/********************************************************************
 * AUTHORS: Trevor Hansen
 *
 * BEGIN DATE: July, 2010
 *
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
********************************************************************/

#ifndef WORKLIST_H_
#define WORKLIST_H_

#include "stp/AST/AST.h"
#include "stp/AST/ASTNode.h"

namespace simplifier
{
namespace constantBitP
{
using std::cerr;
using std::endl;

class WorkList
{
  /* Rough worklist. Constraint Programming people have lovely structures to do
   * this
   * The set (on my machine), is implemented by red-black trees. Deleting just
   * from one end may unbalance the tree??
   */

private:
  // select nodes from the cheap_worklist first.
  std::unordered_set<stp::ASTNode, ASTNode::ASTNodeHasher, ASTNode::ASTNodeEqual> cheap_workList;    
  std::unordered_set<stp::ASTNode, ASTNode::ASTNodeHasher, ASTNode::ASTNodeEqual> expensive_workList; 

  WorkList(const WorkList&); // Shouldn't needed to copy or assign.
  WorkList& operator=(const WorkList&);

  // We add to the worklist any node that immediately depends on a constant.
  void addToWorklist(const stp::ASTNode& n, stp::ASTNodeSet& visited)
  {
    if (n.isConstant())
      return;

    if (visited.find(n) != visited.end())
      return;

    visited.insert(n);

    bool alreadyAdded = false;

    for (unsigned i = 0; i < n.GetChildren().size(); i++)
    {
      if (!alreadyAdded && n[i].isConstant())
      {
        alreadyAdded = true;
        push(n);
      }
      addToWorklist(n[i], visited);
    }
  }

public:
  // Add to the worklist any node that immediately depends on a constant.

  WorkList(const ASTNode& top) { initWorkList(top); }

  int size() { return cheap_workList.size() + expensive_workList.size(); }

  void initWorkList(const ASTNode& n)
  {
    stp::ASTNodeSet visited;
    addToWorklist(n, visited);
  }

  void push(const stp::ASTNode& n)
  {
    if (n.isConstant()) // don't ever add constants to the worklist.
      return;

    // cerr << "WorkList Inserting:" << n.GetNodeNum() << endl;
    if (n.GetKind() == stp::BVMULT || n.GetKind() == stp::BVPLUS ||
        n.GetKind() == stp::BVDIV)
      expensive_workList.insert(n);
    else
      cheap_workList.insert(n);
  }

  stp::ASTNode pop()
  {
    assert(!isEmpty());
    if (cheap_workList.size() > 0)
    {
      ASTNode ret = *cheap_workList.begin();
      cheap_workList.erase(cheap_workList.begin());
      return ret;
    }
    else
    {
      assert(expensive_workList.size() > 0);
      ASTNode ret = *expensive_workList.begin();
      expensive_workList.erase(expensive_workList.begin());
      return ret;
    }
  }

  bool isEmpty()
  {
    return cheap_workList.empty() && expensive_workList.empty();
  }

  void print()
  {
    cerr << "+Worklist" << endl;
    std::unordered_set<stp::ASTNode, ASTNode::ASTNodeHasher, ASTNode::ASTNodeEqual>::const_iterator it = cheap_workList.begin();
    while (it != cheap_workList.end())
    {
      cerr << *it << " ";
      it++;
    }

    it = expensive_workList.begin();
    while (it != expensive_workList.end())
    {
      cerr << *it << " ";
      it++;
    }

    cerr << "-Worklist" << endl;
  }
};
}
}

#endif /* WORKLIST_H_ */
