//////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2017 EMC Corporation
///
/// 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 EMC Corporation
///
/// @author Andrey Abramov
/// @author Vasiliy Nabatchikov
////////////////////////////////////////////////////////////////////////////////

#include "gtest/gtest.h"

#include "../Mocks/StorageEngineMock.h"
#include "common.h"

#include "store/fs_directory.hpp"
#include "utils/log.hpp"
#include "utils/utf8_path.hpp"

#include "Aql/AqlFunctionFeature.h"
#include "Aql/QueryRegistry.h"

#if USE_ENTERPRISE
#include "Enterprise/Ldap/LdapFeature.h"
#endif

#include "Basics/files.h"
#include "Cluster/ClusterFeature.h"
#include "GeneralServer/AuthenticationFeature.h"
#include "IResearch/IResearchAnalyzerFeature.h"
#include "IResearch/IResearchCommon.h"
#include "IResearch/IResearchFeature.h"
#include "IResearch/IResearchLink.h"
#include "IResearch/IResearchMMFilesLink.h"
#include "IResearch/IResearchView.h"
#include "Logger/LogTopic.h"
#include "Logger/Logger.h"
#include "RestServer/AqlFeature.h"
#include "RestServer/DatabaseFeature.h"
#include "RestServer/DatabasePathFeature.h"
#include "RestServer/FlushFeature.h"
#include "RestServer/QueryRegistryFeature.h"
#include "RestServer/ServerIdFeature.h"
#include "RestServer/SystemDatabaseFeature.h"
#include "RestServer/TraverserEngineRegistryFeature.h"
#include "RestServer/ViewTypesFeature.h"
#include "Sharding/ShardingFeature.h"
#include "StorageEngine/EngineSelectorFeature.h"
#include "Transaction/Methods.h"
#include "Transaction/StandaloneContext.h"
#include "Utils/ExecContext.h"
#include "V8Server/V8DealerFeature.h"
#include "VocBase/KeyGenerator.h"
#include "VocBase/LogicalCollection.h"
#include "VocBase/LogicalView.h"

#include <velocypack/Parser.h>

// -----------------------------------------------------------------------------
// --SECTION--                                                 setup / tear-down
// -----------------------------------------------------------------------------

class IResearchLinkTest : public ::testing::Test {
 protected:
  StorageEngineMock engine;
  arangodb::application_features::ApplicationServer server;
  std::vector<std::pair<arangodb::application_features::ApplicationFeature*, bool>> features;
  std::string testFilesystemPath;

  IResearchLinkTest() : engine(server), server(nullptr, nullptr) {
    arangodb::EngineSelectorFeature::ENGINE = &engine;

    arangodb::tests::init();

    // suppress INFO {authentication} Authentication is turned on (system only), authentication for unix sockets is turned on
    // suppress WARNING {authentication} --server.jwt-secret is insecure. Use --server.jwt-secret-keyfile instead
    arangodb::LogTopic::setLogLevel(arangodb::Logger::AUTHENTICATION.name(),
                                    arangodb::LogLevel::ERR);

    // suppress log messages since tests check error conditions
    arangodb::LogTopic::setLogLevel(arangodb::Logger::ENGINES.name(),
                                    arangodb::LogLevel::FATAL);
    arangodb::LogTopic::setLogLevel(arangodb::Logger::FIXME.name(), arangodb::LogLevel::FATAL);
    arangodb::LogTopic::setLogLevel(arangodb::iresearch::TOPIC.name(),
                                    arangodb::LogLevel::FATAL);
    irs::logger::output_le(iresearch::logger::IRL_FATAL, stderr);

    // setup required application features
    features.emplace_back(new arangodb::AqlFeature(server),
                          true);  // required for UserManager::loadFromDB()
    features.emplace_back(new arangodb::AuthenticationFeature(server), true);
    features.emplace_back(new arangodb::DatabaseFeature(server), false);
    features.emplace_back(new arangodb::ShardingFeature(server), false);
    features.emplace_back(new arangodb::ViewTypesFeature(server), true);
    features.emplace_back(new arangodb::QueryRegistryFeature(server), false);
    arangodb::application_features::ApplicationServer::server->addFeature(
        features.back().first);  // need QueryRegistryFeature feature to be added now in order to create the system database
    features.emplace_back(new arangodb::SystemDatabaseFeature(server), true);  // required for IResearchAnalyzerFeature
    features.emplace_back(new arangodb::TraverserEngineRegistryFeature(server),
                          false);  // required for AqlFeature::stop()
    features.emplace_back(new arangodb::DatabasePathFeature(server), false);
    features.emplace_back(new arangodb::aql::AqlFunctionFeature(server), true);  // required for IResearchAnalyzerFeature
    features.emplace_back(new arangodb::iresearch::IResearchAnalyzerFeature(server), true);
    features.emplace_back(new arangodb::iresearch::IResearchFeature(server), true);
    features.emplace_back(new arangodb::FlushFeature(server), false);  // do not start the thread
    features.emplace_back(new arangodb::V8DealerFeature(server),
                          false);  // required for DatabaseFeature::createDatabase(...)

#if USE_ENTERPRISE
    features.emplace_back(new arangodb::LdapFeature(server),
                          false);  // required for AuthenticationFeature with USE_ENTERPRISE
#endif

    // required for V8DealerFeature::prepare(), ClusterFeature::prepare() not required
    arangodb::application_features::ApplicationServer::server->addFeature(
        new arangodb::ClusterFeature(server));

    for (auto& f : features) {
      arangodb::application_features::ApplicationServer::server->addFeature(f.first);
    }

    for (auto& f : features) {
      f.first->prepare();
    }

    auto const databases = arangodb::velocypack::Parser::fromJson(
        std::string("[ { \"name\": \"") +
        arangodb::StaticStrings::SystemDatabase + "\" } ]");
    auto* dbFeature =
        arangodb::application_features::ApplicationServer::lookupFeature<arangodb::DatabaseFeature>(
            "Database");
    dbFeature->loadDatabases(databases->slice());

    for (auto& f : features) {
      if (f.second) {
        f.first->start();
      }
    }

    TransactionStateMock::abortTransactionCount = 0;
    TransactionStateMock::beginTransactionCount = 0;
    TransactionStateMock::commitTransactionCount = 0;

    auto* dbPathFeature =
        arangodb::application_features::ApplicationServer::getFeature<arangodb::DatabasePathFeature>(
            "DatabasePath");
    arangodb::tests::setDatabasePath(*dbPathFeature);  // ensure test data is stored in a unique directory
    testFilesystemPath = dbPathFeature->directory();

    long systemError;
    std::string systemErrorStr;
    TRI_CreateDirectory(testFilesystemPath.c_str(), systemError, systemErrorStr);
  }

  ~IResearchLinkTest() {
    arangodb::application_features::ApplicationServer::lookupFeature<arangodb::SystemDatabaseFeature>()
        ->unprepare();  // release system database before reseting the 'ENGINE'
    TRI_RemoveDirectory(testFilesystemPath.c_str());
    arangodb::LogTopic::setLogLevel(arangodb::iresearch::TOPIC.name(),
                                    arangodb::LogLevel::DEFAULT);
    arangodb::application_features::ApplicationServer::server = nullptr;

    // destroy application features
    for (auto& f : features) {
      if (f.second) {
        f.first->stop();
      }
    }

    for (auto& f : features) {
      f.first->unprepare();
    }

    arangodb::LogTopic::setLogLevel(arangodb::Logger::FIXME.name(),
                                    arangodb::LogLevel::DEFAULT);
    arangodb::LogTopic::setLogLevel(arangodb::Logger::ENGINES.name(),
                                    arangodb::LogLevel::DEFAULT);
    arangodb::LogTopic::setLogLevel(arangodb::Logger::AUTHENTICATION.name(),
                                    arangodb::LogLevel::DEFAULT);
    arangodb::EngineSelectorFeature::ENGINE = nullptr;
  }
};

// -----------------------------------------------------------------------------
// --SECTION--                                                        test suite
// -----------------------------------------------------------------------------

TEST_F(IResearchLinkTest, test_defaults) {
  // no view specified
  {
    engine.views.clear();
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\" }");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto json = arangodb::velocypack::Parser::fromJson("{}");
    try {
      arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, json->slice(), 1, false);
      EXPECT_TRUE(false);
    } catch (arangodb::basics::Exception const& ex) {
      EXPECT_EQ(TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND, ex.code());
    }
  }

  // no view can be found (e.g. db-server coming up with view not available from Agency yet)
  {
    engine.views.clear();
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\" }");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto json = arangodb::velocypack::Parser::fromJson("{ \"view\": \"42\" }");
    EXPECT_NE(nullptr, arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, json->slice(), 1, false));
  }

  // valid link creation
  {
    engine.views.clear();
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto linkJson = arangodb::velocypack::Parser::fromJson(
        "{ \"type\": \"arangosearch\", \"view\": \"42\" }");
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"id\": 42, \"type\": \"arangosearch\" }");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    ASSERT_TRUE((false == !logicalView));

    bool created;
    auto link = logicalCollection->createIndex(linkJson->slice(), created);
    ASSERT_TRUE((false == !link && created));
    EXPECT_TRUE((true == link->canBeDropped()));
    EXPECT_TRUE((logicalCollection.get() == &(link->collection())));
    EXPECT_TRUE((link->fieldNames().empty()));
    EXPECT_TRUE((link->fields().empty()));
    EXPECT_TRUE((false == link->hasExpansion()));
    EXPECT_TRUE((false == link->hasSelectivityEstimate()));
    EXPECT_TRUE((false == link->implicitlyUnique()));
    EXPECT_TRUE((false == link->isSorted()));
    EXPECT_TRUE((0 < link->memory()));
    EXPECT_TRUE((true == link->sparse()));
    EXPECT_TRUE((arangodb::Index::IndexType::TRI_IDX_TYPE_IRESEARCH_LINK == link->type()));
    EXPECT_TRUE((arangodb::iresearch::DATA_SOURCE_TYPE.name() == link->typeName()));
    EXPECT_TRUE((false == link->unique()));

    arangodb::iresearch::IResearchLinkMeta actualMeta;
    arangodb::iresearch::IResearchLinkMeta expectedMeta;
    auto builder = link->toVelocyPack(
        arangodb::Index::makeFlags(arangodb::Index::Serialize::Figures));
    std::string error;

    EXPECT_TRUE((actualMeta.init(builder->slice(), false, error) && expectedMeta == actualMeta));
    auto slice = builder->slice();
    EXPECT_TRUE((slice.hasKey("view") && slice.get("view").isString() &&
                 logicalView->guid() == slice.get("view").copyString() &&
                 slice.hasKey("figures") && slice.get("figures").isObject() &&
                 slice.get("figures").hasKey("memory") &&
                 slice.get("figures").get("memory").isNumber() &&
                 0 < slice.get("figures").get("memory").getUInt()));

    EXPECT_TRUE((logicalCollection->dropIndex(link->id()) &&
                 logicalCollection->getIndexes().empty()));
  }

  // ensure jSON is still valid after unload()
  {
    engine.views.clear();
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto linkJson = arangodb::velocypack::Parser::fromJson(
        "{ \"type\": \"arangosearch\", \"view\": \"42\" }");
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"id\": 42, \"type\": \"arangosearch\" }");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    ASSERT_TRUE((false == !logicalView));

    bool created;
    auto link = logicalCollection->createIndex(linkJson->slice(), created);
    ASSERT_TRUE((false == !link && created));
    EXPECT_TRUE((true == link->canBeDropped()));
    EXPECT_TRUE((logicalCollection.get() == &(link->collection())));
    EXPECT_TRUE((link->fieldNames().empty()));
    EXPECT_TRUE((link->fields().empty()));
    EXPECT_TRUE((false == link->hasExpansion()));
    EXPECT_TRUE((false == link->hasSelectivityEstimate()));
    EXPECT_TRUE((false == link->implicitlyUnique()));
    EXPECT_TRUE((false == link->isSorted()));
    EXPECT_TRUE((0 < link->memory()));
    EXPECT_TRUE((true == link->sparse()));
    EXPECT_TRUE((arangodb::Index::IndexType::TRI_IDX_TYPE_IRESEARCH_LINK == link->type()));
    EXPECT_TRUE((arangodb::iresearch::DATA_SOURCE_TYPE.name() == link->typeName()));
    EXPECT_TRUE((false == link->unique()));

    {
      arangodb::iresearch::IResearchLinkMeta actualMeta;
      arangodb::iresearch::IResearchLinkMeta expectedMeta;
      auto builder = link->toVelocyPack(
          arangodb::Index::makeFlags(arangodb::Index::Serialize::Figures));
      std::string error;

      EXPECT_TRUE((actualMeta.init(builder->slice(), false, error) && expectedMeta == actualMeta));
      auto slice = builder->slice();
      EXPECT_TRUE((slice.hasKey("view") && slice.get("view").isString() &&
                   logicalView->guid() == slice.get("view").copyString() &&
                   slice.hasKey("figures") && slice.get("figures").isObject() &&
                   slice.get("figures").hasKey("memory") &&
                   slice.get("figures").get("memory").isNumber() &&
                   0 < slice.get("figures").get("memory").getUInt()));
    }

    // ensure jSON is still valid after unload()
    {
      link->unload();
      auto builder = link->toVelocyPack(
          arangodb::Index::makeFlags(arangodb::Index::Serialize::Figures));
      auto slice = builder->slice();
      EXPECT_TRUE((slice.hasKey("view") && slice.get("view").isString() &&
                   logicalView->guid() == slice.get("view").copyString() &&
                   slice.hasKey("figures") && slice.get("figures").isObject() &&
                   slice.get("figures").hasKey("memory") &&
                   slice.get("figures").get("memory").isNumber() &&
                   0 < slice.get("figures").get("memory").getUInt()));
    }
  }
}

TEST_F(IResearchLinkTest, test_init) {
  // collection registered with view (collection initially not in view)
  {
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\", \"id\": 100 }");
    auto linkJson = arangodb::velocypack::Parser::fromJson(
        "{ \"type\": \"arangosearch\", \"view\": \"42\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"id\": 42, \"type\": \"arangosearch\" }");
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    ASSERT_TRUE((false == !logicalView));

    // no collections in view before
    {
      std::unordered_set<TRI_voc_cid_t> expected;
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    std::shared_ptr<arangodb::Index> link = arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, linkJson->slice(), 1, false);
    EXPECT_TRUE((false == !link));

    // collection in view after
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    link.reset();

    // collection in view on destruct
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }
  }

  // collection registered with view (collection initially is in view)
  {
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\", \"id\": 101 }");
    auto linkJson = arangodb::velocypack::Parser::fromJson(
        "{ \"type\": \"arangosearch\", \"view\": \"43\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"id\": 43, \"type\": \"arangosearch\", "
        "\"collections\": [ 101 ] }");
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    ASSERT_TRUE((false == !logicalView));

    // collection in view before
    {
      std::unordered_set<TRI_voc_cid_t> expected = {101};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    std::shared_ptr<arangodb::Index> link = arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, linkJson->slice(), 1, false);
    EXPECT_TRUE((false == !link));

    // collection in view after
    {
      std::unordered_set<TRI_voc_cid_t> expected = {101};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    link.reset();

    // collection still in view on destruct
    {
      std::unordered_set<TRI_voc_cid_t> expected = {101};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }
  }
}

TEST_F(IResearchLinkTest, test_self_token) {
  // test empty token
  {
    arangodb::iresearch::IResearchLink::AsyncLinkPtr::element_type empty(nullptr);
    EXPECT_TRUE((nullptr == empty.get()));
  }

  arangodb::iresearch::IResearchLink::AsyncLinkPtr self;

  {
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\" }");
    auto linkJson =
        arangodb::velocypack::Parser::fromJson("{ \"view\": \"testView\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"type\":\"arangosearch\" }");
    Vocbase vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                    "testVocbase");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((false == !logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    EXPECT_TRUE((false == !logicalView));
    std::shared_ptr<arangodb::Index> index =arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, linkJson->slice(), 42, false);
    ASSERT_TRUE((false == !index));
    auto link = std::dynamic_pointer_cast<arangodb::iresearch::IResearchLink>(index);
    ASSERT_TRUE((false == !link));
    self = link->self();
    EXPECT_TRUE((false == !self));
    EXPECT_TRUE((link.get() == self->get()));
  }

  EXPECT_TRUE((false == !self));
  EXPECT_TRUE((nullptr == self->get()));
}

TEST_F(IResearchLinkTest, test_drop) {
  // collection drop (removes collection from view) subsequent destroy does not touch view
  {
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\", \"id\": 100 }");
    auto linkJson = arangodb::velocypack::Parser::fromJson(
        "{ \"type\": \"arangosearch\", \"view\": \"42\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"id\": 42, \"type\": \"arangosearch\" }");
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    ASSERT_TRUE((false == !logicalView));

    std::shared_ptr<arangodb::Index> link0 = arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, linkJson->slice(), 1, false);
    EXPECT_TRUE((false == !link0));

    // collection in view before
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    EXPECT_TRUE((true == (*dynamic_cast<arangodb::iresearch::IResearchLink*>(
                              link0.get()) == *logicalView)));
    EXPECT_TRUE((link0->drop().ok()));
    EXPECT_TRUE((true == (*dynamic_cast<arangodb::iresearch::IResearchLink*>(
                              link0.get()) == *logicalView)));

    // collection not in view after
    {
      std::unordered_set<TRI_voc_cid_t> expected;
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    std::shared_ptr<arangodb::Index> link1 = arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, linkJson->slice(), 1, false);
    EXPECT_TRUE((false == !link1));

    // collection in view before (new link)
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    link0.reset();

    // collection in view after (new link) subsequent destroy does not touch view
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }
  }
}

TEST_F(IResearchLinkTest, test_unload) {
  // index unload does not touch the view (subsequent destroy)
  {
    auto collectionJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testCollection\", \"id\": 100 }");
    auto linkJson = arangodb::velocypack::Parser::fromJson(
        "{ \"type\": \"arangosearch\", \"view\": \"42\" }");
    auto viewJson = arangodb::velocypack::Parser::fromJson(
        "{ \"name\": \"testView\", \"id\": 42, \"type\": \"arangosearch\" }");
    TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                          "testVocbase");
    auto logicalCollection = vocbase.createCollection(collectionJson->slice());
    ASSERT_TRUE((nullptr != logicalCollection));
    auto logicalView = vocbase.createView(viewJson->slice());
    ASSERT_TRUE((false == !logicalView));

    std::shared_ptr<arangodb::Index> link = arangodb::iresearch::IResearchMMFilesLink::factory().instantiate(*logicalCollection, linkJson->slice(), 1, false);
    EXPECT_TRUE((false == !link));

    // collection in view before
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    EXPECT_TRUE((true == (*dynamic_cast<arangodb::iresearch::IResearchLink*>(
                              link.get()) == *logicalView)));
    link->unload();
    EXPECT_TRUE((true == (*dynamic_cast<arangodb::iresearch::IResearchLink*>(
                              link.get()) == *logicalView)));

    // collection in view after unload
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }

    link.reset();

    // collection in view after destruct, subsequent destroy does not touch view
    {
      std::unordered_set<TRI_voc_cid_t> expected = {100};
      std::set<TRI_voc_cid_t> actual;

      EXPECT_TRUE((logicalView->visitCollections([&actual](TRI_voc_cid_t cid) -> bool {
        actual.emplace(cid);
        return true;
      })));

      for (auto& cid : expected) {
        EXPECT_TRUE((1 == actual.erase(cid)));
      }

      EXPECT_TRUE((actual.empty()));
    }
  }
}

TEST_F(IResearchLinkTest, test_write) {
  static std::vector<std::string> const EMPTY;
  auto doc0 = arangodb::velocypack::Parser::fromJson("{ \"abc\": \"def\" }");
  auto doc1 = arangodb::velocypack::Parser::fromJson("{ \"ghi\": \"jkl\" }");
  TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, 1,
                        "testVocbase");
  std::string dataPath = ((((irs::utf8_path() /= testFilesystemPath) /= std::string("databases")) /=
                           (std::string("database-") + std::to_string(vocbase.id()))) /=
                          std::string("arangosearch-42"))
                             .utf8();
  auto linkJson = arangodb::velocypack::Parser::fromJson(
      "{ \"id\": 42, \"type\": \"arangosearch\", \"view\": \"42\", "
      "\"includeAllFields\": true }");
  auto collectionJson = arangodb::velocypack::Parser::fromJson(
      "{ \"name\": \"testCollection\" }");
  auto viewJson = arangodb::velocypack::Parser::fromJson(
      "{ \
    \"id\": 42, \
    \"name\": \"testView\", \
    \"type\": \"arangosearch\" \
  }");
  auto logicalCollection = vocbase.createCollection(collectionJson->slice());
  ASSERT_TRUE((nullptr != logicalCollection));
  auto view = std::dynamic_pointer_cast<arangodb::iresearch::IResearchView>(
      vocbase.createView(viewJson->slice()));
  ASSERT_TRUE((false == !view));
  view->open();
  auto* flush =
      arangodb::application_features::ApplicationServer::lookupFeature<arangodb::FlushFeature>(
          "Flush");
  ASSERT_TRUE((flush));

  dataPath =
      ((((irs::utf8_path() /= testFilesystemPath) /=
         std::string("databases")) /=
        (std::string("database-") + std::to_string(vocbase.id()))) /=
       (std::string("arangosearch-") + std::to_string(logicalCollection->id()) + "_42"))
          .utf8();
  irs::fs_directory directory(dataPath);
  bool created;
  auto link = logicalCollection->createIndex(linkJson->slice(), created);
  ASSERT_TRUE((false == !link && created));
  auto reader = irs::directory_reader::open(directory);
  EXPECT_TRUE((0 == reader.reopen().live_docs_count()));
  {
    arangodb::transaction::Methods trx(arangodb::transaction::StandaloneContext::Create(vocbase),
                                       EMPTY, EMPTY, EMPTY,
                                       arangodb::transaction::Options());
    EXPECT_TRUE((trx.begin().ok()));
    auto* l = dynamic_cast<arangodb::iresearch::IResearchLink*>(link.get());
    ASSERT_TRUE(l != nullptr);
    EXPECT_TRUE((l->insert(trx, arangodb::LocalDocumentId(1), doc0->slice(),
                           arangodb::Index::OperationMode::normal)
                     .ok()));
    EXPECT_TRUE((trx.commit().ok()));
    EXPECT_TRUE((l->commit().ok()));
  }

  EXPECT_TRUE((1 == reader.reopen().live_docs_count()));

  {
    arangodb::transaction::Methods trx(arangodb::transaction::StandaloneContext::Create(vocbase),
                                       EMPTY, EMPTY, EMPTY,
                                       arangodb::transaction::Options());
    EXPECT_TRUE((trx.begin().ok()));
    auto* l = dynamic_cast<arangodb::iresearch::IResearchLink*>(link.get());
    ASSERT_TRUE(l != nullptr);
    EXPECT_TRUE((l->insert(trx, arangodb::LocalDocumentId(2), doc1->slice(),
                           arangodb::Index::OperationMode::normal)
                     .ok()));
    EXPECT_TRUE((trx.commit().ok()));
    EXPECT_TRUE((l->commit().ok()));
  }

  EXPECT_TRUE((2 == reader.reopen().live_docs_count()));

  {
    arangodb::transaction::Methods trx(arangodb::transaction::StandaloneContext::Create(vocbase),
                                       EMPTY, EMPTY, EMPTY,
                                       arangodb::transaction::Options());
    EXPECT_TRUE((trx.begin().ok()));
    auto* l = dynamic_cast<arangodb::iresearch::IResearchLink*>(link.get());
    ASSERT_TRUE(l != nullptr);
    EXPECT_TRUE((l->remove(trx, arangodb::LocalDocumentId(2), doc1->slice(),
                           arangodb::Index::OperationMode::normal)
                     .ok()));
    EXPECT_TRUE((trx.commit().ok()));
    EXPECT_TRUE((l->commit().ok()));
  }

  EXPECT_TRUE((1 == reader.reopen().live_docs_count()));
  logicalCollection->dropIndex(link->id());
  EXPECT_ANY_THROW((reader.reopen()));
}