HomeMonitor/Environment/Service/MessageHandler.cs

using System.Text.Json;
using ChrisKaczor.HomeMonitor.Environment.Service.Data;
using MQTTnet;
using MQTTnet.Client;

namespace ChrisKaczor.HomeMonitor.Environment.Service;

public class MessageHandler : IHostedService
{
    private readonly IConfiguration _configuration;
    private readonly Database _database;
    private readonly IMqttClient _mqttClient;

    private readonly MqttFactory _mqttFactory;
    private readonly string _topic;

    public MessageHandler(IConfiguration configuration, Database database)
    {
        _configuration = configuration;
        _database = database;

        _database.EnsureDatabase();

        _topic = _configuration["Mqtt:Topic"] ?? string.Empty;

        if (string.IsNullOrEmpty(_topic))
            throw new InvalidOperationException("Topic not set");

        _mqttFactory = new MqttFactory();
        _mqttClient = _mqttFactory.CreateMqttClient();

        _mqttClient.ApplicationMessageReceivedAsync += OnApplicationMessageReceivedAsync;
    }

    public async Task StartAsync(CancellationToken cancellationToken)
    {
        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer(_configuration["Mqtt:Server"]).Build();
        await _mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

        var mqttSubscribeOptions = _mqttFactory.CreateSubscribeOptionsBuilder().WithTopicFilter($"{_topic}/#").Build();
        await _mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        await _mqttClient.DisconnectAsync(new MqttClientDisconnectOptionsBuilder().Build(), CancellationToken.None);
    }

    private async Task OnApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs arg)
    {
        var topic = arg.ApplicationMessage.Topic;
        var payload = arg.ApplicationMessage.ConvertPayloadToString();

        WriteLog($"Topic: {topic} = {payload}");

        var message = JsonSerializer.Deserialize<Message>(payload);

        if (message == null)
            return;

        await _database.StoreMessageAsync(message);
    }

    private static void WriteLog(string message)
    {
        Console.WriteLine(message);
    }
}