////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2016 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 Simon Grätzer
////////////////////////////////////////////////////////////////////////////////

#include "GraphStore.h"

#include <algorithm>
#include "Basics/Common.h"
#include "Basics/MutexLocker.h"
#include "Pregel/CommonFormats.h"
#include "Pregel/PregelFeature.h"
#include "Pregel/TypedBuffer.h"
#include "Pregel/Utils.h"
#include "Pregel/WorkerConfig.h"
#include "Scheduler/Scheduler.h"
#include "Scheduler/SchedulerFeature.h"
#include "Transaction/Methods.h"
#include "Transaction/StandaloneContext.h"
#include "Transaction/UserTransaction.h"
#include "Utils/CollectionNameResolver.h"
#include "Utils/OperationCursor.h"
#include "Utils/OperationOptions.h"
#include "VocBase/EdgeCollectionInfo.h"
#include "VocBase/LogicalCollection.h"
#include "VocBase/ticks.h"
#include "VocBase/vocbase.h"

#ifdef _MSC_VER
#include <windows.h>
#else
#include <unistd.h>
#endif

using namespace arangodb;
using namespace arangodb::pregel;

static uint64_t TRI_totalSystemMemory() {
#ifdef _MSC_VER
  MEMORYSTATUSEX status;
  status.dwLength = sizeof(status);
  GlobalMemoryStatusEx(&status);
  return status.ullTotalPhys;
#else
  long pages = sysconf(_SC_PHYS_PAGES);
  long page_size = sysconf(_SC_PAGE_SIZE);
  long mem = pages * page_size;
  return mem > 0 ? (uint64_t)mem : 0;
#endif
}

template <typename V, typename E>
GraphStore<V, E>::GraphStore(TRI_vocbase_t* vb, GraphFormat<V, E>* graphFormat)
    : _vocbaseGuard(vb),
      _graphFormat(graphFormat),
      _localVerticeCount(0),
      _localEdgeCount(0),
      _runningThreads(0) {}

template <typename V, typename E>
GraphStore<V, E>::~GraphStore() {
  _destroyed = true;
  usleep(25 * 1000);
  delete _vertexData;
  delete _edges;
}

template <typename V, typename E>
std::map<ShardID, uint64_t> GraphStore<V, E>::_allocateMemory() {
  if (_vertexData || _edges) {
    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                   "Only allocate messages once");
    //_edges->resize(count);
  }

  double t = TRI_microtime();
  std::unique_ptr<transaction::Methods> countTrx(_createTransaction());
  std::map<ShardID, uint64_t> shardSizes;
  LOG_TOPIC(DEBUG, Logger::PREGEL) << "Allocating memory";
  uint64_t totalMemory = TRI_totalSystemMemory();

  // Allocating some memory
  uint64_t count = 0;
  for (auto const& shard : _config->localVertexShardIDs()) {
    OperationResult opResult = countTrx->count(shard, true);
    if (opResult.failed() || _destroyed) {
      THROW_ARANGO_EXCEPTION(TRI_ERROR_BAD_PARAMETER);
    }
    shardSizes[shard] = opResult.slice().getUInt();
    count += opResult.slice().getUInt();
  }
  _index.resize(count);
  if (_graphFormat->estimatedVertexSize() > 0) {
    size_t requiredMem = count * _graphFormat->estimatedVertexSize();
    if (!_config->lazyLoading() && requiredMem > totalMemory / 2) {
      _vertexData = new MappedFileBuffer<V>(count);
    } else {
      _vertexData = new VectorTypedBuffer<V>(count);
    }
  }

  count = 0;
  for (auto const& shard : _config->localEdgeShardIDs()) {
    OperationResult opResult = countTrx->count(shard, true);
    if (opResult.failed() || _destroyed) {
      THROW_ARANGO_EXCEPTION(TRI_ERROR_BAD_PARAMETER);
    }
    shardSizes[shard] = opResult.slice().getUInt();
    count += opResult.slice().getUInt();
  }

  size_t requiredMem = count * _graphFormat->estimatedEdgeSize();
  if (!_config->lazyLoading() && requiredMem > totalMemory / 2) {
    _edges = new MappedFileBuffer<Edge<E>>(count);
  } else {
    _edges = new VectorTypedBuffer<Edge<E>>(count);
  }

  if (!countTrx->commit().ok()) {
    LOG_TOPIC(WARN, Logger::PREGEL)
        << "Pregel worker: Failed to commit on a read transaction";
  }
  LOG_TOPIC(DEBUG, Logger::PREGEL) << "took " << TRI_microtime() - t << "s";

  return shardSizes;
}

template <typename V, typename E>
void GraphStore<V, E>::loadShards(WorkerConfig* config,
                                  std::function<void()> callback) {
  _config = config;
  std::map<ShardID, uint64_t> shardSizes(_allocateMemory());
  uint64_t vertexOffset = 0, edgeOffset = 0;
  // Contains the shards located on this db server in the right order
  std::map<CollectionID, std::vector<ShardID>> const& vertexCollMap =
      _config->vertexCollectionShards();
  std::map<CollectionID, std::vector<ShardID>> const& edgeCollMap =
      _config->edgeCollectionShards();

  TRI_ASSERT(SchedulerFeature::SCHEDULER != nullptr);
  rest::Scheduler* scheduler = SchedulerFeature::SCHEDULER;

  LOG_TOPIC(DEBUG, Logger::PREGEL) << "Using "
                                   << config->localVertexShardIDs().size()
                                   << " threads to load data";
  for (auto const& pair : vertexCollMap) {
    std::vector<ShardID> const& vertexShards = pair.second;
    for (size_t i = 0; i < vertexShards.size(); i++) {
      // we might have already loaded these shards
      if (_loadedShards.find(vertexShards[i]) != _loadedShards.end()) {
        continue;
      }

      ShardID const& vertexShard = vertexShards[i];
      uint64_t nextEdgeOffset = edgeOffset;
      std::vector<ShardID> edgeLookups;
      // distributeshardslike should cause the edges for a vertex to be
      // in the same shard index. x in vertexShard2 => E(x) in edgeShard2
      for (auto const& pair2 : edgeCollMap) {
        std::vector<ShardID> const& edgeShards = pair2.second;
        if (vertexShards.size() != edgeShards.size()) {
          THROW_ARANGO_EXCEPTION_MESSAGE(
              TRI_ERROR_BAD_PARAMETER,
              "Collections need to have the same number of shards");
        }
        edgeLookups.push_back(edgeShards[i]);
        nextEdgeOffset += shardSizes[edgeShards[i]];
      }

      _loadedShards.insert(vertexShard);
      _runningThreads++;
      scheduler->post([this, &vertexShard, edgeLookups, vertexOffset,
                       edgeOffset, callback] {

        _loadVertices(vertexShard, edgeLookups, vertexOffset, edgeOffset);
        _runningThreads--;

        if (_runningThreads == 0) {
          if (_localEdgeCount < _edges->size()) {
            _edges->resize(_localEdgeCount);
          }
          callback();
        }
      });
      // update to next offset
      vertexOffset += shardSizes[vertexShard];
      edgeOffset = nextEdgeOffset;
    }
  }
}

template <typename V, typename E>
void GraphStore<V, E>::loadDocument(WorkerConfig* config,
                                    std::string const& documentID) {
  if (!_vertexData) {
    _vertexData = new VectorTypedBuffer<V>(100);
  }
  if (!_edges) {
    _edges = new VectorTypedBuffer<Edge<E>>(100);
  }

  // figure out if we got this vertex locally
  PregelID _id = config->documentIdToPregel(documentID);
  if (config->isLocalVertexShard(_id.shard)) {
    loadDocument(config, _id.shard, _id.key);
  }
}

template <typename V, typename E>
void GraphStore<V, E>::loadDocument(WorkerConfig* config,
                                    PregelShard sourceShard,
                                    PregelKey const& _key) {
  _config = config;
  std::unique_ptr<transaction::Methods> trx(_createTransaction());

  ShardID const& vertexShard = _config->globalShardIDs()[sourceShard];
  VPackBuilder builder;
  builder.openObject();
  builder.add(StaticStrings::KeyString, VPackValue(_key));
  builder.close();

  OperationOptions options;
  options.ignoreRevs = false;

  TRI_voc_cid_t cid = trx->addCollectionAtRuntime(vertexShard);
  trx->pinData(cid);  // will throw when it fails
  OperationResult opResult =
      trx->document(vertexShard, builder.slice(), options);
  if (!opResult.successful()) {
    THROW_ARANGO_EXCEPTION(opResult.code);
  }

  std::string documentId = trx->extractIdString(opResult.slice());
  _index.emplace_back(sourceShard, _key);

  VertexEntry& entry = _index.back();
  if (_graphFormat->estimatedVertexSize() > 0) {
    entry._vertexDataOffset = _localVerticeCount;
    entry._edgeDataOffset = _localEdgeCount;

    // allocate space if needed
    if (_vertexData->size() <= _localVerticeCount) {
      if (!_config->lazyLoading()) {
        LOG_TOPIC(ERR, Logger::PREGEL) << "Pregel did not preallocate enough "
                                       << "space for all vertices. This hints "
                                       << "at a bug with collection count()";
        TRI_ASSERT(false);
        THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
      }
      // lazy loading always uses vector backed storage
      ((VectorTypedBuffer<V>*)_vertexData)->appendEmptyElement();
    }
    V* data = _vertexData->data() + _localVerticeCount;
    _graphFormat->copyVertexData(documentId, opResult.slice(), data, sizeof(V));
    _localVerticeCount++;
  }

  // load edges
  std::map<CollectionID, std::vector<ShardID>> const& vertexMap =
      _config->vertexCollectionShards();
  std::map<CollectionID, std::vector<ShardID>> const& edgeMap =
      _config->edgeCollectionShards();
  for (auto const& pair : vertexMap) {
    std::vector<ShardID> const& vertexShards = pair.second;
    auto it = std::find(vertexShards.begin(), vertexShards.end(), vertexShard);
    if (it != vertexShards.end()) {
      size_t pos = (size_t)(it - vertexShards.begin());
      for (auto const& pair2 : edgeMap) {
        std::vector<ShardID> const& edgeShards = pair2.second;
        _loadEdges(trx.get(), edgeShards[pos], entry, documentId);
      }
      break;
    }
  }
  if (!trx->commit().ok()) {
    LOG_TOPIC(WARN, Logger::PREGEL)
        << "Pregel worker: Failed to commit on a read transaction";
  }
}

template <typename V, typename E>
RangeIterator<VertexEntry> GraphStore<V, E>::vertexIterator() {
  return vertexIterator(0, _index.size());
}

template <typename V, typename E>
RangeIterator<VertexEntry> GraphStore<V, E>::vertexIterator(size_t start,
                                                            size_t end) {
  return RangeIterator<VertexEntry>(_index.data() + start, end - start);
}

template <typename V, typename E>
V* GraphStore<V, E>::mutableVertexData(VertexEntry const* entry) {
  return _vertexData->data() + entry->_vertexDataOffset;
}

template <typename V, typename E>
void GraphStore<V, E>::replaceVertexData(VertexEntry const* entry, void* data,
                                         size_t size) {
  // if (size <= entry->_vertexDataOffset)
  void* ptr = _vertexData->data() + entry->_vertexDataOffset;
  memcpy(ptr, data, size);
  LOG_TOPIC(WARN, Logger::PREGEL)
      << "Don't use this function with varying sizes";
}

template <typename V, typename E>
RangeIterator<Edge<E>> GraphStore<V, E>::edgeIterator(
    VertexEntry const* entry) {
  return RangeIterator<Edge<E>>(_edges->data() + entry->_edgeDataOffset,
                                entry->_edgeCount);
}

template <typename V, typename E>
std::unique_ptr<transaction::Methods> GraphStore<V, E>::_createTransaction() {
  transaction::Options transactionOptions;
  transactionOptions.waitForSync = false;
  transactionOptions.allowImplicitCollections = true;
  auto ctx = transaction::StandaloneContext::Create(_vocbaseGuard.vocbase());
  std::unique_ptr<transaction::Methods> trx(
      new transaction::UserTransaction(ctx, {}, {}, {}, transactionOptions));
  Result res = trx->begin();
  if (!res.ok()) {
    THROW_ARANGO_EXCEPTION(res);
  }
  return trx;
}

template <typename V, typename E>
void GraphStore<V, E>::_loadVertices(ShardID const& vertexShard,
                                     std::vector<ShardID> const& edgeShards,
                                     uint64_t vertexOffset,
                                     uint64_t edgeOffset) {
  uint64_t originalVertexOffset = vertexOffset;

  std::unique_ptr<transaction::Methods> trx(_createTransaction());
  TRI_voc_cid_t cid = trx->addCollectionAtRuntime(vertexShard);
  trx->pinData(cid);  // will throw when it fails
  PregelShard sourceShard = (PregelShard)_config->shardId(vertexShard);

  ManagedDocumentResult mmdr;
  std::unique_ptr<OperationCursor> cursor =
      trx->indexScan(vertexShard, transaction::Methods::CursorType::ALL, &mmdr,
                     0, UINT64_MAX, 1000, false);
  if (cursor->failed()) {
    THROW_ARANGO_EXCEPTION_FORMAT(cursor->code, "while looking up shard '%s'",
                                  vertexShard.c_str());
  }

  // tell the formatter the number of docs we are about to load
  LogicalCollection* collection = cursor->collection();
  uint64_t number = collection->numberDocuments(trx.get());
  _graphFormat->willLoadVertices(number);

  auto cb = [&](DocumentIdentifierToken const& token) {
    if (collection->readDocument(trx.get(), token, mmdr)) {
      VPackSlice document(mmdr.vpack());
      if (document.isExternal()) {
        document = document.resolveExternal();
      }

      VertexEntry& ventry = _index[vertexOffset];
      ventry._shard = sourceShard;
      ventry._key = document.get(StaticStrings::KeyString).copyString();
      ventry._edgeDataOffset = edgeOffset;

      // load vertex data
      std::string documentId = trx->extractIdString(document);
      if (_graphFormat->estimatedVertexSize() > 0) {
        ventry._vertexDataOffset = vertexOffset;
        V* ptr = _vertexData->data() + vertexOffset;
        _graphFormat->copyVertexData(documentId, document, ptr, sizeof(V));
      }
      // load edges
      for (ShardID const& edgeShard : edgeShards) {
        _loadEdges(trx.get(), edgeShard, ventry, documentId);
      }
      vertexOffset++;
      edgeOffset += ventry._edgeCount;
    }
  };
  while (cursor->next(cb, 1000)) {
    if (_destroyed) {
      LOG_TOPIC(WARN, Logger::PREGEL) << "Aborted loading graph";
      break;
    }
  }

  // Add all new vertices
  _localVerticeCount += (vertexOffset - originalVertexOffset);

  if (!trx->commit().ok()) {
    LOG_TOPIC(WARN, Logger::PREGEL)
        << "Pregel worker: Failed to commit on a read transaction";
  }
}

template <typename V, typename E>
void GraphStore<V, E>::_loadEdges(transaction::Methods* trx,
                                  ShardID const& edgeShard,
                                  VertexEntry& vertexEntry,
                                  std::string const& documentID) {
  size_t added = 0;
  size_t offset = vertexEntry._edgeDataOffset + vertexEntry._edgeCount;
  // moving pointer to edge

  traverser::EdgeCollectionInfo info(trx, edgeShard, TRI_EDGE_OUT,
                                     StaticStrings::FromString, 0);
  ManagedDocumentResult mmdr;
  std::unique_ptr<OperationCursor> cursor = info.getEdges(documentID, &mmdr);
  if (cursor->failed()) {
    THROW_ARANGO_EXCEPTION_FORMAT(cursor->code,
                                  "while looking up edges '%s' from %s",
                                  documentID.c_str(), edgeShard.c_str());
  }

  auto cb = [&](ManagedDocumentResult const& mdr) {
    VPackSlice document(mdr.vpack());
    if (document.isExternal()) {
      document = document.resolveExternal();
    }

    std::string toValue = document.get(StaticStrings::ToString).copyString();
    std::size_t pos = toValue.find('/');
    std::string collectionName = toValue.substr(0, pos);

    // If this is called from loadDocument we didn't preallocate the vector
    if (_edges->size() <= offset) {
      if (!_config->lazyLoading()) {
        LOG_TOPIC(ERR, Logger::PREGEL) << "Pregel did not preallocate enough "
                                       << "space for all edges. This hints "
                                       << "at a bug with collection count()";
        TRI_ASSERT(false);
        THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
      }
      // lazy loading always uses vector backed storage
      ((VectorTypedBuffer<Edge<E>>*)_edges)->appendEmptyElement();
    }

    Edge<E>* edge = _edges->data() + offset;
    edge->_toKey = toValue.substr(pos + 1, toValue.length() - pos - 1);

    // resolve the shard of the target vertex.
    ShardID responsibleShard;
    int res =
        Utils::resolveShard(_config, collectionName, StaticStrings::KeyString,
                            edge->_toKey, responsibleShard);

    if (res == TRI_ERROR_NO_ERROR) {
      // PregelShard sourceShard = (PregelShard)_config->shardId(edgeShard);
      edge->_targetShard = (PregelShard)_config->shardId(responsibleShard);
      _graphFormat->copyEdgeData(document, edge->data(), sizeof(E));
      if (edge->_targetShard != (PregelShard)-1) {
        added++;
        offset++;
      } else {
        LOG_TOPIC(ERR, Logger::PREGEL)
            << "Could not resolve target shard of edge";
      }
    } else {
      LOG_TOPIC(ERR, Logger::PREGEL)
          << "Could not resolve target shard of edge";
    }
  };
  cursor->allDocuments(cb);

  // Add up all added elements
  vertexEntry._edgeCount += added;
  _localEdgeCount += added;
}

/// Loops over the array starting a new transaction for different shards
/// Should not dead-lock unless we have to wait really long for other threads
template <typename V, typename E>
void GraphStore<V, E>::_storeVertices(std::vector<ShardID> const& globalShards,
                                      RangeIterator<VertexEntry>& it) {
  // transaction on one shard
  std::unique_ptr<transaction::UserTransaction> trx;
  PregelShard currentShard = (PregelShard)-1;
  Result res = TRI_ERROR_NO_ERROR;

  V* vData = _vertexData->data();

  // loop over vertices
  while (it != it.end()) {
    if (it->shard() != currentShard) {
      if (trx) {
        res = trx->finish(res);
        if (!res.ok()) {
          THROW_ARANGO_EXCEPTION(res);
        }
      }
      currentShard = it->shard();
      ShardID const& shard = globalShards[currentShard];
      transaction::Options transactionOptions;
      transactionOptions.waitForSync = false;
      transactionOptions.allowImplicitCollections = false;
      trx.reset(new transaction::UserTransaction(
          transaction::StandaloneContext::Create(_vocbaseGuard.vocbase()), {},
          {shard}, {}, transactionOptions));
      res = trx->begin();
      if (!res.ok()) {
        THROW_ARANGO_EXCEPTION(res);
      }
    }

    transaction::BuilderLeaser b(trx.get());
    b->openArray();
    size_t buffer = 0;
    while (it != it.end() && it->shard() == currentShard && buffer < 1000) {
      // This loop will fill a buffer of vertices until we run into a new
      // collection
      // or there are no more vertices for to store (or the buffer is full)
      V* data = vData + it->_vertexDataOffset;
      b->openObject();
      b->add(StaticStrings::KeyString, VPackValue(it->key()));
      /// bool store =
      _graphFormat->buildVertexDocument(*(b.get()), data, sizeof(V));
      b->close();

      ++it;
      ++buffer;
    }
    b->close();
    if (_destroyed) {
      LOG_TOPIC(WARN, Logger::PREGEL)
          << "Storing data was canceled prematurely";
      trx->abort();
      trx.reset();
      break;
    }

    ShardID const& shard = globalShards[currentShard];
    OperationOptions options;
    OperationResult result = trx->update(shard, b->slice(), options);
    if (result.code != TRI_ERROR_NO_ERROR) {
      THROW_ARANGO_EXCEPTION(result.code);
    }
  }

  if (trx) {
    res = trx->finish(res);
    if (!res.ok()) {
      THROW_ARANGO_EXCEPTION(res);
    }
  }
}

template <typename V, typename E>
void GraphStore<V, E>::storeResults(WorkerConfig* config,
                                    std::function<void()> callback) {
  _config = config;

  double now = TRI_microtime();
  size_t total = _index.size();
  size_t delta = _index.size() / _config->localVertexShardIDs().size();
  if (delta < 1000) {
    delta = _index.size();
  }
  size_t start = 0, end = delta;

  TRI_ASSERT(SchedulerFeature::SCHEDULER != nullptr);
  boost::asio::io_service* ioService = SchedulerFeature::SCHEDULER->ioService();
  TRI_ASSERT(ioService != nullptr);
  do {
    _runningThreads++;
    ioService->post([this, start, end, now, callback] {
      try {
        RangeIterator<VertexEntry> it = vertexIterator(start, end);
        _storeVertices(_config->globalShardIDs(), it);
        // TODO can't just write edges with smart graphs
      } catch (...) {
        LOG_TOPIC(ERR, Logger::PREGEL) << "Storing vertex data failed";
      }
      _runningThreads--;
      if (_runningThreads == 0) {
        LOG_TOPIC(DEBUG, Logger::PREGEL) << "Storing data took "
                                        << (TRI_microtime() - now) << "s";
        callback();
      }
    });
    start = end;
    end = end + delta;
    if (total < end + delta) {  // swallow the rest
      end = total;
    }
  } while (start != end);
}

template class arangodb::pregel::GraphStore<int64_t, int64_t>;
template class arangodb::pregel::GraphStore<float, float>;
template class arangodb::pregel::GraphStore<double, float>;
template class arangodb::pregel::GraphStore<double, double>;

// specific algo combos
template class arangodb::pregel::GraphStore<SCCValue, int8_t>;
template class arangodb::pregel::GraphStore<ECValue, int8_t>;
template class arangodb::pregel::GraphStore<HITSValue, int8_t>;
template class arangodb::pregel::GraphStore<DMIDValue, float>;
template class arangodb::pregel::GraphStore<LPValue, int8_t>;
template class arangodb::pregel::GraphStore<SLPAValue, int8_t>;