/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.solr.search.grouping.distributed.requestfactory;

import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.params.GroupParams;
import org.apache.solr.common.params.ModifiableSolrParams;
import org.apache.solr.common.params.ShardParams;
import org.apache.solr.handler.component.ResponseBuilder;
import org.apache.solr.handler.component.ShardRequest;
import org.apache.solr.search.SolrIndexSearcher;
import org.apache.solr.search.grouping.GroupingSpecification;
import org.apache.solr.search.grouping.distributed.ShardRequestFactory;

/**
 * Concrete implementation of {@link ShardRequestFactory} that creates {@link ShardRequest} instances for getting the
 * search groups from all shards.
 */
public class SearchGroupsRequestFactory implements ShardRequestFactory {

  /**
   * {@inheritDoc}
   */
  @Override
  public ShardRequest[] constructRequest(ResponseBuilder rb) {
    ShardRequest sreq = new ShardRequest();
    GroupingSpecification groupingSpecification = rb.getGroupingSpec();
    if (groupingSpecification.getFields().length == 0) {
      return new ShardRequest[0];
    }

    sreq.purpose = ShardRequest.PURPOSE_GET_TOP_GROUPS;

    sreq.params = new ModifiableSolrParams(rb.req.getParams());
    // TODO: base on current params or original params?

    // don't pass through any shards param
    sreq.params.remove(ShardParams.SHARDS);

    // set the start (offset) to 0 for each shard request so we can properly merge
    // results from the start.
    if(rb.shards_start > -1) {
      // if the client set shards.start set this explicitly
      sreq.params.set(CommonParams.START,rb.shards_start);
    } else {
      sreq.params.set(CommonParams.START, "0");
    }
    // TODO: should we even use the SortSpec?  That's obtained from the QParser, and
    // perhaps we shouldn't attempt to parse the query at this level?
    // Alternate Idea: instead of specifying all these things at the upper level,
    // we could just specify that this is a shard request.
    if(rb.shards_rows > -1) {
      // if the client set shards.rows set this explicity
      sreq.params.set(CommonParams.ROWS,rb.shards_rows);
    } else {
      sreq.params.set(CommonParams.ROWS, rb.getSortSpec().getOffset() + rb.getSortSpec().getCount());
    }

    // in this first phase, request only the unique key field
    // and any fields needed for merging.
    sreq.params.set(GroupParams.GROUP_DISTRIBUTED_FIRST, "true");

    if ( (rb.getFieldFlags() & SolrIndexSearcher.GET_SCORES)!=0 || rb.getSortSpec().includesScore()) {
      sreq.params.set(CommonParams.FL, rb.req.getSchema().getUniqueKeyField().getName() + ",score");
    } else {
      sreq.params.set(CommonParams.FL, rb.req.getSchema().getUniqueKeyField().getName());
    }
    return new ShardRequest[] {sreq};
  }

}