import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import '../../../core/chat/active_session_notifier.dart';
import '../../../core/chat/chat_notifier.dart';
import '../../../core/chat/session_closure_notifier.dart';
import '../../../core/config/app_config_provider.dart';
import '../../../core/constants.dart';
import '../../../core/theme/halo_tokens.dart';
import '../../../core/theme/widgets/halo_snackbar.dart';
import '../widgets/bestie_unavailable_dialog.dart';
import '../widgets/chat_expired_banner.dart';
import '../widgets/closing_message_sheet.dart';
import '../widgets/confirm_end_step1.dart';
import '../widgets/confirm_end_step2.dart';
import '../widgets/pricing_bottom_sheet.dart';

// Chat theme colors
const _kUserBubbleColor = Color(0xFFD4929A);
const _kBgTint = Color(0xFFF5D0D6);
const _kBannerColor = Color(0xFFC4868F);
const _kAccentPink = Color(0xFFBE7C8A);
const _kEndedBannerColor = Color(0xFFFFE0B2); // soft amber for early-end notice
const _kEndedBannerText = Color(0xFF8B5A00);

class ChatScreen extends ConsumerStatefulWidget {
  final String sessionId;
  final String mitraName;

  const ChatScreen({super.key, required this.sessionId, required this.mitraName});

  @override
  ConsumerState<ChatScreen> createState() => _ChatScreenState();
}

class _ChatScreenState extends ConsumerState<ChatScreen> {
  final _messageController = TextEditingController();
  final _goodbyeController = TextEditingController();
  final _scrollController = ScrollController();
  Timer? _typingThrottle;
  StreamSubscription<String>? _warningSub;
  bool _showBestieBanner = true;
  bool _showUserBanner = true;
  bool _rejectPopupShown = false;
  // Per-session-mount idempotency flag for the 3-min snackbar. The backend
  // also guards once-per-session (timers.threeMinFired), but a fresh mount
  // could still receive the event on a refreshed status pull, so we belt-
  // and-braces here.
  bool _threeMinShown = false;

  @override
  void initState() {
    super.initState();
    // The chat WebSocket is owned globally by `App` (see main.dart).
    // We just ask it to be on this session — no-op if it already is.
    Future.microtask(() {
      // Reset any closure state left over from a prior session view (the
      // closure notifier is keepAlive, so e.g. `ClosureCompleteData` from
      // the last goodbye submission would otherwise leak into this mount
      // and suppress the goodbye composer for a fresh `closing` session).
      ref.read(sessionClosureProvider.notifier).reset();
      ref.read(chatProvider.notifier).connectIfNotConnected(widget.sessionId);
    });
    // Subscribe to the chat notifier's session-warning stream. Using stream
    // subscription rather than a `ref.listen` on state because the warning is
    // a one-shot signal, not a persistent state field.
    _warningSub = ref.read(chatProvider.notifier).warningStream.listen((kind) {
      if (kind == 'three_minutes_left' && !_threeMinShown && mounted) {
        _threeMinShown = true;
        HaloSnackbar.show(
          context,
          'sisa 3 menit lagi ya 🤍',
          icon: '⏳',
        );
      }
    });
  }

  @override
  void dispose() {
    _messageController.dispose();
    _goodbyeController.dispose();
    _scrollController.dispose();
    _typingThrottle?.cancel();
    _warningSub?.cancel();
    super.dispose();
    // Intentionally do NOT disconnect the WS here. The global lifecycle in
    // `App` decides when to disconnect (logout / no active session).
  }

  void _scrollToBottom() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (_scrollController.hasClients) {
        _scrollController.animateTo(
          _scrollController.position.maxScrollExtent,
          duration: const Duration(milliseconds: 200),
          curve: Curves.easeOut,
        );
      }
    });
  }

  void _onTextChanged(String text) {
    if (_typingThrottle?.isActive ?? false) return;
    ref.read(chatProvider.notifier).sendTyping();
    _typingThrottle = Timer(const Duration(seconds: 2), () {});
  }

  void _sendMessage() {
    final text = _messageController.text.trim();
    if (text.isEmpty) return;
    ref.read(chatProvider.notifier).sendMessage(text);
    _messageController.clear();
    _scrollToBottom();
  }

  void _exitChat() {
    if (context.canPop()) {
      context.pop();
    } else {
      context.go('/home');
    }
  }

  /// Stage 7 entry point — wired to both the AppBar "akhiri sesi" button and
  /// the menu equivalent. Reads `endSessionTwoStepConfirmProvider`: when the
  /// flag is `true` the user sees step-1 first; when `false` (A/B variant) we
  /// jump straight to step-2 (write-message vs skip).
  Future<void> _onAkhiriSesiTapped() async {
    final twoStep = ref.read(endSessionTwoStepConfirmProvider);
    if (!twoStep) {
      _showStep2();
      return;
    }
    await ConfirmEndStep1.show(context, onConfirm: _showStep2);
  }

  void _showStep2() {
    if (!mounted) return;
    ConfirmEndStep2.show(
      context,
      onWriteMessage: _showClosingSheet,
      onSkip: _closeWithoutMessage,
    );
  }

  void _showClosingSheet() {
    if (!mounted) return;
    ClosingMessageSheet.show(
      context,
      sessionId: widget.sessionId,
      onCompleted: _goToThankYou,
    );
  }

  Future<void> _closeWithoutMessage() async {
    await ref.read(sessionClosureProvider.notifier).closeSession(widget.sessionId);
    // Navigation is driven by the closure listener (success path) or the
    // ClosureRejectedByMitraData branch (409 fallback popup).
  }

  void _goToThankYou() {
    if (!mounted) return;
    context.go('/chat/thank-you');
  }

  Future<void> _showBestieReturningPopup() async {
    if (_rejectPopupShown) return;
    _rejectPopupShown = true;
    if (!mounted) return;
    await BestieOfflinePopup.show(
      context,
      variant: BestieOfflineVariant.returning,
      mitraName: widget.mitraName,
    );
    _rejectPopupShown = false;
    // Reset closure state so the user can retry without a stale-error block.
    ref.read(sessionClosureProvider.notifier).reset();
  }

  @override
  Widget build(BuildContext context) {
    final chatState = ref.watch(chatProvider);
    final closureState = ref.watch(sessionClosureProvider);

    // Stage 7 — closure outcomes drive routing. Success ends in S11 thank-you;
    // 409 surfaces the bestie-returning fallback popup (Stage 8 owns the
    // dedicated component).
    ref.listen(sessionClosureProvider, (prev, next) {
      if (next is ClosureCompleteData) {
        ref.invalidate(activeSessionProvider);
        _goToThankYou();
      } else if (next is ClosureRejectedByMitraData) {
        _showBestieReturningPopup();
      }
    });

    // Listen for chat state changes to manage closure state. Stage 7 removed
    // the legacy `_showSessionExpiredDialog` modal — the Stage 6 ChatExpiredBanner
    // is the in-place replacement, and the user reaches the closing flow via
    // the AppBar "akhiri" button.
    ref.listen(chatProvider, (prev, next) {
      if (next is ChatConnectedData) {
        // Early-end (mitra/customer ended before timer): show goodbye composer.
        if (next.sessionClosing && !next.sessionExpired) {
          final closure = ref.read(sessionClosureProvider);
          if (closure is ClosureInitialData) {
            ref.read(sessionClosureProvider.notifier).declineExtension();
          }
        }
        if (!next.sessionPaused && !next.sessionExpired && !next.sessionClosing) {
          final closure = ref.read(sessionClosureProvider);
          if (closure is! ClosureInitialData) {
            ref.read(sessionClosureProvider.notifier).reset();
          }
        }
        _scrollToBottom();
        final unread = next.messages
            .where((m) => m.senderType == UserType.mitra && m.status != MessageStatus.read)
            .map((m) => m.id)
            .toList();
        if (unread.isNotEmpty) {
          ref.read(chatProvider.notifier).markRead(unread);
          // Optimistically clear the home badge.
          ref.read(activeSessionProvider.notifier).markRead();
        }
      }
    });

    // Phase 4 — derived ticker drives the danger pill / expired banner.
    // Only watched when there's a connected session with a known expires_at.
    final remainingAsync = ref.watch(chatRemainingSecondsProvider);
    final remainingTick = remainingAsync.value;

    return PopScope(
      canPop: false,
      onPopInvokedWithResult: (didPop, _) {
        if (!didPop) _exitChat();
      },
      child: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.white,
          foregroundColor: Colors.black,
          elevation: 0.5,
          centerTitle: true,
          leading: IconButton(
            icon: const Icon(Icons.chevron_left, size: 28),
            onPressed: _exitChat,
          ),
          title: Row(
            mainAxisSize: MainAxisSize.min,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Flexible(
                child: Text(
                  widget.mitraName,
                  overflow: TextOverflow.ellipsis,
                ),
              ),
              if (chatState is ChatConnectedData && chatState.mode == SessionMode.call) ...[
                const SizedBox(width: 8),
                _buildVoiceCallPill(),
              ],
            ],
          ),
          actions: [
            if (chatState is ChatConnectedData && remainingTick != null)
              Padding(
                padding: const EdgeInsets.only(right: 4),
                child: Center(child: _buildTimerPill(remainingTick)),
              ),
            if (chatState is ChatConnectedData &&
                !chatState.sessionClosing)
              TextButton(
                onPressed: _onAkhiriSesiTapped,
                style: TextButton.styleFrom(
                  foregroundColor: HaloTokens.brandDark,
                  textStyle: const TextStyle(
                    fontFamily: HaloTokens.fontBody,
                    fontSize: 13,
                    fontWeight: FontWeight.w600,
                  ),
                ),
                child: const Text('akhiri'),
              ),
          ],
        ),
        body: _buildBody(chatState, closureState, remainingTick),
      ),
    );
  }

  Widget _buildVoiceCallPill() {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 3),
      decoration: const BoxDecoration(
        color: HaloTokens.accent,
        borderRadius: HaloRadius.pill,
      ),
      child: const Text(
        '📞 Voice Call',
        style: TextStyle(
          fontFamily: HaloTokens.fontBody,
          fontSize: 11,
          fontWeight: FontWeight.w600,
          color: Colors.white,
        ),
      ),
    );
  }

  Widget _buildTimerPill(int remaining) {
    final danger = remaining <= 120;
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 4),
      decoration: BoxDecoration(
        color: danger ? HaloTokens.danger : Colors.transparent,
        borderRadius: HaloRadius.pill,
      ),
      child: Text(
        formatCountdown(remaining),
        style: TextStyle(
          fontFamily: HaloTokens.fontMono,
          fontSize: 13,
          fontWeight: danger ? FontWeight.w700 : FontWeight.w600,
          color: danger ? Colors.white : HaloTokens.ink,
        ),
      ),
    );
  }

  Widget _buildBody(ChatData chatState, SessionClosureData closureState, int? remainingTick) {
    if (chatState is ChatConnectingData) {
      return const Center(child: CircularProgressIndicator());
    }
    if (chatState is ChatErrorData) {
      return Center(child: Text(chatState.message));
    }
    if (chatState is ChatConnectedData) {
      return _buildChatBody(chatState, closureState, remainingTick);
    }
    return const SizedBox.shrink();
  }

  Widget _buildChatBody(ChatConnectedData state, SessionClosureData closureState, int? remainingTick) {
    // Show goodbye composer when closure flow is in goodbye/submitting OR when
    // we mounted directly into a `closing` session (e.g. opened from history).
    // The chatProvider listener can't catch this case because it only fires on
    // transitions, not the current state at mount time.
    // Suppress when the customer has already submitted their goodbye — the
    // session can stay in `closing` while waiting for the mitra to submit
    // their own message or for the 5-min grace timer to auto-complete.
    final shouldShowGoodbye = !state.goodbyeSubmitted &&
        (closureState is ClosureShowGoodbyeData ||
            closureState is ClosureSubmittingData ||
            (state.sessionClosing &&
                !state.sessionExpired &&
                closureState is! ClosureCompleteData));
    if (shouldShowGoodbye) {
      return _buildGoodbyeView(closureState);
    }

    if (state.sessionClosing && state.goodbyeSubmitted) {
      return _buildAwaitingMitraGoodbyeView(state);
    }

    if (state.sessionPaused) {
      return _buildPausedView();
    }

    return Stack(
      children: [
        // Background pattern
        Positioned.fill(
          child: Container(
            color: _kBgTint,
            child: Image.asset(
              'assets/images/chat_pattern.png',
              repeat: ImageRepeat.repeat,
              fit: BoxFit.none,
            ),
          ),
        ),
        // Content
        Column(
          children: [
            // Entry banners
            if (_showBestieBanner)
              _buildEntryBanner(
                '[Bestie] Sudah Memasuki Ruangan',
                () => setState(() => _showBestieBanner = false),
              ),
            if (_showUserBanner)
              _buildEntryBanner(
                '[User] Sudah Memasuki Ruangan',
                () => setState(() => _showUserBanner = false),
              ),
            // Messages
            Expanded(
              child: ListView.builder(
                controller: _scrollController,
                padding: const EdgeInsets.all(16),
                itemCount: state.messages.length,
                itemBuilder: (context, index) {
                  final msg = state.messages[index];
                  final isMe = msg.senderType == UserType.customer;
                  return _buildMessageBubble(msg, isMe);
                },
              ),
            ),
            // Typing indicator
            if (state.isOtherTyping)
              const Padding(
                padding: EdgeInsets.symmetric(horizontal: 16, vertical: 4),
                child: Align(
                  alignment: Alignment.centerLeft,
                  child: Text('Bestie sedang mengetik...', style: TextStyle(color: Colors.grey, fontSize: 12)),
                ),
              ),
            // Floating expired banner — visible while the timer has hit zero
            // and the session hasn't been finalized yet (still in closing
            // grace). Tapping `perpanjang` opens the time-up sheet, same as
            // the modal route.
            if (remainingTick != null && remainingTick <= 0)
              ChatExpiredBanner(
                onExtend: () => PricingBottomSheet.showForExtension(
                  context,
                  sessionId: widget.sessionId,
                ),
              ),
            // Input bar — disabled when timer expired (modal handles next step)
            if (!state.sessionExpired) _buildInputBar(),
          ],
        ),
      ],
    );
  }

  Widget _buildEntryBanner(String text, VoidCallback onDismiss) {
    return Container(
      color: _kBannerColor,
      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
      child: Row(
        children: [
          const Icon(Icons.volume_up, color: Colors.white, size: 18),
          const SizedBox(width: 8),
          Expanded(
            child: Text(text, style: const TextStyle(color: Colors.white, fontSize: 13)),
          ),
          GestureDetector(
            onTap: onDismiss,
            child: const Icon(Icons.close, color: Colors.white, size: 18),
          ),
        ],
      ),
    );
  }

  Widget _buildMessageBubble(ChatMessage msg, bool isMe) {
    return Align(
      alignment: isMe ? Alignment.centerRight : Alignment.centerLeft,
      child: Container(
        margin: const EdgeInsets.symmetric(vertical: 4),
        padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
        constraints: BoxConstraints(maxWidth: MediaQuery.of(context).size.width * 0.75),
        decoration: BoxDecoration(
          color: isMe ? _kUserBubbleColor : Colors.white,
          borderRadius: BorderRadius.circular(16),
        ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.end,
          children: [
            Text(msg.content, style: const TextStyle(fontSize: 15)),
            const SizedBox(height: 4),
            Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                Text(
                  '${msg.createdAt.hour.toString().padLeft(2, '0')}:${msg.createdAt.minute.toString().padLeft(2, '0')}',
                  style: TextStyle(fontSize: 10, color: isMe ? Colors.white70 : Colors.grey),
                ),
                if (isMe) ...[
                  const SizedBox(width: 4),
                  _buildStatusIcon(msg.status),
                ],
              ],
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildStatusIcon(String status) {
    switch (status) {
      case 'sending':
        return const Icon(Icons.access_time, size: 14, color: Colors.white70);
      case MessageStatus.sent:
        return const Icon(Icons.check, size: 14, color: Colors.white70);
      case MessageStatus.delivered:
        return const Icon(Icons.done_all, size: 14, color: Colors.white70);
      case MessageStatus.read:
        return const Icon(Icons.done_all, size: 14, color: Colors.white);
      default:
        return const SizedBox.shrink();
    }
  }

  Widget _buildInputBar() {
    return SafeArea(
      child: Container(
        padding: const EdgeInsets.all(8),
        color: Colors.white,
        child: Row(
          children: [
            Expanded(
              child: TextField(
                controller: _messageController,
                onChanged: _onTextChanged,
                textInputAction: TextInputAction.send,
                onSubmitted: (_) => _sendMessage(),
                decoration: InputDecoration(
                  hintText: 'Ketik Pesan',
                  hintStyle: TextStyle(color: Colors.grey.shade400),
                  filled: true,
                  fillColor: Colors.grey.shade100,
                  border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(24),
                    borderSide: BorderSide.none,
                  ),
                  contentPadding: const EdgeInsets.symmetric(horizontal: 16, vertical: 10),
                ),
              ),
            ),
            const SizedBox(width: 8),
            Container(
              decoration: const BoxDecoration(
                color: _kAccentPink,
                shape: BoxShape.circle,
              ),
              child: IconButton(
                icon: const Icon(Icons.send, color: Colors.white, size: 20),
                onPressed: _sendMessage,
              ),
            ),
          ],
        ),
      ),
    );
  }

  // TODO(phase4-followup): Stage 7 moved the customer-initiated goodbye flow
  // to ClosingMessageSheet. This inline composer is still reachable when the
  // mitra ends a session early (sessionClosing fired by the server). Migrate
  // that path to the new sheet too once the early-end UX is finalised.
  Widget _buildGoodbyeView(SessionClosureData closureState) {
    return SingleChildScrollView(
      padding: const EdgeInsets.all(32),
      child: Column(
        children: [
          // Early-end banner — visually distinct, separate from the closing
          // composer below. We don't surface "Perpanjang" in this flow.
          Container(
            width: double.infinity,
            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
            decoration: BoxDecoration(
              color: _kEndedBannerColor,
              borderRadius: BorderRadius.circular(8),
            ),
            child: const Row(
              children: [
                Icon(Icons.info_outline, color: _kEndedBannerText, size: 20),
                SizedBox(width: 8),
                Expanded(
                  child: Text(
                    'Sesi telah ditutup oleh Bestie',
                    style: TextStyle(color: _kEndedBannerText, fontWeight: FontWeight.w600),
                  ),
                ),
              ],
            ),
          ),
          const SizedBox(height: 32),
          const Icon(Icons.waving_hand, size: 64, color: Colors.amber),
          const SizedBox(height: 16),
          const Text('Pesan Penutup', style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
          const SizedBox(height: 8),
          const Text('Tuliskan pesan terakhirmu untuk Bestie', textAlign: TextAlign.center),
          const SizedBox(height: 24),
          TextField(
            controller: _goodbyeController,
            maxLines: 3,
            decoration: InputDecoration(
              hintText: 'Terima kasih, Bestie...',
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(12)),
            ),
          ),
          const SizedBox(height: 16),
          ElevatedButton(
            onPressed: closureState is ClosureSubmittingData
                ? null
                : () {
                    final text = _goodbyeController.text.trim();
                    if (text.isNotEmpty) {
                      ref.read(sessionClosureProvider.notifier).submitGoodbye(
                        widget.sessionId, text,
                      );
                    }
                  },
            child: closureState is ClosureSubmittingData
                ? const SizedBox(width: 20, height: 20, child: CircularProgressIndicator(strokeWidth: 2))
                : const Text('Kirim & Selesai'),
          ),
        ],
      ),
    );
  }

  Widget _buildPausedView() {
    return const Center(
      child: Padding(
        padding: EdgeInsets.all(32),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            CircularProgressIndicator(),
            SizedBox(height: 24),
            Text('Menunggu konfirmasi Bestie...', style: TextStyle(fontSize: 18)),
            SizedBox(height: 8),
            Text('Chat dijeda sementara', style: TextStyle(color: Colors.grey)),
          ],
        ),
      ),
    );
  }

  Widget _buildAwaitingMitraGoodbyeView(ChatConnectedData state) {
    return Stack(
      children: [
        Positioned.fill(
          child: Container(
            color: _kBgTint,
            child: Image.asset(
              'assets/images/chat_pattern.png',
              repeat: ImageRepeat.repeat,
              fit: BoxFit.none,
            ),
          ),
        ),
        Column(
          children: [
            Container(
              width: double.infinity,
              color: _kEndedBannerColor,
              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
              child: const Row(
                children: [
                  Icon(Icons.hourglass_top, color: _kEndedBannerText, size: 20),
                  SizedBox(width: 8),
                  Expanded(
                    child: Text(
                      'Pesan penutupmu sudah terkirim. Menunggu Bestie...',
                      style: TextStyle(color: _kEndedBannerText, fontWeight: FontWeight.w600),
                    ),
                  ),
                ],
              ),
            ),
            Expanded(
              child: ListView.builder(
                controller: _scrollController,
                padding: const EdgeInsets.all(16),
                itemCount: state.messages.length,
                itemBuilder: (context, index) {
                  final msg = state.messages[index];
                  final isMe = msg.senderType == UserType.customer;
                  return _buildMessageBubble(msg, isMe);
                },
              ),
            ),
          ],
        ),
      ],
    );
  }
}