realm-js/src/rpc.hpp

////////////////////////////////////////////////////////////////////////////
//
// Copyright 2016 Realm Inc.
//
// 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.
//
////////////////////////////////////////////////////////////////////////////

#pragma once

#include <functional>
#include <future>
#include <thread>

#include "concurrent_deque.hpp"
#include "json.hpp"
#include "jsc_types.hpp"
#include "jsc_protected.hpp"

namespace realm {

class ObjectSchema;

namespace rpc {

using json = nlohmann::json;

using RPCObjectID = u_int64_t;
using RPCRequest = std::function<json(const json)>;

class RPCWorker {
  public:
    RPCWorker();
    ~RPCWorker();

    void add_task(std::function<json()>);
    json pop_task_result();
    void try_run_task();
    void stop();

  private:
    bool m_stop = false;
    std::thread m_thread;
    ConcurrentDeque<std::packaged_task<json()>> m_tasks;
    ConcurrentDeque<std::future<json>> m_futures;
};

class RPCServer {
  public:
    RPCServer();
    ~RPCServer();
    json perform_request(std::string name, const json &args);

  private:
    JSGlobalContextRef m_context;
    std::mutex m_request_mutex;
    std::map<std::string, RPCRequest> m_requests;
    std::map<RPCObjectID, js::Protected<JSObjectRef>> m_objects;
    std::map<RPCObjectID, js::Protected<JSObjectRef>> m_callbacks;
    // The key here is the same as the value in m_callbacks. We use the raw pointer as a key here,
    // because protecting the value in m_callbacks pins the function object and prevents it from being moved
    // by the garbage collector upon compaction.
    std::map<JSObjectRef, RPCObjectID> m_callback_ids;
    ConcurrentDeque<json> m_callback_results;
    RPCObjectID m_session_id;
    RPCWorker m_worker;

    static void run_callback(JSContextRef, JSObjectRef, JSObjectRef, size_t, const JSValueRef[], jsc::ReturnValue &);

    RPCObjectID store_object(JSObjectRef object);

    json serialize_json_value(JSValueRef value);
    JSValueRef deserialize_json_value(const json dict);

    json serialize_object_schema(const ObjectSchema &objectSchema);
};

} // rpc
} // realm