/*
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html.
 *
 * This file is a derivative of code released under the terms listed below.
 *
 */
/*
 *
 * Copyright (c) 2009-2012,
 *
 *  Adam Fuchs          <afuchs@cs.umd.edu>
 *  Avik Chaudhuri      <avik@cs.umd.edu>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. The names of the contributors may not be used to endorse or promote
 * products derived from this software without specific prior written
 * permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 *
 */

package org.scandroid.prefixtransfer;

import com.ibm.wala.fixpoint.AbstractVariable;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map.Entry;

public class PrefixVariable extends AbstractVariable<PrefixVariable> {

  // map instance keys to their prefixes
  public HashMap<Integer, String> knownPrefixes = new HashMap<>();
  public HashSet<Integer> fullPrefixKnown = new HashSet<>();

  // TODO: keep track of completely known strings (not just known by prefix)
  //  HashMap<Integer, String> knownStrings = new HashMap<Integer,String>();

  @Override
  public void copyState(PrefixVariable v) {
    knownPrefixes.clear();
    knownPrefixes.putAll(v.knownPrefixes);
    fullPrefixKnown.clear();
    fullPrefixKnown.addAll(v.fullPrefixKnown);
  }

  public static String intersect(String one, String two) {
    int i = 0;
    while (i < one.length() && i < two.length()) {
      if (one.charAt(i) != two.charAt(i)) break;
      i++;
    }
    return one.substring(0, i);
  }

  public String getPrefix(int instance) {
    return knownPrefixes.get(instance);
  }

  public boolean updateAll(PrefixVariable other) {
    boolean changed = false;
    for (Entry<Integer, String> e : other.knownPrefixes.entrySet()) {
      changed = update(e.getKey(), e.getValue()) || changed;
    }
    for (Integer i : other.fullPrefixKnown) {
      changed = include(i) || changed;
    }
    return changed;
  }

  public boolean include(Integer i) {
    return fullPrefixKnown.add(i);
  }

  // set an instance key to have a known prefix
  public boolean update(Integer instance, String prefix) {
    String prevPrefix = knownPrefixes.get(instance);

    if (prevPrefix == null) {
      knownPrefixes.put(instance, prefix);
      return true;
    } else {
      String newPrefix = intersect(prevPrefix, prefix);
      if (newPrefix.equals(prevPrefix)) return false;
      knownPrefixes.put(instance, newPrefix);
      return true;
    }
  }

  @Override
  public String toString() {
    return knownPrefixes.toString();
  }

  // set an instance key to be a particular constant
  //  public boolean setConstant(Integer instance, String prefix)
  //  {
  //      return false;
  //  }
}
