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

/// Shown in place of the main shell whenever [ServerProvider.needsUnlock] is
/// true - a fresh app launch with login lock configured, or returning to the
/// foreground after being backgrounded. Prompts automatically on first show
/// and again whenever the app resumes while still locked (e.g. the user
/// switched away to enter their device PIN in the system UI and came back).
class LockScreenView extends StatefulWidget {
  const LockScreenView({super.key});

  @override
  State<LockScreenView> createState() => _LockScreenViewState();
}

class _LockScreenViewState extends State<LockScreenView>
    with WidgetsBindingObserver {
  bool _authenticating = false;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    WidgetsBinding.instance.addPostFrameCallback((_) => _attemptUnlock());
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state != AppLifecycleState.resumed || !mounted || _authenticating) {
      return;
    }
    if (context.read<ServerProvider>().needsUnlock) _attemptUnlock();
  }

  Future<void> _attemptUnlock() async {
    if (_authenticating || !mounted) return;
    setState(() => _authenticating = true);
    await context.read<ServerProvider>().attemptUnlock();
    if (mounted) setState(() => _authenticating = false);
  }

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

    return Scaffold(
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(32),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              // Same monochrome-tinted treatment as the splash screen (see
              // main.dart's _SplashView) - the asset is a plain white
              // silhouette on transparent, meant to be recolored rather
              // than shown as-is.
              ColorFiltered(
                colorFilter: ColorFilter.mode(
                  colorScheme.onSurface,
                  BlendMode.srcIn,
                ),
                child: Image.asset(
                  'assets/icon/app_icon_monochrome.png',
                  width: 80,
                  height: 80,
                ),
              ),
              const SizedBox(height: 24),
              Text(
                'Noo is locked',
                textAlign: TextAlign.center,
                style: theme.textTheme.headlineSmall?.copyWith(
                  fontWeight: FontWeight.w700,
                ),
              ),
              const SizedBox(height: 8),
              Text(
                'Unlock with your PIN or biometrics to continue',
                textAlign: TextAlign.center,
                style: theme.textTheme.bodyMedium?.copyWith(
                  color: colorScheme.onSurfaceVariant,
                ),
              ),
              const SizedBox(height: 32),
              SizedBox(
                height: 54,
                child: FilledButton.icon(
                  onPressed: _authenticating ? null : _attemptUnlock,
                  icon: _authenticating
                      ? SizedBox(
                          width: 20,
                          height: 20,
                          child: CircularProgressIndicator(
                            strokeWidth: 2.5,
                            color: colorScheme.onPrimary,
                          ),
                        )
                      : const Icon(Icons.lock_open_rounded),
                  label: Text(_authenticating ? 'Unlocking…' : 'Unlock'),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}