/* -*- 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