using Evergreen.Health.Application.Health.Sleep;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

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

public sealed class Ib43MqttService(IOptions<Ib43Options> options, IIb43MqttTransportFactory factory,
    Ib43StateStore store, TimeProvider clock, ILogger<Ib43MqttService> logger, IIb43ReportSink sink = null,
    IBedPresenceSink presenceSink = null) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var configuration = options.Value;
        logger.LogInformation("IB43 MQTT startup: Enabled={Enabled}, Host={Host}, Port={Port}, PasswordConfigured={PasswordConfigured}, Devices={Count}",
            configuration.Enabled, configuration.Host, configuration.Port,
            !string.IsNullOrWhiteSpace(configuration.Password), configuration.Devices?.Count ?? 0);
        if (!configuration.Enabled)
        {
            logger.LogInformation("IB43 MQTT disabled; set Ib43__Enabled=true to enable");
            return;
        }
        // 即使直接构造（测试/其他宿主）也不带错误配置进入重试。
        if (!configuration.IsValid()) throw new InvalidOperationException("Invalid Ib43 configuration");
        var failures = 0;
        while (!stoppingToken.IsCancellationRequested)
        {
            var connectedAt = clock.GetUtcNow();
            var connectionId = Guid.NewGuid();
            using var connection = CancellationTokenSource.CreateLinkedTokenSource(stoppingToken);
            var connectionToken = connection.Token;
            try
            {
                using var transport = factory.Create();
                var seenKinds = new HashSet<string>(StringComparer.Ordinal);
                int? lastMatchedBeds = null;
                transport.Message += async (topic, payload, retained) =>
                {
                    var report = store.Receive(topic, payload, retained);
                    if (sink != null && report.Accepted && report.Readings.Count > 0)
                    {
                        var binding = configuration.Devices.Single(d => d.PostTopic == topic);
                        var reportId = Guid.NewGuid().ToString("N");
                        Ib43SavedReport saved;
                        // 等待持久化再结束回调（MQTT 自动 ACK 在此之后）。失败时阻塞重试而非静默丢弃。
                        while (true)
                        {
                            stoppingToken.ThrowIfCancellationRequested();
                            try
                            {
                                saved = await sink.SaveAsync(reportId, binding, report, stoppingToken);
                                break;
                            }
                            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested) { throw; }
                            catch (Exception error)
                            {
                                logger.LogWarning("IB43 persistence failed ({Type}); retrying in 5 seconds", error.GetType().Name);
                                await Task.Delay(TimeSpan.FromSeconds(5), clock, stoppingToken);
                            }
                        }
                        if (saved.MatchedCount != lastMatchedBeds)
                            logger.LogInformation("IB43 persistence: matched beds={Count}; zero means no user observation saved", saved.MatchedCount);
                        lastMatchedBeds = saved.MatchedCount;
                        // 发布失败与写库重试分开，联动问题不能导致重写已保存的报文。
                        try { Ib43PresenceAdapter.Publish(presenceSink, binding, report, saved.ActiveBeds, connectionId, connectionToken); }
                        catch (Exception error)
                        {
                            logger.LogWarning("IB43 presence publication failed ({Type})", error.GetType().Name);
                        }
                    }
                    if (!report.Accepted || report.Issues.Count > 0)
                        logger.LogDebug("IB43 report has {Count} parsing issues", report.Issues.Count);
                    if (report.Accepted && (report.Readings.Count > 0 || report.Fields.Count > 0))
                        foreach (var kind in report.Kinds)
                            if (seenKinds.Add(kind))
                                logger.LogInformation("IB43 first {Kind} report received in this connection", kind);
                };
                transport.OversizedMessage += store.RejectOversized;
                store.SetTransport("connecting");
                using var timeout = CancellationTokenSource.CreateLinkedTokenSource(stoppingToken);
                timeout.CancelAfter(TimeSpan.FromSeconds(15));
                await transport.ConnectAndSubscribeAsync(configuration, timeout.Token);
                store.SetTransport("connected");
                connectedAt = clock.GetUtcNow();
                logger.LogInformation("IB43 MQTT connected and subscribed to {Count} configured devices", configuration.Devices.Count);
                while (transport.IsConnected)
                    await Task.Delay(TimeSpan.FromSeconds(1), clock, stoppingToken);
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested) { break; }
            catch (Exception exception)
            {
                // 不写密码、连接选项、完整异常文本或原始健康报文。
                logger.LogWarning("IB43 MQTT connection/subscription failed ({Type}); retrying", exception.GetType().Name);
            }
            finally
            {
                connection.Cancel();
                store.SetTransport("disconnected");
            }
            if (clock.GetUtcNow() - connectedAt > TimeSpan.FromMinutes(1)) failures = 0;
            var seconds = Math.Min(30, Math.Pow(2, Math.Min(failures++, 5)));
            try { await Task.Delay(TimeSpan.FromSeconds(seconds), clock, stoppingToken); }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested) { break; }
        }
    }
}