using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Formatter;
using MQTTnet.Protocol;

namespace Evergreen.Health.Application.Health.Integrations.Ib43;

public interface IIb43MqttTransport : IDisposable
{
    bool IsConnected { get; }
    event Func<string, string, bool, Task> Message;
    event Action<string> OversizedMessage;
    Task ConnectAndSubscribeAsync(Ib43Options options, CancellationToken cancellationToken);
}

public interface IIb43MqttTransportFactory
{
    IIb43MqttTransport Create();
}

public sealed class Ib43MqttTransportFactory : IIb43MqttTransportFactory
{
    public IIb43MqttTransport Create() => new Ib43MqttTransport();
}

public sealed class Ib43MqttTransport : IIb43MqttTransport
{
    private readonly IMqttClient _client = new MqttFactory().CreateMqttClient();
    public bool IsConnected => _client.IsConnected;
    public event Func<string, string, bool, Task> Message;
    public event Action<string> OversizedMessage;

    public Ib43MqttTransport()
    {
        _client.ApplicationMessageReceivedAsync += async e =>
        {
            var m = e.ApplicationMessage;
            // 在解码前限制长度；不要将大包全部复制进诊断缓存。
            if (m.PayloadSegment.Count > Ib43StateStore.MaxPayloadBytes)
                OversizedMessage?.Invoke(m.Topic);
            else if (Message != null) await Message.Invoke(m.Topic, m.ConvertPayloadToString(), m.Retain);
        };
    }

    public async Task ConnectAndSubscribeAsync(Ib43Options options, CancellationToken cancellationToken)
    {
        var builder = new MqttClientOptionsBuilder().WithTcpServer(options.Host, options.Port)
            .WithClientId(options.ClientId).WithCredentials(options.Username, options.Password)
            .WithProtocolVersion(MqttProtocolVersion.V311).WithCleanSession()
            .WithKeepAlivePeriod(TimeSpan.FromSeconds(30)).WithTimeout(TimeSpan.FromSeconds(10));
        if (options.UseTls) builder.WithTlsOptions(t => t.UseTls());
        await _client.ConnectAsync(builder.Build(), cancellationToken);
        var subscription = new MqttClientSubscribeOptionsBuilder();
        foreach (var device in options.Devices)
            subscription.WithTopicFilter(f => f.WithTopic(device.PostTopic)
                .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce));
        var result = await _client.SubscribeAsync(subscription.Build(), cancellationToken);
        if (result.Items.Count != options.Devices.Count || result.Items.Any(i => (int)i.ResultCode >= 128))
            throw new InvalidOperationException("IB43 subscription rejected");
    }

    public void Dispose() => _client.Dispose();
}