#ifndef ORIGIN_VECTOR_GROW_HPP
#define ORIGIN_VECTOR_GROW_HPP

namespace origin { namespace vector_ {

// TODO: Rewrite the grow strategy so that it is actually responsible for the
// reallocation, moving, and construction of vectors.

/**
 * The never grow strategy will guarantee a static-sized vector.
 * @todo Shoud this grown an exception or invoke some other error handler?
 */
struct grow_never {
    template <typename Vector>
    typename Vector::size_type
    operator()(Vector const& v, typename Vector::size_type) const
    { raise_length_error("grow_never", Vector::get_length_error()); }
};

/**
 * The linear strategy will cause the growth the vector to be linear with
 * respect to the number of elements requested. This growth strategy
 */
struct grow_linear {
    template <typename Vector>
    typename Vector::size_type
    operator()(Vector const& v, typename Vector::size_type req) const
    { return v.size() + req; }
};

/**
 * The times_two strategy will cause the vector to grow exponentially with
 * a growth base of N. By default N == 2, and the size of the vector is doubled
 * when full.
 */
template <std::size_t N = 2u>
struct grow_exponential {
    template <typename Vector>
    typename Vector::size_type
    operator()(Vector const& v, typename Vector::size_type n) const
    { return v.size() + ((N - 1) * std::max(v.size(), n)); }
};

/**
 * @requires GrowStrategy<Strategy>
 */
struct grow_policy { };
template <typename Strategy = grow_exponential<>>
struct grow {
    typedef grow_policy policy_kind;
    typedef Strategy type;

    // Aliases for common policies.
    typedef grow<grow_never> never;
    typedef grow<grow_linear> linear;
    typedef grow<grow_exponential<2>> doubling;
};

template <typename Policies, typename Default>
class extract_grow {
    typedef policy_element<grow_policy, Policies> element;
public:
    typedef typename mpl::if_<
        std::is_same<typename element::type, mpl::none>,
        Default,
        typename element::type
    >::type type;
};

} } // namespace origin::vector_

#endif