/*
 * 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;

import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.solr.schema.SchemaField;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/***
 * SortSpec encapsulates a Lucene Sort and a count of the number of documents
 * to return.
 */
public class SortSpec 
{
  private Sort sort;
  private List<SchemaField> fields;
  private int num = 10;
  private int offset = 0;

  public SortSpec(Sort sort, List<SchemaField> fields, int num, int offset) {
    setSortAndFields(sort, fields);
    this.num = num;
    this.offset = offset;
  }
  public SortSpec(Sort sort, List<SchemaField> fields) {
    setSortAndFields(sort, fields);
  }
  public SortSpec(Sort sort, SchemaField[] fields, int num, int offset) {
    setSortAndFields(sort, Arrays.asList(fields));
    this.num = num;
    this.offset = offset;
  }
  public SortSpec(Sort sort, SchemaField[] fields) {
    setSortAndFields(sort, Arrays.asList(fields));
  }

  /** 
   * the specified SchemaFields must correspond one to one with the Sort's SortFields, 
   * using null where appropriate.
   */
  public void setSortAndFields( Sort s, List<SchemaField> fields )
  {
    
    assert null == s || s.getSort().length == fields.size() 
      : "SortFields and SchemaFields do not have equal lengths";
    this.sort = s;
    this.fields = Collections.unmodifiableList(fields);
  }

  public static boolean includesScore(Sort sort) {
    if (sort==null) return true;
    for (SortField sf : sort.getSort()) {
      if (sf.getType() == SortField.Type.SCORE) return true;
    }
    return false;
  }

  public boolean includesScore() {
    return includesScore(sort);
  }

  /**
   * Gets the Lucene Sort object, or null for the default sort
   * by score descending.
   */
  public Sort getSort() { return sort; }

  /**
   * Gets the Solr SchemaFields that correspond to each of the SortFields used
   * in this sort.  The array may contain null if a SortField doesn't correspond directly 
   * to a SchemaField (ie: score, lucene docid, custom function sorting, etc...)
   *
   * @return an immutable list, may be empty if getSort is null
   */
  public List<SchemaField> getSchemaFields() { return fields; }

  /**
   * Offset into the list of results.
   */
  public int getOffset() { return offset; }
  public void setOffset(int offset) { this.offset = offset; }

  /**
   * Gets the number of documents to return after sorting.
   *
   * @return number of docs to return, or -1 for no cut off (just sort)
   */
  public int getCount() { return num; }
  public void setCount(int count) { this.num = count; }

  @Override
  public String toString() {
    return "start="+offset+ "&rows="+num + (sort==null ? "" : "&sort="+sort); 
  }
}