import 'package:collection/collection.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:intl/date_symbol_data_local.dart';
import 'package:intl/intl.dart';
import 'package:paperless_api/paperless_api.dart';
import 'package:paperless_mobile/core/widgets/documents_list_loading_widget.dart';
import 'package:paperless_mobile/core/widgets/hint_card.dart';
import 'package:paperless_mobile/extensions/dart_extensions.dart';
import 'package:paperless_mobile/extensions/flutter_extensions.dart';
import 'package:paperless_mobile/features/inbox/bloc/inbox_cubit.dart';
import 'package:paperless_mobile/features/inbox/bloc/state/inbox_state.dart';
import 'package:paperless_mobile/features/inbox/view/widgets/inbox_empty_widget.dart';
import 'package:paperless_mobile/features/inbox/view/widgets/inbox_item.dart';
import 'package:paperless_mobile/generated/l10n.dart';
import 'package:paperless_mobile/helpers/message_helpers.dart';
import 'package:paperless_mobile/constants.dart';

class InboxPage extends StatefulWidget {
  const InboxPage({super.key});

  @override
  State<InboxPage> createState() => _InboxPageState();
}

class _InboxPageState extends State<InboxPage> {
  final ScrollController _scrollController = ScrollController();
  final _emptyStateRefreshIndicatorKey = GlobalKey<RefreshIndicatorState>();

  @override
  void initState() {
    super.initState();
    _scrollController.addListener(_listenForLoadNewData);
  }

  @override
  void dispose() {
    _scrollController.removeListener(_listenForLoadNewData);
    super.dispose();
  }

  void _listenForLoadNewData() {
    final currState = context.read<InboxCubit>().state;
    if (_scrollController.offset >=
            _scrollController.position.maxScrollExtent * 0.75 &&
        !currState.isLoading &&
        !currState.isLastPageLoaded) {
      try {
        context.read<InboxCubit>().loadMore();
      } on PaperlessServerException catch (error, stackTrace) {
        showErrorMessage(context, error, stackTrace);
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    const _progressBarHeight = 4.0;
    return Scaffold(
      appBar: PreferredSize(
        preferredSize:
            const Size.fromHeight(kToolbarHeight + _progressBarHeight),
        child: BlocBuilder<InboxCubit, InboxState>(
          builder: (context, state) {
            return AppBar(
              title: Text(S.of(context).bottomNavInboxPageLabel),
              leading: IconButton(
                icon: const Icon(Icons.close),
                onPressed: () => Navigator.pop(context),
              ),
              actions: [
                if (state.hasLoaded)
                  Align(
                    alignment: Alignment.centerRight,
                    child: ClipRRect(
                      borderRadius: BorderRadius.circular(8.0),
                      child: ColoredBox(
                        color: Theme.of(context).colorScheme.secondaryContainer,
                        child: Text(
                          state.value.isEmpty
                              ? '0'
                              : '${state.value.first.count} ' +
                                  S.of(context).inboxPageUnseenText,
                          textAlign: TextAlign.start,
                          style: Theme.of(context).textTheme.bodySmall,
                        ).paddedSymmetrically(horizontal: 4.0),
                      ),
                    ),
                  ).paddedSymmetrically(horizontal: 8)
              ],
              bottom: PreferredSize(
                preferredSize: const Size.fromHeight(4),
                child: state.isLoading && state.hasLoaded
                    ? const LinearProgressIndicator()
                    : const SizedBox(height: _progressBarHeight),
              ),
            );
          },
        ),
      ),
      floatingActionButton: BlocBuilder<InboxCubit, InboxState>(
        builder: (context, state) {
          if (!state.hasLoaded || state.documents.isEmpty) {
            return const SizedBox.shrink();
          }
          return FloatingActionButton.extended(
            label: Text(S.of(context).inboxPageMarkAllAsSeenLabel),
            icon: const Icon(Icons.done_all),
            onPressed: state.hasLoaded && state.documents.isNotEmpty
                ? () => _onMarkAllAsSeen(
                      state.documents,
                      state.inboxTags,
                    )
                : null,
          );
        },
      ),
      body: BlocBuilder<InboxCubit, InboxState>(
        builder: (context, state) {
          if (!state.hasLoaded) {
            return const DocumentsListLoadingWidget();
          }

          if (state.documents.isEmpty) {
            return InboxEmptyWidget(
              emptyStateRefreshIndicatorKey: _emptyStateRefreshIndicatorKey,
            );
          }

          // Build a list of slivers alternating between SliverToBoxAdapter
          // (group header) and a SliverList (inbox items).
          final List<Widget> slivers = _groupByDate(state.documents)
              .entries
              .map(
                (entry) => [
                  SliverToBoxAdapter(
                    child: Align(
                      alignment: Alignment.centerLeft,
                      child: ClipRRect(
                        borderRadius: BorderRadius.circular(32.0),
                        child: Text(
                          entry.key,
                          style: Theme.of(context).textTheme.bodySmall,
                          textAlign: TextAlign.center,
                        ).padded(),
                      ),
                    ).paddedOnly(top: 8.0),
                  ),
                  SliverList(
                    delegate: SliverChildBuilderDelegate(
                      childCount: entry.value.length,
                      (context, index) {
                        if (index < entry.value.length - 1) {
                          return Column(
                            children: [
                              _buildListItem(
                                entry.value[index],
                              ),
                              const Divider(
                                indent: 16,
                                endIndent: 16,
                              ),
                            ],
                          );
                        }
                        return _buildListItem(
                          entry.value[index],
                        );
                      },
                    ),
                  ),
                ],
              )
              .flattened
              .toList()
            ..add(const SliverToBoxAdapter(child: SizedBox(height: 78)));

          return RefreshIndicator(
            onRefresh: () => context.read<InboxCubit>().initializeInbox(),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                Expanded(
                  child: CustomScrollView(
                    controller: _scrollController,
                    slivers: [
                      SliverToBoxAdapter(
                        child: HintCard(
                          show: !state.isHintAcknowledged,
                          hintText: S.of(context).inboxPageUsageHintText,
                          onHintAcknowledged: () =>
                              context.read<InboxCubit>().acknowledgeHint(),
                        ),
                      ),
                      ...slivers,
                    ],
                  ),
                ),
              ],
            ),
          );
        },
      ),
    );
  }

  Widget _buildListItem(DocumentModel doc) {
    return Dismissible(
      direction: DismissDirection.endToStart,
      background: Row(
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          Icon(
            Icons.done_all,
            color: Theme.of(context).colorScheme.primary,
          ).padded(),
          Text(
            S.of(context).inboxPageMarkAsSeenText,
            style: TextStyle(
              color: Theme.of(context).colorScheme.primary,
            ),
          ),
        ],
      ).padded(),
      confirmDismiss: (_) => _onItemDismissed(doc),
      key: UniqueKey(),
      child: InboxItem(
        document: doc,
        onDocumentUpdated: (document) {
          context.read<InboxCubit>().replaceUpdatedDocument(document);
        },
      ),
    );
  }

  Future<void> _onMarkAllAsSeen(
    Iterable<DocumentModel> documents,
    Iterable<int> inboxTags,
  ) async {
    final isActionConfirmed = await showDialog(
          context: context,
          builder: (context) => AlertDialog(
            title: Text(S
                .of(context)
                .inboxPageMarkAllAsSeenConfirmationDialogTitleText),
            content: Text(
              S.of(context).inboxPageMarkAllAsSeenConfirmationDialogText,
            ),
            actions: [
              TextButton(
                onPressed: () => Navigator.of(context).pop(false),
                child: Text(S.of(context).genericActionCancelLabel),
              ),
              TextButton(
                onPressed: () => Navigator.of(context).pop(true),
                child: Text(
                  S.of(context).genericActionOkLabel,
                  style: TextStyle(color: Theme.of(context).colorScheme.error),
                ),
              ),
            ],
          ),
        ) ??
        false;
    if (isActionConfirmed) {
      await context.read<InboxCubit>().clearInbox();
    }
  }

  Future<bool> _onItemDismissed(DocumentModel doc) async {
    try {
      final removedTags = await context.read<InboxCubit>().removeFromInbox(doc);
      showSnackBar(
        context,
        S.of(context).inboxPageDocumentRemovedMessageText,
        action: SnackBarActionConfig(
          label: S.of(context).inboxPageUndoRemoveText,
          onPressed: () => _onUndoMarkAsSeen(doc, removedTags),
        ),
      );
      return true;
    } on PaperlessServerException catch (error, stackTrace) {
      showErrorMessage(context, error, stackTrace);
      return false;
    } catch (error) {
      showErrorMessage(
        context,
        const PaperlessServerException.unknown(),
      );
      return false;
    }
  }

  Future<void> _onUndoMarkAsSeen(
    DocumentModel document,
    Iterable<int> removedTags,
  ) async {
    try {
      await context
          .read<InboxCubit>()
          .undoRemoveFromInbox(document, removedTags);
    } on PaperlessServerException catch (error, stackTrace) {
      showErrorMessage(context, error, stackTrace);
    }
  }

  Map<String, List<DocumentModel>> _groupByDate(
    Iterable<DocumentModel> documents,
  ) {
    return groupBy<DocumentModel, String>(
      documents,
      (doc) {
        if (doc.added.isToday) {
          return S.of(context).inboxPageTodayText;
        }
        if (doc.added.isYesterday) {
          return S.of(context).inboxPageYesterdayText;
        }
        return DateFormat.yMMMMd().format(doc.added);
      },
    );
  }
}