#ifndef TCG_ANY_ITERATOR_H
#define TCG_ANY_ITERATOR_H

#include "base.h"

/*
  \file     any_iterator.h

  \brief    This file contains the implementation of a type-erased iterator template class.

  \details  Type erasure is a C++ idiom about allocating an interface
            to an object who is then hidden as the interface's implementation detail.

            The cost of using a type-erased object instead of its actual type is typically
            measured in a heap access at construction and destruction, and one virtual
            function call per method invocation.

            A type-erased iterator can be useful to hide implementation details about container
            choices, yet providing an iterator-like interface to access the stored data.
*/

#ifndef TCG_RVALUES_SUPPORT
#include <boost/config.hpp>

#ifdef BOOST_NO_RVALUE_REFERENCES
#define TCG_RVALUES_SUPPORT 0
#else
#define TCG_RVALUES_SUPPORT 1
#endif
#endif

namespace tcg
{

//****************************************************************************
//    any_iterator_concept (ie the interface)
//****************************************************************************

template <typename Val, typename ValRef, typename ValPtr, typename Dist>
class any_iterator_concept
{
public:
	virtual ~any_iterator_concept() {}

	virtual any_iterator_concept *clone() const = 0;

	virtual ValRef operator*() const = 0;
	virtual ValPtr operator->() const = 0;

	virtual bool operator==(const any_iterator_concept &other) const = 0;
	virtual bool operator!=(const any_iterator_concept &other) const = 0;

	virtual void operator++() = 0;
	virtual any_iterator_concept *operator++(int)
	{
		assert(false);
		return 0;
	}

	virtual void operator--() { assert(false); }
	virtual any_iterator_concept *operator--(int)
	{
		assert(false);
		return 0;
	}

	virtual bool operator<(const any_iterator_concept &) const
	{
		assert(false);
		return false;
	}
	virtual bool operator>(const any_iterator_concept &) const
	{
		assert(false);
		return false;
	}
	virtual bool operator<=(const any_iterator_concept &) const
	{
		assert(false);
		return false;
	}
	virtual bool operator>=(const any_iterator_concept &) const
	{
		assert(false);
		return false;
	}

	virtual any_iterator_concept *operator+(Dist) const
	{
		assert(false);
		return 0;
	}
	virtual void operator+=(Dist d) { assert(false); }

	virtual any_iterator_concept *operator-(Dist) const
	{
		assert(false);
		return 0;
	}
	virtual void operator-=(Dist d) { assert(false); }

	virtual Dist operator-(const any_iterator_concept &) const
	{
		assert(false);
		return 0;
	}

	virtual ValRef operator[](Dist) const
	{
		assert(false);
		return *(Val *)0;
	}
};

//****************************************************************************
//    any_iterator_model (ie the concrete interface implementations)
//****************************************************************************

template <typename It, typename iterator_cat,
		  typename Val, typename ValRef, typename ValPtr, typename Dist>
class any_iterator_model
	: public any_iterator_concept<Val, ValRef, ValPtr, Dist>
{
	typedef any_iterator_concept<Val, ValRef, ValPtr, Dist> any_it_concept;

public:
	any_iterator_model() : m_it() {}
	any_iterator_model(const It &it) : m_it(it) {}

	any_it_concept *clone() const
	{
		return new any_iterator_model<It, iterator_cat, Val, ValRef, ValPtr, Dist>(*this);
	}

	ValRef operator*() const { return m_it.operator*(); }
	ValPtr operator->() const { return m_it.operator->(); }

	bool operator==(const any_it_concept &other) const
	{
		return m_it == static_cast<const any_iterator_model &>(other).m_it;
	}
	bool operator!=(const any_it_concept &other) const
	{
		return m_it != static_cast<const any_iterator_model &>(other).m_it;
	}

	void operator++() { ++m_it; }
	any_it_concept *operator++(int)
	{
		return new any_iterator_model<It, iterator_cat, Val, ValRef, ValPtr, Dist>(m_it++);
	}

protected:
	It m_it;
};

template <typename It,
		  typename Val, typename ValRef, typename ValPtr, typename Dist>
class any_iterator_model<It, std::bidirectional_iterator_tag, Val, ValRef, ValPtr, Dist>
	: public any_iterator_model<It, std::forward_iterator_tag, Val, ValRef, ValPtr, Dist>
{
	typedef any_iterator_concept<Val, ValRef, ValPtr, Dist> any_it_concept;

	using any_iterator_model<It, std::forward_iterator_tag, Val, ValRef, ValPtr, Dist>::m_it;

public:
	any_iterator_model() {}
	any_iterator_model(const It &it)
		: any_iterator_model<It, std::forward_iterator_tag, Val, ValRef, ValPtr, Dist>(it) {}

	any_it_concept *clone() const
	{
		return new any_iterator_model<It, std::bidirectional_iterator_tag, Val, ValRef, ValPtr, Dist>(*this);
	}

	void operator--() { --m_it; }
	any_it_concept *operator--(int)
	{
		return new any_iterator_model<It, std::bidirectional_iterator_tag, Val, ValRef, ValPtr, Dist>(m_it--);
	}
};

template <typename It, typename Val, typename ValRef, typename ValPtr, typename Dist>
class any_iterator_model<It, std::random_access_iterator_tag, Val, ValRef, ValPtr, Dist>
	: public any_iterator_model<It, std::bidirectional_iterator_tag, Val, ValRef, ValPtr, Dist>
{
	typedef any_iterator_concept<Val, ValRef, ValPtr, Dist> any_it_concept;

	using any_iterator_model<It, std::forward_iterator_tag, Val, ValRef, ValPtr, Dist>::m_it;

public:
	any_iterator_model() {}
	any_iterator_model(const It &it)
		: any_iterator_model<It, std::bidirectional_iterator_tag, Val, ValRef, ValPtr, Dist>(it) {}

	any_it_concept *clone() const
	{
		return new any_iterator_model<It, std::random_access_iterator_tag, Val, ValRef, ValPtr, Dist>(*this);
	}

	bool operator<(const any_it_concept &other) const
	{
		return m_it < static_cast<const any_iterator_model &>(other).m_it;
	}
	bool operator>(const any_it_concept &other) const
	{
		return m_it > static_cast<const any_iterator_model &>(other).m_it;
	}
	bool operator<=(const any_it_concept &other) const
	{
		return m_it <= static_cast<const any_iterator_model &>(other).m_it;
	}
	bool operator>=(const any_it_concept &other) const
	{
		return m_it >= static_cast<const any_iterator_model &>(other).m_it;
	}

	any_it_concept *operator+(Dist d) const
	{
		return new any_iterator_model<It, std::random_access_iterator_tag, Val, ValRef, ValPtr, Dist>(m_it + d);
	}
	void operator+=(Dist d) { m_it += d; }

	any_it_concept *operator-(Dist d) const
	{
		return new any_iterator_model<It, std::random_access_iterator_tag, Val, ValRef, ValPtr, Dist>(m_it - d);
	}
	void operator-=(Dist d) { m_it -= d; }

	Dist operator-(const any_it_concept &other) const
	{
		return m_it - static_cast<const any_iterator_model &>(other).m_it;
	}

	ValRef operator[](Dist d) const { return m_it[d]; }
};

//****************************************************************************
//    any_iterator  (ie the wrapper to the interface)
//****************************************************************************

template <typename Val, typename iterator_cat = tcg::empty_type,
		  typename ValRef = Val &, typename ValPtr = Val *, typename Dist = std::ptrdiff_t>
class any_iterator
	: public std::iterator<iterator_cat, Val, Dist, ValPtr, ValRef>
{
	any_iterator_concept<Val, ValRef, ValPtr, Dist> *m_model;

public:
	any_iterator() : m_model(0) {}
	any_iterator(any_iterator_concept<Val, ValRef, ValPtr, Dist> *model) : m_model(model) {}

	template <typename It>
	any_iterator(const It &it)
		: m_model(new any_iterator_model<It, iterator_cat, Val, ValRef, ValPtr, Dist>(it)) {}

	any_iterator(const any_iterator &other) : m_model(other.m_model->clone()) {}
	any_iterator &operator=(any_iterator other)
	{
		swap(*this, other);
		return *this;
	}

	~any_iterator() { delete m_model; }

	friend void swap(any_iterator &a, any_iterator &b) { std::swap(a.m_model, b.m_model); }

	ValRef operator*() const { return m_model->operator*(); }
	ValPtr operator->() const { return m_model->operator->(); }

	bool operator==(const any_iterator &other) const { return m_model->operator==(*other.m_model); }
	bool operator!=(const any_iterator &other) const { return m_model->operator!=(*other.m_model); }

	any_iterator &operator++()
	{
		++*m_model;
		return *this;
	}
	any_iterator operator++(int) { return any_iterator((*m_model)++); }

	any_iterator &operator--()
	{
		--*m_model;
		return *this;
	}
	any_iterator operator--(int) { return any_iterator((*m_model)--); }

	bool operator<(const any_iterator &other) const { return m_model->operator<(*other.m_model); }
	bool operator>(const any_iterator &other) const { return m_model->operator>(*other.m_model); }
	bool operator<=(const any_iterator &other) const { return m_model->operator<=(*other.m_model); }
	bool operator>=(const any_iterator &other) const { return m_model->operator>=(*other.m_model); }

	any_iterator operator+(Dist d) const { return any_iterator((*m_model) + d); }
	any_iterator &operator+=(Dist d)
	{
		(*m_model) += d;
		return *this;
	}

	any_iterator operator-(Dist d) const { return any_iterator((*m_model) - d); }
	any_iterator &operator-=(Dist d)
	{
		(*m_model) -= d;
		return *this;
	}

	Dist operator-(const any_iterator &other) const { return m_model->operator-(*other.m_model); }

	ValRef operator[](Dist d) const { return m_model->operator[](d); }

#if (TCG_RVALUES_SUPPORT > 0)

	any_iterator(any_iterator &&other) : m_model(other.m_model)
	{
		other.m_model = 0;
	}

#endif
};

//-------------------------------------------------------------------------------

template <typename Val, typename iterator_cat,
		  typename ValRef, typename ValPtr, typename Dist>
any_iterator<Val, iterator_cat, ValRef, ValPtr, Dist> operator+(
	Dist d, const any_iterator<Val, iterator_cat, ValRef, ValPtr, Dist> &it) { return it + d; }

//****************************************************************************
//    Additional typedefs to the actual types
//****************************************************************************

template <typename Val>
struct any_iterator<Val, tcg::empty_type> {
	typedef any_iterator<Val, std::input_iterator_tag> input;
	typedef any_iterator<Val, std::output_iterator_tag> output;
	typedef any_iterator<Val, std::forward_iterator_tag> forward;
	typedef any_iterator<Val, std::bidirectional_iterator_tag> bidirectional;
	typedef any_iterator<Val, std::random_access_iterator_tag> random;
};

template <typename Val, typename ValRef = Val &, typename ValPtr = Val *, typename Dist = std::ptrdiff_t>
struct any_it {
	typedef any_iterator<Val, std::input_iterator_tag, ValRef, ValPtr, Dist> input;
	typedef any_iterator<Val, std::output_iterator_tag, ValRef, ValPtr, Dist> output;
	typedef any_iterator<Val, std::forward_iterator_tag, ValRef, ValPtr, Dist> forward;
	typedef any_iterator<Val, std::bidirectional_iterator_tag, ValRef, ValPtr, Dist> bidirectional;
	typedef any_iterator<Val, std::random_access_iterator_tag, ValRef, ValPtr, Dist> random;
};

} // namespace tcg

#endif // TCG_ANY_ITERATOR_H