master-server/src/network_list.hpp

#pragma once

#include <functional>

#include "console.hpp"
#include "network/address.hpp"
#include "utils/concurrency.hpp"

template <typename T, size_t IPLimit = 0>
class network_list
{
public:
	class iteration_context
	{
	public:
		friend network_list;

		const network::address& get_address() const { return *this->address_; }
		T& get() { return *this->element_; }
		const T& get() const { return *this->element_; }
		void remove() { this->remove_ = true; }
		void stop_iterating() const { this->stop_iterating_ = true; }

	private:
		T* element_{};
		const network::address* address_{};
		bool remove_{false};
		mutable bool stop_iterating_{false};
	};

	using iterate_func = std::function<void (iteration_context&)>;
	using const_iterate_func = std::function<void (const iteration_context&)>;

	using access_func = std::function<void(T&, const network::address&)>;
	using const_access_func = std::function<void(const T&, const network::address&)>;

	using insert_func = std::function<void(T&)>;

	bool find(const network::address& address, const access_func& accessor)
	{
		return this->elements_.template access<bool>([&](list_type& list)
		{
			const auto i = list.find(address);
			if (i == list.end())
			{
				return false;
			}

			accessor(i->second, i->first);
			return true;
		});
	}

	bool find(const network::address& address, const const_access_func& accessor) const
	{
		return this->elements_.template access<bool>([&](const list_type& list)
		{
			const auto i = list.find(address);
			if (i == list.end())
			{
				return false;
			}

			accessor(i->second, i->first);
			return true;
		});
	}

	void iterate(const iterate_func& iterator)
	{
		this->elements_.access([&](list_type& list)
		{
			iteration_context context{};

			for (auto i = list.begin(); i != list.end();)
			{
				context.element_ = &i->second;
				context.address_ = &i->first;
				context.remove_ = false;

				iterator(context);

				if (context.remove_)
				{
					i = list.erase(i);
				}
				else
				{
					++i;
				}

				if (context.stop_iterating_)
				{
					break;
				}
			}
		});
	}

	void iterate(const const_iterate_func& iterator) const
	{
		this->elements_.access([&](const list_type& list)
		{
			iteration_context context{};

			for (const auto& server : list)
			{
				// const_cast is ok here
				context.element_ = const_cast<T*>(&server.second);
				context.address_ = &server.first;

				iterator(context);

				if (context.stop_iterating_)
				{
					break;
				}
			}
		});
	}

protected:
	void insert(const network::address& address, const insert_func& callback)
	{
		this->elements_.access([&](list_type& list)
		{
			auto entry = list.find(address);
			if (entry != list.end())
			{
				callback(entry->second);
				return;
			}

			if (!is_insertion_allowed(list, address))
			{
				console::log("Insertion rejected for target:\t%s", address.to_string().c_str());
				return;
			}

			callback(list[address]);
		});
	}

private:
	using list_type = std::unordered_map<network::address, T>;
	utils::concurrency::container<list_type> elements_;

	static bool is_insertion_allowed(const list_type& list, const network::address& address)
	{
		if constexpr (IPLimit == 0)
		{
			return true;
		}

		const auto target_ip = address.get_in_addr().sin_addr.s_addr;

		size_t occurrences = 0;
		for (const auto& entry : list)
		{
			const auto entry_ip = entry.first.get_in_addr().sin_addr.s_addr;
			if (entry_ip == target_ip)
			{
				if (++occurrences >= IPLimit)
				{
					return false;
				}
			}
		}

		return true;
	}
};