// Copyright (c) 2011-2016 The Cryptonote developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#pragma once

#include <cstddef>
#include <functional>
#include <queue>
#include <stack>

namespace System {

struct NativeContextGroup;

struct NativeContext {
  void* ucontext;
  void* stackPtr;
  bool interrupted;
  NativeContext* next;
  NativeContextGroup* group;
  NativeContext* groupPrev;
  NativeContext* groupNext;
  std::function<void()> procedure;
  std::function<void()> interruptProcedure;
};

struct NativeContextGroup {
  NativeContext* firstContext;
  NativeContext* lastContext;
  NativeContext* firstWaiter;
  NativeContext* lastWaiter;
};

struct OperationContext {
  NativeContext *context;
  bool interrupted;
  uint32_t events;
};

struct ContextPair {
  OperationContext *readContext;
  OperationContext *writeContext;
};

class Dispatcher {
public:
  Dispatcher();
  Dispatcher(const Dispatcher&) = delete;
  ~Dispatcher();
  Dispatcher& operator=(const Dispatcher&) = delete;
  void clear();
  void dispatch();
  NativeContext* getCurrentContext() const;
  void interrupt();
  void interrupt(NativeContext* context);
  bool interrupted();
  void pushContext(NativeContext* context);
  void remoteSpawn(std::function<void()>&& procedure);
  void yield();

  // system-dependent
  int getEpoll() const;
  NativeContext& getReusableContext();
  void pushReusableContext(NativeContext&);
  int getTimer();
  void pushTimer(int timer);

#ifdef __x86_64__
# if __WORDSIZE == 64
  static const int SIZEOF_PTHREAD_MUTEX_T = 40;
# else
  static const int SIZEOF_PTHREAD_MUTEX_T = 32;
# endif
#else
  static const int SIZEOF_PTHREAD_MUTEX_T = 24;
#endif

private:
  void spawn(std::function<void()>&& procedure);
  int epoll;
  alignas(void*) uint8_t mutex[SIZEOF_PTHREAD_MUTEX_T];
  int remoteSpawnEvent;
  ContextPair remoteSpawnEventContext;
  std::queue<std::function<void()>> remoteSpawningProcedures;
  std::stack<int> timers;

  NativeContext mainContext;
  NativeContextGroup contextGroup;
  NativeContext* currentContext;
  NativeContext* firstResumingContext;
  NativeContext* lastResumingContext;
  NativeContext* firstReusableContext;
  size_t runningContextCount;

  void contextProcedure(void* ucontext);
  static void contextProcedureStatic(void* context);
};

}