import 'dart:io';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:go_router/go_router.dart';
import 'package:image_picker/image_picker.dart';
import 'package:social_app/core/chat/agent_stage.dart';
import '../../../../data/network/api_exception.dart';
import '../../../../app/di/injection.dart';
import '../../../../app/router/app_route_observer.dart';
import '../../../../app/router/app_routes.dart';
import '../../../../core/l10n/l10n.dart';
import '../../../../core/theme/design_tokens.dart';
import '../../../../features/messages/data/repositories/inbox_repository.dart';
import '../../../chat/presentation/bloc/chat_bloc.dart';
import '../../data/voice_recorder.dart';
import '../controllers/home_keyboard_inset_calculator.dart';
import '../controllers/home_message_viewport_controller.dart';
import '../controllers/home_viewport_coordinator.dart';
import '../../../../shared/widgets/app_pull_refresh_feedback.dart';
import '../../../../shared/widgets/toast/toast.dart';
import '../../../../shared/widgets/toast/toast_type.dart';
import '../../../../shared/widgets/full_screen_loading.dart';
import 'home_sheet.dart';
import '../widgets/home_background_field.dart';
import '../widgets/home_chat_item_renderer.dart';
import '../widgets/home_conversation_chrome.dart';
import '../widgets/home_floating_header.dart';
import '../widgets/home_input_host.dart';
import '../widgets/home_recording_overlay.dart';
import '../widgets/home_unread_badge.dart';

part 'home_screen_interactions.dart';

/// Layout constants.
const _defaultPadding = 20.0;
const _itemSpacing = 16.0;
const _cancelThreshold = -(AppSpacing.xxl + AppSpacing.xxl);
const _scrollDurationMs = 300;
const _rippleDurationMs = 1200;
const _bottomStackReservedHeight = 116.0;
const _pullRefreshMinVisibleMs = 450;
const _waitingIndicatorReservedHeight = 42.0;

const homeConversationStageKey = ValueKey('home_conversation_stage');
const homeBottomInputStackKey = ValueKey('home_bottom_input_stack');
const homeEmptyStateAmbientKey = ValueKey('home_empty_state_ambient');

class HomeScreen extends StatefulWidget {
  final VoiceRecorder? voiceRecorder;
  final Future<String> Function(String filePath)? onTranscribeAudio;
  final ChatBloc? chatBloc;
  final bool autoLoadHistory;
  final List<XFile> initialSelectedImages;

  const HomeScreen({
    super.key,
    this.voiceRecorder,
    this.onTranscribeAudio,
    this.chatBloc,
    this.autoLoadHistory = true,
    this.initialSelectedImages = const [],
  });

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

class _HomeScreenState extends State<HomeScreen>
    with SingleTickerProviderStateMixin, RouteAware {
  final TextEditingController _messageController = TextEditingController();
  final ScrollController _scrollController = ScrollController();
  late final ChatBloc _chatBloc;
  late final VoiceRecorder _voiceRecorder;
  late final InboxRepository _inboxRepository;
  late final Future<String> Function(String filePath) _transcribeAudio;
  late final AnimationController _listeningAnimationController;
  bool _isRecording = false;
  bool _isRecordingStarting = false;
  bool _isTranscribing = false;
  bool _isCancelGestureActive = false;
  bool _shouldCancelWhenStartCompletes = false;
  bool _shouldStopWhenStartCompletes = false;
  bool _isSendingMessage = false;
  bool _isPullRefreshing = false;
  bool _isHistoryPaginationInFlight = false;
  int _unreadCount = 0;
  int _chatUnreadBadgeCount = 0;
  final List<XFile> _selectedImages = [];
  final HomeViewportCoordinator _viewportCoordinator = HomeViewportCoordinator(
    HomeMessageViewportController(),
  );
  bool _initialHistoryHandled = false;
  int _previousItemCount = 0;
  bool _previousIsLoadingHistory = false;
  bool _routeAwareSubscribed = false;
  double? _historyViewportPixels;
  double? _historyViewportMaxExtent;
  final GlobalKey<HomeInputHostState> _inputHostKey =
      GlobalKey<HomeInputHostState>();

  @override
  void initState() {
    super.initState();
    final providedChatBloc = widget.chatBloc;
    if (providedChatBloc != null) {
      _chatBloc = providedChatBloc;
    } else {
      _chatBloc = context.read<ChatBloc>();
    }
    _voiceRecorder = widget.voiceRecorder ?? RecordVoiceRecorder();
    _inboxRepository = sl<InboxRepository>();
    _transcribeAudio =
        widget.onTranscribeAudio ?? _chatBloc.transcribeAudioFile;
    _listeningAnimationController = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: _rippleDurationMs),
    );
    _selectedImages.addAll(widget.initialSelectedImages);
    if (widget.autoLoadHistory && _chatBloc.state.items.isEmpty) {
      _chatBloc.loadHistory();
    }
    _scrollController.addListener(_handleScrollChanged);
    _previousItemCount = _chatBloc.state.items.length;
    _previousIsLoadingHistory = _chatBloc.state.isLoadingHistory;
    _loadUnreadCount();
  }

  Future<void> _loadUnreadCount() async {
    try {
      final messages = await _inboxRepository.getMessages(isRead: false);
      if (mounted) {
        setState(() => _unreadCount = messages.length);
      }
    } catch (_) {
      // Ignore errors
    }
  }

  @override
  void dispose() {
    _messageController.dispose();
    _scrollController.removeListener(_handleScrollChanged);
    _scrollController.dispose();
    _listeningAnimationController.dispose();
    _voiceRecorder.dispose();
    if (_routeAwareSubscribed) {
      appRouteObserver.unsubscribe(this);
      _routeAwareSubscribed = false;
    }
    super.dispose();
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    final route = ModalRoute.of(context);
    if (!_routeAwareSubscribed && route is PageRoute<dynamic>) {
      appRouteObserver.subscribe(this, route);
      _routeAwareSubscribed = true;
    }
  }

  @override
  void didPopNext() {
    _applyViewportDecision(
      _dispatchViewportEvent(
        type: ViewportEventType.screenResumedFromSubRoute,
        source: ViewportTriggerSource.route,
        deltaCount: 0,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return BlocProvider.value(
      value: _chatBloc,
      child: BlocConsumer<ChatBloc, ChatState>(
        listener: (context, state) {
          if (state.error != null) {
            Toast.show(context, state.error!, type: ToastType.error);
          }

          final loadingFinished =
              _previousIsLoadingHistory && !state.isLoadingHistory;
          if (loadingFinished &&
              !_isHistoryPaginationInFlight &&
              !_initialHistoryHandled &&
              state.items.isNotEmpty) {
            _initialHistoryHandled = true;
            _applyViewportDecision(
              _dispatchViewportEvent(
                type: ViewportEventType.historyInitialLoaded,
                source: ViewportTriggerSource.system,
                deltaCount: 0,
                isFirstEnter: true,
              ),
            );
          }

          final itemDelta = state.items.length - _previousItemCount;
          if (!_isHistoryPaginationInFlight &&
              !state.isLoadingHistory &&
              itemDelta > 0) {
            _applyViewportDecision(
              _dispatchViewportEvent(
                type: ViewportEventType.newMessageAppended,
                source: ViewportTriggerSource.system,
                deltaCount: itemDelta,
              ),
            );
          }

          _previousItemCount = state.items.length;
          _previousIsLoadingHistory = state.isLoadingHistory;
        },
        builder: (context, state) {
          final colorScheme = Theme.of(context).colorScheme;

          return Scaffold(
            backgroundColor: colorScheme.surface,
            resizeToAvoidBottomInset: false,
            body: SafeArea(
              maintainBottomViewPadding: true,
              child: Stack(
                children: [
                  Positioned.fill(child: HomeBackgroundField()),
                  GestureDetector(
                    behavior: HitTestBehavior.translucent,
                    onTap: _dismissKeyboard,
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: [
                        _buildHeader(context),
                        Expanded(child: _buildChatArea(context, state)),
                      ],
                    ),
                  ),
                  if (_chatUnreadBadgeCount > 0) _buildUnreadBadge(),
                  _buildBottomInputStack(context, state),
                  if (_isRecording)
                    HomeRecordingOverlay(
                      isCancel: _isCancelGestureActive,
                      listeningAnimation: _listeningAnimationController,
                    ),
                ],
              ),
            ),
          );
        },
      ),
    );
  }

  Widget _buildHeader(BuildContext context) {
    return HomeFloatingHeader(
      unreadCount: _unreadCount,
      onTapSettings: () => context.push(AppRoutes.settingsMain),
      onTapCalendar: () =>
          context.push('${AppRoutes.calendarDayWeek}?from=home'),
      onTapMessages: () => context.push(AppRoutes.messageInviteList),
    );
  }

  Widget _buildChatArea(BuildContext context, ChatState state) {
    final showWaitingIndicator = _isAgentWaiting(state);
    final inputBottomInset = _effectiveKeyboardInset(context);

    if (state.isLoadingHistory && state.items.isEmpty) {
      return const FullScreenLoading();
    }

    return Padding(
      padding: EdgeInsets.fromLTRB(
        _defaultPadding,
        0,
        _defaultPadding,
        _bottomStackReservedHeight + inputBottomInset,
      ),
      child: KeyedSubtree(
        key: homeConversationStageKey,
        child: Stack(
          children: [
            if (state.items.isEmpty)
              const Positioned.fill(child: _HomeEmptyStateAmbient())
            else
              Positioned.fill(
                child: RefreshIndicator.noSpinner(
                  onRefresh: () => _onRefresh(context),
                  child: ListView.builder(
                    controller: _scrollController,
                    physics: const AlwaysScrollableScrollPhysics(),
                    keyboardDismissBehavior:
                        ScrollViewKeyboardDismissBehavior.onDrag,
                    padding: EdgeInsets.only(
                      top: AppSpacing.sm,
                      bottom: showWaitingIndicator
                          ? _waitingIndicatorReservedHeight
                          : AppSpacing.none,
                    ),
                    itemCount:
                        state.items.length + (state.hasEarlierHistory ? 1 : 0),
                    itemBuilder: (context, index) {
                      if (index == 0 && state.hasEarlierHistory) {
                        return HomeLoadMoreButton(
                          isLoading: state.isLoadingHistory,
                          onTap: () => _onLoadMore(context),
                        );
                      }

                      final itemIndex = state.hasEarlierHistory
                          ? index - 1
                          : index;
                      final item = state.items[itemIndex];

                      final showDateDivider =
                          itemIndex == 0 ||
                          !_isSameDay(
                            state.items[itemIndex - 1].timestamp,
                            item.timestamp,
                          );

                      return Column(
                        crossAxisAlignment: CrossAxisAlignment.stretch,
                        children: [
                          if (showDateDivider)
                            HomeDateDivider(date: item.timestamp),
                          Padding(
                            padding: const EdgeInsets.only(
                              bottom: _itemSpacing,
                            ),
                            child: HomeChatItemRenderer.build(context, item),
                          ),
                        ],
                      );
                    },
                  ),
                ),
              ),
            if (showWaitingIndicator)
              Align(
                alignment: Alignment.bottomLeft,
                child: HomeWaitingIndicator(label: _agentWaitingLabel(state)),
              ),
            Align(
              alignment: Alignment.topCenter,
              child: AppPullRefreshFeedback(visible: _isPullRefreshing),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildUnreadBadge() {
    final inputBottomInset = _effectiveKeyboardInset(context);
    return Positioned(
      right: _defaultPadding,
      bottom: _bottomStackReservedHeight + AppSpacing.md + inputBottomInset,
      child: HomeUnreadBadge(
        count: _chatUnreadBadgeCount,
        onTap: () {
          _scheduleAutoScroll(animated: true);
          if (mounted) {
            setState(() => _chatUnreadBadgeCount = 0);
          }
        },
      ),
    );
  }

  bool _isSameDay(DateTime a, DateTime b) {
    return a.year == b.year && a.month == b.month && a.day == b.day;
  }

  Future<void> _onRefresh(BuildContext context) async {
    if (_isPullRefreshing) {
      return;
    }
    final chatBloc = context.read<ChatBloc>();
    if (chatBloc.state.isLoadingHistory || _isHistoryPaginationInFlight) {
      return;
    }
    final hasEarlierHistory = chatBloc.state.hasEarlierHistory;
    if (mounted) {
      setState(() => _isPullRefreshing = true);
    }
    final startedAt = DateTime.now();
    try {
      if (hasEarlierHistory) {
        await _loadMoreHistoryPreservingViewport(chatBloc);
      }
      _applyViewportDecision(
        _dispatchViewportEvent(
          type: ViewportEventType.sessionRefreshCompleted,
          source: ViewportTriggerSource.user,
          deltaCount: 0,
        ),
      );
    } finally {
      final elapsed = DateTime.now().difference(startedAt);
      final minDuration = const Duration(
        milliseconds: _pullRefreshMinVisibleMs,
      );
      if (elapsed < minDuration) {
        await Future.delayed(minDuration - elapsed);
      }
      if (mounted) {
        setState(() => _isPullRefreshing = false);
      }
    }
  }

  Future<void> _onLoadMore(BuildContext context) async {
    final chatBloc = context.read<ChatBloc>();
    await _loadMoreHistoryPreservingViewport(chatBloc);
  }

  Future<void> _loadMoreHistoryPreservingViewport(ChatBloc chatBloc) async {
    if (_isHistoryPaginationInFlight) {
      return;
    }
    _captureHistoryViewportAnchor();
    _applyViewportDecision(
      _dispatchViewportEvent(
        type: ViewportEventType.historyPagePrependStarted,
        source: ViewportTriggerSource.user,
        deltaCount: 0,
        hasAnchor: _historyViewportPixels != null,
      ),
    );
    if (mounted) {
      setState(() {
        _isHistoryPaginationInFlight = true;
      });
    }
    try {
      await chatBloc.loadMoreHistory();
    } finally {
      final hasAnchor = _historyViewportPixels != null;
      _applyViewportDecision(
        _dispatchViewportEvent(
          type: ViewportEventType.historyPagePrependFinished,
          source: ViewportTriggerSource.system,
          deltaCount: 0,
          hasAnchor: hasAnchor,
        ),
      );
      if (mounted) {
        setState(() {
          _isHistoryPaginationInFlight = false;
        });
      }
    }
  }

  void _captureHistoryViewportAnchor() {
    if (!_scrollController.hasClients) {
      _historyViewportPixels = null;
      _historyViewportMaxExtent = null;
      return;
    }
    final position = _scrollController.position;
    _historyViewportPixels = position.pixels;
    _historyViewportMaxExtent = position.maxScrollExtent;
  }

  void _restoreHistoryViewportAnchor() {
    final previousPixels = _historyViewportPixels;
    final previousMaxExtent = _historyViewportMaxExtent;
    _historyViewportPixels = null;
    _historyViewportMaxExtent = null;
    if (previousPixels == null || previousMaxExtent == null) {
      return;
    }
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!_scrollController.hasClients) {
        return;
      }
      final position = _scrollController.position;
      final extentDelta = position.maxScrollExtent - previousMaxExtent;
      final targetOffset = (previousPixels + extentDelta)
          .clamp(position.minScrollExtent, position.maxScrollExtent)
          .toDouble();
      _scrollController.jumpTo(targetOffset);
    });
  }

  bool _isAgentWaiting(ChatState state) {
    return state.isWaitingFirstToken || state.isStreaming || state.isCancelling;
  }

  String _agentWaitingLabel(ChatState state) {
    if (state.isWaitingFirstToken && !state.hasSeenStep) {
      return context.l10n.agentStageRequesting;
    }
    return stageLabel(state.currentStage);
  }

  void _handleScrollChanged() {
    if (!_scrollController.hasClients) {
      return;
    }
    _applyViewportDecision(
      _dispatchViewportEvent(
        type: ViewportEventType.userScrollStateChanged,
        source: ViewportTriggerSource.user,
        deltaCount: 0,
      ),
    );
  }

  ViewportDecision _dispatchViewportEvent({
    required ViewportEventType type,
    required ViewportTriggerSource source,
    required int deltaCount,
    bool? isFirstEnter,
    bool? hasAnchor,
  }) {
    return _viewportCoordinator.dispatch(
      type: type,
      source: source,
      deltaCount: deltaCount,
      distanceToBottomPx: _distanceToBottom(),
      hasSavedViewport: _historyViewportPixels != null,
      hasAnchor: hasAnchor ?? (_historyViewportPixels != null),
      anchorOffsetPx: _historyViewportPixels,
      isFirstEnter: isFirstEnter ?? false,
    );
  }

  double _distanceToBottom() {
    if (!_scrollController.hasClients) {
      return 0;
    }
    final position = _scrollController.position;
    final keyboardInset = _effectiveKeyboardInset(context);
    return (position.maxScrollExtent - position.pixels - keyboardInset)
        .clamp(0, double.infinity)
        .toDouble();
  }

  double _effectiveKeyboardInset(BuildContext context) {
    final mediaQuery = MediaQuery.of(context);
    return HomeKeyboardInsetCalculator.compute(
      rawViewInsetBottom: mediaQuery.viewInsets.bottom,
      bottomViewPadding: mediaQuery.viewPadding.bottom,
    );
  }

  void _dismissKeyboard() {
    _inputHostKey.currentState?.unfocusInput();
    final focus = FocusManager.instance.primaryFocus;
    focus?.unfocus();
  }

  void _applyViewportDecision(ViewportDecision decision) {
    switch (decision.action) {
      case ViewportAction.jumpBottom:
        _scheduleAutoScroll(animated: false);
        if (mounted) {
          setState(() => _chatUnreadBadgeCount = 0);
        }
        return;
      case ViewportAction.animateBottom:
        _scheduleAutoScroll(animated: true);
        if (mounted) {
          setState(() => _chatUnreadBadgeCount = 0);
        }
        return;
      case ViewportAction.restoreAnchor:
        _restoreHistoryViewportAnchor();
        return;
      case ViewportAction.showUnreadBadge:
        if (mounted) {
          setState(() {
            _chatUnreadBadgeCount = _viewportCoordinator.unreadCount;
          });
        }
        return;
      case ViewportAction.none:
        if (decision.reason == 'entered-at-bottom' && mounted) {
          setState(() => _chatUnreadBadgeCount = 0);
        }
        return;
    }
  }

  void _scheduleAutoScroll({required bool animated}) {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!_scrollController.hasClients) {
        Future<void>.delayed(const Duration(milliseconds: 16), () {
          if (!_scrollController.hasClients) {
            return;
          }
          final maxExtent = _scrollController.position.maxScrollExtent;
          _scrollController.jumpTo(maxExtent);
        });
        return;
      }
      final maxExtent = _scrollController.position.maxScrollExtent;
      if (animated) {
        _scrollController.animateTo(
          maxExtent,
          duration: const Duration(milliseconds: _scrollDurationMs),
          curve: Curves.easeOut,
        );
        return;
      }
      _scrollController.jumpTo(maxExtent);
    });
  }

  Widget _buildBottomInputStack(BuildContext context, ChatState state) {
    final isWaitingAgent = _isSendingMessage || _isAgentWaiting(state);
    final inputBottomInset = _effectiveKeyboardInset(context);
    return HomeInputHost(
      key: _inputHostKey,
      selectedImages: _selectedImages,
      onRemoveImage: _removeImage,
      isRecording: _isRecording,
      isCancelGestureActive: _isCancelGestureActive,
      isTranscribing: _isTranscribing,
      isWaitingAgent: isWaitingAgent,
      messageController: _messageController,
      onTapPlus: _isRecording
          ? () => _stopRecording(autoSendAfterTranscribe: false)
          : () => _showBottomSheet(context),
      onStopGenerating: _onStopGenerating,
      onHoldToSpeakStart: _onHoldToSpeakStart,
      onHoldToSpeakEnd: _onHoldToSpeakEnd,
      onHoldToSpeakMoveUpdate: _onHoldToSpeakMoveUpdate,
      onHoldToSpeakCancel: _onHoldToSpeakCancel,
      onSubmitText: (text) => _sendMessage(context, overrideContent: text),
      keyboardInset: inputBottomInset,
    );
  }

  void _removeImage(int index) {
    setState(() {
      _selectedImages.removeAt(index);
    });
  }

  void _onHoldToSpeakStart() {
    HapticFeedback.selectionClick();
    setState(() {
      _isCancelGestureActive = false;
    });
    _startRecording();
  }

  void _onHoldToSpeakEnd() {
    if (_isRecordingStarting) {
      _shouldCancelWhenStartCompletes = false;
      _shouldStopWhenStartCompletes = true;
      return;
    }
    if (!_isRecording) {
      return;
    }
    if (_isCancelGestureActive) {
      HapticFeedback.selectionClick();
      _cancelRecording(showToast: false);
      return;
    }
    HapticFeedback.selectionClick();
    _stopRecording(autoSendAfterTranscribe: true);
  }

  void _onHoldToSpeakMoveUpdate(LongPressMoveUpdateDetails details) {
    final willCancel = details.offsetFromOrigin.dy < _cancelThreshold;
    if (willCancel != _isCancelGestureActive && mounted) {
      HapticFeedback.selectionClick();
      setState(() {
        _isCancelGestureActive = willCancel;
      });
    }
  }
}

class _HomeEmptyStateAmbient extends StatelessWidget {
  const _HomeEmptyStateAmbient();

  @override
  Widget build(BuildContext context) {
    return const SizedBox.shrink(key: homeEmptyStateAmbientKey);
  }
}