#ifndef EVENTMANAGER_H_
#define  EVENTMANAGER_H_

#include <list>

#include <sys/epoll.h>

// We need a struct to store both the address of the callback fn
// to register with epoll, and the fd that we are listening to, so we can
// pass it in as an argument to the callback fn
typedef void (*CallbackFn)(int fd);
typedef struct CallbackData {
  CallbackFn callback;
  int fd;
} CallbackData;

class EventManager {
 public:
  EventManager();
  ~EventManager();
  // Adds to the global variable epoll_fd, establishing
  // an event handler that waits for fd to be ready
  // to read, at which time it calls callback(fd)
  void RegisterCallback(int fd, CallbackFn callback);
  // Removes the callback corresponding to fd from epoll_fd
  void RemoveCallback(int fd);
  void WaitAndDispatch();
 private:
  int epoll_fd_;
  // This list contains the data for all the fds currently being listened
  // to with epoll_fd, and the address of the callback to invoke
  // Must be a linked list because the kernel maintains pointers to the
  // node payloads through epoll_event.data.ptr
  // Only remove nodes from this list after they have been removed from epoll
  std::list<CallbackData> active_list_;
};

#endif