import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import '../../../core/pairing/pairing_notifier.dart';
import '../widgets/bestie_unavailable_dialog.dart';
import '../widgets/targeted_waiting_overlay.dart';

/// Searching screen, also responsible for routing all downstream pairing
/// transitions:
///
/// - PairingTargetedWaitingData → render the targeted waiting overlay above
///   the searching shell (the customer sees the 20s countdown + cancel CTA).
/// - PairingTargetedUnavailableData → show the bestie-unavailable dialog
///   (intermediate; payment stays confirmed; offers fallback-to-blast).
/// - PairingFailedData → terminal; route to no-bestie screen.
/// - PairingBestieFoundData → existing transition to bestie-found screen.
/// - PairingCancelledData → customer cancelled; back home.
///
/// Per project memory ("Riverpod ref.listen in build is unsafe"), we use
/// ref.listenManual in initState for one-shot side effects rather than
/// build-scoped listeners.
class SearchingScreen extends ConsumerStatefulWidget {
  const SearchingScreen({super.key});

  @override
  ConsumerState<SearchingScreen> createState() => _SearchingScreenState();
}

class _SearchingScreenState extends ConsumerState<SearchingScreen> {
  /// Guard against re-firing the bestie-unavailable dialog if the notifier
  /// briefly emits multiple intermediate states (e.g. WS event arrives just
  /// after a 409 already opened the dialog).
  bool _unavailableDialogShown = false;

  @override
  void initState() {
    super.initState();
    ref.listenManual<PairingData>(pairingProvider, _onPairingState);
    // The pairing state can already be PairingTargetedUnavailableData by
    // the time we mount (the payment screen awaits startTargetedSearch
    // before navigating; a 409 lands while we're still on the previous
    // screen). Inspect once after first frame to handle that case.
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      _onPairingState(null, ref.read(pairingProvider));
    });
  }

  void _onPairingState(PairingData? prev, PairingData next) {
    if (!mounted) return;

    if (next is PairingBestieFoundData) {
      context.go('/chat/found', extra: {
        'sessionId': next.sessionId,
        'mitraName': next.mitraName,
      });
      return;
    }

    if (next is PairingActiveData) {
      // Direct route into the active chat — happens after the brief "found"
      // animation if the user is already on this screen.
      context.go('/chat/session/${next.sessionId}', extra: next.mitraName);
      return;
    }

    if (next is PairingFailedData) {
      // Terminal — payment_session is failed_pairing.
      context.go('/chat/no-bestie');
      return;
    }

    if (next is PairingCancelledData) {
      context.go('/home');
      return;
    }

    if (next is PairingTargetedUnavailableData && !_unavailableDialogShown) {
      _unavailableDialogShown = true;
      // ignore: discarded_futures
      BestieUnavailableDialog.show(
        context,
        paymentSessionId: next.paymentSessionId,
        mitraName: next.mitraName,
        topicSensitivity: next.topicSensitivity,
      ).then((_) {
        if (mounted) _unavailableDialogShown = false;
      });
      return;
    }

    if (next is PairingErrorData) {
      // Inline error UX is preferred over SnackBars (project memory:
      // "Avoid SnackBars for provider errors"). The build below renders
      // a banner when the state is PairingErrorData.
    }
  }

  @override
  Widget build(BuildContext context) {
    final pairingState = ref.watch(pairingProvider);

    return Scaffold(
      body: SafeArea(
        child: Stack(
          children: [
            _SearchingBody(state: pairingState),
            if (pairingState is PairingTargetedWaitingData)
              TargetedWaitingOverlay(waiting: pairingState),
          ],
        ),
      ),
    );
  }
}

class _SearchingBody extends ConsumerWidget {
  final PairingData state;
  const _SearchingBody({required this.state});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final isTargetedWaiting = state is PairingTargetedWaitingData;
    final errorMessage = state is PairingErrorData ? (state as PairingErrorData).message : null;

    return Center(
      child: Padding(
        padding: const EdgeInsets.all(32),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const CircularProgressIndicator(),
            const SizedBox(height: 32),
            Text(
              isTargetedWaiting ? 'Menghubungi bestie...' : 'Mencari Bestie...',
              style: const TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
            ),
            const SizedBox(height: 8),
            const Text(
              'Tunggu sebentar ya, kami sedang mencarikan Bestie untukmu',
              textAlign: TextAlign.center,
              style: TextStyle(fontSize: 16, color: Colors.grey),
            ),
            if (errorMessage != null) ...[
              const SizedBox(height: 24),
              Container(
                padding: const EdgeInsets.all(12),
                decoration: BoxDecoration(
                  color: Colors.red.shade50,
                  borderRadius: BorderRadius.circular(8),
                  border: Border.all(color: Colors.red.shade200),
                ),
                child: Text(
                  errorMessage,
                  style: TextStyle(color: Colors.red.shade900),
                  textAlign: TextAlign.center,
                ),
              ),
            ],
            const SizedBox(height: 48),
            // The targeted-waiting overlay owns its own cancel button — only
            // show the general cancel CTA when we're in a non-overlay state.
            if (!isTargetedWaiting)
              OutlinedButton(
                onPressed: () => ref.read(pairingProvider.notifier).cancelSearch(),
                child: const Text('Batalkan'),
              ),
          ],
        ),
      ),
    );
  }
}