////////////////////////////////////////////////////////////////////////////////
/// @brief Implementation part of generic transactions
///
/// @file Transaction.cpp
///
/// 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 Max Neunhoeffer
/// @author Copyright 2014, triagens GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#include "Utils/transactions.h"
#include "Basics/random.h"
#include "Indexes/PrimaryIndex.h"

using namespace triagens::arango;

////////////////////////////////////////////////////////////////////////////////
/// @brief the following is for the runtime protection check, number of
/// transaction objects in scope in the current thread
////////////////////////////////////////////////////////////////////////////////

#ifdef TRI_ENABLE_MAINTAINER_MODE
thread_local int TransactionBase::_numberTrxInScope = 0;
#endif

////////////////////////////////////////////////////////////////////////////////
/// @brief the following is for the runtime protection check, number of
/// transaction objects in the current thread that are active (between
/// begin and commit()/abort().
////////////////////////////////////////////////////////////////////////////////

#ifdef TRI_ENABLE_MAINTAINER_MODE
thread_local int TransactionBase::_numberTrxActive = 0;
#endif

////////////////////////////////////////////////////////////////////////////////
/// @brief if this pointer is set to an actual set, then for each request
/// sent to a shardId using the ClusterComm library, an X-Arango-Nolock
/// header is generated.
////////////////////////////////////////////////////////////////////////////////

thread_local std::unordered_set<std::string>* Transaction::_makeNolockHeaders = nullptr;

////////////////////////////////////////////////////////////////////////////////
/// @brief read all master pointers, using skip and limit and an internal
/// offset into the primary index. this can be used for incremental access to
/// the documents without restarting the index scan at the begin
////////////////////////////////////////////////////////////////////////////////

int Transaction::readIncremental (TRI_transaction_collection_t* trxCollection,
                                  std::vector<TRI_doc_mptr_copy_t>& docs,
                                  triagens::basics::BucketPosition& internalSkip,
                                  uint64_t batchSize,
                                  uint64_t& skip,
                                  uint64_t limit,
                                  uint64_t& total) {

  TRI_document_collection_t* document = documentCollection(trxCollection);

  // READ-LOCK START
  int res = this->lock(trxCollection, TRI_TRANSACTION_READ);

  if (res != TRI_ERROR_NO_ERROR) {
    return res;
  }

  if (orderDitch(trxCollection) == nullptr) {
    return TRI_ERROR_OUT_OF_MEMORY;
  }

  try {
    if (batchSize > 2048) {
      docs.reserve(2048);
    }
    else if (batchSize > 0) {
      docs.reserve(batchSize);
    }

    auto primaryIndex = document->primaryIndex();
    uint64_t count = 0;

    while (count < batchSize || skip > 0) {
      TRI_doc_mptr_t const* mptr = primaryIndex->lookupSequential(internalSkip, total);

      if (mptr == nullptr) {
        break;
      }
      if (skip > 0) {
        --skip;
      }
      else {
        docs.emplace_back(*mptr);

        if (++count >= limit) {
          break;
        }
      }
    }
  }
  catch (...) {
    this->unlock(trxCollection, TRI_TRANSACTION_READ);
    return TRI_ERROR_OUT_OF_MEMORY;
  }

  this->unlock(trxCollection, TRI_TRANSACTION_READ);
  // READ-LOCK END

  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief read all master pointers, using skip and limit and an internal
/// offset into the primary index. this can be used for incremental access to
/// the documents without restarting the index scan at the begin
////////////////////////////////////////////////////////////////////////////////

int Transaction::readRandom (TRI_transaction_collection_t* trxCollection,
                             std::vector<TRI_doc_mptr_copy_t>& docs,
                             triagens::basics::BucketPosition& initialPosition,
                             triagens::basics::BucketPosition& position,
                             uint64_t batchSize,
                             uint64_t& step,
                             uint64_t& total) {
  TRI_document_collection_t* document = documentCollection(trxCollection);
  // READ-LOCK START
  int res = this->lock(trxCollection, TRI_TRANSACTION_READ);

  if (res != TRI_ERROR_NO_ERROR) {
    return res;
  }
  if (orderDitch(trxCollection) == nullptr) {
    return TRI_ERROR_OUT_OF_MEMORY;
  }

  uint64_t numRead = 0;
  TRI_ASSERT(batchSize > 0);

  while (numRead < batchSize) { 
    auto mptr = document->primaryIndex()->lookupRandom(initialPosition, position, step, total);
    if (mptr == nullptr) {
      // Read all documents randomly
      break;
    }
    docs.emplace_back(*mptr);
    ++numRead;
  }
  this->unlock(trxCollection, TRI_TRANSACTION_READ);
  // READ-LOCK END
  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief read any (random) document
////////////////////////////////////////////////////////////////////////////////

int Transaction::readAny (TRI_transaction_collection_t* trxCollection,
                          TRI_doc_mptr_copy_t* mptr) {

  TRI_document_collection_t* document = documentCollection(trxCollection);

  // READ-LOCK START
  int res = this->lock(trxCollection, TRI_TRANSACTION_READ);

  if (res != TRI_ERROR_NO_ERROR) {
    return res;
  }
  if (orderDitch(trxCollection) == nullptr) {
    return TRI_ERROR_OUT_OF_MEMORY;
  }

  auto idx = document->primaryIndex();
  triagens::basics::BucketPosition intPos;
  triagens::basics::BucketPosition pos;
  uint64_t step = 0;
  uint64_t total = 0;

  TRI_doc_mptr_t* found = idx->lookupRandom(intPos, pos, step, total);
  if (found != nullptr) {
    *mptr = *found;
  }
  this->unlock(trxCollection, TRI_TRANSACTION_READ);
  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief read all documents
////////////////////////////////////////////////////////////////////////////////

int Transaction::readAll (TRI_transaction_collection_t* trxCollection,
                          std::vector<std::string>& ids,
                          bool lock) {

  TRI_document_collection_t* document = documentCollection(trxCollection);

  if (lock) {
    // READ-LOCK START
    int res = this->lock(trxCollection, TRI_TRANSACTION_READ);

    if (res != TRI_ERROR_NO_ERROR) {
      return res;
    }
  }

  if (orderDitch(trxCollection) == nullptr) {
    return TRI_ERROR_OUT_OF_MEMORY;
  }
  auto idx = document->primaryIndex();
  size_t used = idx->size();

  if (used > 0) {
    triagens::basics::BucketPosition step;
    uint64_t total = 0;

    while (true) {
      TRI_doc_mptr_t const* mptr = idx->lookupSequential(step, total);

      if (mptr == nullptr) {
        break;
      }
      ids.emplace_back(TRI_EXTRACT_MARKER_KEY(mptr));
    }
  }

  if (lock) {
    this->unlock(trxCollection, TRI_TRANSACTION_READ);
    // READ-LOCK END
  }

  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief read all master pointers, using skip and limit
////////////////////////////////////////////////////////////////////////////////

int Transaction::readSlice (TRI_transaction_collection_t* trxCollection,
                            std::vector<TRI_doc_mptr_copy_t>& docs,
                            int64_t skip,
                            uint64_t limit,
                            uint64_t& total) {

  TRI_document_collection_t* document = documentCollection(trxCollection);

  if (limit == 0) {
    // nothing to do
    return TRI_ERROR_NO_ERROR;
  }

  // READ-LOCK START
  int res = this->lock(trxCollection, TRI_TRANSACTION_READ);

  if (res != TRI_ERROR_NO_ERROR) {
    return res;
  }

  if (orderDitch(trxCollection) == nullptr) {
    return TRI_ERROR_OUT_OF_MEMORY;
  }

  uint64_t count = 0;
  auto idx = document->primaryIndex();
  TRI_doc_mptr_t const* mptr = nullptr; 

  if (skip < 0) {
    triagens::basics::BucketPosition position;
    do {
      mptr = idx->lookupSequentialReverse(position);
      ++skip;
    }
    while (skip < 0 && mptr != nullptr);

    if (mptr == nullptr) {
      this->unlock(trxCollection, TRI_TRANSACTION_READ);
      // To few elements, skipped all
      return TRI_ERROR_NO_ERROR;
    }

    do {
      mptr = idx->lookupSequentialReverse(position);

      if (mptr == nullptr) {
        break;
      }
      ++count;
      docs.emplace_back(*mptr);
    }
    while (count < limit);

    this->unlock(trxCollection, TRI_TRANSACTION_READ);
    return TRI_ERROR_NO_ERROR;
  }
  triagens::basics::BucketPosition position;

  while (skip > 0) {
    mptr = idx->lookupSequential(position, total);
    --skip;
    if (mptr == nullptr) {
      // To few elements, skipped all
      this->unlock(trxCollection, TRI_TRANSACTION_READ);
      return TRI_ERROR_NO_ERROR;
    }
  }

  do {
    mptr = idx->lookupSequential(position, total);
    if (mptr == nullptr) {
      break;
    }
    ++count;
    docs.emplace_back(*mptr);
  }
  while (count < limit);

  this->unlock(trxCollection, TRI_TRANSACTION_READ);
  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief read all master pointers
////////////////////////////////////////////////////////////////////////////////

int Transaction::readSlice (TRI_transaction_collection_t* trxCollection,
                            std::vector<TRI_doc_mptr_t const*>& docs) {
  TRI_document_collection_t* document = documentCollection(trxCollection);
  // READ-LOCK START
  int res = this->lock(trxCollection, TRI_TRANSACTION_READ);

  if (res != TRI_ERROR_NO_ERROR) {
    return res;
  }

  if (orderDitch(trxCollection) == nullptr) {
    return TRI_ERROR_OUT_OF_MEMORY;
  }

  triagens::basics::BucketPosition position;
  uint64_t total = 0;
  auto idx = document->primaryIndex();
  docs.reserve(idx->size());

  while (true) {
    TRI_doc_mptr_t const* mptr = idx->lookupSequential(position, total);

    if (mptr == nullptr) {
      break;
    }

    docs.emplace_back(mptr);
  }

  this->unlock(trxCollection, TRI_TRANSACTION_READ);
  return TRI_ERROR_NO_ERROR;
}

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