#include <boost/beast/core.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <iostream>
#include <string>
#include <memory>
#include <vector>
#include <mutex>
#include <map>
#include <queue>
#include <sstream>
#include <Eigen/Dense>
#define _USE_MATH_DEFINES
#include <math.h>
#include "../src/network/ClientState.h"
#include <random>
#include <algorithm>
#include <chrono>
#include <unordered_set>

namespace beast = boost::beast;
namespace http = beast::http;
namespace websocket = beast::websocket;
namespace net = boost::asio;
using tcp = net::ip::tcp;

struct DeathInfo {
	int targetId = -1;
	uint64_t serverTime = 0;
	Eigen::Vector3f position = Eigen::Vector3f::Zero();
	int killerId = -1;
};

std::vector<std::string> split(const std::string& s, char delimiter) {
	std::vector<std::string> tokens;
	std::string token;
	std::istringstream tokenStream(s);
	while (std::getline(tokenStream, token, delimiter)) {
		tokens.push_back(token);
	}
	return tokens;
}

// Вспомогательная функция для проверки столкновения снаряда с объектом-сферой
bool checkSegmentSphereCollision(
	int x,
	const Eigen::Vector3f& pStart,
	const Eigen::Vector3f& pEnd,
	const Eigen::Vector3f& targetCenter,
	float combinedRadius)
{
	Eigen::Vector3f segment = pEnd - pStart;
	Eigen::Vector3f toTarget = targetCenter - pStart;

	float segmentLenSq = segment.squaredNorm();
	if (segmentLenSq < 1e-6f) {
		return toTarget.norm() <= combinedRadius;
	}

	// Находим проекцию точки targetCenter на прямую, содержащую отрезок
	// t — это нормализованный параметр вдоль отрезка (от 0 до 1)
	float t = toTarget.dot(segment) / segmentLenSq;

	// Ограничиваем t, чтобы найти ближайшую точку именно на ОТРЕЗКЕ
	t = std::max(0.0f, std::min(1.0f, t));

	// Ближайшая точка на отрезке к центру цели
	Eigen::Vector3f closestPoint = pStart + t * segment;
	/*
	std::cout << "Collision for box: " << x << " pStart: " << pStart
		<< " pEnd: " << pEnd
		<< " targetCenter: " << targetCenter
		<< " closestPoint: " << closestPoint 
		<< " t: " << t << std::endl;
		*/
	// Проверяем расстояние от ближайшей точки до центра цели
	return (targetCenter - closestPoint).squaredNorm() <= (combinedRadius * combinedRadius);
}

struct ServerBox {
	Eigen::Vector3f position;
	Eigen::Matrix3f rotation;
	float collisionRadius = 2.0f;
	bool destroyed = false;
};

struct Projectile {
	int shooterId = -1;
	uint64_t spawnMs = 0;
	Eigen::Vector3f pos;
	Eigen::Vector3f vel;
	float lifeMs = 5000.0f;
};

struct BoxDestroyedInfo {
	int boxIndex = -1;
	uint64_t serverTime = 0;
	Eigen::Vector3f position = Eigen::Vector3f::Zero();
	int destroyedBy = -1;
};

std::vector<ServerBox> g_serverBoxes;
std::mutex g_boxes_mutex;

std::vector<std::shared_ptr<class Session>> g_sessions;
std::mutex g_sessions_mutex;

std::vector<Projectile> g_projectiles;
std::mutex g_projectiles_mutex;

std::unordered_set<int> g_dead_players;
std::mutex g_dead_mutex;

class Session;

void broadcastToAll(const std::string& message);

class Session : public std::enable_shared_from_this<Session> {
	websocket::stream<beast::tcp_stream> ws_;
	beast::flat_buffer buffer_;
	int id_;
	bool is_writing_ = false;
	std::queue<std::shared_ptr<std::string>> writeQueue_;
	std::mutex writeMutex_;

public:
	ClientStateInterval timedClientStates;

	explicit Session(tcp::socket&& socket, int id)
		: ws_(std::move(socket)), id_(id) {
	}

	int get_id() const { return id_; }

	bool fetchStateAtTime(std::chrono::system_clock::time_point targetTime, ClientState& outState) const {
		if (timedClientStates.canFetchClientStateAtTime(targetTime)) {
			outState = timedClientStates.fetchClientStateAtTime(targetTime);
			return true;
		}
		return false;
	}

	void send_message(const std::string& msg) {
		auto ss = std::make_shared<std::string>(msg);
		{
			std::lock_guard<std::mutex> lock(writeMutex_);
			writeQueue_.push(ss);
		}
		doWrite();
	}

	void run() {
		{
			std::lock_guard<std::mutex> lock(g_sessions_mutex);
			g_sessions.push_back(shared_from_this());
		}

		ws_.async_accept([self = shared_from_this()](beast::error_code ec) {
			if (ec) return;
			std::cout << "Client " << self->id_ << " connected\n";
			self->init();
			});
	}

	bool IsMessageValid(const std::string& fullMessage) {
#ifdef ENABLE_NETWORK_CHECKSUM
		size_t hashPos = fullMessage.find("#hash:");
		if (hashPos == std::string::npos) {
			return false; // Хеша нет, хотя он ожидался
		}

		std::string originalContent = fullMessage.substr(0, hashPos);
		std::string receivedHashStr = fullMessage.substr(hashPos + 6); // 6 — длина "#hash:"

		// Вычисляем ожидаемый хеш от контента
		size_t expectedHash = fnv1a_hash(originalContent + NET_SECRET);

		std::stringstream ss;
		ss << std::hex << expectedHash;

		return ss.str() == receivedHashStr;
#else
		return true; // В режиме отладки пропускаем всё
#endif
	}

private:

	void sendBoxesToClient() {
		std::lock_guard<std::mutex> lock(g_boxes_mutex);

		std::string boxMsg = "BOXES:";
		for (const auto& box : g_serverBoxes) {
			Eigen::Quaternionf q(box.rotation);
			boxMsg += std::to_string(box.position.x()) + ":" +
				std::to_string(box.position.y()) + ":" +
				std::to_string(box.position.z()) + ":" +
				std::to_string(q.w()) + ":" +
				std::to_string(q.x()) + ":" +
				std::to_string(q.y()) + ":" +
				std::to_string(q.z()) + "|";
		}

		if (!boxMsg.empty() && boxMsg.back() == '|') boxMsg.pop_back();

		send_message(boxMsg);
	}


public:

	void init()
	{
		sendBoxesToClient();

		auto timer = std::make_shared<net::steady_timer>(ws_.get_executor());
		timer->expires_after(std::chrono::milliseconds(100));
		timer->async_wait([self = shared_from_this(), timer](const boost::system::error_code& ec) {
			if (!ec) {
				int64_t serverNow = std::chrono::duration_cast<std::chrono::milliseconds>(
					std::chrono::system_clock::now().time_since_epoch()).count();
				self->send_message("ID:" + std::to_string(self->id_) + ":" + std::to_string(serverNow)); 
				self->do_read();
			}
			});
	}
	

	ClientState get_latest_state(std::chrono::system_clock::time_point now) {
		if (timedClientStates.timedStates.empty()) {
			return {};
		}

		// 1. Берем самое последнее известное состояние
		ClientState latest = timedClientStates.timedStates.back();

		// 3. Применяем компенсацию лага (экстраполяцию).
		// Функция внутри использует simulate_physics, чтобы переместить объект 
		// из точки lastUpdateServerTime в точку now.
		latest.apply_lag_compensation(now);

		return latest;
	}
	
	void doWrite() {
		std::lock_guard<std::mutex> lock(writeMutex_);
		if (is_writing_ || writeQueue_.empty()) {
			return;
		}

		is_writing_ = true;
		auto message = writeQueue_.front();

		ws_.async_write(net::buffer(*message),
			[self = shared_from_this(), message](beast::error_code ec, std::size_t) {
				if (ec) {
					std::cerr << "Write error: " << ec.message() << std::endl;
					return;
				}
				{
					std::lock_guard<std::mutex> lock(self->writeMutex_);
					self->writeQueue_.pop();
					self->is_writing_ = false;
				}
				self->doWrite();
			});
	}
private:

	void do_read() {
		ws_.async_read(buffer_, [self = shared_from_this()](beast::error_code ec, std::size_t) {
			if (ec) {
				std::lock_guard<std::mutex> lock(g_sessions_mutex);
				g_sessions.erase(std::remove_if(g_sessions.begin(), g_sessions.end(),
					[self](const std::shared_ptr<Session>& session) {
						return session.get() == self.get();
					}), g_sessions.end());
				std::cout << "Client " << self->id_ << " disconnected\n";
				return;
			}

			std::string msg = beast::buffers_to_string(self->buffer_.data());
			self->process_message(msg);

			self->buffer_.consume(self->buffer_.size());
			self->do_read();
			});
	}

	void process_message(const std::string& msg) {
		if (!IsMessageValid(msg)) {
			// Логируем попытку подмены и просто выходим из обработки
			std::cout << "[Security] Invalid packet hash. Dropping message: " << msg << std::endl;
			return;
		}
		std::string cleanMessage = msg.substr(0, msg.find("#hash:"));

		

		std::cout << "Received from player " << id_ << ": " << cleanMessage << std::endl;
		auto parts = split(cleanMessage, ':');

		if (parts.empty()) return;

		std::string type = parts[0];

		if (type == "UPD") {
			{
				std::lock_guard<std::mutex> gd(g_dead_mutex);
				if (g_dead_players.find(id_) != g_dead_players.end()) {
					std::cout << "Server: Ignoring UPD from dead player " << id_ << std::endl;
					return;
				}
			}

			if (parts.size() < 16) return;
			uint64_t clientTimestamp = std::stoull(parts[1]);
			ClientState receivedState;
			receivedState.id = id_;
			std::chrono::system_clock::time_point uptime_timepoint{
				std::chrono::milliseconds(clientTimestamp)
			};
			receivedState.lastUpdateServerTime = uptime_timepoint;
			receivedState.handle_full_sync(parts, 2);
			timedClientStates.add_state(receivedState);

			retranslateMessage(cleanMessage);
		}
		else if (parts[0] == "RESPAWN") {
			{
				std::lock_guard<std::mutex> gd(g_dead_mutex);
				g_dead_players.erase(id_);
			}

			std::string respawnMsg = "RESPAWN_ACK:" + std::to_string(id_);
			broadcastToAll(respawnMsg);

			std::cout << "Server: Player " << id_ << " respawned\n";
		}
		else if (parts[0] == "FIRE") {
			if (parts.size() < 10) return;

			uint64_t clientTime = std::stoull(parts[1]);
			Eigen::Vector3f pos{
				std::stof(parts[2]), std::stof(parts[3]), std::stof(parts[4])
			};
			Eigen::Quaternionf dir(
				std::stof(parts[5]), std::stof(parts[6]), std::stof(parts[7]), std::stof(parts[8])
			);
			float velocity = std::stof(parts[9]);

			int shotCount = 2;
			if (parts.size() >= 11) {
				try { shotCount = std::stoi(parts[10]); }
				catch (...) { shotCount = 2; }
			}

			std::string broadcast = "PROJECTILE:" +
				std::to_string(id_) + ":" +
				std::to_string(clientTime) + ":" +
				std::to_string(pos.x()) + ":" +
				std::to_string(pos.y()) + ":" +
				std::to_string(pos.z()) + ":" +
				std::to_string(dir.w()) + ":" +
				std::to_string(dir.x()) + ":" +
				std::to_string(dir.y()) + ":" +
				std::to_string(dir.z()) + ":" +
				std::to_string(velocity);

			{
				std::lock_guard<std::mutex> lock(g_sessions_mutex);
				for (auto& session : g_sessions) {
					if (session->get_id() != id_) {
						session->send_message(broadcast);
					}
				}
			}

			{
				const std::vector<Eigen::Vector3f> localOffsets = {
					Eigen::Vector3f(-1.5f, 0.9f, 5.0f),
					Eigen::Vector3f(1.5f, 0.9f, 5.0f)
				};

				uint64_t now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
					std::chrono::system_clock::now().time_since_epoch()).count();

				std::lock_guard<std::mutex> pl(g_projectiles_mutex);
				for (int i = 0; i < std::min(shotCount, (int)localOffsets.size()); ++i) {
					Projectile pr;
					pr.shooterId = id_;
					pr.spawnMs = now_ms;
					Eigen::Vector3f shotPos = pos + dir.toRotationMatrix() * localOffsets[i];
					pr.pos = shotPos;
					Eigen::Vector3f localForward(0.0f, 0.0f, -1.0f);
					Eigen::Vector3f worldForward = dir.toRotationMatrix() * localForward;
					float len = worldForward.norm();
					if (len > 1e-6f) worldForward /= len;
					pr.vel = worldForward * velocity;
					pr.lifeMs = 5000.0f;
					g_projectiles.push_back(pr);

					std::cout << "Server: Created projectile from player " << id_
						<< " at pos (" << shotPos.x() << ", " << shotPos.y() << ", " << shotPos.z()
						<< ") vel (" << pr.vel.x() << ", " << pr.vel.y() << ", " << pr.vel.z() << ")" << std::endl;
				}
			}
		}
	}

	void retranslateMessage(const std::string& msg) {
		std::string event_msg = "EVENT:" + std::to_string(id_) + ":" + msg;

		std::lock_guard<std::mutex> lock(g_sessions_mutex);
		for (auto& session : g_sessions) {
			if (session->get_id() != id_) {
				session->send_message(event_msg);
			}
		}
	}
};

void broadcastToAll(const std::string& message) {
	std::lock_guard<std::mutex> lock(g_sessions_mutex);
	for (const auto& session : g_sessions) {
		session->send_message(message);
	}
}

void checkShipBoxCollisions(std::chrono::system_clock::time_point now, uint64_t now_ms, std::vector<BoxDestroyedInfo>& boxDestructions) {
	// Внимание: Мьютексы g_boxes_mutex и g_sessions_mutex должны быть захвачены 
	// внешним кодом в update_world перед вызовом этой функции.

	const float shipCollisionRadius = 15.0f;
	const float boxCollisionRadius = 2.0f;
	const float thresh = shipCollisionRadius + boxCollisionRadius;
	const float threshSq = thresh * thresh;

	for (size_t bi = 0; bi < g_serverBoxes.size(); ++bi) {
		if (g_serverBoxes[bi].destroyed) continue;

		// Центр ящика в мировых координатах
		Eigen::Vector3f boxWorld = g_serverBoxes[bi].position + Eigen::Vector3f(0.0f, 0.0f, 45000.0f);

		for (auto& session : g_sessions) {
			int playerId = session->get_id();

			// Пропускаем мертвых игроков
			{
				// Если g_dead_mutex не захвачен глобально в update_world, раскомментируйте:
				// std::lock_guard<std::mutex> gd(g_dead_mutex); 
				if (g_dead_players.count(playerId)) continue;
			}

			ClientState shipState;
			// Получаем состояние игрока на текущий момент времени сервера
			if (!session->fetchStateAtTime(now, shipState)) continue;

			Eigen::Vector3f diff = shipState.position - boxWorld;

			// Проверка столкновения сфер
			if (diff.squaredNorm() <= threshSq) {
				g_serverBoxes[bi].destroyed = true;

				// Регистрируем уничтожение ящика
				BoxDestroyedInfo destruction;
				destruction.boxIndex = static_cast<int>(bi);
				destruction.serverTime = now_ms;
				destruction.position = boxWorld;
				destruction.destroyedBy = playerId;

				boxDestructions.push_back(destruction);

				std::cout << "Server: Box " << bi << " smashed by player " << playerId << std::endl;

				// Один ящик не может быть уничтожен дважды за один проход
				break;
			}
		}
	}
}

void dispatchEvents(const std::vector<DeathInfo>& deathEvents, const std::vector<BoxDestroyedInfo>& boxDestructions) {
	// 1. Рассылка событий смерти игроков
	for (const auto& death : deathEvents) {
		std::string deadMsg = "DEAD:" +
			std::to_string(death.serverTime) + ":" +
			std::to_string(death.targetId) + ":" +
			std::to_string(death.position.x()) + ":" +
			std::to_string(death.position.y()) + ":" +
			std::to_string(death.position.z()) + ":" +
			std::to_string(death.killerId);

		broadcastToAll(deadMsg);

		std::cout << "Server: Sent DEAD event - Player " << death.targetId
			<< " killed by " << death.killerId << std::endl;
	}

	// 2. Рассылка событий разрушения ящиков

	for (const auto& destruction : boxDestructions) {
			std::string boxMsg = "BOX_DESTROYED:" +
				std::to_string(destruction.boxIndex) + ":" +
				std::to_string(destruction.serverTime) + ":" +
				std::to_string(destruction.position.x()) + ":" +
				std::to_string(destruction.position.y()) + ":" +
				std::to_string(destruction.position.z()) + ":" +
				std::to_string(destruction.destroyedBy);

			broadcastToAll(boxMsg);

			std::cout << "Server: Broadcasted BOX_DESTROYED for box "
				<< destruction.boxIndex << std::endl;
	}
}

void update_world(net::steady_timer& timer, net::io_context& ioc) {
	const std::chrono::milliseconds interval(50);
	timer.expires_after(interval);

	timer.async_wait([&](const boost::system::error_code& ec) {
		if (ec) return;

		auto now = std::chrono::system_clock::now();
		uint64_t now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count();
		float dt = 50.0f / 1000.0f;

		std::vector<DeathInfo> deathEvents;
		std::vector<BoxDestroyedInfo> boxDestructions;
		std::vector<int> projectilesToRemove;

		{
			// Захватываем необходимые данные под мьютексами один раз
			std::lock_guard<std::mutex> pl(g_projectiles_mutex);
			std::lock_guard<std::mutex> bm(g_boxes_mutex);
			std::lock_guard<std::mutex> sm(g_sessions_mutex);
			std::lock_guard<std::mutex> gm(g_dead_mutex);

			for (size_t i = 0; i < g_projectiles.size(); ++i) {
				auto& pr = g_projectiles[i];
				Eigen::Vector3f oldPos = pr.pos;
				pr.pos += pr.vel * dt;
				Eigen::Vector3f newPos = pr.pos;

				// 1. Проверка времени жизни снаряда
				if (now_ms > pr.spawnMs + static_cast<uint64_t>(pr.lifeMs)) {
					projectilesToRemove.push_back(static_cast<int>(i));
					continue;
				}

				bool hitDetected = false;

				// 2. Проверка коллизий снаряда с игроками (Ray-cast)
				for (auto& session : g_sessions) {
					int targetId = session->get_id();
					if (targetId == pr.shooterId || g_dead_players.count(targetId)) continue;

					ClientState targetState;
					if (!session->fetchStateAtTime(now, targetState)) continue;

					if (checkSegmentSphereCollision(0, oldPos, newPos, targetState.position, 15.0f + 1.5f)) {
						deathEvents.push_back({ targetId, now_ms, newPos, pr.shooterId });
						g_dead_players.insert(targetId);
						hitDetected = true;
						break;
					}
				}

				if (hitDetected) {
					projectilesToRemove.push_back(static_cast<int>(i));
					continue;
				}

				// 3. Проверка коллизий снаряда с ящиками (Ray-cast)
				for (size_t bi = 0; bi < g_serverBoxes.size(); ++bi) {
					if (g_serverBoxes[bi].destroyed) continue;

					// Центр ящика с учетом смещения мира
					Eigen::Vector3f boxWorld = g_serverBoxes[bi].position + Eigen::Vector3f(0.0f, 0.0f, 45000.0f);

					if (checkSegmentSphereCollision(bi, oldPos, newPos, boxWorld, 2.0f + 1.5f)) {
						g_serverBoxes[bi].destroyed = true;

						boxDestructions.push_back({ static_cast<int>(bi), now_ms, boxWorld, pr.shooterId });

						hitDetected = true;
						break;
					}
				}

				if (hitDetected) {
					projectilesToRemove.push_back(static_cast<int>(i));
				}
			}

			// Удаляем отработавшие снаряды (с конца)
			std::sort(projectilesToRemove.rbegin(), projectilesToRemove.rend());
			for (int idx : projectilesToRemove) {
				g_projectiles.erase(g_projectiles.begin() + idx);
			}
		}

		// 4. Отдельная проверка столкновения кораблей с ящиками (Point-Sphere)
		// Эту логику оставляем отдельно, так как она не привязана к снарядам
		checkShipBoxCollisions(now, now_ms, boxDestructions);

		// Рассылка событий
		dispatchEvents(deathEvents, boxDestructions);

		update_world(timer, ioc);
		});
}

std::vector<ServerBox> generateServerBoxes(int count) {
	std::vector<ServerBox> boxes;
	std::random_device rd;
	std::mt19937 gen(rd());

	const float MIN_COORD = -100.0f;
	const float MAX_COORD = 100.0f;
	const float MIN_DISTANCE = 3.0f;
	const float MIN_DISTANCE_SQUARED = MIN_DISTANCE * MIN_DISTANCE;
	const int MAX_ATTEMPTS = 1000;

	std::uniform_real_distribution<> posDistrib(MIN_COORD, MAX_COORD);
	std::uniform_real_distribution<> angleDistrib(0.0, M_PI * 2.0);

	for (int i = 0; i < count; i++) {
		bool accepted = false;
		int attempts = 0;

		while (!accepted && attempts < MAX_ATTEMPTS) {
			ServerBox box;
			box.position = Eigen::Vector3f(
				(float)posDistrib(gen),
				(float)posDistrib(gen),
				(float)posDistrib(gen)
			);

			accepted = true;
			for (const auto& existingBox : boxes) {
				Eigen::Vector3f diff = box.position - existingBox.position;
				if (diff.squaredNorm() < MIN_DISTANCE_SQUARED) {
					accepted = false;
					break;
				}
			}

			if (accepted) {
				float randomAngle = (float)angleDistrib(gen);
				Eigen::Vector3f axis = Eigen::Vector3f::Random().normalized();
				box.rotation = Eigen::AngleAxisf(randomAngle, axis).toRotationMatrix();
				boxes.push_back(box);
			}

			attempts++;
		}
	}

	return boxes;
}

int main() {
	try {
		{
			std::lock_guard<std::mutex> lock(g_boxes_mutex);
			g_serverBoxes = generateServerBoxes(50);
			std::cout << "Generated " << g_serverBoxes.size() << " boxes on server\n";
		}
		net::io_context ioc;
		tcp::acceptor acceptor{ ioc, {tcp::v4(), 8081} };

		int next_id = 1000;

		std::cout << "Server started on port 8081...\n";

		auto do_accept = [&](auto& self_fn) -> void {
			acceptor.async_accept([&, self_fn](beast::error_code ec, tcp::socket socket) {
				if (!ec) {
					std::make_shared<Session>(std::move(socket), next_id++)->run();
				}
				self_fn(self_fn);
				});
			};

		net::steady_timer timer(ioc);
		update_world(timer, ioc);

		do_accept(do_accept);
		ioc.run();
	}
	catch (std::exception const& e) {
		std::cerr << "Error: " << e.what() << std::endl;
	}
	return 0;
}