/*
 * 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.ssa.IR;
import com.ibm.wala.ssa.ISSABasicBlock;
import com.ibm.wala.ssa.SSACFG;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Set;

public class BlockSearch {

  private ArrayList<ISSABasicBlock> blockQueue = new ArrayList<>();
  private int location = 0;

  private final SSACFG cfg;

  BlockSearch(IR ir) {
    cfg = ir.getControlFlowGraph();
  }

  public ISSABasicBlock searchFromBlock(ISSABasicBlock b, Set<ISSABasicBlock> targets) {
    blockQueue.clear();
    location = 0;
    Iterator<ISSABasicBlock> startNodes = cfg.getPredNodes(b);
    while (startNodes.hasNext()) {
      blockQueue.add(startNodes.next());
    }

    ISSABasicBlock candidate = null;
    while (location < blockQueue.size()) {
      ISSABasicBlock current = blockQueue.get(location);
      location++;
      // TODO: inspect current for function calls or other instructions that could confuse the
      // analysis
      if (targets.contains(current)) {
        if (candidate == null) {
          candidate = current;
        } else if (candidate != current) {
          return null;
        }
        continue;
      } else {
        Iterator<ISSABasicBlock> predNodes = cfg.getPredNodes(current);
        while (predNodes.hasNext()) {
          blockQueue.add(predNodes.next());
        }
      }
    }
    return candidate;
  }
}
