/**
 * 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.mahout.cf.taste.impl.similarity.precompute;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;

import com.google.common.io.Closeables;
import org.apache.commons.io.Charsets;
import org.apache.mahout.cf.taste.similarity.precompute.SimilarItem;
import org.apache.mahout.cf.taste.similarity.precompute.SimilarItems;
import org.apache.mahout.cf.taste.similarity.precompute.SimilarItemsWriter;

/**
 * Persist the precomputed item similarities to a file that can later be used
 * by a {@link org.apache.mahout.cf.taste.impl.similarity.file.FileItemSimilarity}
 */
public class FileSimilarItemsWriter implements SimilarItemsWriter {

  private final File file;
  private BufferedWriter writer;

  public FileSimilarItemsWriter(File file) {
    this.file = file;
  }

  @Override
  public void open() throws IOException {
    writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), Charsets.UTF_8));
  }

  @Override
  public void add(SimilarItems similarItems) throws IOException {
    String itemID = String.valueOf(similarItems.getItemID());
    for (SimilarItem similarItem : similarItems.getSimilarItems()) {
      writer.write(itemID);
      writer.write(',');
      writer.write(String.valueOf(similarItem.getItemID()));
      writer.write(',');
      writer.write(String.valueOf(similarItem.getSimilarity()));
      writer.newLine();
    }
  }

  @Override
  public void close() throws IOException {
    Closeables.close(writer, false);
  }
}