#ifndef TEXPRESSION_INCLUDED
#define TEXPRESSION_INCLUDED

#include <memory>

// TnzCore includes
#include "tcommon.h"

#undef DVAPI
#undef DVVAR
#ifdef TNZBASE_EXPORTS
#define DVAPI DV_EXPORT_API
#define DVVAR DV_EXPORT_VAR
#else
#define DVAPI DV_IMPORT_API
#define DVVAR DV_IMPORT_VAR
#endif

//========================================================

//    Forward declaration

class TUnit;
class TDoubleParam;

namespace TSyntax
{
class Grammar;
class CalculatorNodeVisitor;
class Calculator;
}

//========================================================

//************************************************************************************
//    TExpression  declaration
//************************************************************************************

//! This class manages a generic expression.
/*!
  An expression is a sequence of characthers and contains:

  \li a \e CalcNode that is a basic element of the expression that must be evaluated;
  \li a \e Grammar that is a sequence of string patterns that define operations on nodes;
  \li a \e Builder that is a sequence or a tree of calcnodes and operations on that;
*/
class DVAPI TExpression
{
	class Imp;
	std::unique_ptr<Imp> m_imp;

public:
	TExpression();
	~TExpression();

	TExpression(const TExpression &);
	TExpression &operator=(TExpression);

	//! Sets the expression's grammar - does \b not acquire ownership.
	void setGrammar(const TSyntax::Grammar *grammar);
	const TSyntax::Grammar *getGrammar() const;

	/*!
    Sets the expression's text - a mix of mathematical expressions
    and grammar-recognized patterns that is able to calculate the
    expression's value at a given frame.
  */
	void setText(std::string text);
	std::string getText() const;

	TSyntax::Calculator *getCalculator();

	/*!
		Returns whether the expression is valid according to actual
      grammar syntax (i.e. it has at least one calculator node).
	*/
	bool isValid();

	std::string getError() const;
	std::pair<int, int> getErrorPos() const;

	void accept(TSyntax::CalculatorNodeVisitor &visitor);

	void setOwnerParameter(TDoubleParam *param);
	TDoubleParam *getOwnerParameter() const;

	bool isCycling() const;

private:
	// The expression is parsed lazily - ie when a getters attempts to
	// evaluate the expression and it was not yet parsed
	void parse();
};

#endif