import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:intl/intl.dart';

import 'package:sharedinbox/core/models/account.dart';
import 'package:sharedinbox/core/models/email.dart';
import 'package:sharedinbox/core/models/undo_action.dart';
import 'package:sharedinbox/core/models/user_preferences.dart';
import 'package:sharedinbox/core/repositories/email_repository.dart';
import 'package:sharedinbox/di.dart';
import 'package:sharedinbox/ui/screens/email_action_helpers.dart';
import 'package:sharedinbox/ui/widgets/email_thread_tile.dart';
import 'package:sharedinbox/ui/widgets/folder_drawer.dart';
import 'package:sharedinbox/ui/widgets/snooze_picker.dart';
import 'package:sharedinbox/ui/widgets/thread_tile.dart';

class EmailListScreen extends ConsumerStatefulWidget {
  const EmailListScreen({
    super.key,
    required this.accountId,
    required this.mailboxPath,
  });

  final String accountId;
  final String mailboxPath;

  @override
  ConsumerState<EmailListScreen> createState() => _EmailListScreenState();
}

class _EmailListScreenState extends ConsumerState<EmailListScreen> {
  final _searchController = SearchController();
  List<Email>? _searchResults;
  bool _searchLoading = false;
  bool get _searching => _searchController.text.isNotEmpty;

  // Error banner — tracks the last error message that the user dismissed.
  String? _dismissedError;

  // Thread-level selection (key = threadId).
  final Set<String> _selectedThreadIds = {};
  // Last-emitted thread list, used to resolve emailIds for batch operations.
  List<EmailThread> _currentThreads = [];
  // Individual email selection used in search results.
  final Set<String> _selectedSearchIds = {};

  // Pagination: number of threads currently requested from the DB.
  static const _pageSize = 50;
  int _limit = _pageSize;

  // Incremented on every search start; stale completions are ignored when the
  // generation has advanced (prevents out-of-order IMAP responses from
  // overwriting fresh results with results for an older query).
  int _searchGeneration = 0;
  // The query whose results are currently settled in _searchResults.
  // Used to skip redundant re-runs when the user presses Enter on an
  // already-settled search (issue #473).
  String? _lastSettledQuery;
  bool get _selecting =>
      _selectedThreadIds.isNotEmpty || _selectedSearchIds.isNotEmpty;

  @override
  void initState() {
    super.initState();
    _searchController.addListener(() {
      if (_searchController.text.isEmpty) {
        setState(() {
          _searchResults = null;
          _searchLoading = false;
          _lastSettledQuery = null;
        });
      }
    });
  }

  @override
  void dispose() {
    _searchController.dispose();
    super.dispose();
  }

  void _toggleThreadSelection(EmailThread thread) {
    setState(() {
      if (_selectedThreadIds.contains(thread.threadId)) {
        _selectedThreadIds.remove(thread.threadId);
      } else {
        _selectedThreadIds.add(thread.threadId);
      }
    });
  }

  void _clearSelection() => setState(() {
        _selectedThreadIds.clear();
        _selectedSearchIds.clear();
      });

  void _selectAll() {
    setState(() {
      if (_searching) {
        _selectedSearchIds.addAll(_searchResults?.map((e) => e.id) ?? []);
      } else {
        _selectedThreadIds.addAll(_currentThreads.map((t) => t.threadId));
      }
    });
  }

  void _toggleSearchSelection(String emailId) {
    setState(() {
      if (_selectedSearchIds.contains(emailId)) {
        _selectedSearchIds.remove(emailId);
      } else {
        _selectedSearchIds.add(emailId);
      }
    });
  }

  // All email IDs for the current selection context.
  List<String> get _selectedEmailIds {
    if (_searching) return _selectedSearchIds.toList();
    return _currentThreads
        .where((t) => _selectedThreadIds.contains(t.threadId))
        .expand((t) => t.emailIds)
        .toList();
  }

  Future<void> _runSearch(String query) async {
    final q = query.trim();
    if (q.isEmpty) {
      setState(() {
        _searchResults = null;
        _lastSettledQuery = null;
      });
      return;
    }
    // Skip if results are already settled for this exact query — prevents the
    // Enter key from re-triggering a search that already completed.
    if (_searchResults != null && !_searchLoading && q == _lastSettledQuery) {
      return;
    }
    final generation = ++_searchGeneration;
    setState(() => _searchLoading = true);
    try {
      final results = await ref
          .read(emailRepositoryProvider)
          .searchEmails(widget.accountId, widget.mailboxPath, q);
      if (mounted && generation == _searchGeneration) {
        setState(() {
          _searchResults = results;
          _lastSettledQuery = q;
        });
      }
    } finally {
      if (mounted && generation == _searchGeneration) {
        setState(() => _searchLoading = false);
      }
    }
  }

  void _onSearchChanged(String value) {
    if (value.trim().isNotEmpty) unawaited(_runSearch(value.trim()));
  }

  @override
  Widget build(BuildContext context) {
    final repo = ref.watch(emailRepositoryProvider);
    final accountAsync = ref.watch(accountByIdProvider(widget.accountId));
    final prefs =
        ref.watch(userPreferencesProvider).value ?? const UserPreferences();
    final menuAtBottom = prefs.menuPosition == MenuPosition.bottom;

    return Scaffold(
      appBar: _buildAppBar(repo, accountAsync, menuAtBottom: menuAtBottom),
      drawer: _selecting
          ? null
          : FolderDrawer(
              accountId: widget.accountId,
              currentMailboxPath: widget.mailboxPath,
            ),
      bottomNavigationBar: _selecting
          ? _selectionBottomBar()
          : (menuAtBottom ? _folderNavBottomBar() : null),
      body: Column(
        children: [
          _buildSyncErrorBanner(),
          Expanded(
            child: (_searchResults != null || _searchLoading)
                ? _buildSearchBody()
                : _buildStreamBody(repo),
          ),
        ],
      ),
    );
  }

  PreferredSizeWidget _buildAppBar(
    EmailRepository emailRepo,
    AsyncValue<Account?> accountAsync, {
    required bool menuAtBottom,
  }) {
    final selectionCount =
        _searching ? _selectedSearchIds.length : _selectedThreadIds.length;

    return AppBar(
      automaticallyImplyLeading: !menuAtBottom,
      leading: _selecting
          ? IconButton(
              icon: const Icon(Icons.close),
              onPressed: _clearSelection,
            )
          : null,
      title: _selecting
          ? Text('$selectionCount selected')
          : Text(widget.mailboxPath),
      actions: _selecting
          ? [
              IconButton(
                icon: const Icon(Icons.select_all),
                tooltip: 'Select all',
                onPressed: _selectAll,
              ),
            ]
          : [
              accountAsync.when(
                loading: () => const SizedBox.shrink(),
                error: (_, __) => const SizedBox.shrink(),
                data: (account) => Padding(
                  padding: const EdgeInsets.only(right: 4),
                  child: Center(
                    child: Text(
                      account?.displayName ?? '',
                      style: Theme.of(context).textTheme.bodySmall,
                    ),
                  ),
                ),
              ),
              _buildSyncButton(emailRepo),
              IconButton(
                icon: const Icon(Icons.edit),
                onPressed: () => context.push(
                  '/compose',
                  extra: {'accountId': widget.accountId},
                ),
              ),
              PopupMenuButton<String>(
                onSelected: (value) async {
                  if (value == 'mark_all_read') {
                    await emailRepo.markAllAsRead(
                      widget.accountId,
                      widget.mailboxPath,
                    );
                  }
                },
                itemBuilder: (_) => const [
                  PopupMenuItem(
                    value: 'mark_all_read',
                    child: Text('Mark all as read'),
                  ),
                ],
              ),
            ],
      bottom: PreferredSize(
        preferredSize: const Size.fromHeight(60),
        child: Padding(
          padding: const EdgeInsets.fromLTRB(8, 0, 8, 8),
          child: SearchBar(
            controller: _searchController,
            hintText: 'Search…',
            leading: const Icon(Icons.search),
            enabled: !_selecting,
            trailing: [
              if (_searchController.text.isNotEmpty && !_selecting)
                IconButton(
                  icon: const Icon(Icons.clear),
                  onPressed: () => _searchController.clear(),
                ),
            ],
            onChanged: _onSearchChanged,
            onSubmitted: _runSearch,
            textInputAction: TextInputAction.search,
          ),
        ),
      ),
    );
  }

  Widget _buildSyncButton(EmailRepository emailRepo) {
    final isSyncing =
        ref.watch(isSyncingProvider(widget.accountId)).value ?? false;
    final hasError =
        ref.watch(syncLastErrorProvider(widget.accountId)).value != null;
    return IconButton(
      tooltip: isSyncing
          ? 'Syncing…'
          : hasError
              ? 'Sync error'
              : 'Sync',
      icon: isSyncing
          ? const SizedBox(
              width: 20,
              height: 20,
              child: CircularProgressIndicator(strokeWidth: 2),
            )
          : hasError
              ? const Icon(Icons.sync_problem, color: Colors.red)
              : const Icon(Icons.sync),
      onPressed: isSyncing
          ? null
          : () async {
              try {
                await emailRepo.syncEmails(
                  widget.accountId,
                  widget.mailboxPath,
                );
              } catch (e) {
                if (!mounted) return;
                ScaffoldMessenger.of(context).showSnackBar(
                  SnackBar(
                    duration: const Duration(seconds: 5),
                    content: Text('Sync failed: $e'),
                  ),
                );
              }
            },
    );
  }

  Widget _folderNavBottomBar() {
    return BottomAppBar(
      child: Row(
        children: [
          Builder(
            builder: (context) => IconButton(
              icon: const Icon(Icons.menu),
              tooltip: 'Open folders',
              onPressed: () => Scaffold.of(context).openDrawer(),
            ),
          ),
        ],
      ),
    );
  }

  Widget _selectionBottomBar() {
    return BottomAppBar(
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          IconButton(
            icon: const Icon(Icons.archive),
            tooltip: 'Archive',
            onPressed: _batchArchive,
          ),
          IconButton(
            icon: const Icon(Icons.delete),
            tooltip: 'Delete',
            onPressed: _batchDelete,
          ),
          IconButton(
            icon: const Icon(Icons.report),
            tooltip: 'Mark as spam',
            onPressed: _batchMarkSpam,
          ),
          IconButton(
            icon: const Icon(Icons.drive_file_move),
            tooltip: 'Move to folder',
            onPressed: _batchMove,
          ),
          IconButton(
            icon: const Icon(Icons.access_time),
            tooltip: 'Snooze',
            onPressed: _batchSnooze,
          ),
        ],
      ),
    );
  }

  Widget _buildSearchBody() {
    if (_searchLoading) {
      return const Center(child: CircularProgressIndicator());
    }
    if (_searchResults == null) {
      return const Center(child: Text('Type a query and press Enter'));
    }
    if (_searchResults!.isEmpty) {
      return const Center(child: Text('No results'));
    }
    return _buildEmailList(_searchResults!);
  }

  Widget _buildSyncErrorBanner() {
    final errorAsync = ref.watch(syncLastErrorProvider(widget.accountId));
    final error = errorAsync.value;
    if (error == null || error == _dismissedError) {
      return const SizedBox.shrink();
    }
    return MaterialBanner(
      padding: const EdgeInsets.fromLTRB(16, 8, 8, 8),
      content: Text(error, maxLines: 2, overflow: TextOverflow.ellipsis),
      leading: Icon(
        Icons.sync_problem,
        color: Theme.of(context).colorScheme.error,
      ),
      backgroundColor: Theme.of(context).colorScheme.errorContainer,
      actions: [
        TextButton(
          onPressed: () {
            ref.read(syncManagerProvider).syncNow(widget.accountId);
          },
          child: const Text('Retry'),
        ),
        TextButton(
          onPressed: () =>
              context.push('/accounts/${widget.accountId}/sync-log'),
          child: const Text('View log'),
        ),
        TextButton(
          onPressed: () => setState(() => _dismissedError = error),
          child: const Text('Dismiss'),
        ),
      ],
    );
  }

  Widget _buildStreamBody(EmailRepository emailRepo) {
    return RefreshIndicator(
      onRefresh: () async {
        // Trigger a background sync cycle immediately.
        ref.read(syncManagerProvider).syncNow(widget.accountId);
        // Also wait for this specific mailbox to sync for immediate feedback.
        await emailRepo.syncEmails(widget.accountId, widget.mailboxPath);
      },
      child: StreamBuilder<List<EmailThread>>(
        stream: emailRepo.observeThreads(
          widget.accountId,
          widget.mailboxPath,
          limit: _limit,
        ),
        builder: (ctx, snap) {
          if (!snap.hasData) {
            return const Center(child: CircularProgressIndicator());
          }
          final threads = snap.data!;
          _currentThreads = threads;
          if (threads.isEmpty) {
            return ListView(
              children: const [
                SizedBox(height: 300, child: Center(child: Text('No emails'))),
              ],
            );
          }
          return _buildThreadList(threads);
        },
      ),
    );
  }

  Future<void> _batchMoveToRole(
    String role, {
    required String dialogTitle,
    required String createFolderName,
  }) async {
    final ids = _selectedEmailIds;
    _clearSelection();

    final mailbox = await resolveMailboxByRole(
      context,
      ref.read(mailboxRepositoryProvider),
      widget.accountId,
      widget.mailboxPath,
      role,
      dialogTitle: dialogTitle,
      createFolderName: createFolderName,
    );

    if (!mounted || mailbox == null) return;

    final repo = ref.read(emailRepositoryProvider);

    // Fetch full email data before moving so we can restore them if user clicks Undo.
    final originalEmails = (await Future.wait(
      ids.map((id) => repo.getEmail(id)),
    ))
        .whereType<Email>()
        .toList();

    for (final id in ids) {
      await repo.moveEmail(id, mailbox.path);
    }

    final action = UndoAction(
      id: DateTime.now().toIso8601String(),
      accountId: widget.accountId,
      type: UndoType.move,
      emailIds: ids,
      sourceMailboxPath: widget.mailboxPath,
      destinationMailboxPath: mailbox.path,
      originalEmails: originalEmails,
    );
    unawaited(ref.read(undoServiceProvider.notifier).pushAction(action));
  }

  Future<void> _batchArchive() => _batchMoveToRole(
        'archive',
        dialogTitle: 'No archive folder found',
        createFolderName: 'Archive',
      );

  Future<void> _refreshSearchAndPopIfEmpty() async {
    if (!mounted || !_searching) return;
    final query = _searchController.text.trim();
    final remaining = await ref
        .read(emailRepositoryProvider)
        .searchEmails(widget.accountId, widget.mailboxPath, query);
    if (!mounted) return;
    if (remaining.isEmpty) {
      if (context.canPop()) {
        context.pop();
      } else {
        _searchController.clear();
      }
    } else {
      setState(() => _searchResults = remaining);
    }
  }

  Future<void> _openSearchResultAndRefresh(String emailId) async {
    await context.push(
      '/accounts/${widget.accountId}/mailboxes'
      '/${Uri.encodeComponent(widget.mailboxPath)}'
      '/emails/${Uri.encodeComponent(emailId)}',
    );
    await _refreshSearchAndPopIfEmpty();
  }

  Future<void> _batchDelete() async {
    final ids = _selectedEmailIds;
    final wasSearching = _searching;
    _clearSelection();
    final repo = ref.read(emailRepositoryProvider);

    // Fetch full email data before deleting so we can restore them if user clicks Undo.
    // This is especially important for IMAP where we hard-delete the row locally.
    final originalEmails = (await Future.wait(
      ids.map((id) => repo.getEmail(id)),
    ))
        .whereType<Email>()
        .toList();

    String? lastDestPath;
    for (final id in ids) {
      lastDestPath = await repo.deleteEmail(id);
    }

    final action = UndoAction(
      id: DateTime.now().toIso8601String(),
      accountId: widget.accountId,
      type: UndoType.delete,
      emailIds: ids,
      sourceMailboxPath: widget.mailboxPath,
      destinationMailboxPath: lastDestPath,
      originalEmails: originalEmails,
    );
    unawaited(ref.read(undoServiceProvider.notifier).pushAction(action));

    if (wasSearching && mounted) {
      // Filter deleted emails out of the local results immediately.
      // Calling searchEmails here would still return deleted rows because the
      // delete is only enqueued — not yet applied to the local DB.
      final deletedIds = ids.toSet();
      final remaining = (_searchResults ?? [])
          .where((e) => !deletedIds.contains(e.id))
          .toList();
      if (remaining.isEmpty) {
        if (context.canPop()) {
          context.pop();
        } else {
          _searchController.clear();
        }
      } else {
        setState(() => _searchResults = remaining);
      }
    }
  }

  Future<void> _batchMarkSpam() => _batchMoveToRole(
        'junk',
        dialogTitle: 'No spam folder found',
        createFolderName: 'Junk',
      );

  Future<void> _batchMove() async {
    final ids = _selectedEmailIds;
    final mailboxes = await ref
        .read(mailboxRepositoryProvider)
        .observeMailboxes(widget.accountId)
        .first;
    final destinations =
        mailboxes.where((m) => m.path != widget.mailboxPath).toList();

    if (!mounted) return;

    final chosen = await showModalBottomSheet<String>(
      context: context,
      builder: (ctx) => ListView(
        shrinkWrap: true,
        children: [
          const ListTile(
            title: Text(
              'Move to…',
              style: TextStyle(fontWeight: FontWeight.bold),
            ),
          ),
          for (final m in destinations)
            ListTile(
              leading: const Icon(Icons.folder_outlined),
              title: Text(m.name),
              onTap: () => Navigator.pop(ctx, m.path),
            ),
        ],
      ),
    );

    if (chosen == null || !mounted) return;
    _clearSelection();
    final repo = ref.read(emailRepositoryProvider);

    // Fetch full email data before moving so we can restore them if user clicks Undo.
    final originalEmails = (await Future.wait(
      ids.map((id) => repo.getEmail(id)),
    ))
        .whereType<Email>()
        .toList();

    for (final id in ids) {
      await repo.moveEmail(id, chosen);
    }

    final action = UndoAction(
      id: DateTime.now().toIso8601String(),
      accountId: widget.accountId,
      type: UndoType.move,
      emailIds: ids,
      sourceMailboxPath: widget.mailboxPath,
      destinationMailboxPath: chosen,
      originalEmails: originalEmails,
    );
    unawaited(ref.read(undoServiceProvider.notifier).pushAction(action));
  }

  Future<void> _batchSnooze() async {
    final ids = _selectedEmailIds;
    final until = await showModalBottomSheet<DateTime>(
      context: context,
      builder: (ctx) => const SnoozePicker(),
    );
    if (until == null || !mounted) return;

    _clearSelection();
    final repo = ref.read(emailRepositoryProvider);
    // Fetch full email data before snoozing so we can restore them if user clicks Undo.
    final originalEmails = (await Future.wait(
      ids.map((id) => repo.getEmail(id)),
    ))
        .whereType<Email>()
        .toList();

    for (final id in ids) {
      await repo.snoozeEmail(id, until);
    }

    final action = UndoAction(
      id: DateTime.now().toIso8601String(),
      accountId: widget.accountId,
      type: UndoType.snooze,
      emailIds: ids,
      sourceMailboxPath: widget.mailboxPath,
      originalEmails: originalEmails,
    );
    unawaited(ref.read(undoServiceProvider.notifier).pushAction(action));

    if (!mounted) return;

    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        duration: const Duration(seconds: 5),
        content: Text(
          'Snoozed ${ids.length} email${ids.length == 1 ? '' : 's'} until ${DateFormat('MMM d, HH:mm').format(until)}',
        ),
      ),
    );
  }

  Widget _buildThreadList(List<EmailThread> threads) {
    final hasMore = threads.length == _limit;
    return ListView.builder(
      itemCount: threads.length + (hasMore ? 1 : 0),
      itemBuilder: (ctx, i) {
        if (i == threads.length) {
          return TextButton(
            onPressed: () => setState(() => _limit += _pageSize),
            child: const Text('Load more'),
          );
        }
        final t = threads[i];
        return EmailThreadTile(
          thread: t,
          isSelected: _selectedThreadIds.contains(t.threadId),
          isSelecting: _selecting,
          onTap: _selecting
              ? () => _toggleThreadSelection(t)
              : t.messageCount > 1
                  ? () => context.push(
                        '/accounts/${widget.accountId}/mailboxes'
                        '/${Uri.encodeComponent(widget.mailboxPath)}'
                        '/threads/${Uri.encodeComponent(t.threadId)}',
                      )
                  : () => context.push(
                        '/accounts/${widget.accountId}/mailboxes'
                        '/${Uri.encodeComponent(widget.mailboxPath)}'
                        '/emails/${Uri.encodeComponent(t.latestEmailId)}',
                      ),
          onLongPress: () => _toggleThreadSelection(t),
          onDismissed: (direction) => _onSwipeDismissed(t, direction),
        );
      },
    );
  }

  Future<void> _onSwipeDismissed(
    EmailThread t,
    DismissDirection direction,
  ) async {
    final repo = ref.read(emailRepositoryProvider);
    final type = direction == DismissDirection.startToEnd
        ? UndoType.move
        : UndoType.delete;

    // Fetch full email data before moving/deleting.
    final originalEmails = (await Future.wait(
      t.emailIds.map((id) => repo.getEmail(id)),
    ))
        .whereType<Email>()
        .toList();

    if (direction == DismissDirection.startToEnd) {
      final archive = await ref
          .read(mailboxRepositoryProvider)
          .findMailboxByRole(widget.accountId, 'archive');
      if (!mounted || archive == null) return;
      for (final id in t.emailIds) {
        await repo.moveEmail(id, archive.path);
      }
      final action = UndoAction(
        id: DateTime.now().toIso8601String(),
        accountId: widget.accountId,
        type: type,
        emailIds: t.emailIds,
        sourceMailboxPath: widget.mailboxPath,
        destinationMailboxPath: archive.path,
        originalEmails: originalEmails,
      );
      unawaited(ref.read(undoServiceProvider.notifier).pushAction(action));
      return;
    }

    String? lastDestPath;
    for (final id in t.emailIds) {
      lastDestPath = await repo.deleteEmail(id);
    }
    final action = UndoAction(
      id: DateTime.now().toIso8601String(),
      accountId: widget.accountId,
      type: type,
      emailIds: t.emailIds,
      sourceMailboxPath: widget.mailboxPath,
      destinationMailboxPath: lastDestPath,
      originalEmails: originalEmails,
    );
    unawaited(ref.read(undoServiceProvider.notifier).pushAction(action));
  }

  // Used for search results, which are individual emails.
  Widget _buildEmailList(List<Email> emails) {
    return ListView.builder(
      itemCount: emails.length,
      itemBuilder: (ctx, i) {
        final e = emails[i];
        final t = EmailThread.fromEmail(e);
        final isSelected = _selectedSearchIds.contains(e.id);
        return ThreadTile(
          thread: t,
          selected: isSelected,
          leading: SizedBox(
            width: 40,
            child: _selecting
                ? Checkbox(
                    value: isSelected,
                    onChanged: (_) => _toggleSearchSelection(e.id),
                  )
                : null,
          ),
          onTap: _selecting
              ? () => _toggleSearchSelection(e.id)
              : () => unawaited(_openSearchResultAndRefresh(e.id)),
          onLongPress: () => _toggleSearchSelection(e.id),
        );
      },
    );
  }
}