/*
 * Copyright 2018 Google
 *
 * 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.
 */

#include "Firestore/core/src/remote/datastore.h"

#include <unordered_set>
#include <utility>

#include "Firestore/core/include/firebase/firestore/firestore_errors.h"
#include "Firestore/core/src/core/database_info.h"
#include "Firestore/core/src/credentials/auth_token.h"
#include "Firestore/core/src/credentials/credentials_provider.h"
#include "Firestore/core/src/model/database_id.h"
#include "Firestore/core/src/model/document.h"
#include "Firestore/core/src/model/document_key.h"
#include "Firestore/core/src/model/mutation.h"
#include "Firestore/core/src/remote/connectivity_monitor.h"
#include "Firestore/core/src/remote/firebase_metadata_provider.h"
#include "Firestore/core/src/remote/grpc_completion.h"
#include "Firestore/core/src/remote/grpc_connection.h"
#include "Firestore/core/src/remote/grpc_nanopb.h"
#include "Firestore/core/src/remote/grpc_stream.h"
#include "Firestore/core/src/remote/grpc_streaming_reader.h"
#include "Firestore/core/src/remote/grpc_unary_call.h"
#include "Firestore/core/src/util/async_queue.h"
#include "Firestore/core/src/util/error_apple.h"
#include "Firestore/core/src/util/executor.h"
#include "Firestore/core/src/util/hard_assert.h"
#include "Firestore/core/src/util/log.h"
#include "Firestore/core/src/util/statusor.h"
#include "absl/memory/memory.h"
#include "absl/strings/str_cat.h"

namespace firebase {
namespace firestore {
namespace remote {
namespace {

using core::DatabaseInfo;
using credentials::AuthCredentialsProvider;
using credentials::AuthToken;
using model::DocumentKey;
using model::Mutation;
using util::AsyncQueue;
using util::Executor;
using util::LogIsDebugEnabled;
using util::Status;
using util::StatusOr;

const auto kRpcNameCommit = "/google.firestore.v1.Firestore/Commit";
const auto kRpcNameLookup = "/google.firestore.v1.Firestore/BatchGetDocuments";

std::unique_ptr<Executor> CreateExecutor() {
  return Executor::CreateSerial("com.google.firebase.firestore.rpc");
}

std::string MakeString(grpc::string_ref grpc_str) {
  return {grpc_str.begin(), grpc_str.size()};
}

absl::string_view MakeStringView(grpc::string_ref grpc_str) {
  return {grpc_str.begin(), grpc_str.size()};
}

void LogGrpcCallFinished(absl::string_view rpc_name,
                         GrpcCall* call,
                         const Status& status) {
  LOG_DEBUG("RPC %s completed. Error: %s: %s", rpc_name, status.code(),
            status.error_message());
  if (LogIsDebugEnabled()) {
    auto headers =
        Datastore::GetAllowlistedHeadersAsString(call->GetResponseHeaders());
    LOG_DEBUG("RPC %s returned headers (allowlisted): %s", rpc_name, headers);
  }
}

}  // namespace

Datastore::Datastore(
    const DatabaseInfo& database_info,
    const std::shared_ptr<AsyncQueue>& worker_queue,
    std::shared_ptr<credentials::AuthCredentialsProvider> auth_credentials,
    std::shared_ptr<credentials::AppCheckCredentialsProvider>
        app_check_credentials,
    ConnectivityMonitor* connectivity_monitor,
    FirebaseMetadataProvider* firebase_metadata_provider)
    : worker_queue_{NOT_NULL(worker_queue)},
      app_check_credentials_{std::move(app_check_credentials)},
      auth_credentials_{std::move(auth_credentials)},
      rpc_executor_{CreateExecutor()},
      connectivity_monitor_{connectivity_monitor},
      grpc_connection_{database_info, worker_queue, &grpc_queue_,
                       connectivity_monitor_, firebase_metadata_provider},
      datastore_serializer_{database_info} {
  if (!database_info.ssl_enabled()) {
    GrpcConnection::UseInsecureChannel(database_info.host());
  }
}

void Datastore::Start() {
  rpc_executor_->Execute([this] { PollGrpcQueue(); });
}

void Datastore::Shutdown() {
  is_shut_down_ = true;

  // Order matters here: shutting down `grpc_connection_`, which will quickly
  // finish any pending gRPC calls, must happen before shutting down the gRPC
  // queue.
  grpc_connection_.Shutdown();

  // `grpc::CompletionQueue::Next` will only return `false` once `Shutdown` has
  // been called and all submitted tags have been extracted. Without this call,
  // `rpc_executor_` will never finish.
  grpc_queue_.Shutdown();
  // Drain the executor to make sure it extracted all the operations from gRPC
  // completion queue.
  rpc_executor_->ExecuteBlocking([] {});
}

void Datastore::PollGrpcQueue() {
  HARD_ASSERT(rpc_executor_->IsCurrentExecutor(),
              "PollGrpcQueue should only be called on the "
              "dedicated Datastore executor");

  void* tag = nullptr;
  bool ok = false;
  while (grpc_queue_.Next(&tag, &ok)) {
    auto completion = static_cast<GrpcCompletion*>(tag);
    // While it's valid in principle, we never deliberately pass a null pointer
    // to gRPC completion queue and expect it back. This assertion might be
    // relaxed if necessary.
    HARD_ASSERT(tag, "gRPC queue returned a null tag");
    completion->Complete(ok);
  }
}

std::shared_ptr<WatchStream> Datastore::CreateWatchStream(
    WatchStreamCallback* callback) {
  return std::make_shared<WatchStream>(
      worker_queue_, auth_credentials_, app_check_credentials_,
      datastore_serializer_.serializer(), &grpc_connection_, callback);
}

std::shared_ptr<WriteStream> Datastore::CreateWriteStream(
    WriteStreamCallback* callback) {
  return std::make_shared<WriteStream>(
      worker_queue_, auth_credentials_, app_check_credentials_,
      datastore_serializer_.serializer(), &grpc_connection_, callback);
}

void Datastore::CommitMutations(const std::vector<Mutation>& mutations,
                                CommitCallback&& callback) {
  ResumeRpcWithCredentials(
      // TODO(c++14): move into lambda.
      [this, mutations, callback](const StatusOr<AuthToken>& auth_token,
                                  const std::string& app_check_token) mutable {
        if (!auth_token.ok()) {
          callback(auth_token.status());
          return;
        }
        CommitMutationsWithCredentials(auth_token.ValueOrDie(), app_check_token,
                                       mutations, std::move(callback));
      });
}

void Datastore::CommitMutationsWithCredentials(
    const credentials::AuthToken& auth_token,
    const std::string& app_check_token,
    const std::vector<Mutation>& mutations,
    CommitCallback&& callback) {
  grpc::ByteBuffer message =
      MakeByteBuffer(datastore_serializer_.EncodeCommitRequest(mutations));

  std::unique_ptr<GrpcUnaryCall> call_owning = grpc_connection_.CreateUnaryCall(
      kRpcNameCommit, auth_token, app_check_token, std::move(message));
  GrpcUnaryCall* call = call_owning.get();
  active_calls_.push_back(std::move(call_owning));

  call->Start(
      // TODO(c++14): move into lambda.
      [this, call, callback](const StatusOr<grpc::ByteBuffer>& result) {
        LogGrpcCallFinished("CommitRequest", call, result.status());
        HandleCallStatus(result.status());

        // Response is deliberately ignored
        callback(result.status());

        RemoveGrpcCall(call);
      });
}

void Datastore::LookupDocuments(const std::vector<DocumentKey>& keys,
                                LookupCallback&& user_callback) {
  ResumeRpcWithCredentials(
      // TODO(c++14): move into lambda.
      [this, keys, user_callback](const StatusOr<AuthToken>& auth_token,
                                  const std::string& app_check_token) mutable {
        if (!auth_token.ok()) {
          user_callback(auth_token.status());
          return;
        }
        LookupDocumentsWithCredentials(auth_token.ValueOrDie(), app_check_token,
                                       keys, std::move(user_callback));
      });
}

void Datastore::LookupDocumentsWithCredentials(
    const credentials::AuthToken& auth_token,
    const std::string& app_check_token,
    const std::vector<DocumentKey>& keys,
    LookupCallback&& user_callback) {
  grpc::ByteBuffer message =
      MakeByteBuffer(datastore_serializer_.EncodeLookupRequest(keys));

  std::unique_ptr<GrpcStreamingReader> call_owning =
      grpc_connection_.CreateStreamingReader(
          kRpcNameLookup, auth_token, app_check_token, std::move(message));
  GrpcStreamingReader* call = call_owning.get();
  active_calls_.push_back(std::move(call_owning));

  // TODO(c++14): lambda captures using move.
  auto responses_callback =
      [this, user_callback](const std::vector<grpc::ByteBuffer>& result) {
        user_callback(datastore_serializer_.MergeLookupResponses(result));
      };

  auto close_callback = [this, user_callback, call](const util::Status& status,
                                                    bool callback_fired) {
    // Trigger user_callback with an error status
    if (!callback_fired) {
      user_callback(status);
    }
    if (!status.ok()) {
      LogGrpcCallFinished("BatchGetDocuments", call, status);
      HandleCallStatus(status);
    }
    RemoveGrpcCall(call);
  };

  call->Start(keys.size(), responses_callback, close_callback);
}

void Datastore::ResumeRpcWithCredentials(const OnCredentials& on_credentials) {
  // Auth/AppCheck may outlive Firestore
  std::weak_ptr<Datastore> weak_this{shared_from_this()};
  auto credentials = std::make_shared<CallCredentials>();

  auto done = [weak_this, credentials, on_credentials](
                  const absl::optional<StatusOr<AuthToken>>& auth,
                  const absl::optional<std::string>& app_check) {
    auto strong_this = weak_this.lock();
    if (!strong_this) {
      return;
    }

    std::lock_guard<std::mutex> lock(credentials->mutex);
    if (auth) {
      credentials->auth = *auth;
      credentials->auth_received = true;
    }

    if (app_check) {
      credentials->app_check = *app_check;
      credentials->app_check_received = true;
    }

    if (!credentials->auth_received || !credentials->app_check_received) {
      return;
    }

    const StatusOr<AuthToken>& auth_token = credentials->auth;
    const std::string& app_check_token = credentials->app_check;

    strong_this->worker_queue_->EnqueueRelaxed(
        [weak_this, auth_token, app_check_token, on_credentials] {
          auto strong_this = weak_this.lock();
          if (!strong_this) {
            return;
          }
          // In case this callback is invoked after Datastore has been shut
          // down.
          if (strong_this->is_shut_down_) {
            return;
          }
          on_credentials(auth_token, app_check_token);
        });
  };

  auth_credentials_->GetToken(
      [done](const StatusOr<AuthToken>& auth) { done(auth, absl::nullopt); });

  app_check_credentials_->GetToken(
      [done](const StatusOr<std::string>& app_check) {
        done(absl::nullopt, app_check.ValueOrDie());  // AppCheck never fails
      });
}

void Datastore::HandleCallStatus(const Status& status) {
  if (status.code() == Error::kErrorUnauthenticated) {
    auth_credentials_->InvalidateToken();
    app_check_credentials_->InvalidateToken();
  }
}

void Datastore::RemoveGrpcCall(GrpcCall* to_remove) {
  auto found = std::find_if(active_calls_.begin(), active_calls_.end(),
                            [to_remove](const std::unique_ptr<GrpcCall>& call) {
                              return call.get() == to_remove;
                            });
  HARD_ASSERT(found != active_calls_.end(), "Missing gRPC call");
  active_calls_.erase(found);
}

bool Datastore::IsAbortedError(const Status& error) {
  return error.code() == Error::kErrorAborted;
}

bool Datastore::IsPermanentError(const Status& error) {
  switch (error.code()) {
    case Error::kErrorOk:
      HARD_FAIL("Treated status OK as error");
    case Error::kErrorCancelled:
    case Error::kErrorUnknown:
    case Error::kErrorDeadlineExceeded:
    case Error::kErrorResourceExhausted:
    case Error::kErrorInternal:
    case Error::kErrorUnavailable:
      // Unauthenticated means something went wrong with our token and we need
      // to retry with new credentials which will happen automatically.
    case Error::kErrorUnauthenticated:
      return false;
    case Error::kErrorInvalidArgument:
    case Error::kErrorNotFound:
    case Error::kErrorAlreadyExists:
    case Error::kErrorPermissionDenied:
    case Error::kErrorFailedPrecondition:
    case Error::kErrorAborted:
      // Aborted might be retried in some scenarios, but that is dependant on
      // the context and should handled individually by the calling code.
      // See https://cloud.google.com/apis/design/errors
    case Error::kErrorOutOfRange:
    case Error::kErrorUnimplemented:
    case Error::kErrorDataLoss:
      return true;
  }

  HARD_FAIL("Unknown status code: %s", error.code());
}

bool Datastore::IsPermanentWriteError(const Status& error) {
  return IsPermanentError(error) && !IsAbortedError(error);
}

std::string Datastore::GetAllowlistedHeadersAsString(
    const GrpcCall::Metadata& headers) {
  static auto* allowlist = new std::unordered_set<std::string>{
      "date", "x-google-backends", "x-google-netmon-label", "x-google-service",
      "x-google-gfe-request-trace"};

  std::string result;
  auto end = allowlist->end();
  for (const auto& kv : headers) {
    if (allowlist->find(MakeString(kv.first)) != end) {
      absl::StrAppend(&result, MakeStringView(kv.first), ": ",
                      MakeStringView(kv.second), "\n");
    }
  }
  return result;
}

}  // namespace remote
}  // namespace firestore
}  // namespace firebase
