backend/README.md

Document Chat Backend

This is the FastAPI backend for the Document Chat application that enables document uploading, processing, and chat-based Q&A functionality.

Project Structure

backend/
├── app/
│   ├── __init__.py
│   ├── main.py          # FastAPI application and route definitions
│   ├── models.py        # Pydantic models for request/response validation
│   ├── services/
│   │   ├── __init__.py
│   │   ├── document_processor.py    # Document processing and chunking
│   │   ├── vector_store.py         # Vector storage and similarity search
│   │   └── chat_service.py         # OpenAI chat completion handling
│   └── dependencies.py   # FastAPI dependencies and shared resources
└── requirements.txt      # Python package dependencies

Setup

1. Create a virtual environment:

python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

2. Install dependencies:

pip install -r requirements.txt

3. Create a .env file in the root directory with your OpenAI API key:

OPENAI_API_KEY=your_api_key_here

4. Run the development server:

uvicorn app.main:app --reload

The API will be available at http://localhost:8000

API Endpoints

• POST /upload

  • Upload PDF or TXT files for processing
  • Returns a session ID for subsequent chat interactions

• POST /chat

  • Send messages to chat with the uploaded document
  • Requires a session ID from a previous upload

Development

• The services directory contains the core business logic:

  • document_processor.py: Handles file uploads and text chunking
  • vector_store.py: Manages document embeddings and similarity search
  • chat_service.py: Interfaces with OpenAI for chat completions

• models.py defines the data structures using Pydantic

• main.py contains the FastAPI application and route handlers

• dependencies.py manages shared resources and dependencies

Requirements

See requirements.txt for a full list of Python dependencies. Key packages include:

• FastAPI
• OpenAI
• PyPDF2
• python-multipart
• python-dotenv
• uvicorn

To create the directory structure, you can run these commands:

```bash
mkdir -p backend/app/services
touch backend/app/__init__.py
touch backend/app/main.py
touch backend/app/models.py
touch backend/app/dependencies.py
touch backend/app/services/__init__.py
touch backend/app/services/document_processor.py
touch backend/app/services/vector_store.py
touch backend/app/services/chat_service.py
touch backend/requirements.txt

This will create all the necessary files and directories in the structure you specified. The README.md provides a clear overview of the project structure, setup instructions, and key components for developers who will work with the backend.