#ifndef UNORDERED_CACHE_H
#define UNORDERED_CACHE_H

#include <functional>
#include <unordered_map>

template <typename KeyType, typename ValType, typename Hasher = std::hash<KeyType>>
class UnorderedCache
{
public:
	UnorderedCache(std::function<ValType(const KeyType&)> calculator);
	ValType getValue(const KeyType& key);

private:
	std::function<ValType(const KeyType&)> m_calculator;
	std::unordered_map<KeyType, ValType, Hasher> m_map;

	size_t m_hitCount;
	size_t m_missCount;
};

template <typename KeyType, typename ValType, typename Hasher>
UnorderedCache<KeyType, ValType, Hasher>::UnorderedCache(std::function<ValType(const KeyType&)> calculator)
	: m_calculator(calculator), m_hitCount(0), m_missCount(0)
{
}

template <typename KeyType, typename ValType, typename Hasher>
ValType UnorderedCache<KeyType, ValType, Hasher>::getValue(const KeyType& key)
{
	auto it = m_map.find(key);
	if (it != m_map.end())
	{
		++m_hitCount;
		return it->second;
	}
	++m_missCount;
	ValType val = m_calculator(key);
	m_map.emplace(key, val);
	return val;
}

#endif	  // UNORDERED_CACHE_H