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

class AboutScreen extends StatelessWidget {
  const AboutScreen({super.key});

  static const String _helpUrl = 'https://addmonths.app/help';
  static const String _privacyUrl = 'https://addmonths.app/privacy';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('About'),
        leading: IconButton(
          icon: const Icon(Icons.arrow_back),
          onPressed: () => Navigator.pop(context),
        ),
      ),
      body: SingleChildScrollView(
        padding: const EdgeInsets.all(24),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            // App name and version
            Center(
              child: Column(
                children: [
                  Container(
                    width: 80,
                    height: 80,
                    decoration: BoxDecoration(
                      color: AppColors.surfaceVariant,
                      borderRadius: BorderRadius.circular(20),
                    ),
                    child: const Icon(
                      Icons.timeline,
                      size: 40,
                      color: AppColors.primary,
                    ),
                  ),
                  const SizedBox(height: 16),
                  Text(
                    'Add Months',
                    style: Theme.of(context).textTheme.headlineMedium,
                  ),
                  const SizedBox(height: 4),
                  Text(
                    'Version 1.2',
                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                          color: AppColors.textSecondary,
                        ),
                  ),
                ],
              ),
            ),
            const SizedBox(height: 32),

            // Description
            Text(
              'What is Add Months?',
              style: Theme.of(context).textTheme.titleMedium,
            ),
            const SizedBox(height: 8),
            Text(
              'Add Months uses evidence-based hazard ratios from peer-reviewed '
              'meta-analyses to identify which single lifestyle change could '
              'have the biggest impact on your lifespan.',
              style: Theme.of(context).textTheme.bodyMedium,
            ),
            const SizedBox(height: 16),
            Text(
              'Answer simple questions about your demographics and habits, '
              'and the app calculates which modifiable factor offers the '
              'greatest potential benefit.',
              style: Theme.of(context).textTheme.bodyMedium,
            ),
            const SizedBox(height: 32),

            // Privacy note
            Container(
              padding: const EdgeInsets.all(16),
              decoration: BoxDecoration(
                color: AppColors.surfaceVariant,
                borderRadius: BorderRadius.circular(12),
              ),
              child: Row(
                children: [
                  const Icon(
                    Icons.lock_outline,
                    color: AppColors.primary,
                  ),
                  const SizedBox(width: 12),
                  Expanded(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          'Your data stays on your device',
                          style: Theme.of(context).textTheme.titleSmall,
                        ),
                        const SizedBox(height: 4),
                        Text(
                          'No accounts, no cloud sync, no analytics. '
                          'Everything is stored locally.',
                          style: Theme.of(context).textTheme.bodySmall,
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            ),
            const SizedBox(height: 32),

            // Links
            _buildLinkButton(
              context,
              icon: Icons.help_outline,
              label: 'How it works',
              onTap: () => _launchUrl(_helpUrl),
            ),
            const SizedBox(height: 12),
            _buildLinkButton(
              context,
              icon: Icons.privacy_tip_outlined,
              label: 'Privacy Policy',
              onTap: () => _launchUrl(_privacyUrl),
            ),
            const SizedBox(height: 32),

            // Disclaimer
            Text(
              'Disclaimer',
              style: Theme.of(context).textTheme.titleSmall?.copyWith(
                    color: AppColors.textSecondary,
                  ),
            ),
            const SizedBox(height: 8),
            Text(
              'This app provides general information based on population-level '
              'research and is not medical advice. Individual results vary widely. '
              'Consult a healthcare provider for personalized guidance.',
              style: Theme.of(context).textTheme.bodySmall?.copyWith(
                    color: AppColors.textSecondary,
                  ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildLinkButton(
    BuildContext context, {
    required IconData icon,
    required String label,
    required VoidCallback onTap,
  }) {
    return InkWell(
      onTap: onTap,
      borderRadius: BorderRadius.circular(12),
      child: Container(
        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 14),
        decoration: BoxDecoration(
          border: Border.all(color: AppColors.divider),
          borderRadius: BorderRadius.circular(12),
        ),
        child: Row(
          children: [
            Icon(icon, color: AppColors.primary),
            const SizedBox(width: 12),
            Text(
              label,
              style: Theme.of(context).textTheme.bodyLarge,
            ),
            const Spacer(),
            const Icon(
              Icons.open_in_new,
              size: 18,
              color: AppColors.textSecondary,
            ),
          ],
        ),
      ),
    );
  }

  Future<void> _launchUrl(String url) async {
    final uri = Uri.parse(url);
    if (await canLaunchUrl(uri)) {
      await launchUrl(uri, mode: LaunchMode.externalApplication);
    }
  }
}