group_by.hpp

#pragma once
 
#include <rpp/observables/details/member_overload.hpp>
#include <rpp/utils/function_traits.hpp>
 
#include <concepts>
#include <functional>
 
 
namespace rpp::details
{
struct group_by_tag;
}
 
namespace rpp::details
{
template<constraint::decayed_type           Type,
         constraint::decayed_type           TKey,
         std::invocable<Type>               KeySelector,
         std::invocable<Type>               ValueSelector,
         std::strict_weak_order<TKey, TKey> KeyComparator>
auto group_by_impl(auto&& observable, KeySelector&& key_selector, ValueSelector&& value_selector, KeyComparator&& comparator);
 
template<constraint::decayed_type Type, typename SpecificObservable>
struct member_overload<Type, SpecificObservable, group_by_tag>
{
    template<std::invocable<Type>               KeySelector,
             std::invocable<Type>               ValueSelector = std::identity,
             typename                           TKey          = rpp::utils::decayed_invoke_result_t<KeySelector, Type>,
             std::strict_weak_order<TKey, TKey> KeyComparator = std::less<TKey>>
    auto group_by(KeySelector&& key_selector, ValueSelector&& value_selector = {}, KeyComparator&& comparator = {}) const& requires is_header_included<group_by_tag, KeySelector, ValueSelector, TKey, KeyComparator>
    {
        return group_by_impl<Type, TKey>(*static_cast<const SpecificObservable*>(this), std::forward<KeySelector>(key_selector), std::forward<ValueSelector>(value_selector), std::forward<KeyComparator>(comparator));
    }
 
    template<std::invocable<Type>               KeySelector,
             std::invocable<Type>               ValueSelector = std::identity,
             typename                           TKey          = rpp::utils::decayed_invoke_result_t<KeySelector, Type>,
             std::strict_weak_order<TKey, TKey> KeyComparator = std::less<TKey>>
    auto group_by(KeySelector&& key_selector, ValueSelector&& value_selector = {}, KeyComparator&& comparator = {}) && requires is_header_included<group_by_tag, KeySelector, ValueSelector, TKey, KeyComparator>
    {
        return group_by_impl<Type, TKey>(std::move(*static_cast<SpecificObservable*>(this)), std::forward<KeySelector>(key_selector), std::forward<ValueSelector>(value_selector), std::forward<KeyComparator>(comparator));
    }    
};
} // namespace rpp::details