cache.hpp

/*
 Copyright (c) 2026 ETIB Corporation
 
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 this software and associated documentation files (the "Software"), to deal in
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 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 of the Software, and to permit persons to whom the Software is furnished to do
 so, subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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 SOFTWARE.
 */
 
#pragma once
 
#include <map>
#include <mutex>
#include <optional>
#include <shared_mutex>
#include <utility>
#include <functional>
#include <concepts>
 
namespace utility
{
 
    template<typename T>
    concept CacheEntry = std::movable<T>;
 
    template<typename Key, typename Compare = std::less<Key>>
    concept CacheKey = requires(const Key &a, const Key &b, Compare comp) {
        { comp(a, b) } -> std::convertible_to<bool>;
    };
 
    template<typename Key, CacheEntry Entry, typename Compare = std::less<Key>>
        requires CacheKey<Key, Compare>
    class Cache
    {
        private:
        std::map<Key, Entry, Compare>
            _entries;    
        mutable std::shared_mutex _mutex;    
 
        public:
        Cache(void) = default;
 
        ~Cache(void) = default;
 
        Cache(const Cache &other) = delete;
 
        Cache &operator=(const Cache &other) = delete;
 
        Cache(Cache &&other) noexcept = delete;
 
        Cache &operator=(Cache &&other) noexcept = delete;
 
        bool contains(const Key &key) const
        {
            std::shared_lock<std::shared_mutex> guard(_mutex);
            return _entries.find(key) != _entries.end();
        }
 
        std::optional<Entry> get(const Key &key) const
        {
            std::shared_lock<std::shared_mutex> guard(_mutex);
            auto it = _entries.find(key);
            if (it == _entries.end()) {
                return std::nullopt;
            }
            return it->second;
        }
 
        void put(const Key &key, const Entry &value)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            _entries.insert_or_assign(key, value);
        }
 
        void put(Key &&key, Entry &&value)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            _entries.insert_or_assign(std::move(key), std::move(value));
        }
 
        template<typename... Args>
        Entry &emplace(const Key &key, Args &&...args)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            auto [it, inserted] =
                _entries.try_emplace(key, std::forward<Args>(args)...);
            return it->second;
        }
 
        template<typename... Args> Entry &emplace(Key &&key, Args &&...args)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            auto [it, inserted] = _entries.try_emplace(
                std::move(key), std::forward<Args>(args)...);
            return it->second;
        }
 
        bool erase(const Key &key)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            return _entries.erase(key) > 0;
        }
 
        void erase_if(
            const std::function<bool(const Key &, const Entry &)> &predicate)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            for (auto it = _entries.begin(); it != _entries.end();) {
                if (predicate(it->first, it->second)) {
                    it = _entries.erase(it);
                } else {
                    ++it;
                }
            }
        }
 
        void apply(const std::function<void(const Key &, Entry &)> &function)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            for (auto &[key, entry]: _entries) {
                function(key, entry);
            }
        }
 
        void clear(void)
        {
            std::unique_lock<std::shared_mutex> guard(_mutex);
            _entries.clear();
        }
 
        std::map<Key, Entry, Compare>::size_type size(void) const
        {
            std::shared_lock<std::shared_mutex> guard(_mutex);
            return _entries.size();
        }
 
        bool empty(void) const
        {
            std::shared_lock<std::shared_mutex> guard(_mutex);
            return _entries.empty();
        }
    };
 
}    // namespace utility