/*
 *  ******************************************************************************
 *  *
 *  *
 *  * This program and the accompanying materials are made available under the
 *  * terms of the Apache License, Version 2.0 which is available at
 *  * https://www.apache.org/licenses/LICENSE-2.0.
 *  *
 *  *  See the NOTICE file distributed with this work for additional
 *  *  information regarding copyright ownership.
 *  * 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.
 *  *
 *  * SPDX-License-Identifier: Apache-2.0
 *  *****************************************************************************
 */

package org.datavec.api.transform.reduce;

import org.datavec.api.transform.ops.IAggregableReduceOp;
import org.datavec.api.transform.schema.Schema;
import org.datavec.api.writable.Writable;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

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

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.WRAPPER_OBJECT)
@JsonSubTypes(value = {@JsonSubTypes.Type(value = Reducer.class, name = "Reducer")})
public interface IAssociativeReducer extends Serializable {

    /**
     *
     * @param schema
     */
    void setInputSchema(Schema schema);

    /**
     *
     * @return
     */
    Schema getInputSchema();

    /**
     *
     * @param schema
     * @return
     */
    Schema transform(Schema schema);

    /**
     * An aggregation that has the property that
     * reduce(List(reduce(List(l1, l2)), l3)) = reduce(List(l1, reduce(List(l2, l3)))
     * @return
     */
    IAggregableReduceOp<List<Writable>, List<Writable>> aggregableReducer();

    /**
     *
     * @return
     */
    List<String> getKeyColumns();

}
