step2.dart

// see Serializing JSON inside model classes in
// https://flutter.dev/docs/development/data-and-backend/json

import 'package:intl/intl.dart';
import 'dart:convert' as convert;
import 'package:flutter/material.dart';

final DateFormat _dateFormatter = DateFormat("yyyy-MM-dd HH:mm:ss");

abstract class Activity {
  late int id;
  late String name;
  DateTime? initialDate;
  DateTime? finalDate;
  late int duration;
  List<dynamic> children = List<dynamic>.empty(growable: true);

  Activity.fromJson(Map<String, dynamic> json)
      : id = json['id'],
        name = json['name'],
        initialDate = json['initialDate']==null ? null : _dateFormatter.parse(json['initialDate']),
        finalDate = json['finalDate']==null ? null : _dateFormatter.parse(json['finalDate']),
        duration = json['duration'];
}


class Project extends Activity {
  Project.fromJson(Map<String, dynamic> json) : super.fromJson(json) {
    if (json.containsKey('activities')) {
      // json has only 1 level because depth=1 or 0 in time_tracker
      for (Map<String, dynamic> jsonChild in json['activities']) {
        if (jsonChild['class'] == "project") {
          children.add(Project.fromJson(jsonChild));
          // condition on key avoids infinite recursion
        } else if (jsonChild['class'] == "task") {
          children.add(Task.fromJson(jsonChild));
        } else {
          assert(false);
        }
      }
    }
  }
}


class Task extends Activity {
  late bool active;
  Task.fromJson(Map<String, dynamic> json) : super.fromJson(json) {
    active = json['active'];
    for (Map<String, dynamic> jsonChild in json['intervals']) {
      children.add(Interval.fromJson(jsonChild));
    }
  }
}


class Interval {
  late int id;
  DateTime? initialDate;
  DateTime? finalDate;
  late int duration;
  late bool active;

  Interval.fromJson(Map<String, dynamic> json)
      : id = json['id'],
        initialDate = json['initialDate']==null ? null : _dateFormatter.parse(json['initialDate']),
        finalDate = json['finalDate']==null ? null : _dateFormatter.parse(json['finalDate']),
        duration = json['duration'],
        active = json['active'];
}


class Tree {
  late Activity root;

  Tree(Map<String, dynamic> dec) {
    // 1 level tree, root and children only, root is either Project or Task. If Project
    // children are Project or Task, that is, Activity. If root is Task, children are Interval.
    assert (dec['class'] == "project" || dec['class']=='task');
    if (dec['class'] == "project") {
      root = Project.fromJson(dec);
    } else {
      root = Task.fromJson(dec);
    }
  }
}


Tree getTree() {
  String strJson = "{"
      "\"name\":\"root\", \"class\":\"project\", \"id\":0, \"initialDate\":\"2020-09-22 16:04:56\", \"finalDate\":\"2020-09-22 16:05:22\", \"duration\":26,"
      "\"activities\": [ "
      "{ \"name\":\"software design\", \"class\":\"project\", \"id\":1, \"initialDate\":\"2020-09-22 16:05:04\", \"finalDate\":\"2020-09-22 16:05:16\", \"duration\":16 },"
      "{ \"name\":\"software testing\", \"class\":\"project\", \"id\":2, \"initialDate\": null, \"finalDate\":null, \"duration\":0 },"
      "{ \"name\":\"databases\", \"class\":\"project\", \"id\":3,  \"finalDate\":null, \"initialDate\":null, \"duration\":0 },"
      "{ \"name\":\"transportation\", \"class\":\"task\", \"id\":6, \"active\":false, \"initialDate\":\"2020-09-22 16:04:56\", \"finalDate\":\"2020-09-22 16:05:22\", \"duration\":10, \"intervals\":[] }"
      "] "
      "}";
  Map<String, dynamic> decoded = convert.jsonDecode(strJson);
  Tree tree = Tree(decoded);
  return tree;
}

testLoadTree() {
  Tree tree = getTree();
  print("root name ${tree.root.name}, duration ${tree.root.duration}");
  for (Activity act in tree.root.children) {
    print("child name ${act.name}, duration ${act.duration}");
  }
}


//void main() {
//  testLoadTree();
//}



void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'TimeTracker',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        textTheme: const TextTheme(
            subtitle1: TextStyle(fontSize:20.0),
            bodyText2:TextStyle(fontSize:20.0)),
      ),
      home: PageActivities(),
    );
  }
}


class PageActivities extends StatefulWidget {
  @override
  _PageActivitiesState createState() => _PageActivitiesState();
}

class _PageActivitiesState extends State<PageActivities> {
  late Tree tree;

  @override
  void initState() {
    super.initState();
    tree = getTree();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(tree.root.name),
        actions: <Widget>[
          IconButton(icon: Icon(Icons.home),
              onPressed: () {}
            // TODO go home page = root
          ),
          //TODO other actions
        ],
      ),
      body: ListView.separated(
        // it's like ListView.builder() but better
        // because it includes a separator between items
        padding: const EdgeInsets.all(16.0),
        itemCount: tree.root.children.length,
        itemBuilder: (BuildContext context, int index) =>
            _buildRow(tree.root.children[index], index),
        separatorBuilder: (BuildContext context, int index) =>
        const Divider(),
      ),
    );
  }

  Widget _buildRow(Activity activity, int index) {
    String strDuration = Duration(seconds: activity.duration).toString().split('.').first;
    // split by '.' and taking first element of resulting list
    // removes the microseconds part
    assert (activity is Project || activity is Task);
    if (activity is Project) {
      return ListTile(
        title: Text('${activity.name}'),
        trailing: Text('$strDuration'),
        onTap: () => {},
        // TODO, navigate down to show children tasks and projects
      );
    } else {
      Task task = activity as Task;
      Widget trailing;
      trailing = Text('$strDuration');
      return ListTile(
        title: Text('${activity.name}'),
        trailing: trailing,
        onTap: () => _navigateDownIntervals(index),
        // TODO, navigate down to show intervals
        onLongPress: () {},
        // TODO start/stop counting the time for this task
      );
    }
  }
  
    void _navigateDownIntervals(int childId) {
    Navigator.of(context)
        .push(MaterialPageRoute<void>(builder: (context) => PageIntervals())
    );
  }
}


Tree getTreeTask() {
  String strJson = "{"
      "\"name\":\"transportation\",\"class\":\"task\", \"id\":6, \"active\":false, \"initialDate\":\"2020-09-22 13:36:08\", \"finalDate\":\"2020-09-22 13:36:34\", \"duration\":10,"
      "\"intervals\":["
      "{\"class\":\"interval\", \"id\":7, \"active\":false, \"initialDate\":\"2020-09-22 13:36:08\", \"finalDate\":\"2020-09-22 13:36:14\", \"duration\":6},"
      "{\"class\":\"interval\", \"id\":8, \"active\":false, \"initialDate\":\"2020-09-22 13:36:30\", \"finalDate\":\"2020-09-22 13:36:34\", \"duration\":4}"
      "]}";
  Map<String, dynamic> decoded = convert.jsonDecode(strJson);
  Tree tree = Tree(decoded);
  return tree;
}

class PageIntervals extends StatefulWidget {
  @override
  _PageIntervalsState createState() => _PageIntervalsState();
}

class _PageIntervalsState extends State<PageIntervals> {
  late Tree tree;

  @override
  void initState() {
    super.initState();
    tree = getTreeTask();
    // the root is a task and the children its intervals
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(tree.root.name),
        actions: <Widget>[
          IconButton(icon: Icon(Icons.home),
              onPressed: () {} // TODO go home page = root
          ),
          //TODO other actions
        ],
      ),
      body: ListView.separated(
        // it's like ListView.builder() but better because it includes a
        // separator between items
        padding: const EdgeInsets.all(16.0),
        itemCount: tree.root.children.length, // number of intervals
        itemBuilder: (BuildContext context, int index) =>
            _buildRow(tree.root.children[index], index),
        separatorBuilder: (BuildContext context, int index) =>
        const Divider(),
      ),
    );
  }

  Widget _buildRow(Interval interval, int index) {
    String strDuration = Duration(seconds: interval.duration).toString().split('.').first;
    String strInitialDate = interval.initialDate.toString().split('.')[0];
    // this removes the microseconds part
    String strFinalDate = interval.finalDate.toString().split('.')[0];
    return ListTile(
      title: Text('from ${strInitialDate} to ${strFinalDate}'),
      trailing: Text('$strDuration'),
    );
  }
}