solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/SortStream.java

/*
 * 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.client.solrj.io.stream;

import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;

import org.apache.solr.client.solrj.io.Tuple;
import org.apache.solr.client.solrj.io.comp.FieldComparator;
import org.apache.solr.client.solrj.io.comp.StreamComparator;
import org.apache.solr.client.solrj.io.stream.expr.Explanation;
import org.apache.solr.client.solrj.io.stream.expr.Expressible;
import org.apache.solr.client.solrj.io.stream.expr.StreamExplanation;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionNamedParameter;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionValue;
import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
import org.apache.solr.client.solrj.io.stream.expr.Explanation.ExpressionType;


/**
 * The SortStream emits a stream of Tuples sorted by a Comparator.
 * @since 6.1.0
 **/

public class SortStream extends TupleStream implements Expressible {

  private static final long serialVersionUID = 1;

  private TupleStream stream;
  private StreamComparator comparator;
  private Worker worker;

  public SortStream(TupleStream stream, StreamComparator comp) throws IOException {
    init(stream,comp);
  }
  
  public SortStream(StreamExpression expression,StreamFactory factory) throws IOException {
    // grab all parameters out
    List<StreamExpression> streamExpressions = factory.getExpressionOperandsRepresentingTypes(expression, Expressible.class, TupleStream.class);
    StreamExpressionNamedParameter byExpression = factory.getNamedOperand(expression, "by");
    
    // validate expression contains only what we want.
    if(expression.getParameters().size() != streamExpressions.size() + 1){
      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - unknown operands found", expression));
    }
    
    if(1 != streamExpressions.size()){
      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - expecting a single stream but found %d",expression, streamExpressions.size()));
    }
    
    if(null == byExpression || !(byExpression.getParameter() instanceof StreamExpressionValue)){
      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - expecting single 'by' parameter listing fields to sort over but didn't find one",expression));
    }
    
    init(
          factory.constructStream(streamExpressions.get(0)),
          factory.constructComparator(((StreamExpressionValue)byExpression.getParameter()).getValue(), FieldComparator.class)
        );
  }
  
  private void init(TupleStream stream, StreamComparator comp) throws IOException{
    this.stream = stream;
    this.comparator = comp;
    
    // standard java modified merge sort
    worker = new Worker() {

      private LinkedList<Tuple> tuples = new LinkedList<Tuple>();
      private Tuple eofTuple;
      
      public void readStream(TupleStream stream) throws IOException {
        Tuple tuple = stream.read();
        while(!tuple.EOF){
          tuples.add(tuple);
          tuple = stream.read();
        }
        eofTuple = tuple;
      }
      
      public void sort() {
        tuples.sort(comparator);
      }
      
      public Tuple read() {
        if(tuples.isEmpty()){
          return eofTuple;
        }
        return tuples.removeFirst();
      }
    };
    
  }

  @Override
  public StreamExpression toExpression(StreamFactory factory) throws IOException{
    return toExpression(factory, true);
  }
  
  private StreamExpression toExpression(StreamFactory factory, boolean includeStreams) throws IOException {
    // function name
    StreamExpression expression = new StreamExpression(factory.getFunctionName(this.getClass()));
    
    if(includeStreams){
      // streams
      if(stream instanceof Expressible){
        expression.addParameter(((Expressible)stream).toExpression(factory));
      }
      else{
        throw new IOException("This SortStream contains a non-expressible TupleStream - it cannot be converted to an expression");
      }
    }
    else{
      expression.addParameter("<stream>");
    }
    
    // by
    if(comparator instanceof Expressible){
      expression.addParameter(new StreamExpressionNamedParameter("by",((Expressible)comparator).toExpression(factory)));
    }
    else{
      throw new IOException("This SortStream contains a non-expressible equalitor - it cannot be converted to an expression");
    }
    
    return expression;   
  }
  
  @Override
  public Explanation toExplanation(StreamFactory factory) throws IOException {

    return new StreamExplanation(getStreamNodeId().toString())
      .withChildren(new Explanation[]{
        stream.toExplanation(factory)
      })
      .withFunctionName(factory.getFunctionName(this.getClass()))
      .withImplementingClass(this.getClass().getName())
      .withExpressionType(ExpressionType.STREAM_DECORATOR)
      .withExpression(toExpression(factory, false).toString())
      .withHelper(comparator.toExplanation(factory));
  }
    
  public void setStreamContext(StreamContext context) {
    this.stream.setStreamContext(context);
  }

  public List<TupleStream> children() {
    List<TupleStream> l =  new ArrayList<TupleStream>();
    l.add(stream);
    return l;
  }

  public void open() throws IOException {
    stream.open();

    worker.readStream(stream);
    worker.sort();
  }

  public void close() throws IOException {
    stream.close();
  }

  public Tuple read() throws IOException {
    // return next from sorted order
    return worker.read();    
  }

  /** Return the stream sort - ie, the order in which records are returned */
  public StreamComparator getStreamSort(){
    return comparator;
  }
  
  public int getCost() {
    return 0;
  }

  private interface Worker {
    public void readStream(TupleStream stream) throws IOException;
    public void sort();
    public Tuple read();
  }
  
}