import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/rendering.dart';
import 'package:rxdart/rxdart.dart';

import 'dart:async';

void main() {
  Firestore.instance.enablePersistence(true);
  FirebaseDatabase.instance.setPersistenceEnabled(false);
  runApp(MaterialApp(title: "Happy.do", home: HappyDo()));
}

class HappyDo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 3,
      child: Scaffold(
        appBar: AppBar(
            title: Text('Happy.do'),
            bottom: TabBar(
              tabs: [
                Tab(
                  text: 'Today',
                ),
                Tab(text: 'This week'),
                Tab(text: 'Next week'),
              ],
            )),
        body: TabBarView(
          children: <Widget>[
            ReordableTodoListView(
              stream: Observable<QuerySnapshot>(Firestore.instance
                  .collection('todos')
                  .where('date', isEqualTo: '2018-09-25')
                  .where('weekly', isEqualTo: false)
                  .snapshots()),
            ),
            ReordableTodoListView(
              stream: Observable<QuerySnapshot>(Firestore.instance
                  .collection('todos')
                  .where('date', isGreaterThanOrEqualTo: '2018-09-24')
                  .where('date', isLessThanOrEqualTo: '2018-09-30')
                  .where('weekly', isEqualTo: false)
                  .snapshots()),
            ),
            ReordableTodoListView(
              stream: Observable<QuerySnapshot>(Firestore.instance
                  .collection('todos')
                  .where('date', isGreaterThanOrEqualTo: '2018-10-01')
                  .where('date', isLessThanOrEqualTo: '2018-10-07')
                  .where('weekly', isEqualTo: true)
                  .snapshots()),
            ),
          ],
        ),
        floatingActionButton: FloatingActionButton(
          child: Icon(Icons.add),
          onPressed: () async {
            await Firestore.instance.collection('todos').document().setData({
              'order': -DateTime.now().millisecondsSinceEpoch.toDouble(),
              'todo': '',
              'date': '2018-09-25',
              'weekly': false,
              'checked': false
            });
          },
        ),
      ),
    );
  }
}

class ReordableTodoListView extends StatelessWidget {
  final Observable<QuerySnapshot> stream;

  ReordableTodoListView({Key key, @required this.stream}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<DocumentSnapshot>>(
        stream: stream.map((s) => s.documents
          ..sort((d1, d2) =>
              ((d1.data['order'] ?? 0) - (d2.data['order'] ?? 0)).toInt())),
        builder: (context, documents) {
          if (documents.data == null) return Container();
          final orderMutation = List<double>();
          // If we want to drag&drop element X between elements Y&Z
          // that's enough to change only X.order to (Y.order+Z.order)*0.5
          //
          // If we want to move element to first or to last position
          // we use -current_time and +current as not the ideal but
          // prototype valid solution.
          //
          // The approach itself is inspired by Trello API.
          for (var i = 0; i < documents.data.length - 1; i++) {
            final order1 = documents.data[i]['order'] ?? 0.0;
            final order2 = documents.data[i + 1]['order'] ?? 0.0;
            orderMutation.add((order1 + order2) * 0.5);
          }
          orderMutation.insert(0, -DateTime.now().millisecondsSinceEpoch.toDouble());
          orderMutation.insert(orderMutation.length,
              DateTime.now().millisecondsSinceEpoch.toDouble());
          debugPrint('hackList = $orderMutation');
          documents.data.toList().fold<List<double>>(
              [-DateTime.now().millisecondsSinceEpoch.toDouble()].toList(),
                  (list, order) {
                return list;
              });
          return Container(
            child: ReorderableListView(
                padding: EdgeInsets.all(8.0),
                onReorder: (oldIndex, newIndex) async {
                  debugPrint('$oldIndex, $newIndex');
                  await Firestore.instance
                      .collection('todos')
                      .document(documents.data[oldIndex].documentID)
                      .updateData({'order': orderMutation[newIndex]});
                },
                children: documents.data
                    .map((document) { return TodoWidget(
                  key: ValueKey(document.documentID),
                  checked: document['checked'],
                  text: document['todo'],
                  documentId: document
                      .documentID, //todo: try to pass text & checked here?
                );})
                    .toList()),
//                child: Column(
//                    children: documents.data
//                        .map((document) => TodoWidget(
//                      key: GlobalObjectKey(document.documentID.hashCode),
//                      documentId: document.documentID,
//                    ))
//                        .toList()),
          );
        });
  }
}

class TodoListWidget extends StatefulWidget {
  final String title;
  final Observable<List<dynamic>> stream;
  final Function addPressed;

  TodoListWidget({Key key, this.title, this.stream, this.addPressed})
      : super(key: key);

  @override
  _TodoListWidgetState createState() => _TodoListWidgetState();
}

class _TodoListWidgetState extends State<TodoListWidget> {
  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(
        builder: (BuildContext context, BoxConstraints constraints) {
          return Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: <Widget>[
              Padding(
                padding: const EdgeInsets.only(left: 16.0),
                child: Row(
                  children: <Widget>[
                    Flexible(
                      child: Text(
                        widget.title,
                        style: TextStyle(
                          fontSize: 20.0,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
                    ),
                    IconButton(
                      icon: Icon(Icons.add),
                      onPressed: () {
                        widget.addPressed();
                      },
                    ),
                  ],
                ),
              ),
              StreamBuilder<List<dynamic>>(
                stream: widget.stream,
                builder: (context, documents) {
                  if (documents.data == null) return Container();
                  return Padding(
                      padding: const EdgeInsets.symmetric(vertical: 16.0),
                      child: Column(
                          mainAxisAlignment: MainAxisAlignment.center,
                          children: List<Widget>()
                            ..addAll(documents.data
                                .map((documentSnapshot) {
                              return TodoWidget(
                                  key: Key(documentSnapshot.documentID),
                                  checked: documentSnapshot["checked"],
                                  documentId: documentSnapshot.documentID);
                            })
                                .fold<List<Widget>>(
                                List<Widget>()..add(Text('123')),
                                    (current, widget) =>
                                current..addAll([widget, Text('123')]))
                                .toList())));
                },
              ),
            ],
          );
        });
  }
}


class TodoWidget extends StatefulWidget {
  final String documentId;
  final String text;
  final bool checked;

  TodoWidget({Key key, this.documentId, this.text = "", this.checked = false}) : super(key: key);

  @override
  _TodoWidgetState createState() => _TodoWidgetState();
}

class _TodoWidgetState extends State<TodoWidget> {
  MyTextEditingController outController = MyTextEditingController(text: '');
  BehaviorSubject<String> subject;
  StreamSubscription<DocumentSnapshot> subscription;
  bool checked = false;

  @override
  void initState() {
    super.initState();
    this.checked = widget.checked;
    this.outController.text = widget.text;
    debugPrint('initState $widget.documentId, $checked, ${widget.text}');
    subscription = Firestore.instance
        .collection('todos')
        .document(widget.documentId)
        .snapshots()
        .listen((documentSnapshot) {
      setState(() {
        outController.text =
        documentSnapshot.exists ? documentSnapshot["todo"] : "[none]";
        checked = documentSnapshot.exists
            ? documentSnapshot["checked"] ?? false
            : false;
      });
    });
    subject = BehaviorSubject<String>();
    subject.debounce(Duration(milliseconds: 750)).listen((text) {
      Firestore.instance
          .collection('todos')
          .document(widget.documentId)
          .updateData({'todo': text, 'checked': checked});
    });
  }

  @override
  void didUpdateWidget(TodoWidget oldWidget) {
    debugPrint('didUpdateWidget ' +
        widget.documentId +
        ' from ' +
        oldWidget.documentId);
    super.didUpdateWidget(oldWidget);
  }

  @override
  void dispose() {
    debugPrint('dispose ' + widget.documentId);
    subject.close();
    subscription.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return _buildTodoRow();
  }

  Row _buildTodoRow() {
    return Row(
      children: <Widget>[
        Checkbox(
          value: (outController.text.trim() != '') ? checked : false,
          onChanged: (changedChecked) async {
            if (outController.text.trim() != '') {
              // TODO: cancel deferred events on subject
              await Firestore.instance
                  .collection('todos')
                  .document(widget.documentId)
                  .updateData(
                  {'checked': changedChecked, 'todo': outController.text});
            }
          },
        ),
        Flexible(
          child: TextField(
            controller: outController,
            onChanged: (text) {
              subject.add(text);
            },
            style: ((outController.text.trim() != '') ? checked : false)
                ? TextStyle(
                color: Colors.black, decoration: TextDecoration.lineThrough)
                : TextStyle(color: Colors.black),
            enabled: !(((outController.text.trim() != '') ? checked : false)),
            decoration: InputDecoration(
                border: InputBorder.none, hintText: "enter new todo here"),
          ),
        ),
        IconButton(
          icon: Icon(Icons.code),
        ),
        IconButton(
          icon: Icon(Icons.delete),
          onPressed: () async {
            await Firestore.instance
                .collection('todos')
                .document(widget.documentId)
                .delete();
          },
        )
      ],
    );
  }
}


/// workaround for https://github.com/flutter/flutter/issues/22171
class MyTextEditingController extends TextEditingController {

  MyTextEditingController({String text}) : super(text: text);

  set text(String newText) {
    try {
      value = value.copyWith(
          text: newText);
    } catch (e) {
      value = value.copyWith(
          text: newText,
          selection: TextSelection.collapsed(offset: -1),
          composing: TextRange.empty);
    }
  }
}