docs/main.md

Detailed Documentation: main.py (The Entry Point)

This file is the central hub of the application. It manages the server lifecycle, global security, and integrates the modular feature sets.

---

1. Environment and Security Initialization

At the very top of the file, we handle environment variables. This is critical because the subsequent imports of core_features and agent_features immediately initialize LLM objects that require an API key.

import os
from dotenv import load_dotenv

# Load environment variables BEFORE importing local modules
load_dotenv()

• Line 5: load_dotenv() reads the .env file. We do this before importing our routers (Lines 13-14) so that those modules find the GROQ_API_KEY in the environment the moment they are loaded.

---

2. FastAPI Application Instance

We define the app and its metadata, which powers the auto-generated documentation.

app = FastAPI(
    title="ToneForgeAI",
    description=(
        "AI-powered email assistant: formalize, translate, reply, "
        "negotiate, and parse legal emails."
    ),
)

• app: The global instance that registers all routes and middleware.
• Swagger UI: By visiting http://localhost:8000/docs, you can see this description and test every endpoint interactively.

---

3. Global Middleware (CORS)

Security logic to allow frontend-backend communication.

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

• CORS: Cross-Origin Resource Sharing.
• Line 26: allow_origins=["*"] allows any frontend (regardless of port or domain) to send requests. Without this, browsers block API calls for security.

---

4. Static Files and Main UI

The backend also serves as the web server for the frontend.

# Mount static files
app.mount("/static", StaticFiles(directory="static"), name="static")

@app.get("/", response_class=HTMLResponse)
async def get_index():
    with open("index.html", "r", encoding="utf-8") as f:
        return f.read()

• Line 33: app.mount maps the local static/ folder to the /static URL path. This is how the browser loads app.js and styles.css.
• Line 36: The root route (/) simply reads and returns your index.html file as the homepage.

---

5. Module Integration (The Routers)

This is the core of the modular architecture designed to prevent merge conflicts.

# Include the routers from our split files
app.include_router(core_router)
app.include_router(agent_router)

• Lines 43-44: Instead of writing logic here, we "mount" the routers from the other two files. This allows Developer 1 and Developer 2 to build independently in their own files without touching main.py.