#include "SessionHandler.hpp"
#include <random>
#include <thread>
#include "crow/logging.h"

using namespace login;

// generate random string
std::string randomString(size_t length) {
    static const char charset[] =
        "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    std::string result;
    result.resize(length);
    std::mt19937 rng(std::random_device{}());
    std::uniform_int_distribution<> dist(0, sizeof(charset)-2);
    for (size_t i = 0; i < length; ++i) result[i] = charset[dist(rng)];
    return result;
}

SessionHandler::SessionHandler()
: cleanupThread(std::thread(&SessionHandler::cleanupWorker, this))
, stopCleanupThread(false)
{
}

SessionHandler::~SessionHandler() {
    stopCleanupThread = true;
    if (cleanupThread.joinable())
        cleanupThread.join();
}

void SessionHandler::cleanupWorker(){
    while (!stopCleanupThread) {
        std::this_thread::sleep_for(std::chrono::minutes(5));
        auto now = std::chrono::steady_clock::now();
        {
            std::lock_guard<std::mutex> lock(sessionMutex);
            for (auto it = sessions.begin(); it != sessions.end();) {
                if (it->second.isExpired(now)){
                    CROW_LOG_INFO << "Session " << it->first << " expired for userId: " << it->second.userId();  
                    it = sessions.erase(it);
                }
                else {
                    ++it;
                }
            }
        }
    }
}

std::optional<std::string> SessionHandler::createSession(int userId){
    std::string sessionId = randomString(Session::SESSION_ID_SIZE);
    std::lock_guard<std::mutex> lock(sessionMutex);
    if (!sessions.emplace(sessionId, Session(userId)).second){
        return {};
    }
    return sessionId;
}

std::optional<int> SessionHandler::isSessionValid(const std::string& sessionId){
    auto now = std::chrono::steady_clock::now();
    std::lock_guard<std::mutex> lock(sessionMutex);
    
    auto it = sessions.find(sessionId);
    if(it != sessions.end()){
        if (it->second.isExpired(now)){
            CROW_LOG_INFO << "Session " << it->first << " expired for userId: " << it->second.userId();  
            it = sessions.erase(it);
            return {};
        }
        it->second.extend(now); // extend session life time
        return it->second.userId();
    }
    return {};
}