import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../providers/verification_session_provider.dart';
import '../../services/face_verification.dart' as face;

/// Screen opened on mobile when the user scans a QR code for cross-device
/// face verification. Performs liveness detection and uploads the result.
class MobileVerificationScreen extends ConsumerStatefulWidget {
  const MobileVerificationScreen({super.key, required this.sessionId});

  final String sessionId;

  @override
  ConsumerState<MobileVerificationScreen> createState() =>
      _MobileVerificationScreenState();
}

class _MobileVerificationScreenState
    extends ConsumerState<MobileVerificationScreen> {
  bool _loading = true;
  bool _verifying = false;
  bool _done = false;
  String? _error;

  @override
  void initState() {
    super.initState();
    _loadSession();
  }

  Future<void> _loadSession() async {
    try {
      final controller = ref.read(verificationSessionControllerProvider);
      final session = await controller.getSession(widget.sessionId);
      if (session == null) {
        setState(() {
          _error = 'Verification session not found.';
          _loading = false;
        });
        return;
      }
      if (session.isExpired) {
        setState(() {
          _error = 'This verification session has expired.';
          _loading = false;
        });
        return;
      }
      if (session.isCompleted) {
        setState(() {
          _error = 'This session has already been completed.';
          _loading = false;
        });
        return;
      }
      setState(() => _loading = false);

      // Automatically start liveness detection
      _startLiveness();
    } catch (e) {
      if (mounted) {
        setState(() {
          _error = 'Failed to load session: $e';
          _loading = false;
        });
      }
    }
  }

  Future<void> _startLiveness() async {
    if (_verifying) return;
    setState(() {
      _verifying = true;
      _error = null;
    });

    try {
      final result = await face.runFaceLiveness(context);

      if (result == null) {
        if (mounted) {
          setState(() {
            _error = 'Liveness check cancelled.';
            _verifying = false;
          });
        }
        return;
      }

      // Upload the photo and complete the session
      final controller = ref.read(verificationSessionControllerProvider);
      await controller.completeSession(
        sessionId: widget.sessionId,
        bytes: result.imageBytes,
        fileName: 'verify.jpg',
      );

      if (mounted) {
        setState(() {
          _done = true;
          _verifying = false;
        });
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          _error = 'Verification failed: $e';
          _verifying = false;
        });
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colors = theme.colorScheme;

    return Scaffold(
      appBar: AppBar(title: const Text('Face Verification')),
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(24),
          child: _buildContent(theme, colors),
        ),
      ),
    );
  }

  Widget _buildContent(ThemeData theme, ColorScheme colors) {
    if (_loading) {
      return const Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          CircularProgressIndicator(),
          SizedBox(height: 16),
          Text('Loading verification session...'),
        ],
      );
    }

    if (_done) {
      return Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(Icons.check_circle, size: 64, color: Colors.green),
          const SizedBox(height: 16),
          Text('Verification Complete', style: theme.textTheme.headlineSmall),
          const SizedBox(height: 8),
          Text(
            'You can close this screen and return to the web app.',
            style: theme.textTheme.bodyMedium?.copyWith(
              color: colors.onSurfaceVariant,
            ),
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 24),
          FilledButton(
            onPressed: () => Navigator.of(context).maybePop(),
            child: const Text('Close'),
          ),
        ],
      );
    }

    if (_error != null) {
      return Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(Icons.error_outline, size: 64, color: colors.error),
          const SizedBox(height: 16),
          Text(
            'Verification Error',
            style: theme.textTheme.headlineSmall?.copyWith(color: colors.error),
          ),
          const SizedBox(height: 8),
          Text(
            _error!,
            style: theme.textTheme.bodyMedium?.copyWith(
              color: colors.onSurfaceVariant,
            ),
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 24),
          FilledButton(
            onPressed: _startLiveness,
            child: const Text('Try Again'),
          ),
          const SizedBox(height: 12),
          TextButton(
            onPressed: () => Navigator.of(context).maybePop(),
            child: const Text('Cancel'),
          ),
        ],
      );
    }

    if (_verifying) {
      return const Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          CircularProgressIndicator(),
          SizedBox(height: 16),
          Text('Processing verification...'),
        ],
      );
    }

    // Fallback: prompt to start
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: [
        Icon(Icons.face, size: 64, color: colors.primary),
        const SizedBox(height: 16),
        Text('Ready to Verify', style: theme.textTheme.headlineSmall),
        const SizedBox(height: 8),
        Text(
          'Tap the button below to start face liveness detection.',
          style: theme.textTheme.bodyMedium?.copyWith(
            color: colors.onSurfaceVariant,
          ),
          textAlign: TextAlign.center,
        ),
        const SizedBox(height: 24),
        FilledButton.icon(
          onPressed: _startLiveness,
          icon: const Icon(Icons.face),
          label: const Text('Start Verification'),
        ),
      ],
    );
  }
}