#pragma once
#include "../object/queue.h"
#include "../types.h"

/*! \file
 *  \brief \ref Semaphore for synchronization of threads.
 */

/*!
 * \defgroup ipc Inter-Process Communication
 * \brief Communication between threads
 */

// Forward declarations to break cyclic includes
struct Vault;
class Thread;

/*! \brief Semaphore used for synchronization of threads.
 *  \ingroup ipc
 *
 *  The class Semaphore implements the concept of counting semaphores.
 *  The waiting list is provided by the base class Waitingroom.
 */
class Semaphore {
  // Prevent copies and assignments
  Semaphore(const Semaphore&) = delete;
  Semaphore& operator=(const Semaphore&) = delete;

  static Thread** thread_link(Thread& obj, unsigned link_index);

 public:
  /*! \brief Constructor; initialized the counter with provided value `c`
   *  \param c Initial counter value
   *
   *  \todo(16) Implement Constructor
   */
  explicit Semaphore(unsigned c = 0);

  /*! \brief Wait for access to the critical area.
   *
   *  Enter/Wait operation: If the counter is greater than 0, then it is
   *  decremented by one. Otherwise the calling thread will be enqueued
   *  into the Waitingroom and marked as blocked.
   *
   *  \todo(16) Implement Method
   */
  void p(Vault& vault);

  /*! \brief Leave the critical area.
   *
   *  Leave operation: If there are threads in the Waitingroom, wake the
   *  first one; otherwise increment the counter by one.
   *
   *  \todo(16) Implement Method
   */
  void v(Vault& vault);
};