////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2017-2017 ArangoDB 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 Michael Hackstein
////////////////////////////////////////////////////////////////////////////////

#include "TraverserCache.h"

#include "Basics/StringHeap.h"
#include "Basics/StringRef.h"
#include "Basics/VelocyPackHelper.h"

#include "Aql/AqlValue.h"
#include "Logger/Logger.h"
#include "Transaction/Methods.h"
#include "VocBase/ManagedDocumentResult.h"

#include <velocypack/Builder.h>
#include <velocypack/Slice.h>
#include <velocypack/velocypack-aliases.h>

using namespace arangodb;
using namespace arangodb::traverser;

TraverserCache::TraverserCache(transaction::Methods* trx)
    : _mmdr(new ManagedDocumentResult{}),
      _trx(trx), _insertedDocuments(0),
      _stringHeap(new StringHeap{4096}) /* arbitrary block-size may be adjusted for perforamnce */ {
}

TraverserCache::~TraverserCache() {}

VPackSlice TraverserCache::lookupInCollection(StringRef id) {
  size_t pos = id.find('/');
  if (pos == std::string::npos) {
    // Invalid input. If we get here somehow we managed to store invalid _from/_to
    // values or the traverser did a let an illegal start through
    TRI_ASSERT(false);
    return basics::VelocyPackHelper::NullValue();
  }
  Result res = _trx->documentFastPathLocal(id.substr(0, pos).toString(),
                                        id.substr(pos + 1).toString(), *_mmdr);

  if (!res.ok() && (res.errorNumber() != TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND)) {
    // ok we are in a rather bad state. Better throw and abort.
    THROW_ARANGO_EXCEPTION(res);
  }

  VPackSlice result;
  if (res.errorNumber() == TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND) {
    // This is expected, we may have dangling edges. Interpret as NULL
    result = basics::VelocyPackHelper::NullValue();
  } else {
    result = VPackSlice(_mmdr->vpack());
  }
  ++_insertedDocuments;
  return result;
}

void TraverserCache::insertIntoResult(StringRef idString,
                                      VPackBuilder& builder) {
  builder.add(lookupInCollection(idString));
}

aql::AqlValue TraverserCache::fetchAqlResult(StringRef idString) {
  return aql::AqlValue(lookupInCollection(idString));
}

void TraverserCache::insertDocument(StringRef idString, arangodb::velocypack::Slice const& document) {
  ++_insertedDocuments;
  return;
}

bool TraverserCache::validateFilter(
    StringRef idString,
    std::function<bool(VPackSlice const&)> filterFunc) {
  VPackSlice slice = lookupInCollection(idString);
  return filterFunc(slice);
}

StringRef TraverserCache::persistString(
    StringRef const idString) {
  auto it = _persistedStrings.find(idString);
  if (it != _persistedStrings.end()) {
    return *it;
  }
  StringRef res = _stringHeap->registerString(idString.begin(), idString.length());
  _persistedStrings.emplace(res);
  return res;
}