BackgroundCollectingTask

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';
import 'package:scoped_model/scoped_model.dart';

class DataSample {
  double temperature1;
  double temperature2;
  double waterpHlevel;
  DateTime timestamp;

  DataSample({
    required this.temperature1,
    required this.temperature2,
    required this.waterpHlevel,
    required this.timestamp,
  });
}

class BackgroundCollectingTask extends Model {
  static BackgroundCollectingTask of(
    BuildContext context, {
    bool rebuildOnChange = false,
  }) =>
      ScopedModel.of<BackgroundCollectingTask>(
        context,
        rebuildOnChange: rebuildOnChange,
      );

  final BluetoothConnection _connection;
  List<int> _buffer = List<int>.empty(growable: true);

  // @TODO , Such sample collection in real code should be delegated
  // (via `Stream<DataSample>` preferably) and then saved for later
  // displaying on chart (or even stright prepare for displaying).
  // @TODO ? should be shrinked at some point, endless colleting data would cause memory shortage.
  List<DataSample> samples = List<DataSample>.empty(growable: true);

  bool inProgress = false;

  BackgroundCollectingTask._fromConnection(this._connection) {
    _connection.input!.listen((data) {
      _buffer += data;

      while (true) {
        // If there is a sample, and it is full sent
        int index = _buffer.indexOf('t'.codeUnitAt(0));
        if (index >= 0 && _buffer.length - index >= 7) {
          final DataSample sample = DataSample(
              temperature1: (_buffer[index + 1] + _buffer[index + 2] / 100),
              temperature2: (_buffer[index + 3] + _buffer[index + 4] / 100),
              waterpHlevel: (_buffer[index + 5] + _buffer[index + 6] / 100),
              timestamp: DateTime.now());
          _buffer.removeRange(0, index + 7);

          samples.add(sample);
          notifyListeners(); // Note: It shouldn't be invoked very often - in this example data comes at every second, but if there would be more data, it should update (including repaint of graphs) in some fixed interval instead of after every sample.
          //print("${sample.timestamp.toString()} -> ${sample.temperature1} / ${sample.temperature2}");
        }
        // Otherwise break
        else {
          break;
        }
      }
    }).onDone(() {
      inProgress = false;
      notifyListeners();
    });
  }

  static Future<BackgroundCollectingTask> connect(
      BluetoothDevice server) async {
    final BluetoothConnection connection =
        await BluetoothConnection.toAddress(server.address);
    return BackgroundCollectingTask._fromConnection(connection);
  }

  void dispose() {
    _connection.dispose();
  }

  Future<void> start() async {
    inProgress = true;
    _buffer.clear();
    samples.clear();
    notifyListeners();
    _connection.output.add(ascii.encode('start'));
    await _connection.output.allSent;
  }

  Future<void> cancel() async {
    inProgress = false;
    notifyListeners();
    _connection.output.add(ascii.encode('stop'));
    await _connection.finish();
  }

  Future<void> pause() async {
    inProgress = false;
    notifyListeners();
    _connection.output.add(ascii.encode('stop'));
    await _connection.output.allSent;
  }

  Future<void> reasume() async {
    inProgress = true;
    notifyListeners();
    _connection.output.add(ascii.encode('start'));
    await _connection.output.allSent;
  }

  Iterable<DataSample> getLastOf(Duration duration) {
    DateTime startingTime = DateTime.now().subtract(duration);
    int i = samples.length;
    do {
      i -= 1;
      if (i <= 0) {
        break;
      }
    } while (samples[i].timestamp.isAfter(startingTime));
    return samples.getRange(i, samples.length);
  }
}