// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef PERIDOT_BIN_CLOUD_PROVIDER_FIRESTORE_FIRESTORE_FIRESTORE_SERVICE_IMPL_H_
#define PERIDOT_BIN_CLOUD_PROVIDER_FIRESTORE_FIRESTORE_FIRESTORE_SERVICE_IMPL_H_

#include <memory>
#include <thread>

#include <lib/async/dispatcher.h>
#include <lib/callback/auto_cleanable.h>
#include <lib/fit/function.h>

#include "peridot/bin/cloud_provider_firestore/firestore/firestore_service.h"
#include "peridot/bin/cloud_provider_firestore/firestore/listen_call.h"
#include "peridot/bin/cloud_provider_firestore/grpc/read_stream_drainer.h"

namespace cloud_provider_firestore {

template <typename ResponseType>
using SingleResponseReader = grpc::ClientAsyncResponseReader<ResponseType>;

template <typename ResponseType>
struct SingleResponseCall {
  void set_on_empty(fit::closure on_empty) {
    this->on_empty = std::move(on_empty);
  }

  // Context used to make the remote call.
  grpc::ClientContext context;

  // Reader used to retrieve the result of the remote call.
  std::unique_ptr<SingleResponseReader<ResponseType>> response_reader;

  // Response of the remote call.
  ResponseType response;

  // Response status of the remote call.
  grpc::Status status;

  // Callback to be called upon completing the remote call.
  fit::function<void(bool)> on_complete;

  // Callback to be called when the call object can be deleted.
  fit::closure on_empty;
};

using DocumentResponseCall =
    SingleResponseCall<google::firestore::v1beta1::Document>;

using CommitResponseCall =
    SingleResponseCall<google::firestore::v1beta1::CommitResponse>;

using ListDocumentsResponseCall =
    SingleResponseCall<google::firestore::v1beta1::ListDocumentsResponse>;

using EmptyResponseCall = SingleResponseCall<google::protobuf::Empty>;

using RunQueryCall =
    ReadStreamDrainer<grpc::ClientAsyncReaderInterface<
                          google::firestore::v1beta1::RunQueryResponse>,
                      google::firestore::v1beta1::RunQueryResponse>;

// Implementation of the FirestoreService interface.
//
// This class is implemented as a wrapper over the Firestore connection. We use
// a polling thread to wait for request completion on the completion queue and
// expose a callback-based API to the client.
class FirestoreServiceImpl : public FirestoreService {
 public:
  FirestoreServiceImpl(std::string server_id, async_dispatcher_t* dispatcher,
                       std::shared_ptr<grpc::Channel> channel);

  ~FirestoreServiceImpl() override;

  // FirestoreService:
  const std::string& GetDatabasePath() override { return database_path_; }

  const std::string& GetRootPath() override { return root_path_; }

  void GetDocument(
      google::firestore::v1beta1::GetDocumentRequest request,
      std::shared_ptr<grpc::CallCredentials> call_credentials,
      fit::function<void(grpc::Status, google::firestore::v1beta1::Document)>
          callback) override;

  void ListDocuments(
      google::firestore::v1beta1::ListDocumentsRequest request,
      std::shared_ptr<grpc::CallCredentials> call_credentials,
      fit::function<void(grpc::Status,
                         google::firestore::v1beta1::ListDocumentsResponse)>
          callback) override;

  void CreateDocument(
      google::firestore::v1beta1::CreateDocumentRequest request,
      std::shared_ptr<grpc::CallCredentials> call_credentials,
      fit::function<void(grpc::Status, google::firestore::v1beta1::Document)>
          callback) override;

  void DeleteDocument(google::firestore::v1beta1::DeleteDocumentRequest request,
                      std::shared_ptr<grpc::CallCredentials> call_credentials,
                      fit::function<void(grpc::Status)> callback) override;

  void Commit(google::firestore::v1beta1::CommitRequest request,
              std::shared_ptr<grpc::CallCredentials> call_credentials,
              fit::function<void(grpc::Status,
                                 google::firestore::v1beta1::CommitResponse)>
                  callback) override;

  void RunQuery(google::firestore::v1beta1::RunQueryRequest request,
                std::shared_ptr<grpc::CallCredentials> call_credentials,
                fit::function<void(
                    grpc::Status,
                    std::vector<google::firestore::v1beta1::RunQueryResponse>)>
                    callback) override;

  std::unique_ptr<ListenCallHandler> Listen(
      std::shared_ptr<grpc::CallCredentials> call_credentials,
      ListenCallClient* client) override;

  void ShutDown(fit::closure callback) override;

 private:
  void SetUpContext(grpc::ClientContext* context,
                    std::shared_ptr<grpc::CallCredentials> call_credentials);

  void Poll();

  const std::string server_id_;
  const std::string database_path_;
  const std::string root_path_;

  async_dispatcher_t* const dispatcher_;
  std::thread polling_thread_;

  std::unique_ptr<google::firestore::v1beta1::Firestore::Stub> firestore_;
  grpc::CompletionQueue cq_;

  // Single-request single-response calls.
  callback::AutoCleanableSet<DocumentResponseCall> document_response_calls_;
  callback::AutoCleanableSet<CommitResponseCall> commit_response_calls_;
  callback::AutoCleanableSet<ListDocumentsResponseCall>
      list_documents_response_calls_;
  callback::AutoCleanableSet<EmptyResponseCall> empty_response_calls_;

  // Single-request stream-response calls.
  callback::AutoCleanableSet<RunQueryCall> run_query_calls_;

  // Stream-request stream-response calls.
  callback::AutoCleanableSet<ListenCall> listen_calls_;
};

}  // namespace cloud_provider_firestore

#endif  // PERIDOT_BIN_CLOUD_PROVIDER_FIRESTORE_FIRESTORE_FIRESTORE_SERVICE_IMPL_H_