runtime_view.hpp

#ifndef ENTT_ENTITY_RUNTIME_VIEW_HPP
#define ENTT_ENTITY_RUNTIME_VIEW_HPP
 
#include <algorithm>
#include <iterator>
#include <type_traits>
#include <utility>
#include <vector>
#include "../config/config.h"
#include "entity.hpp"
#include "fwd.hpp"
#include "sparse_set.hpp"
 
namespace entt {
 
namespace internal {
 
template<typename Type>
class runtime_view_iterator final {
    [[nodiscard]] bool valid() const {
        return std::all_of(pools->begin(), pools->end(), [entt = *it](const auto *curr) { return curr->contains(entt); })
               && std::none_of(filter->cbegin(), filter->cend(), [entt = *it](const auto *curr) { return curr && curr->contains(entt); });
    }
 
public:
    using iterator_type = typename Type::iterator;
    using difference_type = typename iterator_type::difference_type;
    using value_type = typename iterator_type::value_type;
    using pointer = typename iterator_type::pointer;
    using reference = typename iterator_type::reference;
    using iterator_category = std::bidirectional_iterator_tag;
 
    runtime_view_iterator() ENTT_NOEXCEPT = default;
 
    runtime_view_iterator(const std::vector<const Type *> &cpools, const std::vector<const Type *> &ignore, iterator_type curr) ENTT_NOEXCEPT
        : pools{&cpools},
          filter{&ignore},
          it{curr} {
        if(it != (*pools)[0]->end() && !valid()) {
            ++(*this);
        }
    }
 
    runtime_view_iterator &operator++() {
        while(++it != (*pools)[0]->end() && !valid()) {}
        return *this;
    }
 
    runtime_view_iterator operator++(int) {
        runtime_view_iterator orig = *this;
        return ++(*this), orig;
    }
 
    runtime_view_iterator &operator--() ENTT_NOEXCEPT {
        while(--it != (*pools)[0]->begin() && !valid()) {}
        return *this;
    }
 
    runtime_view_iterator operator--(int) ENTT_NOEXCEPT {
        runtime_view_iterator orig = *this;
        return operator--(), orig;
    }
 
    [[nodiscard]] pointer operator->() const {
        return it.operator->();
    }
 
    [[nodiscard]] reference operator*() const {
        return *operator->();
    }
 
    [[nodiscard]] bool operator==(const runtime_view_iterator &other) const ENTT_NOEXCEPT {
        return it == other.it;
    }
 
    [[nodiscard]] bool operator!=(const runtime_view_iterator &other) const ENTT_NOEXCEPT {
        return !(*this == other);
    }
 
private:
    const std::vector<const Type *> *pools;
    const std::vector<const Type *> *filter;
    iterator_type it;
};
 
} // namespace internal
 
template<typename Entity>
class basic_runtime_view final {
    using basic_common_type = basic_sparse_set<Entity>;
 
    [[nodiscard]] bool valid() const {
        return !pools.empty() && pools.front();
    }
 
public:
    using entity_type = Entity;
    using size_type = std::size_t;
    using iterator = internal::runtime_view_iterator<basic_common_type>;
 
    basic_runtime_view() ENTT_NOEXCEPT
        : pools{},
          filter{} {}
 
    basic_runtime_view(std::vector<const basic_common_type *> cpools, std::vector<const basic_common_type *> epools) ENTT_NOEXCEPT
        : pools{std::move(cpools)},
          filter{std::move(epools)} {
        auto candidate = std::min_element(pools.begin(), pools.end(), [](const auto *lhs, const auto *rhs) {
            return (!lhs && rhs) || (lhs && rhs && lhs->size() < rhs->size());
        });
 
        // brings the best candidate (if any) on front of the vector
        std::rotate(pools.begin(), candidate, pools.end());
    }
 
    [[nodiscard]] size_type size_hint() const {
        return valid() ? pools.front()->size() : size_type{};
    }
 
    [[nodiscard]] iterator begin() const {
        return valid() ? iterator{pools, filter, pools[0]->begin()} : iterator{};
    }
 
    [[nodiscard]] iterator end() const {
        return valid() ? iterator{pools, filter, pools[0]->end()} : iterator{};
    }
 
    [[nodiscard]] bool contains(const entity_type entt) const {
        return valid() && std::all_of(pools.cbegin(), pools.cend(), [entt](const auto *curr) { return curr->contains(entt); })
               && std::none_of(filter.cbegin(), filter.cend(), [entt](const auto *curr) { return curr && curr->contains(entt); });
    }
 
    template<typename Func>
    void each(Func func) const {
        for(const auto entity: *this) {
            func(entity);
        }
    }
 
private:
    std::vector<const basic_common_type *> pools;
    std::vector<const basic_common_type *> filter;
};
 
} // namespace entt
 
#endif