iter_value.hpp

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//
//  CeresEngine - A game development framework
//
//  Created by Rogiel Sulzbach.
//  Copyright (c) 2018-2022 Rogiel Sulzbach. All rights reserved.
//
 
#pragma once
 
#include "CeresEngine/Foundation/Traits/has_element_type.hpp"
#include "CeresEngine/Foundation/Traits/has_iterator_traits_value_type.hpp"
#include "CeresEngine/Foundation/Traits/has_value_type.hpp"
#include "CeresEngine/Foundation/Traits/remove_cvref.hpp"
 
#include <iterator>
#include <type_traits>
 
namespace CeresEngine::traits {
 
    template<class T, class = void> struct iter_value {};
 
    template<class T> struct iter_value<T, std::enable_if_t<has_iterator_traits_value_type_v<remove_cvref_t<T>>>> {
        using type = typename std::iterator_traits<remove_cvref_t<T>>::value_type;
    };
 
    template<class T> struct iter_value<T, std::enable_if_t<!has_iterator_traits_value_type_v<remove_cvref_t<T>> && std::is_pointer_v<T>>> {
        using type = decltype(*std::declval<std::remove_cv_t<T>>());
    };
 
    template<class T>
    struct iter_value<T, std::enable_if_t<!has_iterator_traits_value_type_v<remove_cvref_t<T>> && !std::is_pointer_v<T> && std::is_array_v<T>>> {
        using type = std::remove_cv_t<std::remove_extent_t<T>>;
    };
 
    template<class T>
    struct iter_value<T,
        std::enable_if_t<!has_iterator_traits_value_type_v<remove_cvref_t<T>> && !std::is_pointer_v<T> && !std::is_array_v<T> && std::is_const_v<T>>> {
        using type = typename iter_value<std::remove_const_t<T>>::type;
    };
 
    template<class T>
    struct iter_value<T,
        std::enable_if_t<!has_iterator_traits_value_type_v<remove_cvref_t<T>> && !std::is_pointer_v<T> && !std::is_array_v<T> && !std::is_const_v<T> &&
            has_value_type_v<T>>> {
        using type = typename T::value_type;
    };
 
    template<class T>
    struct iter_value<T,
        std::enable_if_t<!has_iterator_traits_value_type_v<remove_cvref_t<T>> && !std::is_pointer_v<T> && !std::is_array_v<T> && !std::is_const_v<T> &&
            !has_value_type_v<T> && has_element_type_v<T>>> {
        using type = typename T::element_type;
    };
 
    template<class T> using iter_value_t = typename iter_value<T>::type;
 
} // namespace CeresEngine::traits