/*
 * This file is part of the source code of the software program
 * Vampire. It is protected by applicable
 * copyright laws.
 *
 * This source code is distributed under the licence found here
 * https://vprover.github.io/license.html
 * and in the source directory
 */
/**
 * @file BestLiteralSelector.hpp
 * Defines classes BestLiteralSelector and CompleteBestLiteralSelector.
 */


#ifndef __BestLiteralSelector__
#define __BestLiteralSelector__

#include <algorithm>

#include "Forwards.hpp"

#include "Lib/Comparison.hpp"
#include "Lib/DArray.hpp"
#include "Lib/Set.hpp"
#include "Lib/Stack.hpp"

#include "Term.hpp"
#include "Clause.hpp"
#include "Ordering.hpp"

#include "LiteralSelector.hpp"

namespace Kernel {

using namespace Lib;

/**
 * A literal selector class template that selects the best literal
 * (i.e. the maximal literal in quality ordering specified by
 * QComparator class). Using this literal selector does not
 * maintain completeness.
 *
 * Objects of the QComparator class must provide a method
 * Lib::Comparison compare(Literal*, Literal*)
 * that compares the quality of two literals.
 */
template<class QComparator>
class BestLiteralSelector
    : public LiteralSelector
      {
      public:
  BestLiteralSelector(const Ordering& ordering, const Options& options) : LiteralSelector(ordering, options)
  {
    _comp.attachSelector(this);
  }

  bool isBGComplete() const override { return false; }
protected:
  void doSelection(Clause* c, unsigned eligible) override
  {
    unsigned besti=0;
    Literal* best=(*c)[0];
    for(unsigned i=1;i<eligible;i++) {
      Literal* lit=(*c)[i];
      if(_comp.compare(best, lit)==LESS) {
        besti=i;
        best=lit;
      }
    }
    if(besti>0) {
      std::swap((*c)[0], (*c)[besti]);
    }
    c->setSelected(1);

#if VDEBUG
    ensureSomeColoredSelected(c, eligible);
    ASS_EQ(c->numSelected(), 1); //if there is colored, it should be selected by the QComparator
#endif
  }

      private:
  QComparator _comp;
      };


/**
 * A literal selector class template, that tries select the best
 * literal (i.e. the maximal literal in quality ordering specified by
 * QComparator class), but takes completeness of the selection into
 * account.
 *
// * If the best literal is negative, it is selected. If it is among
// * maximal literals, and there is no negative literal among them,
// * they all are selected. If there is a negative literal among
// * maximal literals, we select the best negative literal. If
// * the best literal is neither negative nor maximal, we consider
// * similarly the second best etc...
 * If the worst of maximal positive literal is better than all negative
 * literals, all maximal positive literals are selected. Otherwise the
 * best negative literal is selected.
 *
 * Objects of the QComparator class must provide a method
 * Lib::Comparison compare(Literal*, Literal*)
 * that compares the quality of two literals.
 */
template<class QComparator>
class CompleteBestLiteralSelector
    : public LiteralSelector
{
public:
  CompleteBestLiteralSelector(const Ordering& ordering, const Options& options) : LiteralSelector(ordering, options)
  {
    _comp.attachSelector(this);
  }

  bool isBGComplete() const override { return true; }
protected:
  void doSelection(Clause* c, unsigned eligible) override
  {
    ASS_G(eligible, 1); //trivial cases should be taken care of by the base LiteralSelector

    static DArray<Literal*> litArr(64);
    static Set<unsigned> maxTermHeads;
    maxTermHeads.reset();
    litArr.initFromArray(eligible,*c);
    litArr.sortInversed(_comp);

    LiteralList* maximals=0;
    Literal* singleSelected=0; //If equals to 0 in the end, all maximal

    //literals will be selected.
    bool allSelected=false;

    if(isNegativeForSelection(litArr[0])) {
      singleSelected=litArr[0];
    } else {
      fillMaximals(maximals, litArr);
      unsigned besti=0;
      LiteralList* nextMax=maximals;
      while(true) {
        if(nextMax->head()==litArr[besti]) {
          nextMax=nextMax->tail();
          if(nextMax==0) {
            break;
          }
        }
        besti++;
        ASS_L(besti,eligible);
        if(isNegativeForSelection(litArr[besti])){
          singleSelected=litArr[besti];
          break;
        }
      }
    }
    if(!singleSelected && !maximals->tail()) {
      //there is only one maximal literal
      singleSelected=maximals->head();
    }
    if(!singleSelected) {
      unsigned selCnt=0;
      for(LiteralList* mit=maximals; mit; mit=mit->tail()) {
        ASS(isPositiveForSelection(mit->head()));
        selCnt++;
      }
      if(selCnt==eligible) {
        allSelected=true;
      }
    }
    if(allSelected) {
      c->setSelected(eligible);
    } else if(!singleSelected) {
      //select multiple maximal literals
      static Stack<Literal*> replaced(16);
      Set<Literal*> maxSet;
      unsigned selCnt=0;

      for(LiteralList* mit=maximals; mit; mit=mit->tail()) {
        maxSet.insert(mit->head());
      }

      while(maximals) {
        if(!maxSet.contains((*c)[selCnt])) {
          replaced.push((*c)[selCnt]);
        }
        (*c)[selCnt]=LiteralList::pop(maximals);
        selCnt++;
      }
      ASS_G(selCnt,1);
      ASS_LE(selCnt,eligible);

      //put back non-selected literals that were removed
      unsigned i=selCnt;
      while(replaced.isNonEmpty()) {
        while(!maxSet.contains((*c)[i])) {
          i++;
          ASS_L(i,eligible);
        }
        (*c)[i++]=replaced.pop();
      }

      c->setSelected(selCnt);
    } else {
      unsigned besti=c->getLiteralPosition(singleSelected);
      if(besti!=0) {
        std::swap((*c)[0],(*c)[besti]);
      }
      c->setSelected(1);
    }
    LiteralList::destroy(maximals);

    ensureSomeColoredSelected(c, eligible);
  }

  void fillMaximals(LiteralList*& maximals, DArray<Literal*>& litArr)
  {
    DArray<Literal*>::ReversedIterator rlit(litArr);
    while(rlit.hasNext()) {
      Literal* lit=rlit.next();
      LiteralList::push(lit,maximals);
    }
    _ord.removeNonMaximal(maximals);
  }

private:
  QComparator _comp;
};

};

#endif /* __BestLiteralSelector__ */
