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package com.ibm.wala.demandpa.alg;

import java.util.Collection;
import java.util.Collections;

import com.ibm.wala.demandpa.flowgraph.SimpleDemandPointerFlowGraph;
import com.ibm.wala.demandpa.util.MemoryAccessMap;
import com.ibm.wala.ipa.callgraph.AnalysisOptions;
import com.ibm.wala.ipa.callgraph.CGNode;
import com.ibm.wala.ipa.callgraph.CallGraph;
import com.ibm.wala.ipa.callgraph.propagation.HeapModel;
import com.ibm.wala.ipa.callgraph.propagation.InstanceKey;
import com.ibm.wala.ipa.callgraph.propagation.LocalPointerKey;
import com.ibm.wala.ipa.callgraph.propagation.PointerKey;
import com.ibm.wala.ipa.cha.IClassHierarchy;
import com.ibm.wala.util.Predicate;
import com.ibm.wala.util.debug.UnimplementedError;
import com.ibm.wala.util.graph.traverse.SlowDFSDiscoverTimeIterator;

/**
 * Purely field-based, context-insensitive demand-driven points-to analysis with
 * very simple implementation.
 * 
 * @author Manu Sridharan
 * 
 */
public class SimpleDemandPointsTo extends AbstractDemandPointsTo {

  private static final boolean VERBOSE = false;

  public SimpleDemandPointsTo(CallGraph cg, HeapModel model, MemoryAccessMap fam, IClassHierarchy cha, AnalysisOptions options) {
    super(cg, model, fam, cha, options);
  }

  @Override
  @SuppressWarnings("unchecked")
  public Collection<InstanceKey> getPointsTo(PointerKey pk) throws IllegalArgumentException, UnimplementedError {

    if (pk == null) {
      throw new IllegalArgumentException("pk == null");
    }
    assert pk instanceof LocalPointerKey : "we only handle locals";
    LocalPointerKey lpk = (LocalPointerKey) pk;
    // Create an (initially empty) dependence graph
    SimpleDemandPointerFlowGraph g = new SimpleDemandPointerFlowGraph(cg, heapModel, mam, cha);

    // initialize the graph with the subgraph of x's method
    CGNode node = lpk.getNode();
    g.addSubgraphForNode(node);

    if (!g.containsNode(pk)) {
      return Collections.emptySet();
    }

    if (VERBOSE) {
      System.err.println(g.toString());
    }

    Predicate iKeyFilter = new Predicate() {
      @Override
      public boolean test(Object o) {
        return o instanceof InstanceKey;
      }
    };

    SlowDFSDiscoverTimeIterator<Object> dfs = new SlowDFSDiscoverTimeIterator<Object>(g, pk);
    return Predicate.filter(dfs, iKeyFilter);
  }

}