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/*
 * 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.lucene.queries.function.valuesource;

import java.io.IOException;
import java.util.Arrays;
import java.util.Map;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.queries.function.docvalues.FloatDocValues;
import org.apache.lucene.search.IndexSearcher;

/**
 * Abstract {@link ValueSource} implementation which wraps multiple ValueSources and applies an
 * extendible float function to their values.
 */
public abstract class MultiFloatFunction extends ValueSource {
  protected final ValueSource[] sources;

  public MultiFloatFunction(ValueSource[] sources) {
    this.sources = sources;
  }

  protected abstract String name();

  protected abstract float func(int doc, FunctionValues[] valsArr) throws IOException;

  /**
   * Called by {@link FunctionValues#exists} for each document.
   *
   * Default impl returns true if all of the specified values {@link
   * FunctionValues#exists} for the specified doc, else false.
   *
   * @see FunctionValues#exists
   * @see MultiFunction#allExists
   */
  protected boolean exists(int doc, FunctionValues[] valsArr) throws IOException {
    return MultiFunction.allExists(doc, valsArr);
  }

  @Override
  public String description() {
    StringBuilder sb = new StringBuilder();
    sb.append(name()).append('(');
    boolean firstTime = true;
    for (ValueSource source : sources) {
      if (firstTime) {
        firstTime = false;
      } else {
        sb.append(',');
      }
      sb.append(source);
    }
    sb.append(')');
    return sb.toString();
  }

  @Override
  public FunctionValues getValues(Map context, LeafReaderContext readerContext)
      throws IOException {
    final FunctionValues[] valsArr = new FunctionValues[sources.length];
    for (int i = 0; i < sources.length; i++) {
      valsArr[i] = sources[i].getValues(context, readerContext);
    }

    return new FloatDocValues(this) {
      @Override
      public float floatVal(int doc) throws IOException {
        return func(doc, valsArr);
      }

      @Override
      public boolean exists(int doc) throws IOException {
        return MultiFloatFunction.this.exists(doc, valsArr);
      }

      @Override
      public String toString(int doc) throws IOException {
        return MultiFunction.toString(name(), valsArr, doc);
      }
    };
  }

  @Override
  public void createWeight(Map context, IndexSearcher searcher) throws IOException {
    for (ValueSource source : sources) {
      source.createWeight(context, searcher);
    }
  }

  @Override
  public int hashCode() {
    return Arrays.hashCode(sources) + name().hashCode();
  }

  @Override
  public boolean equals(Object o) {
    if (this.getClass() != o.getClass()) return false;
    MultiFloatFunction other = (MultiFloatFunction) o;
    return this.name().equals(other.name()) && Arrays.equals(this.sources, other.sources);
  }
}