Z3D/include/util/file_id_lookup.hpp

#pragma once

#include <unordered_map>
#include <filesystem>
#include <ranges>
#include <vector>
#include <mutex>
#include <shared_mutex>

template<typename ID>
class file_id_lookup
{
public:
	using container_type = std::unordered_map<std::filesystem::path, ID>;
	using key_type = typename container_type::key_type;
	using mapped_type = typename container_type::mapped_type;
	using value_type = typename container_type::value_type;
	using size_type = typename container_type::size_type;
	using difference_type = typename container_type::difference_type;
	using hasher = typename container_type::hasher;
	using key_equal = typename container_type::key_equal;
	using allocator_type = typename container_type::allocator_type;
	using reference = typename container_type::reference;
	using const_reference = typename container_type::const_reference;
	using pointer = typename container_type::pointer;
	using const_pointer = typename container_type::const_pointer;
	using iterator = typename container_type::iterator;
	using const_iterator = typename container_type::const_iterator;
	using local_iterator = typename container_type::local_iterator;
	using const_local_iterator = typename container_type::const_local_iterator;
	using node_type = typename container_type::node_type;
	using insert_return_type = typename container_type::insert_return_type;


	std::pair<iterator, bool> try_emplace(const key_type& path)
	{
		std::unique_lock lock(m_mutex);
		auto it = m_container.find(path);
		const auto is_new = it == m_container.end();
		if (is_new) {
			it = m_container.emplace_hint(it, path, ID::next());
		}
		return { it, is_new };
	}

    [[nodiscard]] bool empty() const noexcept
	{
        std::shared_lock lock(m_mutex);
        return m_container.empty();
    }
    [[nodiscard]] size_type size() const noexcept
	{
        std::shared_lock lock(m_mutex);
        return m_container.size();
    }
    [[nodiscard]] size_type max_size() const noexcept
	{
        std::shared_lock lock(m_mutex);
        return m_container.max_size();
    }

    void by_extension(const std::string_view extension, std::vector<const_pointer>& dst) const
	{
        std::shared_lock lock(m_mutex);
        std::ranges::copy(
            m_container |
            std::views::filter([
                &](const value_type& entry) {
                    return entry.first.extension() == extension;
                }
            ) |
            std::views::transform([
                &](const value_type& entry) {
                    return &entry;
                }
            ),
            std::back_inserter(dst)
        );
    }


    [[nodiscard]] bool contains(const key_type& key) const
	{
        std::shared_lock lock(m_mutex);
        return m_container.contains(key);
    }
    [[nodiscard]] size_type count(const key_type& key) const
	{
        std::shared_lock lock(m_mutex);
        return m_container.count(key);
    }
    [[nodiscard]] iterator find(const key_type& key)
	{
        std::shared_lock lock(m_mutex);
        return m_container.find(key);
    }
    [[nodiscard]] const_iterator find(const key_type& key) const
	{
        std::shared_lock lock(m_mutex);
        return m_container.find(key);
    }

    iterator erase(iterator pos)
	{
        std::unique_lock lock(m_mutex);
        return m_container.erase(pos);
    }
    iterator erase(const_iterator pos)
	{
        std::unique_lock lock(m_mutex);
        return m_container.erase(pos);
    }
    iterator erase(const_iterator first, const_iterator last)
	{
        std::unique_lock lock(m_mutex);
        return m_container.erase(first, last);
    }
    size_type erase(const key_type& key)
	{
        std::unique_lock lock(m_mutex);
        return m_container.erase(key);
    }
    void clear() noexcept
	{
        std::unique_lock lock(m_mutex);
        m_container.clear();
    }

	[[nodiscard]] iterator begin() noexcept { return m_container.begin(); }
	[[nodiscard]] const_iterator begin() const noexcept { return m_container.begin(); }
	[[nodiscard]] const_iterator cbegin() const noexcept { return m_container.cbegin(); }
	[[nodiscard]] iterator end() noexcept { return m_container.end(); }
	[[nodiscard]] const_iterator end() const noexcept { return m_container.end(); }
	[[nodiscard]] const_iterator cend() const noexcept { return m_container.cend(); }


private:
	static auto extension_filter(const std::string_view& extension)
	{
		return std::views::filter(
			[extension](const key_type& path)
			{
				return path.extension() == extension;
			}
		);
	}

	container_type m_container;
	mutable std::shared_mutex m_mutex;
};