#pragma once

#include "resources/resource.hpp"

#include <vector>
#include <unordered_map>

// Doesn't own resources, only holds weak_ptrs

class ResourceManager {

public:
	ResourceManager();
	ResourceManager(const ResourceManager&) = delete;
	ResourceManager& operator=(const ResourceManager&) = delete;
	~ResourceManager() = default;

	template <class T>
	std::shared_ptr<T> create(const std::string& name);

	// creates the resource if it is not in the map or the weak_ptr has expired
	template <class T>
	std::shared_ptr<T> get(const std::string& name);

	std::unique_ptr<std::string> getResourcesListString();

	std::vector<std::weak_ptr<Resource>> getAllResourcesOfType(const std::string& type);

	std::filesystem::path getFilePath(const std::string& name);

private:
	std::filesystem::path m_resourcesPath;
	std::unordered_map<std::string, std::weak_ptr<Resource>> m_resources;

};

template <class T>
std::shared_ptr<T> ResourceManager::create(const std::string& name)
{
	if (std::is_base_of<Resource, T>::value == false) {
		throw std::runtime_error("ResourceManager::create() error: specified type is not a subclass of 'Resource'");
	}
	auto resource = std::make_shared<T>(getFilePath(name));
	m_resources.emplace(name, std::dynamic_pointer_cast<Resource>(resource));
	return resource;
}

template <class T>
std::shared_ptr<T> ResourceManager::get(const std::string& name)
{

	if (std::is_base_of<Resource, T>::value == false) {
		throw std::runtime_error("ResourceManager::get() error: specified type is not a subclass of 'Resource'");
	}

	if (m_resources.contains(name)) {

		std::weak_ptr<Resource> res = m_resources.at(name);

		if (res.expired() == false) {
			// resource definitely exists
			auto castedSharedPtr = std::dynamic_pointer_cast<T>(res.lock());
			if (castedSharedPtr == nullptr) {
				throw std::runtime_error("error: attempt to get Resource which already exists as another type");
			}
			else {
				return castedSharedPtr;
			}
		}
		else {
			// Resource in map but no longer exists. Delete it.
			m_resources.erase(name);
		}

	}
	
	return create<T>(name);

}