app/lib/screens/onboarding_screen.dart

import 'package:flutter/material.dart';
import '../theme.dart';
import 'baseline_screen.dart';

class OnboardingScreen extends StatefulWidget {
  const OnboardingScreen({super.key});

  @override
  State<OnboardingScreen> createState() => _OnboardingScreenState();
}

class _OnboardingScreenState extends State<OnboardingScreen> {
  final _controller = PageController();
  int _currentPage = 0;

  final _slides = const [
    _SlideData(
      icon: Icons.person_outline,
      title: 'Tell us your baseline',
      description: 'Age, sex, country, and any existing health conditions.',
    ),
    _SlideData(
      icon: Icons.checklist_outlined,
      title: 'Answer a few questions',
      description: 'Simple inputs about sleep, activity, and daily habits.',
    ),
    _SlideData(
      icon: Icons.insights_outlined,
      title: 'See your biggest lever',
      description: 'Discover which single change could add the most months to your life.',
    ),
  ];

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            Expanded(
              child: PageView.builder(
                controller: _controller,
                itemCount: _slides.length,
                onPageChanged: (index) => setState(() => _currentPage = index),
                itemBuilder: (context, index) => _buildSlide(_slides[index]),
              ),
            ),
            Padding(
              padding: const EdgeInsets.all(32),
              child: Column(
                children: [
                  // Page indicators
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: List.generate(
                      _slides.length,
                      (index) => _buildDot(index),
                    ),
                  ),
                  const SizedBox(height: 32),
                  // Button
                  SizedBox(
                    width: double.infinity,
                    child: ElevatedButton(
                      onPressed: _onButtonPressed,
                      child: Text(_currentPage == _slides.length - 1
                          ? 'Get Started'
                          : 'Next'),
                    ),
                  ),
                  const SizedBox(height: 12),
                  // Skip button (not on last page)
                  if (_currentPage < _slides.length - 1)
                    TextButton(
                      onPressed: _skip,
                      child: Text(
                        'Skip',
                        style: TextStyle(color: AppColors.textTertiary),
                      ),
                    )
                  else
                    const SizedBox(height: 40),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildSlide(_SlideData slide) {
    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 40),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Container(
            width: 120,
            height: 120,
            decoration: BoxDecoration(
              color: AppColors.primary.withAlpha(26),
              shape: BoxShape.circle,
            ),
            child: Icon(
              slide.icon,
              size: 56,
              color: AppColors.primary,
            ),
          ),
          const SizedBox(height: 48),
          Text(
            slide.title,
            style: Theme.of(context).textTheme.headlineLarge,
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 16),
          Text(
            slide.description,
            style: Theme.of(context).textTheme.bodyLarge?.copyWith(
                  color: AppColors.textSecondary,
                ),
            textAlign: TextAlign.center,
          ),
        ],
      ),
    );
  }

  Widget _buildDot(int index) {
    final isActive = index == _currentPage;
    return AnimatedContainer(
      duration: const Duration(milliseconds: 200),
      margin: const EdgeInsets.symmetric(horizontal: 4),
      width: isActive ? 24 : 8,
      height: 8,
      decoration: BoxDecoration(
        color: isActive ? AppColors.primary : AppColors.divider,
        borderRadius: BorderRadius.circular(4),
      ),
    );
  }

  void _onButtonPressed() {
    if (_currentPage < _slides.length - 1) {
      _controller.nextPage(
        duration: const Duration(milliseconds: 300),
        curve: Curves.easeInOut,
      );
    } else {
      _navigateToBaseline();
    }
  }

  void _skip() {
    _navigateToBaseline();
  }

  void _navigateToBaseline() {
    Navigator.of(context).pushReplacement(
      MaterialPageRoute(builder: (_) => const BaselineScreen()),
    );
  }
}

class _SlideData {
  final IconData icon;
  final String title;
  final String description;

  const _SlideData({
    required this.icon,
    required this.title,
    required this.description,
  });
}