import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/material.dart';

import '../theme/app_theme.dart';
import '../widgets/benefit_row.dart';
import '../widgets/google_sign_in_button.dart';

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

  @override
  State<LandingScreen> createState() => _LandingScreenState();
}

class _LandingScreenState extends State<LandingScreen> {
  String? _errorMessage;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: DecoratedBox(
        decoration: const BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: <Color>[
              AppColors.background,
              Color(0xFF0C1222),
              Color(0xFF0A1628),
            ],
          ),
        ),
        child: Stack(
          children: <Widget>[
            const _BackgroundGlow(),
            SafeArea(
              child: LayoutBuilder(
                builder: (BuildContext context, BoxConstraints constraints) {
                  final bool wide = constraints.maxWidth >= 720;
                  return Center(
                    child: ConstrainedBox(
                      constraints: const BoxConstraints(maxWidth: 960),
                      child: wide
                          ? _WideLayout(
                              errorMessage: _errorMessage,
                              onError: _handleError,
                            )
                          : _NarrowLayout(
                              errorMessage: _errorMessage,
                              onError: _handleError,
                            ),
                    ),
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }

  void _handleError(Object error) {
    setState(() {
      _errorMessage = _friendlyError(error);
    });
  }

  String _friendlyError(Object error) {
    if (error is FirebaseAuthException) {
      switch (error.code) {
        case 'unauthorized-domain':
          final String origin = kIsWeb ? Uri.base.origin : 'this app';
          return 'Add $origin under Firebase Console → Authentication → '
              'Settings → Authorized domains.';
        case 'operation-not-allowed':
          return 'Google sign-in is not enabled. Turn on the Google provider '
              'in Firebase Console → Authentication → Sign-in method.';
        case 'popup-blocked':
          return 'The sign-in popup was blocked. Allow popups for this site '
              'or try again.';
        case 'popup-closed-by-user':
        case 'cancelled-popup-request':
          return 'Sign-in was cancelled. Tap below to try again.';
      }
    }

    final String raw = error.toString();
    if (raw.contains('missing initial state') ||
        raw.contains('sessionStorage')) {
      return 'This browser blocked sign-in storage (common in Firefox). '
          'Set googleWebOAuthClientId in lib/config/auth_config.dart, allow '
          'popups for this site, or try Chrome.';
    }
    if (raw.contains('canceled') || raw.contains('cancelled')) {
      return 'Sign-in was cancelled. Tap below to try again.';
    }
    if (raw.contains('network')) {
      return 'Network error. Check your connection and try again.';
    }
    if (raw.contains('googleWebOAuthClientId')) {
      return raw.replaceFirst('Bad state: ', '');
    }
    return 'Could not sign in. Please try again.';
  }
}

class _BackgroundGlow extends StatelessWidget {
  const _BackgroundGlow();

  @override
  Widget build(BuildContext context) {
    return IgnorePointer(
      child: Stack(
        children: <Widget>[
          Positioned(
            top: -120,
            right: -80,
            child: Container(
              width: 320,
              height: 320,
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                gradient: RadialGradient(
                  colors: <Color>[
                    AppColors.accent.withValues(alpha: 0.18),
                    Colors.transparent,
                  ],
                ),
              ),
            ),
          ),
          Positioned(
            bottom: -100,
            left: -60,
            child: Container(
              width: 280,
              height: 280,
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                gradient: RadialGradient(
                  colors: <Color>[
                    AppColors.accentMuted.withValues(alpha: 0.12),
                    Colors.transparent,
                  ],
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _NarrowLayout extends StatelessWidget {
  const _NarrowLayout({required this.errorMessage, required this.onError});

  final String? errorMessage;
  final void Function(Object error) onError;

  @override
  Widget build(BuildContext context) {
    return SingleChildScrollView(
      padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 16),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          const _BrandHeader(),
          const SizedBox(height: 32),
          const _HeroCopy(),
          const SizedBox(height: 28),
          const _BenefitsList(),
          const SizedBox(height: 32),
          _CtaSection(errorMessage: errorMessage, onError: onError),
          const SizedBox(height: 24),
          const _TrustFooter(),
        ],
      ),
    );
  }
}

class _WideLayout extends StatelessWidget {
  const _WideLayout({required this.errorMessage, required this.onError});

  final String? errorMessage;
  final void Function(Object error) onError;

  @override
  Widget build(BuildContext context) {
    return SingleChildScrollView(
      padding: const EdgeInsets.symmetric(horizontal: 40, vertical: 24),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          const Expanded(
            flex: 5,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                _BrandHeader(),
                SizedBox(height: 40),
                _HeroCopy(),
                SizedBox(height: 36),
                _BenefitsList(),
              ],
            ),
          ),
          const SizedBox(width: 48),
          Expanded(
            flex: 4,
            child: _CtaCard(errorMessage: errorMessage, onError: onError),
          ),
        ],
      ),
    );
  }
}

class _BrandHeader extends StatelessWidget {
  const _BrandHeader();

  @override
  Widget build(BuildContext context) {
    return Row(
      children: <Widget>[
        Container(
          width: 40,
          height: 40,
          decoration: BoxDecoration(
            gradient: const LinearGradient(
              colors: <Color>[AppColors.accent, AppColors.accentMuted],
            ),
            borderRadius: BorderRadius.circular(10),
          ),
          child: const Icon(
            Icons.shield_outlined,
            color: AppColors.background,
            size: 22,
          ),
        ),
        const SizedBox(width: 12),
        Text(
          'Cyber Hybrid Hub',
          style: Theme.of(context).textTheme.titleLarge?.copyWith(
            letterSpacing: -0.2,
          ),
        ),
      ],
    );
  }
}

class _HeroCopy extends StatelessWidget {
  const _HeroCopy();

  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Container(
          padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
          decoration: BoxDecoration(
            color: AppColors.success.withValues(alpha: 0.12),
            borderRadius: BorderRadius.circular(20),
            border: Border.all(
              color: AppColors.success.withValues(alpha: 0.35),
            ),
          ),
          child: const Row(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              Icon(Icons.bolt, size: 16, color: AppColors.success),
              SizedBox(width: 6),
              Text(
                'Free to get started',
                style: TextStyle(
                  fontSize: 13,
                  fontWeight: FontWeight.w600,
                  color: AppColors.success,
                ),
              ),
            ],
          ),
        ),
        const SizedBox(height: 20),
        Text(
          'Your hybrid security\ncommand center',
          style: Theme.of(context).textTheme.headlineLarge,
        ),
        const SizedBox(height: 16),
        Text(
          'Unify threat monitoring, team collaboration, and compliance '
          'workflows in one secure workspace — built for modern hybrid teams.',
          style: Theme.of(context).textTheme.bodyLarge?.copyWith(
            fontSize: 17,
          ),
        ),
      ],
    );
  }
}

class _BenefitsList extends StatelessWidget {
  const _BenefitsList();

  static const List<({IconData icon, String title, String subtitle})> _items =
      <({IconData icon, String title, String subtitle})>[
        (
          icon: Icons.radar,
          title: 'Real-time threat visibility',
          subtitle: 'See alerts and incidents as they happen, not hours later.',
        ),
        (
          icon: Icons.groups_outlined,
          title: 'Built for hybrid teams',
          subtitle: 'On-site and remote staff share one source of truth.',
        ),
        (
          icon: Icons.verified_user_outlined,
          title: 'Sign in securely with Google',
          subtitle: 'No new passwords — enterprise-ready OAuth in one tap.',
        ),
      ];

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        for (int i = 0; i < _items.length; i++) ...<Widget>[
          if (i > 0) const SizedBox(height: 20),
          BenefitRow(
            icon: _items[i].icon,
            title: _items[i].title,
            subtitle: _items[i].subtitle,
          ),
        ],
      ],
    );
  }
}

class _CtaSection extends StatelessWidget {
  const _CtaSection({required this.errorMessage, required this.onError});

  final String? errorMessage;
  final void Function(Object error) onError;

  @override
  Widget build(BuildContext context) {
    return _CtaCard(errorMessage: errorMessage, onError: onError);
  }
}

class _CtaCard extends StatelessWidget {
  const _CtaCard({required this.errorMessage, required this.onError});

  final String? errorMessage;
  final void Function(Object error) onError;

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(24),
      decoration: BoxDecoration(
        color: AppColors.surfaceElevated,
        borderRadius: BorderRadius.circular(16),
        border: Border.all(color: Colors.white.withValues(alpha: 0.08)),
        boxShadow: <BoxShadow>[
          BoxShadow(
            color: AppColors.accent.withValues(alpha: 0.08),
            blurRadius: 40,
            offset: const Offset(0, 12),
          ),
        ],
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          Text(
            'Get started in seconds',
            style: Theme.of(context).textTheme.headlineMedium?.copyWith(
              fontSize: 22,
            ),
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 8),
          Text(
            'Use your Google account — no credit card required.',
            style: Theme.of(context).textTheme.bodyLarge,
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 24),
          if (errorMessage != null) ...<Widget>[
            Container(
              padding: const EdgeInsets.all(12),
              decoration: BoxDecoration(
                color: Theme.of(context).colorScheme.error.withValues(
                  alpha: 0.12,
                ),
                borderRadius: BorderRadius.circular(8),
              ),
              child: Text(
                errorMessage!,
                style: TextStyle(
                  color: Theme.of(context).colorScheme.error,
                  fontSize: 14,
                ),
                textAlign: TextAlign.center,
              ),
            ),
            const SizedBox(height: 16),
          ],
          GoogleSignInButton(
            label: 'Get started with Google',
            onError: onError,
          ),
          const SizedBox(height: 16),
          const _SocialProof(),
        ],
      ),
    );
  }
}

class _SocialProof extends StatelessWidget {
  const _SocialProof();

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        const Icon(Icons.lock_outline, size: 14, color: AppColors.textSecondary),
        const SizedBox(width: 6),
        Flexible(
          child: Text(
            'Secured by Firebase · Google OAuth',
            style: Theme.of(context).textTheme.bodyLarge?.copyWith(fontSize: 12),
            textAlign: TextAlign.center,
            overflow: TextOverflow.ellipsis,
            maxLines: 2,
          ),
        ),
      ],
    );
  }
}

class _TrustFooter extends StatelessWidget {
  const _TrustFooter();

  @override
  Widget build(BuildContext context) {
    return Text(
      'By continuing, you agree to our Terms of Service and Privacy Policy.',
      style: Theme.of(context).textTheme.bodyLarge?.copyWith(fontSize: 12),
      textAlign: TextAlign.center,
    );
  }
}