utils.hpp

//                  ReactivePlusPlus library
//
//          Copyright Aleksey Loginov 2023 - present.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/AlexInLog/ReactivePlusPlus
//
 
#pragma once
 
#include <rpp/defs.hpp>
#include <rpp/utils/constraints.hpp>
#include <rpp/utils/tuple.hpp>
 
#include <algorithm>
#include <mutex>
#include <variant>
 
namespace rpp::utils
{
 
    struct none
    {
    };
 
    template<typename... Args>
    struct types
    {
    };
 
    template<constraint::iterable T>
    using iterable_value_t = std::iter_value_t<decltype(std::begin(std::declval<T>()))>;
 
    namespace details
    {
        template<template<typename...> typename Base>
        struct traits
        {
            template<typename... Types>
            constexpr static rpp::utils::tuple<Types...> extract_params(const Base<Types...>*);
            constexpr static std::false_type             extract_params(...);
        };
    } // namespace details
 
    template<typename T, template<typename...> typename Base>
    concept is_base_of_v = !std::is_same_v<decltype(details::traits<Base>::extract_params(std::declval<std::decay_t<T>*>())), std::false_type>;
 
    template<typename T, template<typename...> typename Base>
        requires is_base_of_v<T, Base>
    using extract_base_type_params_t = decltype(details::traits<Base>::extract_params(std::declval<std::decay_t<T>*>()));
 
    template<class T>
    constexpr std::add_const_t<T>& as_const(const T& v) noexcept
    {
        return v;
    }
 
    template<class T>
    constexpr T&& as_const(T&& v) noexcept
        requires std::is_rvalue_reference_v<T&&>
    {
        return std::forward<T>(v);
    }
 
    struct convertible_to_any
    {
        convertible_to_any() = default;
 
        template<typename T>
        operator T&() const;
 
        template<typename T>
        operator const T&() const;
 
        template<typename T>
        operator T&&() const;
    };
 
    template<typename Cont, std::invocable<iterable_value_t<Cont>> Fn>
    void for_each(Cont&& container, Fn&& fn)
    {
        std::for_each(std::begin(container), std::end(container), std::forward<Fn>(fn));
    }
 
    template<typename Cont, std::predicate<iterable_value_t<Cont>> Fn>
    bool all_of(const Cont& container, const Fn& fn)
    {
        return std::all_of(std::cbegin(container), std::cend(container), fn);
    }
 
    template<auto Fn, bool Inverse = false>
        requires std::is_member_function_pointer_v<decltype(Fn)>
    struct static_mem_fn
    {
        template<typename TT>
            requires (Inverse == false && std::invocable<decltype(Fn), TT &&>)
        auto operator()(TT&& d) const
        {
            return (std::forward<TT>(d).*Fn)();
        }
 
        template<typename TT>
            requires (Inverse == true && std::invocable<decltype(Fn), TT &&>)
        auto operator()(TT&& d) const
        {
            return !(std::forward<TT>(d).*Fn)();
        }
    };
 
    template<auto Fn>
    using static_not_mem_fn = static_mem_fn<Fn, true>;

    template<std::invocable Fn>
    class finally_action
    {
    public:
        explicit finally_action(Fn&& fn)
            : m_fn{std::move(fn)}
        {
        }
 
        explicit finally_action(const Fn& fn)
            : m_fn{fn}
        {
        }
 
        finally_action(const finally_action&)     = delete;
        finally_action(finally_action&&) noexcept = delete;
 
        ~finally_action() noexcept { m_fn(); }
 
    private:
        RPP_NO_UNIQUE_ADDRESS Fn m_fn;
    };
 
    template<rpp::constraint::decayed_type T>
    class repeated_container
    {
    public:
        repeated_container(T&& value, size_t count)
            : m_value{std::move(value)}
            , m_count{count}
        {
        }
 
        repeated_container(const T& value, size_t count)
            : m_value{value}
            , m_count{count}
        {
        }
 
        class iterator
        {
        public:
            iterator(const repeated_container* container, size_t index)
                : m_container{container}
                , m_index{index}
            {
            }
 
            using iterator_category = std::input_iterator_tag;
            using difference_type   = std::ptrdiff_t;
            using value_type        = T;
            using pointer           = T*;
 
            const value_type& operator*() const { return m_container->m_value; }
 
            iterator& operator++()
            {
                ++m_index;
                return *this;
            }
 
            iterator operator++(int)
            {
                auto old = *this;
                ++(*this);
                return old;
            }
 
            bool operator==(const iterator&) const = default;
            bool operator!=(const iterator&) const = default;
 
        private:
            const repeated_container* m_container;
            size_t                    m_index;
        };
 
        iterator begin() const { return {this, 0}; }
 
        iterator end() const { return {this, m_count}; }
 
    private:
        RPP_NO_UNIQUE_ADDRESS T m_value;
        size_t                  m_count;
    };
 
    template<rpp::constraint::decayed_type T>
    class infinite_repeated_container
    {
    public:
        infinite_repeated_container(T&& value)
            : m_value{std::move(value)}
        {
        }
 
        infinite_repeated_container(const T& value)
            : m_value{value}
        {
        }
 
        class iterator
        {
        public:
            iterator(const infinite_repeated_container* container)
                : m_container{container}
            {
            }
 
            using iterator_category = std::input_iterator_tag;
            using difference_type   = std::ptrdiff_t;
            using value_type        = T;
            using pointer           = T*;
 
            const value_type& operator*() const { return m_container->m_value; }
 
            iterator& operator++() { return *this; }
 
            iterator operator++(int) { return *this; }
 
            bool operator==(const iterator&) const = default;
            bool operator!=(const iterator&) const = default;
 
        private:
            const infinite_repeated_container* m_container;
        };
 
        iterator begin() const { return {this}; }
 
        iterator end() const { return {nullptr}; }
 
    private:
        RPP_NO_UNIQUE_ADDRESS T m_value;
    };
 
    struct none_mutex
    {
        static constexpr void lock() { }
        static constexpr void unlock() { }
        static constexpr void try_lock() { }
    };
 
    template<typename T>
    class value_with_mutex
    {
    public:
        value_with_mutex() = default;
 
        explicit value_with_mutex(const T& v)
            : m_value{v}
        {
        }
 
        explicit value_with_mutex(T&& v)
            : m_value{std::move(v)}
        {
        }
 
        class pointer_under_lock
        {
        public:
            pointer_under_lock(value_with_mutex<T>&& value) = delete;
 
            pointer_under_lock(value_with_mutex<T>& value)
                : pointer_under_lock{value.m_value, value.m_mutex}
            {
            }
 
        private:
            pointer_under_lock(T& val, std::mutex& mutex)
                : m_ptr{&val}
                , m_lock{mutex}
            {
            }
 
        public:
            T*       operator->() { return m_ptr; }
            const T* operator->() const { return m_ptr; }
 
            T&       operator*() { return *m_ptr; }
            const T& operator*() const { return *m_ptr; }
 
        private:
            T*                           m_ptr;
            std::scoped_lock<std::mutex> m_lock;
        };
 
        pointer_under_lock lock() { return *this; }
 
        std::mutex& get_mutex() { return m_mutex; }
        T&          get_value_unsafe() { return m_value; }
 
    private:
        RPP_NO_UNIQUE_ADDRESS T m_value{};
        std::mutex              m_mutex{};
    };
 
    template<typename T>
    using pointer_under_lock = typename value_with_mutex<T>::pointer_under_lock;
 
    namespace details
    {
        template<typename T, typename... Ts>
        struct unique_variant_t : std::type_identity<T>
        {
        };
 
        template<typename... Ts, typename U, typename... Us>
            requires (std::is_same_v<U, Ts> || ...)
        struct unique_variant_t<std::variant<Ts...>, U, Us...> : unique_variant_t<std::variant<Ts...>, Us...>
        {
        };
 
        template<typename... Ts, typename U, typename... Us>
        struct unique_variant_t<std::variant<Ts...>, U, Us...> : public unique_variant_t<std::variant<Ts..., U>, Us...>
        {
        };
    } // namespace details
 
    template<typename... Ts>
    using unique_variant = typename details::unique_variant_t<std::variant<>, Ts...>::type; // inspired by https://stackoverflow.com/a/57528226/17771792
 
 
#define RPP_CALL_DURING_CONSTRUCTION(...) RPP_NO_UNIQUE_ADDRESS rpp::utils::none _ = [&]() { \
    __VA_ARGS__;                                                                             \
    return rpp::utils::none{};                                                               \
}()
} // namespace rpp::utils