Pascal Engeler
Blackjack

Repository

// All request types of your imlementation
enum RequestType {
    join_game,
    start_game,
    make_bet,
    hit,
    stand,
};

class client_request : public serializable {
protected:
    RequestType _type;   // stores the type of request, such that the receiving end knows how to deserialize it
    std::string _req_id; // unique id of this request
    std::string _player_id; // id of the player sending the request
    std::string _game_id;   // id of the game this request is for

    ...
private:
    // for deserializing RequestType (contains mappings from string to RequestType)
    // IMPORTANT: Add mapping for your own RequestTypes to this unordered_map
    static const std::unordered_map<std::string, RequestType> _string_to_request_type;

    // for serializing RequestType (contains mappings from RequestType to string)
    // IMPORTANT: Add mapping for your own RequestTypes to this unordered_map
    static const std::unordered_map<RequestType, std::string> _request_type_to_string;

public:
    // DESERIALIZATION: Attempts to create the specific client_request from the provided json.
    static client_request* from_json(const rapidjson::Value& json);

    // SERIALIZATION: Serializes the client_request into a json object that can be sent over the network
    virtual void write_into_json(rapidjson::Value& json, rapidjson::Document::AllocatorType& allocator) const override;
};
// Implementation in the base-class client_request
void client_request::write_into_json(rapidjson::Value &json,
                                     rapidjson::MemoryPoolAllocator<rapidjson::CrtAllocator> &allocator) const {
    // Look up string value of this client_request's RequestType and store it in the json document
    rapidjson::Value type_val(_request_type_to_string.at(this->_type).c_str(), allocator);
    json.AddMember("type", type_val, allocator);

    // Save player_id in the JSON document
    rapidjson::Value player_id_val(_player_id.c_str(), allocator);
    json.AddMember("player_id", player_id_val, allocator);

    // Save game_id in the JSON document
    rapidjson::Value game_id_val(_game_id.c_str(), allocator);
    json.AddMember("game_id", game_id_val, allocator);
    ...
}

##### Deserialization

The deserialization of `client_request` JSONs always goes through the `from_json(...)` function of the `client_request` class. In this function, the "type" field, stored in the JSON, is inspected to determine, which subclass should be called to perform the deserialization:

```cpp
if (json.HasMember("type") && json["type"].IsString()) {
        // Get the RequestType stored as a string in the JSON
        const std::string type = json["type"].GetString();
        // Lookup the actual RequestType per string from a pre-defined unordered_map
        const RequestType request_type = client_request::_string_to_request_type.at(type);

        // Call the correct from_json() specialization
        if (request_type == RequestType::play_card) {
            return play_card_request::from_json(json);
        }
        else if (request_type == RequestType::draw_card) {
            return draw_card_request::from_json(json);
        }
        else if (...) {
            ...
        } else {
            throw BlackjackException("Encountered unknown ClientRequest type " + type);
        }
    }
    throw BlackjackException("Could not determine type of ClientRequest. JSON was:\n" + json_utils::to_string(&json));
bool game_instance::start_game(player* player, std::string &err) {
    modification_lock.lock();   // make sure only one request can modify the game_state at a time

    // Try to start the game
    if (_game_state->start_game(err)) {
        // create a full_state_response (subclass of server_response) with the full game_state inside
        full_state_response state_update_msg = full_state_response(this->get_id(), *_game_state);
        // BROADCAST new game_state to all other players
        server_network_manager::broadcast_message(state_update_msg, _game_state->get_players(), player);

        modification_lock.unlock(); // allow other threads to modify the game_state
        return true;
    }
    modification_lock.unlock();
    return false;
}
target_compile_definitions(Blackjack-server PRIVATE PRINT_NETWORK_MESSAGES=1)
#include "source/general/serialization/json_utils.h"
#include "rapidjson/include/rapidjson/document.h"

...
// Create a request to serialize
join_game_request* req = new join_game_request(player->get_id(), player->get_player_name());

// serialize the request object
rapidjson::Document* req_json = req->to_json();

// print serialization to the console.
std::cout << json_utils::to_string(req_json) << std::endl;
class game_state : public unique_serializable {
public:

...

private:
    std::vector<player*> _players;
    shoe* _shoe;
    hand* _dealers_hand;
    serializable_value<bool>* _is_started;
    serializable_value<bool>* _is_finished;
    serializable_value<int>* _round_number;
    serializable_value<int>* _current_player_idx;
    serializable_value<int>* _starting_player_idx; // very possible this variable is NOT needed

    // from_diff constructor
    game_state(std::string id);

    // deserialization constructor
    game_state(
            std::string id,
            std::vector<player*>& players,
            shoe* shoe,
            hand* dealers_hand,
            serializable_value<bool>* is_started,
            serializable_value<bool>* is_finished,
            serializable_value<int>* round_number,
            serializable_value<int>* current_player_idx,
            serializable_value<int>* starting_player_idx);

    // returns the index of 'player' in the '_players' vector
    int get_player_index(player* player) const;
public:
    game_state();

    ...
    // SERIALIZATION
    virtual void write_into_json(rapidjson::Value& json, rapidjson::Document::AllocatorType& allocator) const override;
    // DESERIALIZATION
    static game_state* from_json(const rapidjson::Value& json);
};