#ifndef IMPROVEMENT_OPERATOR_HPP
#define IMPROVEMENT_OPERATOR_HPP

#include "IdSet.hpp"
#include "MaxStrategy.hpp"

template<typename Domain>
struct ImprovementOperator {
  virtual ~ImprovementOperator() { }
  virtual bool improve(
      ConcreteMaxStrategy<Domain>& strat,
      const VariableAssignment<Domain>& rho,
      IdSet<Variable<Domain> >& changedIn,
      IdSet<Variable<Domain> >& changedOut
  ) const  = 0;
};

template<typename Domain>
unsigned int bestStrategy(const MaxStrategy<Domain>& strat, const MaxExpression<Domain>& expr, const VariableAssignment<Domain>& rho) {
  Domain bestValue = MaxStrategyExpression<Domain>(expr, strat).eval(rho);
  unsigned int bestIndex = strat.get(expr);

  const std::vector<Expression<Domain>*>& args = expr.arguments();
  for (unsigned int j = 0, length = args.size();
       j < length;
       ++j) {
    const Domain value = MaxStrategyExpression<Domain>(*args[j], strat).eval(rho);
    std::cout << bestValue << " < " << value << ": ";
    if (bestValue < value) {
      std::cout << "change!" << std::endl;
      bestValue = value;
      bestIndex = j;
    }
    std::cout << std::endl;
  }
  return bestIndex;
}

template<typename Domain>
struct NaiveImprovementOperator : public ImprovementOperator<Domain> {
  bool improve(
      ConcreteMaxStrategy<Domain>& strat,
      const VariableAssignment<Domain>& rho,
      IdSet<Variable<Domain> >& changedIn,
      IdSet<Variable<Domain> >& changedOut
  ) const {
    bool changed = false;
    for (unsigned int i = 0, length = strat.maxExpressionCount();
         i < length;
         ++i) {
      MaxExpression<Domain>& expr = strat.maxExpression(i);
      // this relies on the fact that an expression will only be proessed after the expressions
      // it depends on (which should always be true, as they form a DAG)
      unsigned int index = bestStrategy(strat, expr, rho);

      if (index != strat.get(expr)) {
        changed = true;
        strat.set(expr, index);
      }
    }
    return changed;
  }
};
  
template<typename Domain>
struct RepeatedImprovementOperator : public ImprovementOperator<Domain> {
  RepeatedImprovementOperator(const ImprovementOperator<Domain>& op)
    : _subImprovement(op) { }

  bool improve(
      ConcreteMaxStrategy<Domain>& strat,
      const VariableAssignment<Domain>& rho,
      IdSet<Variable<Domain> >& changedIn,
      IdSet<Variable<Domain> >& changedOut
  ) const {
    if (_subImprovement.improve(strat, rho, changedIn, changedOut)) {
      VariableAssignment<Domain>* rho2 = strat.eval(rho);
      improve(strat, *rho2, changedIn, changedOut);
      delete rho2;
      return true;
    }
    return false;
  }
  private:
  const ImprovementOperator<Domain>& _subImprovement;
};

template<typename Domain>
struct SmartImprovementOperator : public ImprovementOperator<Domain> {
  SmartImprovementOperator(const ConcreteEquationSystem<Domain>& system)
    : _system(system),
      _influence(system.maxExpressionCount(), IdSet<MaxExpression<Domain> >(system.maxExpressionCount())) {
  }

  struct DynamicMaxStrategy : public MaxStrategy<Domain> {
    DynamicMaxStrategy(
        ConcreteMaxStrategy<Domain>& strat,
        IdMap<MaxExpression<Domain>,IdSet<MaxExpression<Domain> > >& influence,
        const VariableAssignment<Domain>& rho,
        IdSet<MaxExpression<Domain> >& stable,
        IdSet<MaxExpression<Domain> >& changed
    ) : MaxStrategy<Domain>(strat),
        _rho(rho),
        _values(strat),
        _stable(stable),
        _changed(changed),
        _influence(influence) {
    }

    unsigned int get(const MaxExpression<Domain>& e) const {
      solve(e);
      return _values.get(e);
    }

    private:
    void solve(const MaxExpression<Domain>& x) const {
      if (!_stable.contains(x)) {
        _stable.insert(x);

        unsigned int val = bestStrategy(DependencyStrategy(*this, x), x, _rho);
        //MaxStrategyExpression(x, DependencyStrategy(_values, x));

        if (val != _values.get(x)) {
          IdSet<MaxExpression<Domain> > oldInfluence = _influence[x];
          _influence[x].clear();
          _values.set(x, val);
          _changed.insert(x);
          std::cout << x << std::endl;

          _stable.filter(oldInfluence);

          for (typename IdSet<MaxExpression<Domain> >::iterator it = oldInfluence.begin();
               it != oldInfluence.end();
               ++it) {
            solve(_values.maxExpression(*it));
          }
          _influence[x] = oldInfluence;
        }
      }
    }

    struct DependencyStrategy : public MaxStrategy<Domain> {
      DependencyStrategy(const DynamicMaxStrategy& strat, const MaxExpression<Domain>& expr)
        : MaxStrategy<Domain>(strat),
          _strat(strat),
          _expr(expr) {
      }
      unsigned int get(const MaxExpression<Domain>& e) const {
        _strat.solve(e);
        _strat._influence[e].insert(_expr);
        return _strat._values.get(e);
      }
      private:
      const DynamicMaxStrategy& _strat;
      const MaxExpression<Domain>& _expr;
    };

    private:
    const VariableAssignment<Domain>& _rho;
    ConcreteMaxStrategy<Domain>& _values;
    IdSet<MaxExpression<Domain> >& _stable;
    IdSet<MaxExpression<Domain> >& _changed;
    IdMap<MaxExpression<Domain>,IdSet<MaxExpression<Domain> > >& _influence;
  };

  void invalidate(IdSet<MaxExpression<Domain> >& set, MaxExpression<Domain>& expr) const {
    for (typename IdSet<MaxExpression<Domain> >::iterator it = _influence[expr].begin(),
                                                          end = _influence[expr].end();
         it != end;
         ++it) {
      set.insert(_system.maxExpression(*it));
      invalidate(set, expr);
    }
  }

  bool improve(
      ConcreteMaxStrategy<Domain>& stratOut,
      const VariableAssignment<Domain>& rho,
      IdSet<Variable<Domain> >& changedIn,
      IdSet<Variable<Domain> >& changedOut
  ) const {
    IdSet<MaxExpression<Domain> > invalidSet(_system.maxExpressionCount());
    IdSet<MaxExpression<Domain> > changedSet(_system.maxExpressionCount());
    for (typename IdSet<Variable<Domain> >::iterator it = changedIn.begin(),
                                                     end = changedIn.end();
         it != end;
         ++it) {
      invalidate(invalidSet, *_system[_system.variable(*it)]);
    }
    invalidSet.invert();

    std::cout << std::endl;
    DynamicMaxStrategy strat(stratOut, _influence, rho, invalidSet, changedSet);
    std::cout << std::endl;
    for (typename IdSet<MaxExpression<Domain> >::iterator it = changedSet.begin(),
                                                          end = changedSet.end();
         it != end;
         ++it) {
      Variable<Domain>* var = strat.varFromExpr(_system.maxExpression(*it));
      if (var) {
        changedOut.insert(*var);
      }
    }
    std::cout << changedSet << std::endl;
    std::cout << changedOut << std::endl;
    return changedOut.size() != 0;
  }
  private:
  const ConcreteEquationSystem<Domain>& _system;
  mutable IdMap<MaxExpression<Domain>,IdSet<MaxExpression<Domain> > > _influence;
};

#endif