////////////////////////////////////////////////////////////////////////////////
/// @brief ditches for documents, datafiles etc.
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2014 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 Dr. Frank Celler
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2011-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#include "Ditch.h"
#include "Basics/logging.h"
#include "Basics/MutexLocker.h"
#include "VocBase/document-collection.h"

using namespace triagens::arango;

// -----------------------------------------------------------------------------
// --SECTION--                                                       class Ditch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

Ditch::Ditch (Ditches* ditches,
              char const* filename,
              int line)
  : _ditches(ditches),
    _prev(nullptr),
    _next(nullptr),
    _filename(filename),
    _line(line) {
}

Ditch::~Ditch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                                    public methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief return the associated collection
////////////////////////////////////////////////////////////////////////////////

TRI_document_collection_t* Ditch::collection () const {
  return _ditches->collection();
}

// -----------------------------------------------------------------------------
// --SECTION--                                               class DocumentDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

DocumentDitch::DocumentDitch (Ditches* ditches,
                              bool usedByTransaction,
                              char const* filename,
                              int line)
  : Ditch(ditches, filename, line),
    _usedByExternal(0),
    _usedByTransaction(usedByTransaction) {
}

DocumentDitch::~DocumentDitch () {
}

////////////////////////////////////////////////////////////////////////////////
/// @brief sets the _usedByTransaction flag, using the required lock
////////////////////////////////////////////////////////////////////////////////

void DocumentDitch::setUsedByTransaction () {
  auto callback = [this] () -> void {
    _usedByTransaction = true;
  };
  _ditches->executeProtected(callback);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief increases the _usedByExternal value, using the required lock
////////////////////////////////////////////////////////////////////////////////

void DocumentDitch::setUsedByExternal () {
  auto callback = [this] () -> void {
    ++_usedByExternal;
  };
  _ditches->executeProtected(callback);
}

// -----------------------------------------------------------------------------
// --SECTION--                                            class ReplicationDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

ReplicationDitch::ReplicationDitch (Ditches* ditches,
                                    char const* filename,
                                    int line)
  : Ditch(ditches, filename, line) {
}

ReplicationDitch::~ReplicationDitch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                             class CompactionDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

CompactionDitch::CompactionDitch (Ditches* ditches,
                                  char const* filename,
                                  int line)
  : Ditch(ditches, filename, line) {
}

CompactionDitch::~CompactionDitch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                           class DropDatafileDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

DropDatafileDitch::DropDatafileDitch (Ditches* ditches, 
                                      TRI_datafile_t* datafile,
                                      void* data,
                                      std::function<void(TRI_datafile_t*, void*)> callback,
                                      char const* filename,
                                      int line)
  : Ditch(ditches, filename, line),
    _datafile(datafile),
    _data(data),
    _callback(callback) {
}

DropDatafileDitch::~DropDatafileDitch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                         class RenameDatafileDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

RenameDatafileDitch::RenameDatafileDitch (Ditches* ditches,
                                          TRI_datafile_t* datafile,
                                          void* data,
                                          std::function<void(TRI_datafile_t*, void*)> callback,
                                          char const* filename,
                                          int line)
  : Ditch(ditches, filename, line),
    _datafile(datafile),
    _data(data),
    _callback(callback) {
}

RenameDatafileDitch::~RenameDatafileDitch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                       class UnloadCollectionDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

UnloadCollectionDitch::UnloadCollectionDitch (Ditches* ditches,
                                              TRI_collection_t* collection,
                                              void* data,
                                              std::function<bool(TRI_collection_t*, void*)> callback,
                                              char const* filename,
                                              int line)
  : Ditch(ditches, filename, line),
    _collection(collection),
    _data(data),
    _callback(callback) {
}

UnloadCollectionDitch::~UnloadCollectionDitch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                         class DropCollectionDitch
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

DropCollectionDitch::DropCollectionDitch (Ditches* ditches,
                                          TRI_collection_t* collection,
                                          void* data,
                                          std::function<bool(TRI_collection_t*, void*)> callback,
                                          char const* filename,
                                          int line)
  : Ditch(ditches, filename, line),
    _collection(collection),
    _data(data),
    _callback(callback) {
}

DropCollectionDitch::~DropCollectionDitch () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                                     class Ditches
// -----------------------------------------------------------------------------
  
Ditches::Ditches (TRI_document_collection_t* collection)
  : _collection(collection),
    _lock(),
    _begin(nullptr),
    _end(nullptr),
    _numDocumentDitches(0) {

  TRI_ASSERT(_collection != nullptr);

}

Ditches::~Ditches () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                                    public methods
// -----------------------------------------------------------------------------
  
////////////////////////////////////////////////////////////////////////////////
/// @brief destroy the ditches - to be called on shutdown only
////////////////////////////////////////////////////////////////////////////////

void Ditches::destroy () {
  auto* ptr = _begin;

  while (ptr != nullptr) {
    auto* next = ptr->next();
    auto const type = ptr->type();

    if (type == Ditch::TRI_DITCH_COLLECTION_UNLOAD ||
        type == Ditch::TRI_DITCH_COLLECTION_DROP ||
        type == Ditch::TRI_DITCH_DATAFILE_DROP ||
        type == Ditch::TRI_DITCH_DATAFILE_RENAME ||
        type == Ditch::TRI_DITCH_REPLICATION ||
        type == Ditch::TRI_DITCH_COMPACTION) {

      delete ptr;
    }
    else if (type == Ditch::TRI_DITCH_DOCUMENT) {
      LOG_ERROR("logic error. shouldn't have document ditches on unload");
    }
    else {
      LOG_ERROR("unknown ditch type");
    }

    ptr = next;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief return the associated collection
////////////////////////////////////////////////////////////////////////////////

TRI_document_collection_t* Ditches::collection () const {
  return _collection;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief run a user-defined function under the lock
////////////////////////////////////////////////////////////////////////////////

void Ditches::executeProtected (std::function<void()> callback) {
  MUTEX_LOCKER(_lock);
  callback();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief process the first element from the list
/// the list will remain unchanged if the first element is either a
/// DocumentDitch, a ReplicationDitch or a CompactionDitch, or if the list 
/// contains any DocumentDitches.
////////////////////////////////////////////////////////////////////////////////

Ditch* Ditches::process (bool& popped,
                         std::function<bool(Ditch const*)> callback) {
  popped = false;

  MUTEX_LOCKER(_lock);
  
  auto ditch = _begin;

  if (ditch == nullptr) {
    // nothing to do
    return nullptr;
  }
  
  TRI_ASSERT(ditch != nullptr);

  auto const type = ditch->type();

  // if it is a DocumentDitch, it means that there is still a reference held
  // to document data in a datafile. We must then not unload or remove a file
  if (type == Ditch::TRI_DITCH_DOCUMENT ||
      type == Ditch::TRI_DITCH_REPLICATION ||
      type == Ditch::TRI_DITCH_COMPACTION ||
      _numDocumentDitches > 0) {
    // did not find anything at the head of the barrier list or found an element marker
    // this means we must exit and cannot throw away datafiles and can unload collections
    return nullptr;
  }

  // no DocumentDitch at the head of the ditches list. This means that there is
  // some other action we can perform (i.e. unloading a datafile or a collection)

  // note that there is no need to check the entire list for a DocumentDitch as
  // the list is filled up in chronological order. New ditches are always added to the
  // tail of the list, and if we have the following list
  // HEAD -> TRI_DITCH_DATAFILE_CALLBACK -> TRI_DITCH_DOCUMENT
  // then it is still safe to execute the datafile callback operation, even if there
  // is a TRI_DITCH_DOCUMENT after it.
  // This is the case because the TRI_DITCH_DATAFILE_CALLBACK is only put into the
  // ditches list after changing the pointers in all headers. After the pointers are
  // changed, it is safe to unload/remove an old datafile (that noone points to). And
  // any newer TRI_DITCH_DOCUMENTs will always reference data inside other datafiles.

  if (! callback(ditch)) {
    return ditch;
  }

  // found an element to go on with - now unlink the element from the list
  unlink(ditch);
  popped = true;

  return ditch;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief check whether the ditches contain a ditch of a certain type
////////////////////////////////////////////////////////////////////////////////

bool Ditches::contains (Ditch::DitchType type) {
  MUTEX_LOCKER(_lock);

  if (type == Ditch::TRI_DITCH_DOCUMENT) {
    // shortcut
    return (_numDocumentDitches > 0);
  }

  auto const* ptr = _begin;

  while (ptr != nullptr) {
    if (ptr->type() == type) {
      return true;
    }

    ptr = ptr->_next;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief removes and frees a ditch
////////////////////////////////////////////////////////////////////////////////

void Ditches::freeDitch (Ditch* ditch) {
  TRI_ASSERT(ditch != nullptr);

  {
    MUTEX_LOCKER(_lock);

    unlink(ditch);

    if (ditch->type() == Ditch::TRI_DITCH_DOCUMENT) {
      // decrease counter
      --_numDocumentDitches;
    }
  }

  delete ditch;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief removes and frees a ditch
/// this is used for ditches used by transactions or by externals to protect
/// the flags by the lock
////////////////////////////////////////////////////////////////////////////////

void Ditches::freeDocumentDitch (DocumentDitch* ditch, 
                                 bool fromTransaction) {
  TRI_ASSERT(ditch != nullptr);

  bool shouldFree = false;
  {
    MUTEX_LOCKER(_lock); // FIX_MUTEX

    // First see who might still be using the ditch:
    if (fromTransaction) {
      TRI_ASSERT(ditch->_usedByTransaction == true);
      ditch->_usedByTransaction = false;
    }
    else {
      // note: _usedByExternal may or may not be set when we get here
      // the reason is that there are ditches not linked at all
      // (when a ditch is created ahead of operations but the operations are
      // not executed etc.) 
      if (ditch->_usedByExternal > 0) {
        --ditch->_usedByExternal;
      }
    }

    if (ditch->_usedByTransaction == false &&
        ditch->_usedByExternal == 0) {
      // Really free it:

      unlink(ditch);

      // decrease counter
      --_numDocumentDitches;

      // free the ditch
      shouldFree = true;
    }
  }

  if (shouldFree) {
    delete ditch;
  }
} 

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new document ditch and links it
////////////////////////////////////////////////////////////////////////////////

DocumentDitch* Ditches::createDocumentDitch (bool usedByTransaction,
                                             char const* filename,
                                             int line) {
  try {
    auto ditch = new DocumentDitch(this, usedByTransaction, filename, line);
    link(ditch);
 
    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new replication ditch and links it
////////////////////////////////////////////////////////////////////////////////

ReplicationDitch* Ditches::createReplicationDitch (char const* filename,
                                                   int line) {
  try {
    auto ditch = new ReplicationDitch(this, filename, line);
    link(ditch);

    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new compaction ditch and links it
////////////////////////////////////////////////////////////////////////////////

CompactionDitch* Ditches::createCompactionDitch (char const* filename,
                                                 int line) {
  try {
    auto ditch = new CompactionDitch(this, filename, line);
    link(ditch);

    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new datafile deletion ditch
////////////////////////////////////////////////////////////////////////////////

DropDatafileDitch* Ditches::createDropDatafileDitch (TRI_datafile_t* datafile,
                                                     void* data,
                                                     std::function<void(struct TRI_datafile_s*, void*)> callback,
                                                     char const* filename,
                                                     int line) {
  try {
    auto ditch = new DropDatafileDitch(this, datafile, data, callback, filename, line);
    link(ditch);

    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new datafile rename ditch
////////////////////////////////////////////////////////////////////////////////

RenameDatafileDitch* Ditches::createRenameDatafileDitch (TRI_datafile_t* datafile,
                                                         void* data,
                                                         std::function<void(struct TRI_datafile_s*, void*)> callback,
                                                         char const* filename,
                                                         int line) {
  try {
    auto ditch = new RenameDatafileDitch(this, datafile, data, callback, filename, line);
    link(ditch);

    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new collection unload ditch
////////////////////////////////////////////////////////////////////////////////

UnloadCollectionDitch* Ditches::createUnloadCollectionDitch (TRI_collection_t* collection,
                                                             void* data,
                                                             std::function<bool(TRI_collection_t*, void*)> callback,
                                                             char const* filename,
                                                             int line) {
  try {
    auto ditch = new UnloadCollectionDitch(this, collection, data, callback, filename, line);
    link(ditch);

    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a new datafile drop ditch
////////////////////////////////////////////////////////////////////////////////

DropCollectionDitch* Ditches::createDropCollectionDitch (TRI_collection_t* collection,
                                                         void* data,
                                                         std::function<bool(TRI_collection_t*, void*)> callback,
                                                         char const* filename,
                                                         int line) {
  try {
    auto ditch = new DropCollectionDitch(this, collection, data, callback, filename, line);
    link(ditch);

    return ditch;
  }
  catch (...) {
    return nullptr;
  }
}

// -----------------------------------------------------------------------------
// --SECTION--                                                   private methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief inserts the ditch into the linked list of ditches
////////////////////////////////////////////////////////////////////////////////

void Ditches::link (Ditch* ditch) {
  TRI_ASSERT(ditch != nullptr);
  
  MUTEX_LOCKER(_lock); // FIX_MUTEX

  // empty list
  if (_end == nullptr) {
    ditch->_next = nullptr;
    ditch->_prev = nullptr;

    _begin = ditch;
    _end = ditch;
  }

  // add to the end
  else {
    ditch->_next = nullptr;
    ditch->_prev = _end;

    _end->_next = ditch;
    _end = ditch;
  }

  if (ditch->type() == Ditch::TRI_DITCH_DOCUMENT) {
    // increase counter
    ++_numDocumentDitches;
  }
}
    
////////////////////////////////////////////////////////////////////////////////
/// @brief unlinks the ditch from the linked list of ditches
////////////////////////////////////////////////////////////////////////////////

void Ditches::unlink (Ditch* ditch) {
  // ditch is at the beginning of the chain
  if (ditch->_prev == nullptr) {
    _begin = ditch->_next;
  }
  else {
    ditch->_prev->_next = ditch->_next;
  }

  // ditch is at the end of the chain
  if (ditch->_next == nullptr) {
    _end = ditch->_prev;
  }
  else {
    ditch->_next->_prev = ditch->_prev;
  }
}

// -----------------------------------------------------------------------------
// --SECTION--                                                       END-OF-FILE
// -----------------------------------------------------------------------------

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