///////////////////////////////////////////////////////////////////////////////
// matchable.hpp
//
//  Copyright 2004 Eric Niebler. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_XPRESSIVE_DETAIL_DYNAMIC_MATCHABLE_HPP_EAN_10_04_2005
#define BOOST_XPRESSIVE_DETAIL_DYNAMIC_MATCHABLE_HPP_EAN_10_04_2005

// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

#include <utility>
#include <boost/assert.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/xpressive/detail/core/state.hpp>
#include <boost/xpressive/detail/core/quant_style.hpp>
#include <boost/xpressive/regex_error.hpp>

namespace boost { namespace xpressive { namespace detail
{

template<typename BidiIter>
struct matchable;

///////////////////////////////////////////////////////////////////////////////
// sequence
//
template<typename BidiIter>
struct sequence
  : std::pair
    <
        shared_ptr<matchable<BidiIter> const>
      , shared_ptr<matchable<BidiIter> const> *
    >
{
    typedef shared_ptr<matchable<BidiIter> const> matchable_ptr_t;
    typedef std::pair<matchable_ptr_t, matchable_ptr_t *> base_t;

    explicit sequence(matchable_ptr_t head = matchable_ptr_t(), matchable_ptr_t *tail_ptr = 0)
      : base_t(head, tail_ptr)
    {
    }

    bool is_empty() const
    {
        return !this->first;
    }

    sequence &operator +=(sequence that)
    {
        if(is_empty())
        {
            *this = that;
        }
        else if(!that.is_empty())
        {
            *this->second = that.first;
            this->second = that.second;
        }
        return *this;
    }
};

//////////////////////////////////////////////////////////////////////////
// quant_spec
//
struct quant_spec
{
    unsigned int min_;
    unsigned int max_;
    bool greedy_;
};

///////////////////////////////////////////////////////////////////////////////
// matchable
//
template<typename BidiIter>
struct matchable
  : xpression_base
{
    typedef typename iterator_value<BidiIter>::type char_type;

    virtual ~matchable() {}

    virtual bool match(state_type<BidiIter> &state) const = 0;

    virtual std::size_t get_width(state_type<BidiIter> *state) const = 0;

    virtual void link(xpression_linker<char_type> &) const {}

    virtual void peek(xpression_peeker<char_type> &peeker) const
    {
        peeker.fail();
    }

    virtual sequence<BidiIter> quantify
    (
        quant_spec const & //spec
      , std::size_t & //hidden_mark_count
      , sequence<BidiIter> //seq
      , alternates_factory<BidiIter> const &//factory
    ) const
    {
        throw regex_error(regex_constants::error_badrepeat, "expression cannot be quantified");
    }

    virtual bool is_quantifiable() const
    {
        BOOST_ASSERT(false);
        throw regex_error(regex_constants::error_internal, "internal error, sorry!");
    }

    ///////////////////////////////////////////////////////////////////////////////////////////////
    // The following 4 functions (push_match, top_match, pop_match and skip_match) are
    // used to implement looping and branching across the matchers. Call push_match to record
    // a position. Then, another matcher further down the xpression chain has the
    // option to call either top_match, pop_match or skip_match. top_match and pop_match will
    // jump back to the place recorded by push_match, whereas skip_match will skip the jump and
    // pass execution down the xpression chain. top_match will leave the xpression on top of the
    // stack, whereas pop_match will remove it. Each function comes in 2 flavors: one for
    // statically bound xpressions and one for dynamically bound xpressions.
    //

    template<typename Top>
    bool push_match(state_type<BidiIter> &state) const
    {
        BOOST_MPL_ASSERT((is_same<Top, matchable<BidiIter> >));
        return this->match(state);
    }

    static bool top_match(state_type<BidiIter> &state, xpression_base const *top)
    {
        return static_cast<matchable<BidiIter> const *>(top)->match(state);
    }

    static bool pop_match(state_type<BidiIter> &state, xpression_base const *top)
    {
        return static_cast<matchable<BidiIter> const *>(top)->match(state);
    }

    bool skip_match(state_type<BidiIter> &state) const
    {
        return this->match(state);
    }
};

}}} // namespace boost::xpressive::detail

#endif