Reduce.java

/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2013, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.issue.lbcore224;

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Reduce a file consisting of lock and unlock operations by removing matching lock/unlocks.
 */
public class Reduce {

  static int NA = -1;

  enum OperationType {LOCK, UNLOCK}

  public static void main(String[] args) throws IOException {
    File inputFile = new File(args[0]);
    if(!inputFile.exists()) {
      throw new IllegalArgumentException("Missing file ["+args[0]+"]");
    }
    List<String> lines = readFile(inputFile);
    System.out.println("Lines count=" + lines.size());
    List<Structure> structuredLines = structure(lines);
    List<Structure> reduction = reduce(structuredLines);
    if (reduction.isEmpty()) {
      System.out.println("Reduction is EMPTY as it should be.");
    } else {
      System.out.println("Non-empty reduction!!! WTF?");
      System.out.println(reduction);
    }


  }

  private static List<String> readFile(File  inputFile) throws IOException {
    BufferedReader reader = null;
    List<String> lines = new ArrayList();
    try {
      reader = new BufferedReader(new FileReader(inputFile));
      String line;
      while ((line = reader.readLine()) != null) {
        lines.add(line);
      }
    } finally {
      if (reader != null)
        try {
          reader.close();
        } catch (IOException e) {
        }
    }
    return lines;
  }

  private static List<Structure> reduce(List<Structure> structuredLines) {
    List<Structure> matching = new ArrayList<Structure>();
    int lockIndex = 0;
    while (lockIndex < structuredLines.size()) {
      lockIndex = findNearestLock(structuredLines, lockIndex);
      if (lockIndex == NA)
        break;
      else {
        int unlockIndex = findNearestUnlockInSameThread(structuredLines, lockIndex);
        if (unlockIndex != NA) {
          matching.add(structuredLines.get(lockIndex));
          matching.add(structuredLines.get(unlockIndex));
        }
        lockIndex++;
      }
    }
    System.out.println("matching list size: " + matching.size());
    List<Structure> reduction = new ArrayList<Structure>();
    for (Structure s : structuredLines) {
      if (!matching.contains(s)) {
        reduction.add(s);
      }
    }
    return reduction;

  }

  private static int findNearestLock(List<Structure> reduction, int index) {
    for (int i = index; i < reduction.size(); i++) {
      Structure s = reduction.get(i);
      if (s.operationType == OperationType.LOCK) {
        return i;
      }
    }
    return NA;
  }

  private static int findNearestUnlockInSameThread(List<Structure> reduction, int lockIndex) {
    int firstCandidateIndex = lockIndex+1;
    Structure lockStructure = reduction.get(lockIndex);
    for (int i = firstCandidateIndex; i < reduction.size(); i++) {
      Structure s = reduction.get(i);
      if (s.operationType == OperationType.UNLOCK && lockStructure.thread.equals(s.thread)) {
        return i;
      }
    }
    return NA;
  }

  static List<Structure> structure(List<String> lines) {
    List<Structure> structuredLines = new ArrayList();
    Pattern p = Pattern.compile("(\\d{2,5})\\ +(.*) (LOCK|UNLOCK)");

    for (String line : lines) {
      Matcher m = p.matcher(line);
      if (m.matches()) {
        String relTime = m.group(1);
        String t = m.group(2);
        String opStr = m.group(3);
        Structure structure = buildStructure(relTime, t, opStr);
        structuredLines.add(structure);
      } else {
        System.out.println("NON MATCHING LINE: ["+ line+"]");
      }

    }
    return structuredLines;
  }

  private static Structure buildStructure(String relTime, String t, String opStr) {
    long r = Long.parseLong(relTime);
    OperationType operationType;
    if (opStr.equals("LOCK"))
      operationType = OperationType.LOCK;
    else if (opStr.equals("UNLOCK")) {
      operationType = OperationType.UNLOCK;
    } else {
      throw new IllegalArgumentException(opStr + " is not LOCK|UNLOCK");
    }
    return new Structure(r, t, operationType);
  }


  static class Structure {
    long time;
    String thread;
    OperationType operationType;

    Structure(long time, String thread, OperationType operationType) {
      this.time = time;
      this.thread = thread;
      this.operationType = operationType;
    }

    @Override
    public String toString() {
      return "Structure{" +
              "time=" + time +
              ", thread='" + thread + '\'' +
              ", operationType=" + operationType +
              '}';
    }
  }

}