/*
 * Ivory: A Hadoop toolkit for Web-scale information retrieval
 * 
 * Licensed 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 ivory.lsh.data;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import edu.umd.cloud9.debug.MemoryUsageUtils;

/**
 * <p>
 * Array-based implementation of <code>DfTable</code>. Binary search is used
 * for lookup.
 * </p>
 * 
 * @author Jimmy Lin
 * 
 */
public class DfTableArray implements DfTable {
  private int mNumDocs;
  private int mNumTerms;

  private int mMaxDf = 0;
  private String mMaxDfTerm;

  private int mDfOne = 0;

  private String[] mTerms;
  private int[] mDfs;

  /**
   * Creates a <code>DfTableArray</code> object.
   * 
   * @param file
   *            collection frequency data file
   * @throws IOException
   */
  public DfTableArray(String file) throws IOException {
    this(file, FileSystem.get(new Configuration()));
    //		for(int i=0;i<20;i++){
    //			int j= 100*i+1000;
    //			while(mDfs[j]==1){
    //				j++;
    //			}
    //			System.out.println(mTerms[j]+" "+mDfs[j]);
    //
    //		}
  }

  /**
   * Creates a <code>DfTableArray</code> object.
   * 
   * @param file
   *            collection frequency data file
   * @param fs
   *            FileSystem to read from
   * @throws IOException
   */
  public DfTableArray(String file, FileSystem fs) throws IOException {
    FSDataInputStream in = fs.open(new Path(file));

    this.mNumDocs = in.readInt();
    this.mNumTerms = in.readInt();

    mTerms = new String[mNumTerms];
    mDfs = new int[mNumTerms];

    for (int i = 0; i < mNumTerms; i++) {
      String term = in.readUTF();

      //changed by Ferhan Ture : df table isn't read properly with commented line
      //int df = WritableUtils.readVInt(in);
      int df = in.readInt();

      mTerms[i] = term;
      mDfs[i] = df;

      if (df > mMaxDf) {
        mMaxDf = df;
        mMaxDfTerm = term;
      }

      if (df == 1) {
        mDfOne++;
      }
    }

    in.close();
  }

  public int getDf(String term) {
    int index = Arrays.binarySearch(mTerms, term);

    if (index < 0)
      return -1;

    return mDfs[index];
  }

  public int getDocumentCount() {
    return mNumDocs;
  }

  public int getVocabularySize() {
    return mNumTerms;
  }

  public int getMaxDf() {
    return mMaxDf;
  }

  public String getMaxDfTerm() {
    return mMaxDfTerm;
  }

  public int getCountOfTermWithDfOne() {
    return mDfOne;
  }

  public static void main(String[] args) throws Exception {
    if (args.length != 1) {
      System.out.println("usage: [df-file]");
      System.exit(-1);
    }

    long startingMemoryUse = MemoryUsageUtils.getUsedMemory();

    DfTableArray dfs = new DfTableArray(args[0]);

    System.out.println("Number of documents: " + dfs.getDocumentCount());
    System.out.println("Vocab size: " + dfs.getVocabularySize());
    System.out.println("term with max df is " + dfs.getMaxDfTerm() + ", df=" + dfs.getMaxDf());
    System.out.println(dfs.getCountOfTermWithDfOne() + " terms have df=1");

    long endingMemoryUse = MemoryUsageUtils.getUsedMemory();

    System.out.println("Memory usage: " + (endingMemoryUse - startingMemoryUse) + " bytes\n");

    String term = null;
    BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Look up df of stemmed term> ");
    while ((term = stdin.readLine()) != null) {
      System.out.println(term + ", df=" + dfs.getDf(term));
      System.out.print("Look up df of stemmed term > ");
    }
  }
}