EverWrath/src/common/Containers.h

/*
 * Copyright (C) 2016+     AzerothCore <www.azerothcore.org>
 * Copyright (C) 2008-2016 TrinityCore <http://www.trinitycore.org/>
 * Copyright (C) 2005-2009 MaNGOS <http://getmangos.com/>
 */

#ifndef ACORE_CONTAINERS_H
#define ACORE_CONTAINERS_H

#include "Define.h"
#include <algorithm>
#include <exception>
#include <iterator>
#include <utility>
#include <list>
#include <vector>
#include <type_traits>

//! Because circular includes are bad
extern uint32 urand(uint32 min, uint32 max);
extern uint32 urandweighted(size_t count, double const* chances);

namespace acore
{
    template<class T>
    constexpr inline T* AddressOrSelf(T* ptr)
    {
        return ptr;
    }

    template<class T>
    constexpr inline T* AddressOrSelf(T& not_ptr)
    {
        return std::addressof(not_ptr);
    }

    template <class T>
    class CheckedBufferOutputIterator
    {
    public:
        using iterator_category = std::output_iterator_tag;
        using value_type = void;
        using pointer = T*;
        using reference = T&;
        using difference_type = std::ptrdiff_t;

        CheckedBufferOutputIterator(T* buf, size_t n) : _buf(buf), _end(buf + n) {}

        T& operator*() const { check(); return *_buf; }
        CheckedBufferOutputIterator& operator++() { check(); ++_buf; return *this; }
        CheckedBufferOutputIterator operator++(int) { CheckedBufferOutputIterator v = *this; operator++(); return v; }

        [[nodiscard]] size_t remaining() const { return (_end - _buf); }

    private:
        T* _buf;
        T* _end;
        void check() const
        {
            if (!(_buf < _end))
                throw std::out_of_range("index");
        }
    };

    namespace Containers
    {
        // replace with std::size in C++17
        template<class C>
        constexpr inline std::size_t Size(C const& container)
        {
            return container.size();
        }

        template<class T, std::size_t size>
        constexpr inline std::size_t Size(T const(&)[size]) noexcept
        {
            return size;
        }

        // resizes <container> to have at most <requestedSize> elements
        // if it has more than <requestedSize> elements, the elements to keep are selected randomly
        template<class C>
        void RandomResize(C& container, std::size_t requestedSize)
        {
            static_assert(std::is_base_of<std::forward_iterator_tag, typename std::iterator_traits<typename C::iterator>::iterator_category>::value, "Invalid container passed to acore::Containers::RandomResize");
            if (Size(container) <= requestedSize)
            {
                return;
            }

            auto keepIt = std::begin(container), curIt = std::begin(container);
            uint32 elementsToKeep = requestedSize, elementsToProcess = Size(container);
            while (elementsToProcess)
            {
                // this element has chance (elementsToKeep / elementsToProcess) of being kept
                if (urand(1, elementsToProcess) <= elementsToKeep)
                {
                    if (keepIt != curIt)
                        *keepIt = std::move(*curIt);
                    ++keepIt;
                    --elementsToKeep;
                }

                ++curIt;
                --elementsToProcess;
            }

            container.erase(keepIt, std::end(container));
        }

        template<class C, class Predicate>
        void RandomResize(C& container, Predicate&& predicate, std::size_t requestedSize)
        {
            //! First use predicate filter
            C containerCopy;
            std::copy_if(std::begin(container), std::end(container), std::inserter(containerCopy, std::end(containerCopy)), predicate);

            if (requestedSize)
            {
                RandomResize(containerCopy, requestedSize);
            }

            container = std::move(containerCopy);
        }

        /* Select a random element from a container. Note: make sure you explicitly empty check the container */
        template <class C> typename C::value_type const& SelectRandomContainerElement(C const& container)
        {
            typename C::const_iterator it = container.begin();
            std::advance(it, urand(0, container.size() - 1));
            return *it;
        }

        /*  Select a random element from a container where each element has a different chance to be selected. */
        template <class C> typename C::value_type const& SelectRandomWeightedContainerElement(C const& container, std::vector<double> const& weights)
        {
            typename C::const_iterator it = container.begin();
            std::advance(it, urandweighted(weights.size(), weights.data()));
            return *it;
        }

        template <typename Container, typename Predicate>
        std::enable_if_t<std::is_move_assignable_v<decltype(*std::declval<Container>().begin())>, void> EraseIf(Container& c, Predicate p)
        {
            auto wpos = c.begin();
            for (auto rpos = c.begin(), end = c.end(); rpos != end; ++rpos)
            {
                if (!p(*rpos))
                {
                    if (rpos != wpos)
                    {
                        std::swap(*rpos, *wpos);
                    }
                    ++wpos;
                }
            }
            c.erase(wpos, c.end());
        }

        template <typename Container, typename Predicate>
        std::enable_if_t<!std::is_move_assignable_v<decltype(*std::declval<Container>().begin())>, void> EraseIf(Container& c, Predicate p)
        {
            for (auto it = c.begin(); it != c.end();)
            {
                if (p(*it))
                {
                    it = c.erase(it);
                }
                else
                {
                    ++it;
                }
            }
        }

        template<class K, class V, template<class, class, class...> class M, class... Rest>
        void MultimapErasePair(M<K, V, Rest...>& multimap, K const& key, V const& value)
        {
            auto range = multimap.equal_range(key);
            for (auto itr = range.first; itr != range.second;)
            {
                if (itr->second == value)
                    itr = multimap.erase(itr);
                else
                    ++itr;
            }
        }
    }
    //! namespace Containers
}
//! namespace acore

#endif //! #ifdef ACORE_CONTAINERS_H