////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2018 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 Andrey Abramov
/// @author Vasiliy Nabatchikov
////////////////////////////////////////////////////////////////////////////////

#include "IResearchViewCoordinator.h"
#include "IResearchCommon.h"
#include "IResearchLinkCoordinator.h"
#include "IResearchLinkHelper.h"

#include <velocypack/Builder.h>
#include <velocypack/Collection.h>
#include <velocypack/Parser.h>
#include "Basics/StaticStrings.h"
#include "Basics/StringUtils.h"
#include "Cluster/ClusterFeature.h"
#include "Cluster/ClusterInfo.h"
#include "Cluster/ServerState.h"
#include "IResearch/IResearchFeature.h"
#include "IResearch/VelocyPackHelper.h"
#include "RestServer/ViewTypesFeature.h"
#include "Transaction/Methods.h"
#include "Transaction/StandaloneContext.h"
#include "Utils/CollectionNameResolver.h"
#include "Utils/ExecContext.h"
#include "VocBase/LogicalCollection.h"
#include "VocBase/Methods/Indexes.h"

namespace {

typedef irs::async_utils::read_write_mutex::read_mutex ReadMutex;
typedef irs::async_utils::read_write_mutex::write_mutex WriteMutex;

}  // namespace

namespace arangodb {
namespace iresearch {

////////////////////////////////////////////////////////////////////////////////
/// @brief IResearchView-specific implementation of a ViewFactory
////////////////////////////////////////////////////////////////////////////////
struct IResearchViewCoordinator::ViewFactory : public arangodb::ViewFactory {
  virtual arangodb::Result create(arangodb::LogicalView::ptr& view, TRI_vocbase_t& vocbase,
                                  arangodb::velocypack::Slice const& definition) const override {
    auto* ci = ClusterInfo::instance();

    if (!ci) {
      return arangodb::Result(
          TRI_ERROR_INTERNAL,
          std::string("failure to find 'ClusterInfo' instance while creating "
                      "arangosearch View in database '") +
              vocbase.name() + "'");
    }

    auto& properties = definition.isObject() ? definition : emptyObjectSlice();  // if no 'info' then assume defaults
    auto links = properties.hasKey(StaticStrings::LinksField)
                     ? properties.get(StaticStrings::LinksField)
                     : arangodb::velocypack::Slice::emptyObjectSlice();
    auto res = IResearchLinkHelper::validateLinks(vocbase, links);

    if (!res.ok()) {
      return res;
    }

    arangodb::LogicalView::ptr impl;

    res = instantiate(impl, vocbase, definition, 0);

    if (!res.ok()) {
      return res;
    }

    if (!impl) {
      return arangodb::Result(TRI_ERROR_INTERNAL,
                              std::string(
                                  "failure during instantiation while creating "
                                  "arangosearch View in database '") +
                                  vocbase.name() + "'");
    }

    arangodb::velocypack::Builder builder;

    builder.openObject();
    res = impl->properties(builder, true, true);  // include links so that Agency will always have a full definition

    if (!res.ok()) {
      return res;
    }

    builder.close();

    std::string error;
    auto resNum = ci->createViewCoordinator(vocbase.name(), std::to_string(impl->id()),
                                            builder.slice(), error);

    if (TRI_ERROR_NO_ERROR != resNum) {
      if (error.empty()) {
        error = TRI_errno_string(resNum);
      }

      return arangodb::Result(
          resNum,
          std::string("failure during ClusterInfo persistance of created view "
                      "while creating arangosearch View in database '") +
              vocbase.name() + "', error: " + error);
    }

    // create links on a best-effor basis
    // link creation failure does not cause view creation failure
    try {
      std::unordered_set<TRI_voc_cid_t> collections;

      res = IResearchLinkHelper::updateLinks(collections, vocbase, *impl, links);

      if (!res.ok()) {
        LOG_TOPIC(WARN, arangodb::iresearch::TOPIC)
            << "failed to create links while creating arangosearch view '"
            << impl->name() << "': " << res.errorNumber() << " " << res.errorMessage();
      }
    } catch (arangodb::basics::Exception const& e) {
      IR_LOG_EXCEPTION();
      LOG_TOPIC(WARN, arangodb::iresearch::TOPIC)
          << "caught exception while creating links while creating "
             "arangosearch view '"
          << impl->name() << "': " << e.code() << " " << e.what();
    } catch (std::exception const& e) {
      IR_LOG_EXCEPTION();
      LOG_TOPIC(WARN, arangodb::iresearch::TOPIC)
          << "caught exception while creating links while creating "
             "arangosearch view '"
          << impl->name() << "': " << e.what();
    } catch (...) {
      IR_LOG_EXCEPTION();
      LOG_TOPIC(WARN, arangodb::iresearch::TOPIC)
          << "caught exception while creating links while creating "
             "arangosearch view '"
          << impl->name() << "'";
    }

    view = ci->getView(vocbase.name(), std::to_string(impl->id()));  // refresh view from Agency

    if (view) {
      view->open();  // open view to match the behaviour in StorageEngine::openExistingDatabase(...) and original behaviour of TRI_vocbase_t::createView(...)
    }

    return arangodb::Result();
  }

  virtual arangodb::Result instantiate(arangodb::LogicalView::ptr& view,
                                       TRI_vocbase_t& vocbase,
                                       arangodb::velocypack::Slice const& definition,
                                       uint64_t planVersion) const override {
    std::string error;
    auto impl = std::shared_ptr<IResearchViewCoordinator>(
        new IResearchViewCoordinator(vocbase, definition, planVersion));

    if (!impl->_meta.init(definition, error)) {
      return arangodb::Result(
          TRI_ERROR_BAD_PARAMETER,
          error.empty()
              ? (std::string("failed to initialize arangosearch View '") +
                 impl->name() + "' from definition: " + definition.toString())
              : (std::string("failed to initialize arangosearch View '") +
                 impl->name() + "' from definition, error in attribute '" +
                 error + "': " + definition.toString()));
    }

    view = impl;

    return arangodb::Result();
  }
};

arangodb::Result IResearchViewCoordinator::appendVelocyPackDetailed(
    arangodb::velocypack::Builder& builder, bool forPersistence) const {
  if (!builder.isOpenObject()) {
    return arangodb::Result(TRI_ERROR_BAD_PARAMETER,
                            std::string("invalid builder provided for "
                                        "IResearchViewCoordinator definition"));
  }

  static const std::function<bool(irs::string_ref const& key)> acceptor =
      [](irs::string_ref const& key) -> bool {
    return key != StaticStrings::VersionField;  // ignored fields
  };
  static const std::function<bool(irs::string_ref const& key)> persistenceAcceptor =
      [](irs::string_ref const&) -> bool { return true; };
  arangodb::velocypack::Builder sanitizedBuilder;

  sanitizedBuilder.openObject();

  if (!_meta.json(sanitizedBuilder) ||
      !mergeSliceSkipKeys(builder, sanitizedBuilder.close().slice(),
                          forPersistence ? persistenceAcceptor : acceptor)) {
    return arangodb::Result(
        TRI_ERROR_INTERNAL,
        std::string("failure to generate definition while generating "
                    "properties jSON for IResearch View in database '") +
            vocbase().name() + "'");
  }

  arangodb::velocypack::Builder links;

  // links are not persisted, their definitions are part of the corresponding collections
  if (!forPersistence) {
    // open up a read transaction and add all linked collections to verify that
    // the current user has access

    std::vector<std::string> collections;
    for (auto& entry : _collections) {
      collections.emplace_back(entry.second.first);
    }

    Result result = arangodb::basics::catchToResult([this, &collections]() -> arangodb::Result {
      static std::vector<std::string> const EMPTY;
      // use default lock timeout
      arangodb::transaction::Options options;
      options.waitForSync = false;
      options.allowImplicitCollections = false;

      transaction::StandaloneContext ctx{vocbase()};
      std::shared_ptr<transaction::StandaloneContext> ptr;
      arangodb::transaction::Methods trx(std::shared_ptr<transaction::StandaloneContext>(ptr, &ctx),
                                         collections,  // readCollections
                                         EMPTY,        // writeCollections
                                         EMPTY,        // exclusiveCollections
                                         options);
      auto res = trx.begin();

      if (!res.ok()) {
        return res;  // nothing more to output
      }

      trx.commit();
      return res;
    });
    if (result.fail()) {
      IR_LOG_EXCEPTION();
      return arangodb::Result(result.errorNumber(),
                              "caught exception while generating json for "
                              "arangosearch view '" +
                                  name() + "': " + result.errorMessage());
    }

    ReadMutex mutex(_mutex);
    SCOPED_LOCK(mutex);  // '_collections' can be asynchronously modified

    links.openObject();

    for (auto& entry : _collections) {
      links.add(entry.second.first, entry.second.second.slice());
    }

    links.close();
    builder.add(StaticStrings::LinksField, links.slice());
  }

  return arangodb::Result();
}

bool IResearchViewCoordinator::emplace(TRI_voc_cid_t cid, std::string const& key,
                                       arangodb::velocypack::Slice const& value) {
  LOG_TOPIC(TRACE, arangodb::iresearch::TOPIC)
      << "beginning IResearchViewCoordinator::emplace";
  static const std::function<bool(irs::string_ref const& key)> acceptor =
      [](irs::string_ref const& key) -> bool {
    return key != arangodb::StaticStrings::IndexId &&
           key != arangodb::StaticStrings::IndexType &&
           key != StaticStrings::ViewIdField;  // ignored fields
  };
  arangodb::velocypack::Builder builder;

  builder.openObject();

  // strip internal keys (added in createLink(...)) from externally visible link definition
  if (!mergeSliceSkipKeys(builder, value, acceptor)) {
    LOG_TOPIC(WARN, iresearch::TOPIC)
        << "failed to generate externally visible link definition while "
           "emplacing "
        << "link definition into arangosearch view '" << name()
        << "' collection '" << cid << "'";

    return false;
  }

  builder.close();

  WriteMutex mutex(_mutex);
  SCOPED_LOCK(mutex);  // '_collections' can be asynchronously read

  return _collections
      .emplace(std::piecewise_construct, std::forward_as_tuple(cid),
               std::forward_as_tuple(key, std::move(builder)))
      .second;
}

/*static*/ arangodb::ViewFactory const& IResearchViewCoordinator::factory() {
  static const ViewFactory factory;

  return factory;
}

IResearchViewCoordinator::IResearchViewCoordinator(TRI_vocbase_t& vocbase,
                                                   velocypack::Slice info, uint64_t planVersion)
    : LogicalViewClusterInfo(vocbase, info, planVersion) {
  TRI_ASSERT(ServerState::instance()->isCoordinator());
}

bool IResearchViewCoordinator::visitCollections(CollectionVisitor const& visitor) const {
  ReadMutex mutex(_mutex);
  SCOPED_LOCK(mutex);  // '_collections' can be asynchronously modified

  for (auto& entry : _collections) {
    if (!visitor(entry.first)) {
      return false;
    }
  }

  return true;
}

arangodb::Result IResearchViewCoordinator::properties(velocypack::Slice const& slice,
                                                      bool partialUpdate) {
  auto* engine = arangodb::ClusterInfo::instance();

  if (!engine) {
    return arangodb::Result(TRI_ERROR_INTERNAL,
                            std::string("failure to get storage engine while "
                                        "updating arangosearch view '") +
                                name() + "'");
  }

  try {
    auto links = slice.hasKey(StaticStrings::LinksField)
                     ? slice.get(StaticStrings::LinksField)
                     : arangodb::velocypack::Slice::emptyObjectSlice();
    auto res = IResearchLinkHelper::validateLinks(vocbase(), links);

    if (!res.ok()) {
      return res;
    }

    // check link auth as per https://github.com/arangodb/backlog/issues/459
    if (arangodb::ExecContext::CURRENT) {
      // check existing links
      for (auto& entry : _collections) {
        auto collection =
            engine->getCollection(vocbase().name(), std::to_string(entry.first));

        if (collection &&
            !arangodb::ExecContext::CURRENT->canUseCollection(
                vocbase().name(), collection->name(), arangodb::auth::Level::RO)) {
          return arangodb::Result(TRI_ERROR_FORBIDDEN,
                                  std::string(
                                      "while updating arangosearch definition, "
                                      "error: collection '") +
                                      collection->name() +
                                      "' not authorised for read access");
        }
      }
    }

    std::string error;
    IResearchViewMeta meta;

    auto const& defaults = partialUpdate ? _meta : IResearchViewMeta::DEFAULT();

    if (!meta.init(slice, error, defaults)) {
      return arangodb::Result(
          TRI_ERROR_BAD_PARAMETER,
          error.empty() ? (std::string("failed to update arangosearch view '") +
                           name() + "' from definition: " + slice.toString())
                        : (std::string("failed to update arangosearch view '") +
                           name() + "' from definition, error in attribute '" +
                           error + "': " + slice.toString()));
    }

    // reset non-updatable values to match current meta
    meta._locale = _meta._locale;

    // only trigger persisting of properties if they have changed
    if (_meta != meta) {
      arangodb::velocypack::Builder builder;

      builder.openObject();
      meta.json(builder);

      auto result = properties(builder, false, true);

      if (!result.ok()) {
        return result;
      }

      builder.close();
      result = engine->setViewPropertiesCoordinator(vocbase().name(),
                                                    std::to_string(id()),
                                                    builder.slice());

      if (!result.ok()) {
        return result;
      }
    }

    if (links.isEmptyObject() && partialUpdate) {
      return arangodb::Result();  // nothing more to do
    }

    // ...........................................................................
    // update links if requested (on a best-effort basis)
    // indexing of collections is done in different threads so no locks can be held and rollback is not possible
    // as a result it's also possible for links to be simultaneously modified via a different callflow (e.g. from collections)
    // ...........................................................................

    arangodb::velocypack::Builder currentLinks;
    std::unordered_set<TRI_voc_cid_t> currentCids;

    {
      ReadMutex mutex(_mutex);
      SCOPED_LOCK(mutex);  // '_collections' can be asynchronously modified

      currentLinks.openObject();

      for (auto& entry : _collections) {
        currentCids.emplace(entry.first);
        currentLinks.add(entry.second.first, entry.second.second.slice());
      }

      currentLinks.close();
    }

    std::unordered_set<TRI_voc_cid_t> collections;

    if (partialUpdate) {
      return IResearchLinkHelper::updateLinks(collections, vocbase(), *this, links);
    }

    return IResearchLinkHelper::updateLinks(collections, vocbase(), *this, links, currentCids);
  } catch (arangodb::basics::Exception& e) {
    LOG_TOPIC(WARN, iresearch::TOPIC)
        << "caught exception while updating properties for arangosearch view '"
        << name() << "': " << e.code() << " " << e.what();
    IR_LOG_EXCEPTION();

    return arangodb::Result(
        e.code(),
        std::string("error updating properties for arangosearch view '") +
            name() + "'");
  } catch (std::exception const& e) {
    LOG_TOPIC(WARN, iresearch::TOPIC)
        << "caught exception while updating properties for arangosearch view '"
        << name() << "': " << e.what();
    IR_LOG_EXCEPTION();

    return arangodb::Result(
        TRI_ERROR_BAD_PARAMETER,
        std::string("error updating properties for arangosearch view '") +
            name() + "'");
  } catch (...) {
    LOG_TOPIC(WARN, iresearch::TOPIC)
        << "caught exception while updating properties for arangosearch view '"
        << name() << "'";
    IR_LOG_EXCEPTION();

    return arangodb::Result(
        TRI_ERROR_BAD_PARAMETER,
        std::string("error updating properties for arangosearch view '") +
            name() + "'");
  }
}

Result IResearchViewCoordinator::dropImpl() {
  auto* engine = arangodb::ClusterInfo::instance();

  if (!engine) {
    return arangodb::Result(TRI_ERROR_INTERNAL,
                            std::string("failure to get storage engine while "
                                        "dropping arangosearch view '") +
                                name() + "'");
  }

  // drop links first
  {
    std::unordered_set<TRI_voc_cid_t> currentCids;

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

    // check link auth as per https://github.com/arangodb/backlog/issues/459
    if (arangodb::ExecContext::CURRENT) {
      for (auto& entry : currentCids) {
        auto collection = engine->getCollection(vocbase().name(), std::to_string(entry));

        if (collection &&
            !arangodb::ExecContext::CURRENT->canUseCollection(
                vocbase().name(), collection->name(), arangodb::auth::Level::RO)) {
          return arangodb::Result(TRI_ERROR_FORBIDDEN);
        }
      }
    }

    std::unordered_set<TRI_voc_cid_t> collections;
    auto res = IResearchLinkHelper::updateLinks(collections, vocbase(), *this,
                                                arangodb::velocypack::Slice::emptyObjectSlice(),
                                                currentCids);

    if (!res.ok()) {
      return arangodb::Result(
          res.errorNumber(),
          std::string(
              "failed to remove links while removing arangosearch view '") +
              name() + "': " + res.errorMessage());
    }
  }

  return {};
}

}  // namespace iresearch
}  // namespace arangodb

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