import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import '../../core/auth/auth_notifier.dart';
import '../../core/availability/mitra_availability_notifier.dart';
import '../../core/chat/active_session_notifier.dart';
import '../chat/widgets/topic_selection_bottom_sheet.dart';

/// Home screen.
///
/// 1. The "Mulai Curhat" CTA is gated on real-time mitra availability
///    (polling owned by the [mitraAvailabilityProvider]). Polling is paused
///    on background and resumed on foreground via [WidgetsBindingObserver].
/// 2. Tapping the enabled CTA pushes `/payment` so the customer must confirm
///    a payment session before any blast fires.
class HomeScreen extends ConsumerStatefulWidget {
  const HomeScreen({super.key});

  @override
  ConsumerState<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends ConsumerState<HomeScreen> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    // Kick the availability poll on once the first frame settles. Doing it
    // here (rather than in build) avoids re-firing on every rebuild.
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      ref.read(mitraAvailabilityProvider.notifier).setActive(true);
    });
  }

  @override
  void dispose() {
    // Stop polling when leaving home.
    ref.read(mitraAvailabilityProvider.notifier).setActive(false);
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    final notifier = ref.read(mitraAvailabilityProvider.notifier);
    if (state == AppLifecycleState.resumed) {
      // Re-fetch in case a session ended/started while backgrounded.
      ref.read(activeSessionProvider.notifier).refresh();
      notifier.setActive(true);
    } else if (state == AppLifecycleState.paused || state == AppLifecycleState.inactive) {
      notifier.setActive(false);
    }
  }

  Future<void> _onStartChatPressed(BuildContext context) async {
    final topic = await TopicSelectionBottomSheet.show(context);
    if (topic == null || !context.mounted) return;
    context.push('/payment', extra: {'topicSensitivity': topic});
  }

  @override
  Widget build(BuildContext context) {
    final authState = ref.watch(authProvider);
    final authData = authState.valueOrNull;
    final activeSessionAsync = ref.watch(activeSessionProvider);
    final availabilityAsync = ref.watch(mitraAvailabilityProvider);

    final displayName = switch (authData) {
      AuthAuthenticatedData d => d.profile['display_name'] as String? ?? '',
      AuthAnonymousData d => d.displayName,
      _ => '',
    };

    // Poll-failure / loading both default to "no bestie available" (greyed-out).
    // Never optimistically enable.
    final mitraAvailable = availabilityAsync.valueOrNull ?? false;

    return Scaffold(
      appBar: AppBar(
        title: const Text('Halo Bestie'),
        actions: [
          IconButton(
            icon: const Icon(Icons.history),
            onPressed: () => context.push('/chat/history'),
          ),
          IconButton(
            icon: const Icon(Icons.logout),
            onPressed: () => ref.read(authProvider.notifier).logout(),
          ),
        ],
      ),
      body: RefreshIndicator(
        onRefresh: () async {
          // Pull-to-refresh kicks both the active-session and availability polls.
          await Future.wait([
            ref.read(activeSessionProvider.notifier).refresh(),
            ref.read(mitraAvailabilityProvider.notifier).refresh(),
          ]);
        },
        child: ListView(
          // Force-scroll so RefreshIndicator can fire even on a short body.
          physics: const AlwaysScrollableScrollPhysics(),
          padding: const EdgeInsets.all(32),
          children: [
            const SizedBox(height: 32),
            Center(child: Text('Halo, $displayName!', style: const TextStyle(fontSize: 24))),
            const SizedBox(height: 32),
            Center(
              child: activeSessionAsync.when(
                loading: () => const CircularProgressIndicator(),
                error: (_, __) => _StartChatButton(
                  enabled: mitraAvailable,
                  onPressed: () => _onStartChatPressed(context),
                ),
                data: (snapshot) {
                  // Hide the "Sesi Aktif" CTA when the session is in `closing`
                  // — the conversation is over, only the goodbye composer
                  // remains. Backend auto-completes such sessions after a
                  // grace period; until then the user shouldn't be invited
                  // back into them from home.
                  final status = snapshot.session?['status'] as String?;
                  final isCurhatable = snapshot.hasSession && status != 'closing';
                  if (isCurhatable) {
                    return _ActiveSessionCard(
                      mitraName: snapshot.mitraName,
                      unreadCount: snapshot.unreadCount,
                      onTap: () {
                        final sessionId = snapshot.sessionId;
                        if (sessionId == null) return;
                        context.push('/chat/session/$sessionId', extra: snapshot.mitraName);
                      },
                    );
                  }
                  return _StartChatButton(
                    enabled: mitraAvailable,
                    onPressed: () => _onStartChatPressed(context),
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _StartChatButton extends StatelessWidget {
  final bool enabled;
  final VoidCallback onPressed;
  const _StartChatButton({required this.enabled, required this.onPressed});

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        const SizedBox(height: 16),
        ElevatedButton(
          style: ElevatedButton.styleFrom(
            padding: const EdgeInsets.symmetric(horizontal: 48, vertical: 16),
          ),
          onPressed: enabled ? onPressed : null,
          child: const Text('Mulai Curhat', style: TextStyle(fontSize: 18)),
        ),
        const SizedBox(height: 12),
        if (!enabled)
          Text(
            'Belum ada bestie tersedia',
            style: TextStyle(fontSize: 14, color: Colors.grey.shade600),
          ),
      ],
    );
  }
}

class _ActiveSessionCard extends StatelessWidget {
  final String mitraName;
  final int unreadCount;
  final VoidCallback onTap;

  const _ActiveSessionCard({
    required this.mitraName,
    required this.unreadCount,
    required this.onTap,
  });

  @override
  Widget build(BuildContext context) {
    return Card(
      elevation: 2,
      child: InkWell(
        onTap: onTap,
        borderRadius: BorderRadius.circular(12),
        child: Padding(
          padding: const EdgeInsets.all(20),
          child: Row(
            children: [
              Badge(
                isLabelVisible: unreadCount > 0,
                label: Text('$unreadCount'),
                child: const CircleAvatar(
                  backgroundColor: Colors.green,
                  child: Icon(Icons.chat, color: Colors.white),
                ),
              ),
              const SizedBox(width: 16),
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    const Text(
                      'Sesi Aktif',
                      style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
                    ),
                    const SizedBox(height: 4),
                    Text(
                      'Sedang curhat dengan $mitraName',
                      style: const TextStyle(fontSize: 14, color: Colors.grey),
                    ),
                  ],
                ),
              ),
              const Icon(Icons.chevron_right),
            ],
          ),
        ),
      ),
    );
  }
}