#pragma once
#include <Arduino.h>
#include <freertos/FreeRTOS.h>
#include <freertos/semphr.h> // Required for mutex

// Represents an active session.
// An empty username (username[0] == '\0') indicates the slot is free.
struct Session {
    char username[33];
    char token[17];           // 16 chars + null terminator
    unsigned long expiry_time; // Expiration timestamp from millis()
};

class SessionManager {
public:
    SessionManager();
    ~SessionManager(); // Destructor to clean up the mutex

    const char* createSession(const char* username);
    const char* validateSession(const char* token);
    bool endSession(const char* token);
    void cleanupExpiredSessions();

private:
    static constexpr size_t MAX_SESSIONS = 3;
    Session sessions_[MAX_SESSIONS];
    SemaphoreHandle_t session_mutex_; // Mutex to protect access to sessions_

    void generateToken(char* buffer, size_t buffer_size);
};

// Central, global instance.
extern SessionManager sessionManager;