/*
 * Copyright (c) 2006 IBM Corporation.
 * All rights reserved. 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
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 */
package com.ibm.wala.ipa.slicer;

import com.ibm.wala.dataflow.IFDS.IFlowFunction;
import com.ibm.wala.dataflow.IFDS.IFlowFunctionMap;
import com.ibm.wala.dataflow.IFDS.IUnaryFlowFunction;
import com.ibm.wala.dataflow.IFDS.VectorGenFlowFunction;
import com.ibm.wala.util.intset.SparseIntSet;

/** Trivial flow functions to represent simple reachability. All functions simply return "0" */
public class ReachabilityFunctions<T> implements IFlowFunctionMap<T> {

  public static final VectorGenFlowFunction FLOW_REACHES =
      VectorGenFlowFunction.make(SparseIntSet.singleton(0));

  public static final IUnaryFlowFunction KILL_FLOW =
      new IUnaryFlowFunction() {
        @Override
        public SparseIntSet getTargets(int d1) {
          // kill even the reachability predicate 0.
          return new SparseIntSet();
        }

        @Override
        public String toString() {
          return "killFlow";
        }
      };

  public static <T> ReachabilityFunctions<T> createReachabilityFunctions() {
    return new ReachabilityFunctions<>();
  }

  private ReachabilityFunctions() {}

  @Override
  public IUnaryFlowFunction getCallNoneToReturnFlowFunction(T src, T dest) {
    return FLOW_REACHES;
  }

  @Override
  public IUnaryFlowFunction getCallToReturnFlowFunction(T src, T dest) {
    // force flow into callee and back.
    return KILL_FLOW;
  }

  @Override
  public IUnaryFlowFunction getNormalFlowFunction(T src, T dest) {
    return FLOW_REACHES;
  }

  @Override
  public IFlowFunction getReturnFlowFunction(T call, T src, T dest) {
    return FLOW_REACHES;
  }

  @SuppressWarnings("unused")
  public IFlowFunction getReturnFlowFunction(T src, T dest) {
    return FLOW_REACHES;
  }

  @Override
  public IUnaryFlowFunction getCallFlowFunction(T src, T dest, T ret) {
    return FLOW_REACHES;
  }
}
