#include "SharedBufferManager.h"

#include "../Utils.h"
#include "../log/Log.h"

#include <boost/date_time/posix_time/posix_time.hpp>

using namespace boost::interprocess;

namespace {
  const bool doTrace = getBoolEnv("CEF_SERVER_TRACE_SharedBuffer");
  size_t nearestMemorySize(size_t len) {
    constexpr int latticeSizeBits = 19; // i.e. 512 Kb
    return ((len >> latticeSizeBits) + 1) << latticeSizeBits;
  }
}

SharedBuffer::SharedBuffer(std::string uid, size_t len)
    : myUid(uid), myLen(len) {
  static int additionalBytes = -1;
  if (additionalBytes < 0) {
    const long defVal = 300; // NOTE: 256 isn't enough in Ubuntu24 arm64
    additionalBytes = getLongEnv("CEF_SERVER_ADDITIONAL_SHARED_BYTES", defVal);
    if (additionalBytes != defVal) {
      if (additionalBytes < 0) additionalBytes = 0;
      if (additionalBytes > 1024*8) additionalBytes = 1024*8;
      Log::debug("SharedBuffer: set additional bytes for shared memory: %d bytes\n", additionalBytes);
    }
  }

  if (doTrace)
    Log::trace("SharedBuffer: allocate shared buffer '%s' | %.2f Mb", uid.c_str(), len/(1024*1024.f));
  const std::chrono::steady_clock::time_point startTime = std::chrono::steady_clock::now();
  shared_memory_object::remove(uid.c_str());

  const std::chrono::steady_clock::time_point t1 = std::chrono::steady_clock::now();
  // TODO: check allocation errors, catch and process exceptions
#ifdef WIN32
  mySharedSegment = new managed_windows_shared_memory(create_only, uid.c_str(),
                                              len + additionalBytes);
#else
  mySharedSegment = new managed_shared_memory(create_only, uid.c_str(),len + additionalBytes);
#endif
  const std::chrono::steady_clock::time_point t2 = std::chrono::steady_clock::now();
  mySharedMem = mySharedSegment->allocate(len);
  mySharedMemHandle = mySharedSegment->get_handle_from_address(mySharedMem);

  const std::chrono::steady_clock::time_point t3 = std::chrono::steady_clock::now();
  named_mutex::remove(myUid.c_str());

  const std::chrono::steady_clock::time_point t4 = std::chrono::steady_clock::now();
  myMutex = new named_mutex(create_only, myUid.c_str());

  if (doTrace && Log::isTraceEnabled()) {
    const std::chrono::steady_clock::time_point entTime = std::chrono::steady_clock::now();
    const long spentMs = (long)std::chrono::duration_cast<std::chrono::microseconds>(entTime - startTime).count();
    if (spentMs > 5*1000) {
      auto d1 = std::chrono::duration_cast<std::chrono::microseconds>(t1 - startTime);
      auto d2 = std::chrono::duration_cast<std::chrono::microseconds>(t2 - t1);
      auto d3 = std::chrono::duration_cast<std::chrono::microseconds>(t3 - t2);
      auto d4 = std::chrono::duration_cast<std::chrono::microseconds>(t4 - t3);
      auto d5 = std::chrono::duration_cast<std::chrono::microseconds>(entTime - t4);
      Log::trace("SharedBuffer '%s': %d bytes, ctor spent mcs: remove mem %d; ctor %d; alloc %d; remove mutex %d; mutex ctor %d",
                 uid.c_str(), len, (int)d1.count(), (int)d2.count(), (int)d3.count(), (int)d4.count(), (int)d5.count());
    }
  }
}

void SharedBuffer::_releaseShared() {
  if (mySharedSegment != nullptr) {
    // TODO: remove unnecessary dealloc (since going to remove whole shared
    // segment)
    mySharedSegment->deallocate(mySharedMem);
    delete mySharedSegment;

    mySharedSegment = nullptr;
    mySharedMem = nullptr;
  }
  if (myMutex != nullptr) {
    delete myMutex;
    myMutex = nullptr;
  }
  shared_memory_object::remove(myUid.c_str());
  named_mutex::remove(myUid.c_str());
}

void SharedBuffer::lock() {
  if (myMutex != nullptr)
    myMutex->lock();
}

bool SharedBuffer::tryLock() {
  return myMutex != nullptr ? myMutex->try_lock() : false;
}

void SharedBuffer::unlock() {
  if (myMutex != nullptr)
    myMutex->unlock();
}

SharedBuffer::~SharedBuffer() {
  _releaseShared();
}

SharedBuffer* SharedBufferManager::_getOrCreateBuffer(size_t size, int index) {
  SharedBuffer* buf = myPool[index];
  if (buf == nullptr || buf->size() < size) {
    if (buf != nullptr) {
      delete buf;
      myPool[index] = buf = nullptr;
    }
    try {
      // NOTE:
      // Allocation of shared memory can fail with exception.
      // Use unique name for each buffer to avoid filename collisions.
      static std::atomic<int> counter(0);
      myPool[index] = buf =
          new SharedBuffer(string_format("R%d_%d", utils::GetPid(), counter.fetch_add(1)),nearestMemorySize(size));
    } catch (const std::exception& e) {
      Log::error("SharedBuffer: exception during shared buffer allocation, err: %s", e.what());
    } catch (...) {
      Log::error("SharedBuffer: unknown exception during shared buffer allocation");
    }
  }
  return buf;
}

SharedBuffer* SharedBufferManager::getLockedBuffer(size_t size) {
  myLastUsed = (myLastUsed + 1) % POOL_SIZE;
  SharedBuffer* buf = _getOrCreateBuffer(size, myLastUsed);
  if (buf == nullptr)
    return nullptr;

  if (!buf->tryLock()) {
    // It seems that selected buffer is used now. Select another.
    myLastUsed = (myLastUsed + 1) % POOL_SIZE;
    buf = _getOrCreateBuffer(size, myLastUsed);
    buf->lock();
  }

  return buf;
}

SharedBufferManager::~SharedBufferManager() {
  for (int c = 0; c < POOL_SIZE; ++c)
    if (myPool[c] != nullptr) {
      delete myPool[c];
      myPool[c] = nullptr;
    }
}