// clients in epoll loop

enum{max_clients=32};

typedef struct ping_state ping_state;
struct ping_state {
  enum{wait_to_ping, wait_for_pong} state;
  int64_t target_time; // ping or pong send/timeout
};

typedef struct ws_client {
  int fd;                      // 0 => unused slot (stdin never used)
  bool is_websocket;           // http or websocket connection (ephemeral or permanent)
  str user_id;                 // verfified credential - allocated in persistent arena
  str username;                // verfified credential - allocated in persistent arena
  str room_id;                 // current room - backed by local buffer (must never exceed ulid_byte_len)
  int64_t last_activity_ms;    // last activity (for timeouts)
  int64_t expiry_monotonic_ms; // CLOCK_MONOTONIC BWT expiry time relative to boot time
  ping_state ping_state;
                               // WebSocket fragmentation state
  int expecting_continuation;
  int current_opcode;
  str partial_payload;
                               // memory arenas
  arena *A;                    // pointer to per request, scratch arena
  arena perm;                  // full client lifetime (for session credentials)
  uint8_t perm_buf[256];
  uint8_t room_id_buf[ulid_byte_len];  // backing store for room_id field
} ws_client_t;