////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Daniel H. Larkin
////////////////////////////////////////////////////////////////////////////////

#include "Cache/TransactionManager.h"
#include "Cache/State.h"
#include "Cache/Transaction.h"

#include <stdint.h>
#include <atomic>

using namespace arangodb::cache;

TransactionManager::TransactionManager()
    : _state(), _openReads(0), _openSensitive(0), _openWrites(0), _term(0) {}

Transaction* TransactionManager::begin(bool readOnly) {
  _state.lock();
  Transaction* tx = new Transaction(readOnly);

  if (readOnly) {
    _openReads++;
    if (_openWrites.load() > 0) {
      tx->sensitive = true;
      _openSensitive++;
    }
  } else {
    tx->sensitive = true;
    _openWrites++;
    if (++_openSensitive == 1) {
      _term++;
      _openSensitive += _openReads.load();
    }
  }
  tx->term = _term;
  _state.unlock();

  return tx;
}

void TransactionManager::end(Transaction* tx) {
  TRI_ASSERT(tx != nullptr);
  _state.lock();
  // if currently in sensitive phase, and transaction term is old, it was
  // upgraded to sensitive status
  if (((_term & static_cast<uint64_t>(1)) > 0) && (_term > tx->term)) {
    tx->sensitive = true;
  }

  if (tx->readOnly) {
    _openReads--;
  } else {
    _openWrites--;
  }

  if (tx->sensitive && (--_openSensitive == 0)) {
    _term++;
  }

  _state.unlock();
  delete tx;
}

uint64_t TransactionManager::term() { return _term.load(); }