using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Config;

namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy;

/// <summary>
///     In-process .NET 10 Galaxy driver — the v2 replacement for the Galaxy.Host /
///     Galaxy.Proxy pair. PR 4.0 ships the project skeleton with <see cref="IDriver"/>
///     bodies that wire to a future <c>IGalaxyGatewayClient</c> abstraction. Capability
///     interfaces (browse, read, write, subscribe, history routing, host probes) land in
///     PRs 4.1–4.7; the wiring sequence keeps every intermediate state buildable so the
///     <c>Galaxy:Backend</c> flag (PR 4.W) can flip between legacy-host and mxgateway
///     for parity testing.
/// </summary>
/// <remarks>
///     This driver is registered as a Tier A in-process driver alongside Modbus / S7 / etc.
///     The legacy <c>GalaxyProxyDriver</c> (Driver.Galaxy.Proxy) coexists until PR 7.2;
///     <see cref="GalaxyDriverFactoryExtensions"/> registers under driver-type name
///     "GalaxyMxGateway" so both paths can be live simultaneously during parity testing.
/// </remarks>
public sealed class GalaxyDriver : IDriver, IDisposable
{
    private readonly string _driverInstanceId;
    private readonly GalaxyDriverOptions _options;
    private readonly ILogger<GalaxyDriver> _logger;

    private DriverHealth _health = new(DriverState.Unknown, null, null);
    private bool _disposed;

    public GalaxyDriver(
        string driverInstanceId,
        GalaxyDriverOptions options,
        ILogger<GalaxyDriver>? logger = null)
    {
        _driverInstanceId = !string.IsNullOrWhiteSpace(driverInstanceId)
            ? driverInstanceId
            : throw new ArgumentException("Driver instance id required.", nameof(driverInstanceId));
        _options = options ?? throw new ArgumentNullException(nameof(options));
        _logger = logger ?? NullLogger<GalaxyDriver>.Instance;
    }

    /// <inheritdoc />
    public string DriverInstanceId => _driverInstanceId;

    /// <inheritdoc />
    public string DriverType => GalaxyDriverFactoryExtensions.DriverTypeName;

    /// <summary>Test-visible options snapshot.</summary>
    internal GalaxyDriverOptions Options => _options;

    /// <inheritdoc />
    public Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);

        // PR 4.0 skeleton — capability bodies (PRs 4.1-4.7) replace this stub with real
        // MxGatewayClient session opening. The skeleton keeps the IDriver shape buildable
        // so the Galaxy:Backend flag (PR 4.W) can register the driver factory now.
        _logger.LogInformation(
            "GalaxyDriver {InstanceId} initializing — endpoint={Endpoint} clientName={ClientName} (skeleton; real gateway connect in PR 4.1+)",
            _driverInstanceId, _options.Gateway.Endpoint, _options.MxAccess.ClientName);
        _health = new DriverHealth(DriverState.Healthy, DateTime.UtcNow, null);
        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
    {
        // In-place config reapply. PR 4.5's reconnect supervisor will swap the
        // gateway-client options under the lock; for the skeleton we just refresh health.
        ObjectDisposedException.ThrowIf(_disposed, this);
        _health = new DriverHealth(DriverState.Healthy, DateTime.UtcNow, null);
        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task ShutdownAsync(CancellationToken cancellationToken)
    {
        if (_disposed) return Task.CompletedTask;
        _logger.LogInformation("GalaxyDriver {InstanceId} shutting down", _driverInstanceId);
        _health = new DriverHealth(DriverState.Unknown, _health.LastSuccessfulRead, null);
        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public DriverHealth GetHealth() => _health;

    /// <inheritdoc />
    public long GetMemoryFootprint() => 0; // PR 4.4 sets this from SubscriptionRegistry size.

    /// <inheritdoc />
    public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;

    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;
        // No owned IDisposables until PR 4.2's GalaxyMxSession lands.
    }
}