////////////////////////////////////////////////////////////////////////////////
/// 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 "CollectionScanner.h"

using namespace arangodb::aql;

CollectionScanner::CollectionScanner(
    arangodb::AqlTransaction* trx, TRI_transaction_collection_t* trxCollection)
    : trx(trx), trxCollection(trxCollection), totalCount(0) {}

CollectionScanner::~CollectionScanner() {}

RandomCollectionScanner::RandomCollectionScanner(
    arangodb::AqlTransaction* trx, TRI_transaction_collection_t* trxCollection)
    : CollectionScanner(trx, trxCollection), step(0) {}

int RandomCollectionScanner::scan(std::vector<TRI_doc_mptr_copy_t>& docs,
                                  size_t batchSize) {
  return trx->readRandom(trxCollection, docs, initialPosition, position,
                         static_cast<uint64_t>(batchSize), step, totalCount);
}

int RandomCollectionScanner::forward(size_t batchSize, size_t& skipped) {
  // Basic implementation, no gain
  std::vector<TRI_doc_mptr_copy_t> unusedDocs;
  unusedDocs.reserve(batchSize);
  int res = scan(unusedDocs, batchSize);
  skipped += unusedDocs.size();
  // TRI_doc_mptr_copy_t is never freed
  unusedDocs.clear();
  return res;
}

void RandomCollectionScanner::reset() {
  initialPosition.reset();
  position.reset();
  step = 0;
}

LinearCollectionScanner::LinearCollectionScanner(
    arangodb::AqlTransaction* trx, TRI_transaction_collection_t* trxCollection)
    : CollectionScanner(trx, trxCollection) {}

int LinearCollectionScanner::scan(std::vector<TRI_doc_mptr_copy_t>& docs,
                                  size_t batchSize) {
  uint64_t skip = 0;
  return trx->readIncremental(trxCollection, docs, position,
                              static_cast<uint64_t>(batchSize), skip,
                              UINT64_MAX, totalCount);
}

int LinearCollectionScanner::forward(size_t batchSize, size_t& skipped) {
  // Basic implementation, no gain
  std::vector<TRI_doc_mptr_copy_t> unusedDocs;
  uint64_t toSkip = static_cast<uint64_t>(batchSize);

  int res = trx->readIncremental(trxCollection, unusedDocs, position, 0,
                                 toSkip,  // Will be modified. Will reach 0 if
                                 // batchSize many docs have been skipped
                                 UINT64_MAX, totalCount);
  uint64_t reallySkipped = static_cast<uint64_t>(batchSize) - toSkip;
  skipped += static_cast<size_t>(reallySkipped);
  TRI_ASSERT(unusedDocs.empty());
  return res;
}

void LinearCollectionScanner::reset() { position.reset(); }