nifexpr.h

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#ifndef NIFEXPR_H
#define NIFEXPR_H
#pragma once

#include <QVariant>
#include <QString>

class Expression
{
   enum Operator {
      e_nop, e_not_eq, e_eq, e_gte, e_lte, e_gt, e_lt, e_bit_and, e_bit_or, 
      e_add, e_sub, e_bool_and, e_bool_or, e_not,
   };
   QVariant lhs;
   QVariant rhs;
   Operator opcode;

public:
   explicit Expression()
   {
      opcode = Expression::e_nop;
   }

   Expression(const QString & cond, int startpos, int endpos)
   {
      opcode = Expression::e_nop;
      partition(cond.mid(startpos, endpos-startpos+1));
   }

   Expression(const QString & cond)
   {
      opcode = Expression::e_nop;
      partition(cond);
   }

   QString toString() const;

public:
   template <class F>
   QVariant evaluateValue( const F& convert ) const
   {
      QVariant l = convertValue(lhs, convert);
      QVariant r = convertValue(rhs, convert);
      NormalizeVariants(l, r);

      switch (opcode)
      {
      case Expression::e_not:
         return QVariant::fromValue( !r.toBool() );
      case Expression::e_not_eq:
         return QVariant::fromValue(l != r);
      case Expression::e_eq:
         return QVariant::fromValue(l == r);
      case Expression::e_gte:
         return QVariant::fromValue(l.toUInt() >= r.toUInt());
      case Expression::e_lte:
         return QVariant::fromValue(l.toUInt() <= r.toUInt());
      case Expression::e_gt:
         return QVariant::fromValue(l.toUInt() > r.toUInt());
      case Expression::e_lt:
         return QVariant::fromValue(l.toUInt() < r.toUInt());
      case Expression::e_bit_and:
         return QVariant::fromValue(l.toUInt() & r.toUInt());
      case Expression::e_bit_or:
         return QVariant::fromValue(l.toUInt() | r.toUInt());
      case Expression::e_add:
         return QVariant::fromValue(l.toUInt() + r.toUInt());
      case Expression::e_sub:
         return QVariant::fromValue(l.toUInt() - r.toUInt());
      case Expression::e_bool_and:
         return QVariant::fromValue(l.toBool() && r.toBool());
      case Expression::e_bool_or:
         return QVariant::fromValue(l.toBool() || r.toBool());
      case Expression::e_nop:
         return l;
      }
      return l;
   }

   template <class F>
   bool evaluateBool( const F& convert ) const
   {
      return evaluateValue(convert).toBool();
   }

   template <class F>
   int evaluateUInt( const F& convert ) const
   {
      return evaluateValue(convert).toUInt();
   }
private:
   static Operator operatorFromString(const QString& str);
   void partition(const QString & cond, int offset = 0);
   void NormalizeVariants(QVariant &l, QVariant &r) const;

   template <class F>
   QVariant convertValue(const QVariant& v, const F& convert ) const
   {
      if (v.type() == QVariant::UserType)
      {
         if ( v.canConvert<Expression>() )
            return v.value<Expression>().evaluateValue(convert);
      }
      return convert(v);
   }
};

Q_DECLARE_METATYPE(Expression)

#endif