/* -*- C++ -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2003-2008

  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 #ifndef LEMON_BITS_VARIANT_H

 #define LEMON_BITS_VARIANT_H

 #include <lemon/error.h>

 /// \file

 /// \brief Variant types

 namespace lemon {

   namespace _variant_bits {

     template <int left, int right>

     struct CTMax {

       static const int value = left < right ? right : left;

     };

   }

   /// \brief Simple Variant type for two types

   ///

   /// Simple Variant type for two types. The Variant type is a type

   /// safe union. The C++ has strong limitations for using unions, by

   /// example we can not store type with non default constructor or

   /// destructor in an union. This class always knowns the current

   /// state of the variant and it cares for the proper construction

   /// and destruction.

   template <typename _First, typename _Second>

   class BiVariant {

   public:

     /// \brief The \c First type.

     typedef _First First;

     /// \brief The \c Second type.

     typedef _Second Second;

     struct WrongStateError : public lemon::LogicError {

     public:

       virtual const char* what() const throw() {

         return "lemon::BiVariant::WrongStateError";

       }

     };

     /// \brief Constructor

     ///

     /// This constructor initalizes to the default value of the \c First

     /// type.

     BiVariant() {

       flag = true;

       new(reinterpret_cast<First*>(data)) First();

     }

     /// \brief Constructor

     ///

     /// This constructor initalizes to the given value of the \c First

     /// type.

     BiVariant(const First& f) {

       flag = true;

       new(reinterpret_cast<First*>(data)) First(f);

     }

     /// \brief Constructor

     ///

     /// This constructor initalizes to the given value of the \c

     /// Second type.

     BiVariant(const Second& s) {

       flag = false;

       new(reinterpret_cast<Second*>(data)) Second(s);

     }

     /// \brief Copy constructor

     ///

     /// Copy constructor

     BiVariant(const BiVariant& bivariant) {

       flag = bivariant.flag;

       if (flag) {

         new(reinterpret_cast<First*>(data)) First(bivariant.first());      

       } else {

         new(reinterpret_cast<Second*>(data)) Second(bivariant.second());      

       }

     }

     /// \brief Destrcutor

     ///

     /// Destructor

     ~BiVariant() {

       destroy();

     }

     /// \brief Set to the default value of the \c First type.

     ///

     /// This function sets the variant to the default value of the \c

     /// First type.

     BiVariant& setFirst() {

       destroy();

       flag = true;

       new(reinterpret_cast<First*>(data)) First();   

       return *this;

     }

     /// \brief Set to the given value of the \c First type.

     ///

     /// This function sets the variant to the given value of the \c

     /// First type.

     BiVariant& setFirst(const First& f) {

       destroy();

       flag = true;

       new(reinterpret_cast<First*>(data)) First(f);   

       return *this;

     }

     /// \brief Set to the default value of the \c Second type.

     ///

     /// This function sets the variant to the default value of the \c

     /// Second type.

     BiVariant& setSecond() {

       destroy();

       flag = false;

       new(reinterpret_cast<Second*>(data)) Second();   

       return *this;

     }

     /// \brief Set to the given value of the \c Second type.

     ///

     /// This function sets the variant to the given value of the \c

     /// Second type.

     BiVariant& setSecond(const Second& s) {

       destroy();

       flag = false;

       new(reinterpret_cast<Second*>(data)) Second(s);   

       return *this;

     }

     /// \brief Operator form of the \c setFirst()

     BiVariant& operator=(const First& f) {

       return setFirst(f);

     }

     /// \brief Operator form of the \c setSecond()

     BiVariant& operator=(const Second& s) {

       return setSecond(s);

     }

     /// \brief Assign operator

     BiVariant& operator=(const BiVariant& bivariant) {

       if (this == &bivariant) return *this;

       destroy();

       flag = bivariant.flag;

       if (flag) {

         new(reinterpret_cast<First*>(data)) First(bivariant.first());      

       } else {

         new(reinterpret_cast<Second*>(data)) Second(bivariant.second());      

       }

       return *this;

     }

     /// \brief Reference to the value

     ///

     /// Reference to the value of the \c First type.

     /// \pre The BiVariant should store value of \c First type.

     First& first() {

       LEMON_ASSERT(flag, WrongStateError());

       return *reinterpret_cast<First*>(data); 

     }

     /// \brief Const reference to the value

     ///

     /// Const reference to the value of the \c First type.

     /// \pre The BiVariant should store value of \c First type.

     const First& first() const { 

       LEMON_ASSERT(flag, WrongStateError());

       return *reinterpret_cast<const First*>(data); 

     }

     /// \brief Operator form of the \c first()

     operator First&() { return first(); }

     /// \brief Operator form of the const \c first()

     operator const First&() const { return first(); }

     /// \brief Reference to the value

     ///

     /// Reference to the value of the \c Second type.

     /// \pre The BiVariant should store value of \c Second type.

     Second& second() { 

       LEMON_ASSERT(!flag, WrongStateError());

       return *reinterpret_cast<Second*>(data); 

     }

     /// \brief Const reference to the value

     ///

     /// Const reference to the value of the \c Second type.

     /// \pre The BiVariant should store value of \c Second type.

     const Second& second() const { 

       LEMON_ASSERT(!flag, WrongStateError());

       return *reinterpret_cast<const Second*>(data); 

     }

     /// \brief Operator form of the \c second()

     operator Second&() { return second(); }

     /// \brief Operator form of the const \c second()

     operator const Second&() const { return second(); }

     /// \brief %True when the variant is in the first state

     ///

     /// %True when the variant stores value of the \c First type.

     bool firstState() const { return flag; }

     /// \brief %True when the variant is in the second state

     ///

     /// %True when the variant stores value of the \c Second type.

     bool secondState() const { return !flag; }

   private:

     void destroy() {

       if (flag) {

         reinterpret_cast<First*>(data)->~First();

       } else {

         reinterpret_cast<Second*>(data)->~Second();

       }

     }

     char data[_variant_bits::CTMax<sizeof(First), sizeof(Second)>::value];

     bool flag;

   };

   namespace _variant_bits {

     template <int _idx, typename _TypeMap>

     struct Memory {

       typedef typename _TypeMap::template Map<_idx>::Type Current;

       static void destroy(int index, char* place) {

         if (index == _idx) {

           reinterpret_cast<Current*>(place)->~Current();

         } else {

           Memory<_idx - 1, _TypeMap>::destroy(index, place);

         }

       }

       static void copy(int index, char* to, const char* from) {

         if (index == _idx) {

           new (reinterpret_cast<Current*>(to))

             Current(reinterpret_cast<const Current*>(from));

         } else {

           Memory<_idx - 1, _TypeMap>::copy(index, to, from);

         }

       }

     };

     template <typename _TypeMap>

     struct Memory<-1, _TypeMap> {

       static void destroy(int, char*) {

         LEMON_ASSERT(false, "Wrong Variant Index.");

       }

       static void copy(int, char*, const char*) {

         LEMON_ASSERT(false, "Wrong Variant Index.");

       }

     };

     template <int _idx, typename _TypeMap>

     struct Size {

       static const int value = 

       CTMax<sizeof(typename _TypeMap::template Map<_idx>::Type), 

             Size<_idx - 1, _TypeMap>::value>::value;

     };

     template <typename _TypeMap>

     struct Size<0, _TypeMap> {

       static const int value = 

       sizeof(typename _TypeMap::template Map<0>::Type);

     };

   }

   /// \brief Variant type

   ///

   /// Simple Variant type. The Variant type is a type safe union. The

   /// C++ has strong limitations for using unions, by example we

   /// cannot store type with non default constructor or destructor in

   /// a union. This class always knowns the current state of the

   /// variant and it cares for the proper construction and

   /// destruction.

   ///

   /// \param _num The number of the types which can be stored in the

   /// variant type.

   /// \param _TypeMap This class describes the types of the Variant. The

   /// _TypeMap::Map<index>::Type should be a valid type for each index 

   /// in the range {0, 1, ..., _num - 1}. The \c VariantTypeMap is helper

   /// class to define such type mappings up to 10 types.

   ///

   /// And the usage of the class:

   ///\code

   /// typedef Variant<3, VariantTypeMap<int, std::string, double> > MyVariant;

   /// MyVariant var;

   /// var.set<0>(12);

   /// std::cout << var.get<0>() << std::endl;

   /// var.set<1>("alpha");

   /// std::cout << var.get<1>() << std::endl;

   /// var.set<2>(0.75);

   /// std::cout << var.get<2>() << std::endl;

   ///\endcode

   ///

   /// The result of course:

   ///\code

   /// 12

   /// alpha

   /// 0.75

   ///\endcode

   template <int _num, typename _TypeMap>

   class Variant {

   public:

     static const int num = _num;

     typedef _TypeMap TypeMap;

     struct WrongStateError : public lemon::LogicError {

     public:

       virtual const char* what() const throw() {

         return "lemon::Variant::WrongStateError";

       }

     };

     /// \brief Constructor

     ///

     /// This constructor initalizes to the default value of the \c type

     /// with 0 index.

     Variant() {

       flag = 0;

       new(reinterpret_cast<typename TypeMap::template Map<0>::Type*>(data)) 

         typename TypeMap::template Map<0>::Type();

     }

     /// \brief Copy constructor

     ///

     /// Copy constructor

     Variant(const Variant& variant) {

       flag = variant.flag;

       _variant_bits::Memory<num - 1, TypeMap>::copy(flag, data, variant.data);

     }

     /// \brief Assign operator

     ///

     /// Assign operator

     Variant& operator=(const Variant& variant) {

       if (this == &variant) return *this;

       _variant_bits::Memory<num - 1, TypeMap>::

         destroy(flag, data);

       flag = variant.flag;

       _variant_bits::Memory<num - 1, TypeMap>::

         copy(flag, data, variant.data);

       return *this;

     }

     /// \brief Destrcutor

     ///

     /// Destructor

     ~Variant() {

       _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);

     }

     /// \brief Set to the default value of the type with \c _idx index.

     ///

     /// This function sets the variant to the default value of the

     /// type with \c _idx index.

     template <int _idx>

     Variant& set() {

       _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);

       flag = _idx;

       new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data)) 

         typename TypeMap::template Map<_idx>::Type();

       return *this;

     }

     /// \brief Set to the given value of the type with \c _idx index.

     ///

     /// This function sets the variant to the given value of the type

     /// with \c _idx index.

     template <int _idx>

     Variant& set(const typename _TypeMap::template Map<_idx>::Type& init) {

       _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);

       flag = _idx;

       new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data)) 

         typename TypeMap::template Map<_idx>::Type(init);

       return *this;

     }

     /// \brief Gets the current value of the type with \c _idx index.

     ///

     /// Gets the current value of the type with \c _idx index.

     template <int _idx>

     const typename TypeMap::template Map<_idx>::Type& get() const {

       LEMON_ASSERT(_idx == flag, "Wrong Variant Index.");

       return *reinterpret_cast<const typename TypeMap::

         template Map<_idx>::Type*>(data); 

     }

     /// \brief Gets the current value of the type with \c _idx index.

     ///

     /// Gets the current value of the type with \c _idx index.

     template <int _idx>

     typename _TypeMap::template Map<_idx>::Type& get() {

       LEMON_ASSERT(_idx == flag, "Wrong Variant Index.");

       return *reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>

         (data); 

     }

     /// \brief Returns the current state of the variant.

     ///

     /// Returns the current state of the variant.

     int state() const {

       return flag;

     }

   private:

     char data[_variant_bits::Size<num - 1, TypeMap>::value];

     int flag;

   };

   namespace _variant_bits {

     template <int _index, typename _List>

     struct Get {

       typedef typename Get<_index - 1, typename _List::Next>::Type Type;

     };

     template <typename _List>

     struct Get<0, _List> {

       typedef typename _List::Type Type;

     };

     struct List {};

     template <typename _Type, typename _List>

     struct Insert {

       typedef _List Next;

       typedef _Type Type;

     };

     template <int _idx, typename _T0, typename _T1, typename _T2, 

               typename _T3, typename _T5, typename _T4, typename _T6,

               typename _T7, typename _T8, typename _T9>

     struct Mapper {

       typedef List L10;

       typedef Insert<_T9, L10> L9;

       typedef Insert<_T8, L9> L8;

       typedef Insert<_T7, L8> L7;

       typedef Insert<_T6, L7> L6;

       typedef Insert<_T5, L6> L5;

       typedef Insert<_T4, L5> L4;

       typedef Insert<_T3, L4> L3;

       typedef Insert<_T2, L3> L2;

       typedef Insert<_T1, L2> L1;

       typedef Insert<_T0, L1> L0;

       typedef typename Get<_idx, L0>::Type Type;

     };

   }

   /// \brief Helper class for Variant

   ///

   /// Helper class to define type mappings for Variant. This class

   /// converts the template parameters to be mappable by integer.

   /// \see Variant

   template <

     typename _T0, 

     typename _T1 = void, typename _T2 = void, typename _T3 = void,

     typename _T5 = void, typename _T4 = void, typename _T6 = void,

     typename _T7 = void, typename _T8 = void, typename _T9 = void>

   struct VariantTypeMap {

     template <int _idx>

     struct Map {

       typedef typename _variant_bits::

       Mapper<_idx, _T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8, _T9>::Type

       Type;

     };

   };

 }

 #endif