comparer.hpp

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#pragma once
#include "../icomparer.hpp"
#include "../../../icomparable.hpp"
#include "../../../int32.hpp"
#include "../../../helpers/strictly_ordered.hpp"

namespace xtd {
  namespace collections {
    namespace generic {
      namespace helpers {
        template<class value_t = void>
        struct comparer {
          
          using first_argument_type = value_t;
          using second_argument_type = value_t;
          using result_type = xtd::int32;
          
          
          comparer() = default;
          explicit comparer(const xtd::collections::generic::icomparer<value_t>& comparer) : comparer_ {&comparer} {}
          
          
          constexpr auto operator()(const first_argument_type& x, const second_argument_type& y) const -> result_type {
            if (&x == &y) return 0;
            if (comparer_) return comparer_->compare(x, y);
            if constexpr(std::is_polymorphic_v<first_argument_type> && std::is_base_of_v<xtd::icomparable<first_argument_type>, first_argument_type>) return static_cast<const xtd::icomparable<first_argument_type>&>(x).compare_to(y);
            else if constexpr(xtd::helpers::strictly_ordered<first_argument_type>) return x < y ? -1 : (x > y ? 1 : 0);
            else return &x < &y ? -1 : 1;
          }

          
        private:
          const xtd::collections::generic::icomparer<value_t>* comparer_ = nullptr;
        };
      }
    }
  }
}