// Copyright 2015-2019 Hans Dembinski
//
// 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_HISTOGRAM_FWD_HPP
#define BOOST_HISTOGRAM_FWD_HPP

/**
  \file boost/histogram/fwd.hpp
  Forward declarations, tag types and type aliases.
*/

#include <boost/config.hpp> // BOOST_ATTRIBUTE_NODISCARD
#include <boost/core/use_default.hpp>
#include <tuple>
#include <type_traits>
#include <vector>

namespace boost {
namespace histogram {

/// Tag type to indicate use of a default type
using boost::use_default;

namespace axis {

/// Integral type for axis indices
using index_type = int;

/// Real type for axis indices
using real_index_type = double;

/// Empty metadata type
struct null_type {
  template <class Archive>
  void serialize(Archive&, unsigned /* version */) {}
};

/// Another alias for an empty metadata type
using empty_type = null_type;

// some forward declarations must be hidden from doxygen to fix the reference docu :(
#ifndef BOOST_HISTOGRAM_DOXYGEN_INVOKED

namespace transform {

struct id;

struct log;

struct sqrt;

struct pow;

} // namespace transform

template <class Value = double, class Transform = use_default,
          class MetaData = use_default, class Options = use_default>
class regular;

template <class Value = int, class MetaData = use_default, class Options = use_default>
class integer;

template <class Value = double, class MetaData = use_default, class Options = use_default,
          class Allocator = std::allocator<Value>>
class variable;

template <class Value = int, class MetaData = use_default, class Options = use_default,
          class Allocator = std::allocator<Value>>
class category;

template <class MetaData = use_default>
class boolean;

template <class... Ts>
class variant;

#endif // BOOST_HISTOGRAM_DOXYGEN_INVOKED

} // namespace axis

#ifndef BOOST_HISTOGRAM_DOXYGEN_INVOKED

template <class T>
struct weight_type;

template <class T>
struct sample_type;

namespace accumulators {

template <class ValueType = double>
class count;

template <class ValueType = double>
class sum;

template <class ValueType = double>
class weighted_sum;

template <class ValueType = double>
class mean;

template <class ValueType = double>
class weighted_mean;

template <class T>
class thread_safe;

template <class T>
struct is_thread_safe : std::false_type {};
template <class T>
struct is_thread_safe<thread_safe<T>> : std::true_type {};

} // namespace accumulators

struct unsafe_access;

template <class Allocator = std::allocator<char>>
class unlimited_storage;

template <class T>
class storage_adaptor;

#endif // BOOST_HISTOGRAM_DOXYGEN_INVOKED

/// Vector-like storage for fast zero-overhead access to cells.
template <class T, class A = std::allocator<T>>
using dense_storage = storage_adaptor<std::vector<T, A>>;

/// Default storage, optimized for unweighted histograms
using default_storage = unlimited_storage<>;

/// Dense storage which tracks sums of weights and a variance estimate.
using weight_storage = dense_storage<accumulators::weighted_sum<>>;

/// Dense storage which tracks means of samples in each cell.
using profile_storage = dense_storage<accumulators::mean<>>;

/// Dense storage which tracks means of weighted samples in each cell.
using weighted_profile_storage = dense_storage<accumulators::weighted_mean<>>;

// some forward declarations must be hidden from doxygen to fix the reference docu :(
#ifndef BOOST_HISTOGRAM_DOXYGEN_INVOKED

template <class Axes, class Storage = default_storage>
class BOOST_ATTRIBUTE_NODISCARD histogram;

#endif // BOOST_HISTOGRAM_DOXYGEN_INVOKED

namespace detail {

/* Most of the histogram code is generic and works for any number of axes. Buffers with a
 * fixed maximum capacity are used in some places, which have a size equal to the rank of
 * a histogram. The buffers are statically allocated to improve performance, which means
 * that they need a preset maximum capacity. 32 seems like a safe upper limit for the rank
 * (you can nevertheless increase it here if necessary): the simplest non-trivial axis has
 * 2 bins; even if counters are used which need only a byte of storage per bin, 32 axes
 * would generate of 4 GB.
 */
#ifndef BOOST_HISTOGRAM_DETAIL_AXES_LIMIT
#define BOOST_HISTOGRAM_DETAIL_AXES_LIMIT 32
#endif

template <class T>
struct buffer_size_impl
    : std::integral_constant<std::size_t, BOOST_HISTOGRAM_DETAIL_AXES_LIMIT> {};

template <class... Ts>
struct buffer_size_impl<std::tuple<Ts...>>
    : std::integral_constant<std::size_t, sizeof...(Ts)> {};

template <class T>
using buffer_size = typename buffer_size_impl<T>::type;

} // namespace detail

} // namespace histogram
} // namespace boost

#endif
