RAG App (FastAPI + React/Vite)

Full‑stack RAG playground with a FastAPI backend and a React (Vite) frontend. Backend uploads documents to S3 and proxies chat requests to a Modal endpoint.

Tech Stack

• Frontend: React 19 + Vite
• Backend: FastAPI (served via uvicorn)
• Storage: AWS S3

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Prerequisites

• Conda (Miniconda or Anaconda)
• Node.js 18+ and npm
• AWS credentials with access to the target S3 bucket

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1) Clone and install

git clone <your-repo-url>
cd RagApp

# Python deps via Conda
conda env create -f environment.yml
conda activate rag_app

# Frontend deps
npm install

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2) Configure environment

Create a .env file in the project root with:

AWS_S3_BUCKET_NAME=your-bucket
AWS_S3_REGION=your-region
AWS_ACCESS_KEY_ID=your-access-key-id
AWS_SECRET_ACCESS_KEY=your-secret-access-key

MODAL_UPLOAD_URL=https://your-modal-upload-endpoint
MODAL_CHAT_URL=https://your-modal-chat-endpoint
MODAL_API_TOKEN=your-modal-api-token

Notes:

• CORS is currently allowed for http://localhost:5174 and http://127.0.0.1:5174 in the backend. Run Vite on port 5174 to avoid CORS errors.

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3) Run the app

• Backend (FastAPI via uvicorn):

npm start

This runs uvicorn main:app (default at http://127.0.0.1:8000).

• Frontend (Vite on port 5174):

npm run dev -- --port 5174

Vite dev server will be available at http://localhost:5174.

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API Overview

• POST /api/upload

  • Form‑data: file (document to upload)
  • Action: uploads file to S3 and calls MODAL_UPLOAD_URL
  • Returns: { session_id, filename }

• POST /api/chat

  • JSON body: { "session_id": string, "message": string }
  • Action: forwards to MODAL_CHAT_URL with { session_id, questions: [message] }
  • Returns: Modal response JSON

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Project Scripts

{
  "start": "uvicorn main:app",
  "dev": "vite",
  "build": "vite build",
  "preview": "vite preview"
}

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Repo structure

RagApp/
├─ main.py                 # FastAPI app (S3 upload, chat proxy)
├─ environment.yml         # Conda environment (python + deps)
├─ package.json            # Frontend scripts and deps
├─ src/                    # React app source
├─ public/                 # Static assets
├─ vite.config.js          # Vite config
└─ README.md

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Troubleshooting

• If you see CORS errors, ensure the frontend runs on 5174 or update allowed origins in main.py.
• Ensure your AWS creds and bucket/region are correct; main.py constructs public S3 URLs as https://{bucket}.s3.{region}.amazonaws.com/{key}.
• Modal endpoints must accept the shapes documented above and the Authorization: Bearer <MODAL_API_TOKEN> header.

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License

MIT (or your preferred license)