import 'dart:async';

import 'package:flutter/material.dart';
import 'package:stream_chat_flutter/stream_chat_flutter.dart';

import 'routes/routes.dart';
import 'search_text_field.dart';

class NewGroupChatScreen extends StatefulWidget {
  @override
  _NewGroupChatScreenState createState() => _NewGroupChatScreenState();
}

class _NewGroupChatScreenState extends State<NewGroupChatScreen> {
  TextEditingController _controller;

  String _userNameQuery = '';

  final _selectedUsers = <User>{};

  bool _isSearchActive = false;

  Timer _debounce;

  void _userNameListener() {
    if (_debounce?.isActive ?? false) _debounce.cancel();
    _debounce = Timer(const Duration(milliseconds: 350), () {
      if (mounted) {
        setState(() {
          _userNameQuery = _controller.text;
          _isSearchActive = _userNameQuery.isNotEmpty;
        });
      }
    });
  }

  @override
  void initState() {
    super.initState();
    _controller = TextEditingController()..addListener(_userNameListener);
  }

  @override
  void dispose() {
    _controller?.clear();
    _controller?.removeListener(_userNameListener);
    _controller?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: StreamChatTheme.of(context).colorTheme.whiteSnow,
      appBar: AppBar(
        elevation: 1,
        backgroundColor: StreamChatTheme.of(context).colorTheme.white,
        leading: const StreamBackButton(),
        title: Text(
          'Add Group Members',
          style: TextStyle(
            color: StreamChatTheme.of(context).colorTheme.black,
            fontSize: 16,
          ),
        ),
        centerTitle: true,
        actions: [
          if (_selectedUsers.isNotEmpty)
            IconButton(
              icon: StreamSvgIcon.arrow_right(
                color: StreamChatTheme.of(context).colorTheme.accentBlue,
              ),
              onPressed: () async {
                final updatedList = await Navigator.pushNamed(
                  context,
                  Routes.NEW_GROUP_CHAT_DETAILS,
                  arguments: _selectedUsers.toList(growable: false),
                );
                if (updatedList != null) {
                  setState(() {
                    _selectedUsers
                      ..clear()
                      ..addAll(updatedList);
                  });
                }
              },
            )
        ],
      ),
      body: NestedScrollView(
        floatHeaderSlivers: true,
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return <Widget>[
            SliverToBoxAdapter(
              child: SearchTextField(
                controller: _controller,
              ),
            ),
            if (_selectedUsers.isNotEmpty)
              SliverToBoxAdapter(
                child: Container(
                  height: 104,
                  child: ListView.separated(
                    scrollDirection: Axis.horizontal,
                    itemCount: _selectedUsers.length,
                    padding: const EdgeInsets.all(8),
                    separatorBuilder: (_, __) => SizedBox(width: 16),
                    itemBuilder: (_, index) {
                      final user = _selectedUsers.elementAt(index);
                      return Column(
                        children: [
                          Stack(
                            children: [
                              UserAvatar(
                                onlineIndicatorAlignment: Alignment(0.9, 0.9),
                                user: user,
                                showOnlineStatus: true,
                                borderRadius: BorderRadius.circular(32),
                                constraints: BoxConstraints.tightFor(
                                  height: 64,
                                  width: 64,
                                ),
                              ),
                              Positioned(
                                top: -4,
                                right: -4,
                                child: GestureDetector(
                                  onTap: () {
                                    if (_selectedUsers.contains(user)) {
                                      setState(
                                          () => _selectedUsers.remove(user));
                                    }
                                  },
                                  child: Container(
                                    decoration: BoxDecoration(
                                      color: StreamChatTheme.of(context)
                                          .colorTheme
                                          .white,
                                      shape: BoxShape.circle,
                                      border: Border.all(
                                        color: StreamChatTheme.of(context)
                                            .colorTheme
                                            .whiteSnow,
                                      ),
                                    ),
                                    child: StreamSvgIcon.close(
                                      color: StreamChatTheme.of(context)
                                          .colorTheme
                                          .black,
                                      size: 24,
                                    ),
                                  ),
                                ),
                              )
                            ],
                          ),
                          SizedBox(height: 4),
                          Text(
                            user.name.split(' ')[0],
                            style: TextStyle(
                              fontWeight: FontWeight.bold,
                              fontSize: 12,
                            ),
                          ),
                        ],
                      );
                    },
                  ),
                ),
              ),
            SliverPersistentHeader(
              pinned: true,
              delegate: _HeaderDelegate(
                height: 30,
                child: Container(
                  width: double.maxFinite,
                  decoration: BoxDecoration(
                    gradient: StreamChatTheme.of(context).colorTheme.bgGradient,
                  ),
                  child: Padding(
                    padding: const EdgeInsets.symmetric(
                      vertical: 8,
                      horizontal: 8,
                    ),
                    child: Text(
                      _isSearchActive
                          ? 'Matches for \"$_userNameQuery\"'
                          : 'On the platform',
                      style: TextStyle(
                        color: StreamChatTheme.of(context).colorTheme.grey,
                      ),
                    ),
                  ),
                ),
              ),
            ),
          ];
        },
        body: GestureDetector(
          behavior: HitTestBehavior.opaque,
          onPanDown: (_) => FocusScope.of(context).unfocus(),
          child: UsersBloc(
            child: UserListView(
              selectedUsers: _selectedUsers,
              pullToRefresh: false,
              groupAlphabetically: _isSearchActive ? false : true,
              onUserTap: (user, _) {
                if (!_selectedUsers.contains(user)) {
                  setState(() {
                    _selectedUsers.add(user);
                  });
                } else {
                  setState(() {
                    _selectedUsers.remove(user);
                  });
                }
              },
              pagination: PaginationParams(
                limit: 25,
              ),
              filter: {
                if (_userNameQuery.isNotEmpty)
                  'name': {
                    r'$autocomplete': _userNameQuery,
                  },
                'id': {
                  r'$ne': StreamChat.of(context).user.id,
                }
              },
              sort: [
                SortOption(
                  'name',
                  direction: 1,
                ),
              ],
              emptyBuilder: (_) {
                return LayoutBuilder(
                  builder: (context, viewportConstraints) {
                    return SingleChildScrollView(
                      physics: AlwaysScrollableScrollPhysics(),
                      child: ConstrainedBox(
                        constraints: BoxConstraints(
                          minHeight: viewportConstraints.maxHeight,
                        ),
                        child: Center(
                          child: Column(
                            children: [
                              Padding(
                                padding: const EdgeInsets.all(24),
                                child: StreamSvgIcon.search(
                                  size: 96,
                                  color: StreamChatTheme.of(context)
                                      .colorTheme
                                      .grey,
                                ),
                              ),
                              Text(
                                'No user matches these keywords...',
                                style: StreamChatTheme.of(context)
                                    .textTheme
                                    .footnote
                                    .copyWith(
                                      color: StreamChatTheme.of(context)
                                          .colorTheme
                                          .grey,
                                    ),
                              ),
                            ],
                          ),
                        ),
                      ),
                    );
                  },
                );
              },
            ),
          ),
        ),
      ),
    );
  }
}

class _HeaderDelegate extends SliverPersistentHeaderDelegate {
  final Widget child;
  final double height;

  const _HeaderDelegate({
    @required this.child,
    @required this.height,
  });

  @override
  Widget build(
      BuildContext context, double shrinkOffset, bool overlapsContent) {
    return Container(
      color: StreamChatTheme.of(context).colorTheme.white,
      child: child,
    );
  }

  @override
  double get maxExtent => height;

  @override
  double get minExtent => height;

  @override
  bool shouldRebuild(_HeaderDelegate oldDelegate) => true;
}