////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 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 Jan Steemann
////////////////////////////////////////////////////////////////////////////////

#include "TransactionContext.h"
#include "Basics/MutexLocker.h"
#include "Basics/StringBuffer.h"
#include "RestServer/TransactionManagerFeature.h"
#include "MMFiles/MMFilesDatafileHelper.h"
#include "MMFiles/MMFilesLogfileManager.h"
#include "Utils/CollectionNameResolver.h"
#include "Utils/TransactionMethods.h"
#include "VocBase/Ditch.h"
#include "VocBase/LogicalCollection.h"
#include "VocBase/ManagedDocumentResult.h"

#include <velocypack/Builder.h>
#include <velocypack/Dumper.h>
#include <velocypack/Options.h>
#include <velocypack/velocypack-aliases.h>

using namespace arangodb;

// custom type value handler, used for deciphering the _id attribute
struct CustomTypeHandler final : public VPackCustomTypeHandler {
  CustomTypeHandler(TRI_vocbase_t* vocbase, CollectionNameResolver const* resolver)
      : vocbase(vocbase), resolver(resolver) {}

  ~CustomTypeHandler() {} 

  void dump(VPackSlice const& value, VPackDumper* dumper,
            VPackSlice const& base) override final {

    dumper->appendString(toString(value, nullptr, base));
  }
  
  std::string toString(VPackSlice const& value, VPackOptions const* options,
                       VPackSlice const& base) override final {
    return TransactionMethods::extractIdString(resolver, value, base);
  }

  TRI_vocbase_t* vocbase;
  CollectionNameResolver const* resolver;
};

//////////////////////////////////////////////////////////////////////////////
/// @brief create the context
//////////////////////////////////////////////////////////////////////////////

TransactionContext::TransactionContext(TRI_vocbase_t* vocbase) 
    : _vocbase(vocbase), 
      _resolver(nullptr), 
      _customTypeHandler(),
      _ditches(),
      _builders{_arena},
      _stringBuffer(),
      _options(arangodb::velocypack::Options::Defaults),
      _dumpOptions(arangodb::velocypack::Options::Defaults),
      _transaction{ 0, false }, 
      _ownsResolver(false) {
  _dumpOptions.escapeUnicode = true;        
}

//////////////////////////////////////////////////////////////////////////////
/// @brief destroy the context
//////////////////////////////////////////////////////////////////////////////

TransactionContext::~TransactionContext() {
  // unregister the transaction from the logfile manager
  if (_transaction.id > 0) {
    TransactionManagerFeature::MANAGER->unregisterTransaction(_transaction.id, _transaction.hasFailedOperations);
  }

  for (auto& it : _ditches) {
    // we're done with this ditch
    auto& ditch = it.second;
    ditch->ditches()->freeDocumentDitch(ditch, true /* fromTransaction */);
    // If some external entity is still using the ditch, it is kept!
  }

  // free all VPackBuilders we handed out
  for (auto& it : _builders) {
    delete it;
  }

  if (_ownsResolver) {
    delete _resolver;
  }
  _resolver = nullptr;
}

//////////////////////////////////////////////////////////////////////////////
/// @brief factory to create a custom type handler, not managed
//////////////////////////////////////////////////////////////////////////////

VPackCustomTypeHandler* TransactionContext::createCustomTypeHandler(TRI_vocbase_t* vocbase, 
                                                                    CollectionNameResolver const* resolver) {
  return new CustomTypeHandler(vocbase, resolver);
}
  
//////////////////////////////////////////////////////////////////////////////
/// @brief order a document ditch for the collection
/// this will create one if none exists. if no ditch can be created, the
/// function will return a nullptr!
//////////////////////////////////////////////////////////////////////////////

DocumentDitch* TransactionContext::orderDitch(LogicalCollection* collection) {

  TRI_voc_cid_t cid = collection->cid();

  auto it = _ditches.find(cid);

  if (it != _ditches.end()) {
    // tell everyone else this ditch is still in use,
    // at least until the transaction is over
    TRI_ASSERT((*it).second->usedByTransaction());
    // ditch already exists, return it
    return (*it).second;
  }

  // this method will not throw, but may return a nullptr
  auto ditch = collection->ditches()->createDocumentDitch(true, __FILE__, __LINE__);

  if (ditch != nullptr) {
    try {
      _ditches.emplace(cid, ditch);
    }
    catch (...) {
      ditch->ditches()->freeDocumentDitch(ditch, true);
      ditch = nullptr; // return a nullptr
    }
  }

  return ditch;
}
  
//////////////////////////////////////////////////////////////////////////////
/// @brief return the ditch for a collection
/// this will return a nullptr if no ditch exists
//////////////////////////////////////////////////////////////////////////////
  
DocumentDitch* TransactionContext::ditch(TRI_voc_cid_t cid) const {
  auto it = _ditches.find(cid);

  if (it == _ditches.end()) {
    return nullptr;
  }
  return (*it).second;
}
  
//////////////////////////////////////////////////////////////////////////////
/// @brief temporarily lease a StringBuffer object
//////////////////////////////////////////////////////////////////////////////

basics::StringBuffer* TransactionContext::leaseStringBuffer(size_t initialSize) {
  if (_stringBuffer == nullptr) {
    _stringBuffer.reset(new basics::StringBuffer(TRI_UNKNOWN_MEM_ZONE, initialSize, false));
  } else {
    _stringBuffer->reset();
  }

  return _stringBuffer.release();
}

//////////////////////////////////////////////////////////////////////////////
/// @brief return a temporary StringBuffer object
//////////////////////////////////////////////////////////////////////////////

void TransactionContext::returnStringBuffer(basics::StringBuffer* stringBuffer) {
  _stringBuffer.reset(stringBuffer);
}

//////////////////////////////////////////////////////////////////////////////
/// @brief temporarily lease a Builder object
//////////////////////////////////////////////////////////////////////////////

VPackBuilder* TransactionContext::leaseBuilder() {
  if (_builders.empty()) {
    // create a new builder and return it
    return new VPackBuilder();
  }

  // re-use an existing builder
  VPackBuilder* b = _builders.back();
  b->clear();
  _builders.pop_back();

  return b;
}
  
//////////////////////////////////////////////////////////////////////////////
/// @brief return a temporary Builder object
//////////////////////////////////////////////////////////////////////////////

void TransactionContext::returnBuilder(VPackBuilder* builder) {
  try {
    // put builder back into our vector of builders
    _builders.emplace_back(builder);
  } catch (...) {
    // no harm done. just wipe the builder
    delete builder;
  }
}
  
//////////////////////////////////////////////////////////////////////////////
/// @brief get velocypack options with a custom type handler
//////////////////////////////////////////////////////////////////////////////
  
VPackOptions* TransactionContext::getVPackOptions() {
  if (_customTypeHandler == nullptr) {
    // this modifies options!
    orderCustomTypeHandler();
  }
  return &_options;
}

//////////////////////////////////////////////////////////////////////////////
/// @brief get velocypack options with a custom type handler for dumping
//////////////////////////////////////////////////////////////////////////////
  
VPackOptions* TransactionContext::getVPackOptionsForDump() {
  if (_customTypeHandler == nullptr) {
    // this modifies options!
    orderCustomTypeHandler();
  }
  return &_dumpOptions;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief create a resolver
////////////////////////////////////////////////////////////////////////////////
    
CollectionNameResolver const* TransactionContext::createResolver() {
  TRI_ASSERT(_resolver == nullptr);
  _resolver = new CollectionNameResolver(_vocbase);
  _ownsResolver = true;
  return _resolver;
}

//////////////////////////////////////////////////////////////////////////////
/// @brief unregister the transaction
/// this will save the transaction's id and status locally
//////////////////////////////////////////////////////////////////////////////

void TransactionContext::storeTransactionResult(TRI_voc_tid_t id, bool hasFailedOperations) {
  TRI_ASSERT(_transaction.id == 0);

  _transaction.id = id;
  _transaction.hasFailedOperations = hasFailedOperations;
}