ActionScheduler_TimezoneHelper::set_local_timezone( $next );
		return $next->format( 'Y-m-d H:i:s' );
	}

	/**
	 * Validate that we could decode action arguments.
	 *
	 * @param mixed $args      The decoded arguments.
	 * @param int   $action_id The action ID.
	 *
	 * @throws ActionScheduler_InvalidActionException When the decoded arguments are invalid.
	 */
	protected function validate_args( $args, $action_id ) {
		// Ensure we have an array of args.
		if ( ! is_array( $args ) ) {
			throw ActionScheduler_InvalidActionException::from_decoding_args( $action_id );
		}

		// Validate JSON decoding if possible.
		if ( function_exists( 'json_last_error' ) && JSON_ERROR_NONE !== json_last_error() ) {
			throw ActionScheduler_InvalidActionException::from_decoding_args( $action_id, $args );
		}
	}

	/**
	 * Validate a ActionScheduler_Schedule object.
	 *
	 * @param mixed $schedule  The unserialized ActionScheduler_Schedule object.
	 * @param int   $action_id The action ID.
	 *
	 * @throws ActionScheduler_InvalidActionException When the schedule is invalid.
	 */
	protected function validate_schedule( $schedule, $action_id ) {
		if ( empty( $schedule ) || ! is_a( $schedule, 'ActionScheduler_Schedule' ) ) {
			throw ActionScheduler_InvalidActionException::from_schedule( $action_id, $schedule );
		}
	}

	/**
	 * InnoDB indexes have a maximum size of 767 bytes by default, which is only 191 characters with utf8mb4.
	 *
	 * Previously, AS wasn't concerned about args length, as we used the (unindex) post_content column. However,
	 * with custom tables, we use an indexed VARCHAR column instead.
	 *
	 * @param  ActionScheduler_Action $action Action to be validated.
	 * @throws InvalidArgumentException When json encoded args is too long.
	 */
	protected function validate_action( ActionScheduler_Action $action ) {
		if ( strlen( json_encode( $action->get_args() ) ) > static::$max_args_length ) {
			throw new InvalidArgumentException( sprintf( __( 'ActionScheduler_Action::$args too long. To ensure the args column can be indexed, action args should not be more than %d characters when encoded as JSON.', 'action-scheduler' ), static::$max_args_length ) );
		}
	}

	/**
	 * Cancel pending actions by hook.
	 *
	 * @since 3.0.0
	 *
	 * @param string $hook Hook name.
	 *
	 * @return void
	 */
	public function cancel_actions_by_hook( $hook ) {
		$action_ids = true;
		while ( ! empty( $action_ids ) ) {
			$action_ids = $this->query_actions(
				array(
					'hook'     => $hook,
					'status'   => self::STATUS_PENDING,
					'per_page' => 1000,
					'orderby'  => 'action_id',
				)
			);

			$this->bulk_cancel_actions( $action_ids );
		}
	}

	/**
	 * Cancel pending actions by group.
	 *
	 * @since 3.0.0
	 *
	 * @param string $group Group slug.
	 *
	 * @return void
	 */
	public function cancel_actions_by_group( $group ) {
		$action_ids = true;
		while ( ! empty( $action_ids ) ) {
			$action_ids = $this->query_actions(
				array(
					'group'    => $group,
					'status'   => self::STATUS_PENDING,
					'per_page' => 1000,
					'orderby'  => 'action_id',
				)
			);

			$this->bulk_cancel_actions( $action_ids );
		}
	}

	/**
	 * Cancel a set of action IDs.
	 *
	 * @since 3.0.0
	 *
	 * @param array $action_ids List of action IDs.
	 *
	 * @return void
	 */
	private function bulk_cancel_actions( $action_ids ) {
		foreach ( $action_ids as $action_id ) {
			$this->cancel_action( $action_id );
		}

		do_action( 'action_scheduler_bulk_cancel_actions', $action_ids );
	}

	/**
	 * @return array
	 */
	public function get_status_labels() {
		return array(
			self::STATUS_COMPLETE => __( 'Complete', 'action-scheduler' ),
			self::STATUS_PENDING  => __( 'Pending', 'action-scheduler' ),
			self::STATUS_RUNNING  => __( 'In-progress', 'action-scheduler' ),
			self::STATUS_FAILED   => __( 'Failed', 'action-scheduler' ),
			self::STATUS_CANCELED => __( 'Canceled', 'action-scheduler' ),
		);
	}

	/**
	 * Check if there are any pending scheduled actions due to run.
	 *
	 * @param ActionScheduler_Action $action
	 * @param DateTime $scheduled_date (optional)
	 * @return string
	 */
	public function has_pending_actions_due() {
		$pending_actions = $this->query_actions( array(
			'date'    => as_get_datetime_object(),
			'status'  => ActionScheduler_Store::STATUS_PENDING,
			'orderby' => 'none',
		) );

		return ! empty( $pending_actions );
	}

	/**
	 * Callable initialization function optionally overridden in derived classes.
	 */
	public function init() {}

	/**
	 * Callable function to mark an action as migrated optionally overridden in derived classes.
	 */
	public function mark_migrated( $action_id ) {}

	/**
	 * @return ActionScheduler_Store
	 */
	public static function instance() {
		if ( empty( self::$store ) ) {
			$class = apply_filters( 'action_scheduler_store_class', self::DEFAULT_CLASS );
			self::$store = new $class();
		}
		return self::$store;
	}
}