Nutrilytics Backend API

This repository contains the backend server for Nutrilytics, a mobile application for logging meals and tracking nutrition. This API handles user authentication, meal data storage, and meal generation using FastAPI and Google Firestore.

The API also integrates with Redis for caching Firebase ID tokens and generated meal drafts, significantly improving performance and reducing redundant computation.

It uses another one of my projects: the meal-generator Python library. Check it out!

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Features

• User Authentication: Secure user management via Firebase Authentication.
• Meal Logging: Full CRUD (Create, Read, Update, Delete) operations for user meals.
• AI-Powered Meal Generation: Asynchronously generate detailed meal nutritional profiles from simple text descriptions.
• Secure Data Storage: All user data is securely stored and tied to individual user accounts in Firestore.
• Redis Caching: Speeds up authentication checks and meal draft polling by caching Firebase tokens and in-progress meal generations.

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Tech Stack

• Framework: FastAPI
• Database: Google Firestore
• Authentication: Firebase Authentication
• Caching: Redis (for token validation and meal draft caching)
• Server: Uvicorn
• Data Validation: Pydantic
• AI: Google Gemini

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Local Setup

To get the project running locally, follow these steps:

1. Prerequisites

• Python 3.8+
• Redis server running locally or remotely
• A Google Firebase project with Firestore and Authentication enabled
• A Google AI Studio API Key for Gemini

2. Clone & Setup

# Clone the repository
git clone https://github.com/TomMcKenna1/nutrilytics-backend
cd nutrilytics-backend

# Install dependencies
pip install -r requirements.txt

3. Environment Setup

• Download your service account key from the Firebase console, rename it to service-account.json, and place it in the project's root directory.
• Create a .env file in the root directory and add your project credentials:

Sample .env file:

GOOGLE_APPLICATION_CREDENTIALS="service-account.json"
FIREBASE_PROJECT_ID="your-firebase-project-id"
GEMINI_API_KEY="your-google-ai-studio-api-key"
REDIS_URL="redis://localhost:6379"  # or your hosted Redis URL

4. Run the Server

uvicorn app.main:app --reload

The API will be available at: http://127.0.0.1:8000

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API Endpoints

All v1 endpoints are prefixed with /api/v1.
Authentication is handled via Firebase ID tokens passed as a Bearer token in the Authorization header.
Redis is used internally to cache validated tokens and reduce the number of external verification requests.

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Root

GET /
Description: A welcome message to verify that the API is running.

Response 200 OK

{
  "message": "Welcome to the Meal Tracker API"
}

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Authentication

Base path: /api/v1/auth

GET /api/v1/auth/me

Description: Retrieves the profile of the currently authenticated user. Validated Firebase tokens are cached in Redis to speed up future authentication.

Response 200 OK

{
  "uid": "user_firebase_uid",
  "email": "user@example.com",
  "name": "example"
}

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Meal Drafts

Base path: /api/v1/meal_drafts

POST /api/v1/meal_drafts/

Description: Starts a background task to generate a meal from a user's description. Results are cached in Redis and can be polled.

Status Code: 202 ACCEPTED
Request Body

{
  "description": "A bowl of spaghetti bolognese"
}

Response 202 ACCEPTED

{
  "draftId": "a_unique_draft_id"
}

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GET /api/v1/meal_drafts/{draft_id}

Description: Poll to check the status of a meal generation task. Cached in Redis until complete.

Pending State Response

{
  "status": "pending",
  "uid": "user_firebase_uid",
  "meal": null
}

Complete State Response

{
  "status": "complete",
  "uid": "user_firebase_uid",
  "meal": {
    "name": "Spaghetti Bolognese",
    "calories": 600,
    "protein": 30,
    "carbohydrates": 70,
    "fat": 20,
    ...
  }
}

Errors:

• 403 Forbidden
• 404 Not Found

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DELETE /api/v1/meal_drafts/{draft_id}

Description: Deletes a meal draft from the Redis cache.

Status Code: 204 NO CONTENT
Errors:

• 403 Forbidden
• 404 Not Found

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Meals

Base path: /api/v1/meals

POST /api/v1/meals/

Description: Promotes a completed meal draft to be saved in the Firestore database.

Status Code: 201 CREATED
Request Body

{
  "draft_id": "the_completed_draft_id"
}

Response 201 CREATED

Returns the completed Meal, timestamp and Firestore ID.

Errors:

• 403 Forbidden
• 404 Not Found
• 409 Conflict

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GET /api/v1/meals/{meal_id}

Description: Retrieves a specific meal by its Firestore document ID.

Response 200 OK

Returns the requested Meal, timestamp and Firestore ID.

Errors:

• 403 Forbidden
• 404 Not Found

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Contact

For any questions or contributions, please reach out via GitHub Issues.

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