Contact person: Business Client

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Location: Wilmington, United States

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"I have a Flutter mobile app under development for a weight-loss project.
The app will include:

Bluetooth integration with a smart body-fat scale

Firebase Authentication

Firestore database

User measurement dashboard (weight, body fat %, etc.)

Basic UI screens

I need a developer to add three additional features on top of the existing codebase.
This is not a full app build; only additional modules.

The app is part of a structured 30-day weight-loss challenge, activated through codes inside each scale package.

Feature 1 — One-Time Activation Code System

Each purchased scale package contains a unique activation code that unlocks the 30-day challenge inside the app.

Requirements:

Build an Activation Screen where users enter a 6–10 character code

Validate the code against a Firestore collection

Unlock the challenge only if the code is valid and unused

Mark code as used and store userId + timestamp

Firestore structure (suggested):

Collection: activationCodes

Fields: code, used, userId, createdAt

Build a CSV import mechanism so I can upload new code batches whenever new inventory arrives

A simple cloud function or upload script is enough

No complex admin dashboard required

Feature 2 — Human Coach Chat ([login to view URL] Integration)

Add a “Mindset Coach” chat screen inside the app.

Requirements:

Load a [login to view URL] widget via WebView or official SDK integration

Autofill Firebase user details (email or UID) into Tawk attributes if possible

Add a “Book Kickoff Session” button—opens a Calendly/[login to view URL] link externally

No admin panel needed; coaches reply from the existing Tawk dashboard

This is a straightforward WebView integration within a dedicated Flutter screen.

Feature 3 — AI Diet Coach (GPT-4 / GPT-4o Integration)

Add an AI-based diet coach inside the app.
The AI must be trained with my predefined nutritional guidelines and behavior rules.

Frontend (Flutter):

Chat interface (message bubbles, scroll, loading indicators)

Connect to backend API

Save chat history per user in Firestore

Retrieve user metrics (weight, body fat %, etc.) from Firestore to customize the answer

Backend (Node.js, Vercel or AWS):

Build one endpoint: /diet-chat

Input:

User message

Firebase user ID

User body metrics from Firestore

Apply my provided dietitian rulebook and prompt structure
(AI must follow these rules to behave like a structured weight-loss guide)

Call the OpenAI API with these rules

Return formatted responses

Add basic safety filtering (no medical diagnosis)

Hosting:

Deploy on Vercel or AWS Lambda using my available cloud credits

Must be lightweight and cost-efficient

No admin interface needed.

Deliverables

Updated Flutter project including:

Activation code system

[login to view URL] mindset coach screen

AI Diet Coach chat screen

Node.js backend deployed and connected

Firestore integration for activation codes and chat history

A working APK for testing

Clean, maintainable code with comments

Required Skills

Flutter and Dart

Firebase Auth and Firestore

WebView integration

Node.js (Express or serverless)

OpenAI API usage

Experience with chat interfaces

Ability to work inside an existing codebase" (client-provided description)