/*
 * Copyright (c) 2011-2015 EPFL DATA Laboratory
 * Copyright (c) 2014-2015 The Squall Collaboration (see NOTICE)
 *
 * All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package ch.epfl.data.squall.operators;

import java.io.Serializable;
import java.util.List;

import ch.epfl.data.squall.visitors.OperatorVisitor;

public interface Operator extends Serializable {
    public void accept(OperatorVisitor ov);

    /*
     * Used mainly for Preaggregations
     */
    public List<String> getContent();

    /*
     * This is now decoupled from printContent
     */
    public int getNumTuplesProcessed();

    /* return true if an operator is blocking (can revoke previously sent tuple) */
    public boolean isBlocking();

    /*
     * if hasPerstistentStorage returns true, printContent can be invoked For
     * nonPersistantStorages, printing is pefromed as soon as tuple arrives. It
     * is done outside Operator class, since there are situations when operators
     * are not called at all, and still printing has to be performed -
     * StormDataSrouce class. It is responsability of Storm component to
     * perfrorm desired printing in that case. This method is invoked when we
     * are sure that no more tuples will arive at the component (i.e when
     * topology is to be killed). Used for UI
     */
    public String printContent();

    public List<List<String>> process(List<String> tuple, long lineageTimestamp);
}