import 'dart:async';
import 'dart:math' as math;

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

import '../../core/theme/app_colors.dart';
import 'lock_controller.dart';
import 'pin_pad.dart';

/// Full-screen gate shown only when the launcher is cold-started with a PIN
/// configured. It never re-locks a running session.
class LockScreen extends StatefulWidget {
  const LockScreen({super.key});

  @override
  State<LockScreen> createState() => _LockScreenState();
}

class _LockScreenState extends State<LockScreen>
    with SingleTickerProviderStateMixin {
  String _pin = '';
  bool _busy = false;
  Timer? _tick;
  late final AnimationController _shake = AnimationController(
    vsync: this,
    duration: const Duration(milliseconds: 380),
  );

  @override
  void initState() {
    super.initState();
    _tick = Timer.periodic(const Duration(seconds: 1), (_) {
      if (mounted) setState(() {});
    });
  }

  @override
  void dispose() {
    _tick?.cancel();
    _shake.dispose();
    super.dispose();
  }

  void _onDigit(String digit) {
    if (_busy || _pin.length >= 4) return;
    final lock = context.read<LockController>();
    if (lock.isCoolingDown) return;
    setState(() => _pin += digit);
    if (_pin.length == 4) {
      setState(() => _busy = true);
      Future<void>.delayed(const Duration(milliseconds: 110), _submit);
    }
  }

  void _onBackspace() {
    if (_busy || _pin.isEmpty) return;
    setState(() => _pin = _pin.substring(0, _pin.length - 1));
  }

  Future<void> _submit() async {
    if (!mounted) return;
    final lock = context.read<LockController>();
    final success = await lock.unlock(_pin);
    if (!mounted) return;
    if (success) {
      return; // The root widget removes this screen.
    }
    setState(() {
      _pin = '';
      _busy = false;
    });
    _shake.forward(from: 0);
  }

  @override
  Widget build(BuildContext context) {
    final colors = context.colors;
    final theme = Theme.of(context);
    final lock = context.watch<LockController>();
    final error = lock.isCoolingDown
        ? 'Too many attempts. Try again in ${lock.cooldownSecondsRemaining}s.'
        : lock.errorMessage;

    return PopScope(
      canPop: false,
      child: Scaffold(
        backgroundColor: colors.canvas,
        body: Container(
          decoration: BoxDecoration(
            gradient: LinearGradient(
              begin: Alignment.topLeft,
              end: Alignment.bottomRight,
              colors: Theme.of(context).brightness == Brightness.dark
                  ? [colors.canvas, colors.canvasDeep]
                  : [colors.canvas, const Color(0xFFF7F5EF)],
            ),
          ),
          child: SafeArea(
            child: Center(
              child: SingleChildScrollView(
                padding: const EdgeInsets.symmetric(
                  horizontal: 32,
                  vertical: 28,
                ),
                child: ConstrainedBox(
                  constraints: const BoxConstraints(maxWidth: 420),
                  child: Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      const BrandMark(size: 7, gap: 6),
                      const SizedBox(height: 16),
                      Text(
                        'CarDash',
                        style: theme.textTheme.titleLarge?.copyWith(
                          letterSpacing: 0.2,
                          color: colors.inkMuted,
                        ),
                      ),
                      const SizedBox(height: 34),
                      Text('Enter PIN', style: theme.textTheme.headlineLarge),
                      const SizedBox(height: 8),
                      Text(
                        'CarDash is locked.',
                        style: theme.textTheme.bodyMedium?.copyWith(
                          color: colors.inkMuted,
                        ),
                      ),
                      const SizedBox(height: 30),
                      AnimatedBuilder(
                        animation: _shake,
                        builder: (context, child) {
                          final progress = _shake.value;
                          final offset =
                              math.sin(progress * math.pi * 6) *
                              9 *
                              (1 - progress);
                          return Transform.translate(
                            offset: Offset(offset, 0),
                            child: child,
                          );
                        },
                        child: PinDots(
                          length: 4,
                          filled: _pin.length,
                          error: error != null,
                        ),
                      ),
                      const SizedBox(height: 14),
                      SizedBox(
                        height: 42,
                        child: _busy
                            ? Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: [
                                  SizedBox(
                                    width: 16,
                                    height: 16,
                                    child: CircularProgressIndicator(
                                      strokeWidth: 2,
                                      color: colors.accent,
                                    ),
                                  ),
                                  const SizedBox(width: 9),
                                  Text(
                                    'Checking…',
                                    style: theme.textTheme.bodySmall?.copyWith(
                                      color: colors.inkMuted,
                                    ),
                                  ),
                                ],
                              )
                            : AnimatedSwitcher(
                                duration: const Duration(milliseconds: 160),
                                child: Text(
                                  error ?? 'Enter your four-digit PIN',
                                  key: ValueKey(error ?? 'hint'),
                                  textAlign: TextAlign.center,
                                  style: theme.textTheme.bodySmall?.copyWith(
                                    color: error == null
                                        ? colors.inkFaint
                                        : colors.danger,
                                  ),
                                ),
                              ),
                      ),
                      const SizedBox(height: 12),
                      PinKeypad(
                        enabled: !_busy && !lock.isCoolingDown,
                        onDigit: _onDigit,
                        onBackspace: _onBackspace,
                      ),
                    ],
                  ),
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}