fullstack-integration

What I do

• Connect Clojure backend APIs to React frontend
• Design WebSocket communication patterns
• Set up API contracts and type definitions
• Configure CORS and proxy settings
• Implement authentication and session management
• Debug integration issues across the stack

When to use me

Use me when integrating full stack applications, especially when:

• Adding new API endpoints and frontend calls
• Setting up WebSocket connections
• Configuring CORS and proxy settings
• Managing authentication and session state
• Debugging communication between backend and frontend

API contract patterns

• Define API interfaces in shared types file
• Use discriminated unions for response types
• Document endpoints in /docs/notes
• Keep payload keys in snake_case on both sides
• Validate input on backend, trust on frontend

Example types

// types/api.ts
export type WsMessage =
  | { op: "tick"; tick: number; agents: Agent[] }
  | { op: "agent-update"; id: number; x: number; y: number }
  | { op: "error"; message: string };

export interface Agent {
  id: number;
  x: number;
  y: number;
  type: "villager" | "shrine";
}

export interface ApiResponse<T> {
  success: boolean;
  data: T;
  error?: string;
}

HTTP patterns

• Use fetch or axios for API calls
• Implement retry logic for failed requests
• Abort requests on component unmount
• Cache responses with React Query or SWR
• Handle loading and error states in UI

WebSocket patterns

// Use WSClient helper
import { WSClient } from "./ws";

const ws = new WSClient("ws://localhost:3000/ws");

// Send messages
ws.send({ op: "reset", seed: 42 });

// Handle messages
ws.on("tick", (data) => {
  setAgents(data.agents);
});

// Clean up
return () => ws.close();

Clojure backend patterns

• Use reitit for HTTP routing
• Provide JSON responses with cheshire
• Include CORS headers: {"access-control-allow-origin" "*"}
• Send WS ops with :op keyword: {:op "tick" :tick 42}
• Validate input before processing

CORS configuration

;; Backend HTTP handler
(defn json-resp [status body]
  {:status status
   :headers {"content-type" "application/json"
             "access-control-allow-origin" "*"
             "access-control-allow-methods" "GET, POST, PUT, DELETE, OPTIONS"
             "access-control-allow-headers" "content-type"}
   :body (json/generate-string body)})

Vite proxy configuration

// vite.config.ts
export default defineConfig({
  server: {
    proxy: {
      "/api": "http://localhost:3000",
      "/ws": {
        target: "ws://localhost:3000",
        ws: true
      }
    }
  }
});

Environment management

• Backend: Use env vars or CLI flags (not hardcoded)
• Frontend: Use import.meta.env.VITE_* for client-side vars
• Share environment config in /docs/notes
• Never commit secrets or API keys

Authentication patterns

• Backend: Generate JWT or session tokens
• Frontend: Store token in localStorage or cookie
• Include token in Authorization header: Bearer {token}
• Handle token expiration and refresh

Debugging integration

• Log WS payloads on both sides with structure
• Use browser DevTools Network tab for HTTP
• Check console for WebSocket connection errors
• Verify CORS headers in DevTools
• Test endpoints with curl before frontend integration

State synchronization

• Backend sends state updates via WebSocket
• Frontend keeps local state in sync with server
• Use optimistic updates for better UX
• Revert optimistic updates on server error
• Implement conflict resolution for concurrent updates

Error handling

• Backend: Return structured errors {:error "message"}
• Frontend: Display user-friendly error messages
• Log full errors on backend, short messages on frontend
• Implement retry for transient errors
• Show fallback UI for failed requests

Testing integration

• Test backend endpoints independently (curl, Postman)
• Test frontend with mock responses (MSW)
• Test full stack with docker-compose
• Record WS payloads for manual verification
• Document smoke-test flows in PRs