CLAUDE: platform/client/ (@mattermost/client)

Purpose

• Implements the Client4 HTTP layer and WebSocket client used by all Mattermost web apps and plugins.
• Source of truth for API endpoint definitions and low-level networking helpers.

Structure

• src/client4.ts – REST endpoints, auth handling, retries.
• src/websocket.ts – WebSocket manager for real-time events.
• src/helpers.ts / errors.ts – shared logic for response parsing and error types.

Client4 Usage

Singleton HTTP client for all Mattermost API requests. Methods return Promise<ClientResponse<T>>:

interface ClientResponse<T> {
    response: Response;  // Fetch Response object
    headers: Headers;    // Response headers
    data: T;            // Parsed response data
}

Usage Rules

1. Actions Only: Client4 should only be called from Redux actions, never directly in components.
2. Error Handling: Always handle errors appropriately.

Adding New Endpoints

Add new API methods to client4.ts. Keep signatures Promise-based.

getSomething = (id: string) => {
    return this.doFetch<SomethingType>(
        `${this.getSomethingRoute(id)}`,
        {method: 'get'},
    );
};

Error Handling

• Throw ClientError (see errors.ts) with enough context.
• Include forceLogoutIfNecessary logic upstream in calling actions; do not couple that here.

WebSocket Client

websocket.ts provides real-time event handling, connection management, and automatic reconnection. Accessed via WebSocketClient wrapper in web app.

Guidelines

• Follow webapp/STYLE_GUIDE.md → Networking.
• Each new server API must be added here first, including TypeScript types and tests.
• Never reference React or browser globals—this package must run in Node.