Client | HTTP Gateway Wrapper

The client_http module acts as a lightweight REST interface wrapper for operations outside the scope of the FIX protocol.

Overview

While the bulk of low-latency trading traffic routes over FIX, operations like User Registration, Profile Management, and downloading deep historical datasets securely utilize this HTTP gateway. This module abstracts away raw socket connections and JSON serialization.

Key Responsibilities

• Establish secure REST connections to the exchange_api gateway.
• Serialize C++ domain structs into JSON requests.
• Parse incoming JSON responses into C++ domain structs.
• Provide a non-blocking asynchronous API to prevent UI freezes.

Architecture

graph LR
    classDef net fill:#1f2833,stroke:#66fcf1,stroke-width:2px,color:white;
    classDef data fill:#2d142c,stroke:#ee4540,stroke-width:2px,color:white;
 
    subgraph "client_http Module"
        API[ApiClient]:::net --> |POST /api/register| HTTP[httplib::Client]:::net
        JSON[JSON Serializer]:::data --> API
    end
 
    subgraph "Exchange Server"
        GATEWAY(exchange_api) 
    end
 
    HTTP <-->|REST over TCP| GATEWAY

Class Diagram

classDiagram
    class ApiClient {
        +registerUser(username, password) : std::future~RegisterResponse~
        +fetchProfile(token) : std::future~ProfileResponse~
        -m_host: string
        -m_port: int
        -m_client: httplib::Client
    }
    
    class RegisterResponse {
        +success: bool
        +client_id: string
        +error_msg: string
    }
    
    class Serializer {
        +toJson(username, password) : nlohmann::json
        +fromJson(string) : RegisterResponse
    }
 
    ApiClient *--> Serializer : Uses
    ApiClient ..> RegisterResponse : Returns

Component Responsibilities

Component	Description
**ApiClient**	The primary public surface. Wraps .get() and .post() operations, abstracting endpoints into semantic C++ methods.
**Serializer**	Contains static methods that utilize nlohmann/json to translate to/from API payload strings.
**RegisterResponse**	A Plain-Old-Data (POD) struct representing the status of an account creation request.

Critical Design Conventions

• Asynchronous Interface: All network calls return std::future<T> or utilize callbacks to ensure the client_app render loop is never blocked by network latency or timeouts.
• Header-Only Backbone: Built cleanly on top of cpp-httplib and nlohmann/json to ensure cross-platform compatibility without heavy binary linking.