using FieldLogger.Models;
using FieldLogger.Services.Data;
using Microsoft.Extensions.Logging;
using SyncCore = FieldLogger.Sync;

namespace FieldLogger.Services.Sync;

/// <summary>
/// Bridges the MAUI capture database to the workload-free durable MQTT engine. Network loss never
/// deletes a capture: the local point and outbound queue are separate durable records, and an
/// application acknowledgement is the only path that marks the local point synced.
/// </summary>
public sealed class MqttSyncService : IMqttSyncService
{
    private readonly SettingsService _settings;
    private readonly AppDatabase _database;
    private readonly ILogger<MqttSyncService> _logger;
    private readonly SyncCore.SqliteOutboundStore _store;
    private readonly SemaphoreSlim _connectionGate = new(1, 1);
    private readonly SemaphoreSlim _pumpGate = new(1, 1);
    private CancellationTokenSource? _lifetime;
    private Task? _backgroundLoop;
    private SyncCore.MqttnetTransport? _transport;
    private SyncCore.MqttSyncEngine? _engine;
    private bool _started;

    public bool IsConnected => _transport?.IsConnected == true;
    public string Status { get; private set; } = "Not started";
    public event EventHandler<string>? StatusChanged;
    public event EventHandler<PointSyncFailureEventArgs>? PointRejected;

    public MqttSyncService(SettingsService settings, AppDatabase database, ILogger<MqttSyncService> logger)
    {
        _settings = settings;
        _database = database;
        _logger = logger;
        _store = new SyncCore.SqliteOutboundStore(
            Path.Combine(FileSystem.AppDataDirectory, "fieldlogger-sync.db3"));
    }

    public async Task StartAsync(CancellationToken cancellationToken = default)
    {
        if (_started) return;
        _started = true;
        await _store.InitAsync();
        _lifetime = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        _backgroundLoop = RunAsync(_lifetime.Token);

        if (_settings.MqttEnabled)
        {
            try
            {
                await ConnectAsync(cancellationToken);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Initial MQTT connection failed; durable retry loop remains active");
                SetStatus($"Waiting to reconnect: {ex.Message}");
            }
        }
        else
        {
            SetStatus("Sync disabled");
        }
    }

    public async Task StopAsync()
    {
        _lifetime?.Cancel();
        if (_backgroundLoop is not null)
        {
            try { await _backgroundLoop; }
            catch (OperationCanceledException) { }
        }
        await DisconnectTransportAsync();
        SetStatus("Stopped");
    }

    public async Task ConnectAsync(CancellationToken cancellationToken = default)
    {
        await ConnectCoreAsync(forceReconnect: true, cancellationToken);
        await QueueUnsyncedAsync(cancellationToken);
        await DrainAsync(cancellationToken);
    }

    public async Task DisconnectAsync()
    {
        await DisconnectTransportAsync();
        SetStatus("Disconnected");
    }

    public async Task PublishPointAsync(LoggedPoint point, CancellationToken cancellationToken = default)
    {
        await _pumpGate.WaitAsync(cancellationToken);
        try
        {
            await QueuePointAsync(point, cancellationToken);
            if (IsConnected && _engine is not null)
                await _engine.DrainOnceAsync(cancellationToken);
        }
        finally
        {
            _pumpGate.Release();
        }
    }

    private async Task QueuePointAsync(LoggedPoint point, CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(point.SyncPointId))
        {
            point.SyncPointId = Guid.CreateVersion7().ToString();
            point.Synced = false;
            await _database.UpdatePointAsync(point);
        }

        if (string.IsNullOrWhiteSpace(_settings.MqttOrgId))
        {
            await RecordFailureAsync(point, "SYNC_NOT_CONFIGURED");
            return;
        }

        var job = await _database.GetJobAsync(point.JobId);
        if (job is null)
        {
            await RecordFailureAsync(point, "LOCAL_JOB_NOT_FOUND");
            return;
        }

        try
        {
            var record = ToSyncPoint(point);
            var topic = $"ul/{_settings.MqttOrgId}/app/{_settings.MqttClientId}/log/points";
            string? remoteJobId = string.IsNullOrWhiteSpace(job.RemoteId) ? null : job.RemoteId;
            string? ticket = remoteJobId is null ? TicketFor(job) : null;
            var outbound = SyncCore.OutboundMessage.FromPoint(
                record,
                topic,
                DateTimeOffset.UtcNow,
                jobId: remoteJobId,
                ticket: ticket);
            await _store.EnqueueAsync(outbound);
            point.SyncError = null;
            await _database.UpdatePointAsync(point);
        }
        catch (SyncCore.PointNotPublishableException ex)
        {
            await RecordFailureAsync(point, ex.ReasonCode);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to enqueue point {PointId}", point.SyncPointId);
            await RecordFailureAsync(point, "QUEUE_ERROR");
        }
        cancellationToken.ThrowIfCancellationRequested();
    }

    private async Task QueueUnsyncedAsync(CancellationToken cancellationToken)
    {
        foreach (var point in await _database.GetUnsyncedPointsAsync())
        {
            cancellationToken.ThrowIfCancellationRequested();
            // Permanent capture/server rejections require operator action, not an automatic loop.
            if (point.SyncError is not null && point.SyncError is not "SYNC_NOT_CONFIGURED" and not "QUEUE_ERROR")
                continue;
            await QueuePointAsync(point, cancellationToken);
        }
    }

    private async Task ConnectCoreAsync(bool forceReconnect, CancellationToken cancellationToken)
    {
        if (!_settings.MqttEnabled)
            throw new InvalidOperationException("MQTT sync is disabled in Settings.");
        if (string.IsNullOrWhiteSpace(_settings.MqttHost) || string.IsNullOrWhiteSpace(_settings.MqttOrgId))
            throw new InvalidOperationException("MQTT host and organization id are required.");
        string password = await _settings.GetMqttPasswordAsync()
            ?? throw new InvalidOperationException("MQTT password is required.");

        await _connectionGate.WaitAsync(cancellationToken);
        try
        {
            if (IsConnected && !forceReconnect) return;
            await DisconnectTransportAsync();

            _transport = new SyncCore.MqttnetTransport(new SyncCore.MqttBrokerConfig
            {
                Host = _settings.MqttHost,
                Port = _settings.MqttPort,
                WebSocketUri = _settings.MqttPort == 443
                    ? $"wss://{_settings.MqttHost}/mqtt"
                    : null,
                ClientId = _settings.MqttClientId,
                Username = _settings.MqttOrgId,
                Password = password,
                UseTls = true,
            });
            _engine = new SyncCore.MqttSyncEngine(
                _transport,
                _store,
                new SyncCore.SyncOptions
                {
                    OrgId = _settings.MqttOrgId,
                    ClientId = _settings.MqttClientId,
                });
            _engine.PointAccepted += HandleAcceptedAsync;
            _engine.PointRejected += HandleRejectedAsync;
            await _engine.ConnectAsync(cancellationToken);
            SetStatus("Connected");
        }
        finally
        {
            _connectionGate.Release();
        }
    }

    private async Task RunAsync(CancellationToken cancellationToken)
    {
        using var timer = new PeriodicTimer(TimeSpan.FromSeconds(5));
        while (await timer.WaitForNextTickAsync(cancellationToken))
        {
            if (!_settings.MqttEnabled)
            {
                SetStatus("Sync disabled");
                continue;
            }
            try
            {
                if (!IsConnected)
                {
                    SetStatus("Connecting…");
                    await ConnectCoreAsync(forceReconnect: false, cancellationToken);
                    await QueueUnsyncedAsync(cancellationToken);
                }
                await DrainAsync(cancellationToken);
            }
            catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
            {
                throw;
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "MQTT sync iteration failed; queued data retained");
                SetStatus($"Offline — retrying: {ex.Message}");
            }
        }
    }

    private async Task DrainAsync(CancellationToken cancellationToken)
    {
        if (_engine is null || !IsConnected) return;
        await _pumpGate.WaitAsync(cancellationToken);
        try
        {
            int published = await _engine.DrainOnceAsync(cancellationToken);
            if (published > 0) SetStatus($"Connected — {published} point(s) awaiting ack");
        }
        finally
        {
            _pumpGate.Release();
        }
    }

    private async Task HandleAcceptedAsync(string pointId)
    {
        await _database.MarkPointSyncedAsync(pointId);
        SetStatus("Connected — synced");
    }

    private async Task HandleRejectedAsync(SyncCore.OutboundMessage message)
    {
        string reason = message.LastReason ?? "REJECTED";
        await _database.MarkPointSyncErrorAsync(message.PointId, reason);
        var point = await _database.GetPointBySyncIdAsync(message.PointId);
        if (point is not null) PointRejected?.Invoke(this, new PointSyncFailureEventArgs(point, reason));
        SetStatus($"Point rejected: {reason}");
    }

    private async Task RecordFailureAsync(LoggedPoint point, string reasonCode)
    {
        point.SyncError = reasonCode;
        point.Synced = false;
        await _database.UpdatePointAsync(point);
        PointRejected?.Invoke(this, new PointSyncFailureEventArgs(point, reasonCode));
        SetStatus($"Point not queued: {reasonCode}");
    }

    private async Task DisconnectTransportAsync()
    {
        if (_transport is null) return;
        try { await _transport.DisposeAsync(); }
        finally
        {
            _transport = null;
            _engine = null;
        }
    }

    private void SetStatus(string value)
    {
        if (Status == value) return;
        Status = value;
        StatusChanged?.Invoke(this, value);
    }

    private static string TicketFor(Job job)
    {
        string value = $"FL-{job.Id}-{job.Name}".Trim();
        return value.Length <= 64 ? value : value[..64];
    }

    private static SyncCore.PointRecord ToSyncPoint(LoggedPoint point)
    {
        var timestamp = new DateTimeOffset(DateTime.SpecifyKind(point.TimestampUtc, DateTimeKind.Utc));
        DateTimeOffset? positionEpoch = point.GpsUnixTimestamp > 0
            ? DateTimeOffset.FromUnixTimeSeconds(point.GpsUnixTimestamp)
            : null;
        return new SyncCore.PointRecord
        {
            PointId = point.SyncPointId!,
            Origin = SyncCore.PointOrigin.APP,
            UploadPath = SyncCore.UploadPath.APP_MQTT,
            CaptureTrigger = SyncCore.CaptureTrigger.LOCATOR_BUTTON,
            CreatedAt = timestamp,
            Position = point.GpsValid
                ? new SyncCore.PositionGroup
                {
                    Lat = point.Latitude,
                    Lon = point.Longitude,
                    EllipsoidalHeight = point.Altitude,
                    OrthometricHeight = point.AltitudeCorrected,
                    PositionEpoch = positionEpoch,
                }
                : null,
            Gnss = new SyncCore.GnssGroup
            {
                FixType = FixType(point.FixStatusEnum),
                SatsUsed = point.SatellitesUsed,
                Hdop = point.Hdop,
                Hrms = point.Hrms,
                Vrms = point.Vrms,
                CorrectionAge = point.CorrectionAgeSeconds,
                ReceiverSerial = point.GpsSerialNumber,
                TiltAngle = point.TiltAngle,
                Source = string.IsNullOrWhiteSpace(point.GpsSerialNumber) ? "PHONE" : "MAGLINK",
            },
            Locate = new SyncCore.LocateGroup
            {
                Depth = point.DepthMeters,
                DepthUnits = point.DepthMeters is null ? null : "m",
                SignalCurrent = point.CurrentMilliamps,
                SignalStrength = point.Signal,
                Frequency = point.Frequency,
                Gain = point.GainDb,
                LocateMode = LocateMode(point),
                PhaseDegrees = point.LdPhase,
                CompassDegrees = point.CompassAngle,
                LocatorModel = point.LocatorModel,
                LocatorSerial = point.LocatorSerialNumber,
                TelemetryEpoch = timestamp,
            },
            Attributes = new SyncCore.AttributesGroup { UtilityType = UtilityType(point.UtilityEnum) },
            Quality = new SyncCore.QualityGroup
            {
                QualityFlag = point.GpsValid && point.Hrms > 0 && point.Hrms <= 0.10
                    ? "IN_SPEC"
                    : "OUT_OF_SPEC",
            },
        };
    }

    private static string FixType(GnssFixStatus status) => status switch
    {
        GnssFixStatus.Single => "AUTONOMOUS",
        GnssFixStatus.Dgps => "DGPS",
        GnssFixStatus.RtkFloat => "FLOAT",
        GnssFixStatus.RtkFixed => "FIXED",
        _ => "NO_FIX",
    };

    private static string UtilityType(UmUtility utility) => utility switch
    {
        UmUtility.Gas => "GAS",
        UmUtility.Power => "ELECTRIC",
        UmUtility.Communications => "TELECOM",
        UmUtility.Water => "WATER",
        UmUtility.Sewer => "SEWER",
        UmUtility.Fiber => "FIBER",
        _ => "UNKNOWN",
    };

    private static string LocateMode(LoggedPoint point) => point.FreqType == (int)UmFreqType.Sonde
        ? "SONDE"
        : (UmMode)point.Mode switch
        {
            UmMode.Null => "NULL",
            UmMode.Omni or UmMode.TwinOmni => "BROAD_PEAK",
            _ => "PEAK",
        };
}