Health‑AI Fitness App — Cross‑Platform with React Native, GenKit & Firebase

An intelligent fitness companion that generates adaptive workout plans, personalized health insights, and conversational data intake—Cross-platform using React Native, an AI engine powered by GenKit, and Firebase backend services.

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🧠 Project Overview

An end‑to‑end, AI-powered fitness app designed to:

• Dynamically build user profiles through intelligent, chat-style + traditional check-mark based questionnaires.
• Generate adaptive, goal-driven workout plans that evolve with user progress.
• Provide personalized health insights and notifications based on user data and habits.
• Offer a conversational interface for seamless data intake.
• Integrate securely with Firebase for authentication, storage, analytics, and AI logic.
• Plot personalized workout and meal schedules on a daily calendar view for better planning.
• Include reminders and push notifications to improve adherence to plans.
• Implement a sophisticated algorithm considering health standards like the PAR-Q+ questionnaire and established fitness guidelines.
• Aim for future migration to native development for maximum performance and deep integration with device sensors and OS-level features.

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🔧 Tech Stack

Layer	Technology
Front-end	React Native (iOS & Android)
AI Engine	GenKit (AI orchestration, structured JSON)
Backend	Firebase Auth, Firestore, Analytics
UI Components	GiftedChat, FlatList, Calendar libraries

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📌 Core Features & Code Snippets

1. Adaptive Questionnaire UI

Collects user data such as weight, goals, and detailed health screening questions based on PAR-Q+ standards:

const questions = [
  { id: 'weight', prompt: "What's your current weight?" },
  { id: 'goal', prompt: "What's your main fitness goal?" },
  { id: 'parq', prompt: "Do you have any known health issues that affect exercise?" },
];

const handleAnswer = async (id, answer) => {
  console.log('Answer:', id, answer);
  await firestore.collection('profiles').doc(user.uid)
    .set({ [id]: answer }, { merge: true });
  proceedToNextQuestion();
};

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2. AI‑Driven Complex Workout & Nutrition Algorithm

Constructs personalized plans considering user goals, health constraints, and standards:

async function generatePlan(profile) {
  const prompt = `
Design a workout and meal plan:
- Age: ${profile.age}
- Weight: ${profile.weight}
- Goal: ${profile.goal}
- Health issues: ${profile.parq}

Include a full day's schedule mapped to time slots, with calories, macros, and exercise details. Ensure all exercises are safe given any health limitations and follow ACSM and PAR-Q+ standards.`;

  const response = await genkit.call({ model: 'AI-Model_from_a _popular_provider', prompt });
  try {
    return JSON.parse(response.text);
  } catch (e) {
    console.error('JSON parse error:', e);
    return null;
  }
}

3. Calendar Integration for Daily Planning

Maps the generated plan onto a calendar UI, making adherence easy:

<Calendar
  markedDates={
    plan.days.reduce((acc, day) => {
      acc[day.date] = { marked: true };
      return acc;
    }, {})
  }
  onDayPress={day => showPlanForDay(day.date)}
/>

4. Notifications for Adherence

Schedules reminders to improve consistency:

import PushNotification from 'react-native-push-notification';

PushNotification.localNotificationSchedule({
  message: "Time for your workout!",
  date: new Date(Date.now() + 60 * 1000) // triggers in 1 minute
});

5. Conversational Data Intake

Uses chat UI for logs:

import { GiftedChat } from 'react-native-gifted-chat';

const onSend = async newMessages => {
  setMessages(prev => GiftedChat.append(prev, newMessages));
  const text = newMessages[0].text;
  await firestore.collection('logs').add({
    userID: user.uid,
    text,
    timestamp: firebase.firestore.FieldValue.serverTimestamp()
  });
};

6. Firebase Authentication & Data Storage

Authenticates and manages user data:

import auth from '@react-native-firebase/auth';

const signIn = async (email, pass) => {
  try {
    await auth().signInWithEmailAndPassword(email, pass);
  } catch (err) {
    console.error('Auth error:', err);
  }
};

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🛠️ Complex Algorithm Insights

• Factors in user biometrics, goals, and PAR-Q+ health constraints.
• Matches workouts and meals to ACSM guidelines for safety and efficacy.
• Dynamically adjusts caloric intake and workout intensity over time.
• Maps activities into time slots to produce a full-day schedule.
• Handles JSON parsing errors robustly.

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🎨 UI/UX Highlights

• Clean questionnaire with progress indicators.
• Calendar view showing planned activities.
• Conversational UI for logs and progress updates.
• Visual tracking for calories, macros, and exercise history.
• Smooth navigation between daily schedules and progress charts.

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🚀 Future Enhancements

• Transition from React Native to fully native Swift (iOS) and Kotlin (Android) apps for:

  • Deeper hardware integration (sensors, health APIs)
  • Improved performance for animations and large data sets
  • Custom native components for advanced UI/UX

• Offline support with local caching.

• AI-driven predictions for plateaus and injury prevention.

• Integration with wearables for real-time biofeedback.

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✅ Summary

This project aspires to build a truly intelligent personal trainer that:

• Generates safe, adaptive plans based on recognized health standards.
• Fits workouts and meals into each user's unique daily schedule.
• Engages users through conversational logging and reminders.
• Evolves toward native development for performance and precision.

All while maintaining clean architecture, strong security, and user-centric design.