using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using ZB.MOM.WW.OtOpcUa.Core.Hosting;
using ZB.MOM.WW.OtOpcUa.Server.OpcUa;

namespace ZB.MOM.WW.OtOpcUa.Server;

/// <summary>
///     BackgroundService that owns the OPC UA server lifecycle (decision #30, replacing TopShelf).
///     Bootstraps config, starts the <see cref="DriverHost"/>, starts the OPC UA server via
///     <see cref="OpcUaApplicationHost"/>, drives each driver's discovery into the address space,
///     runs until stopped.
/// </summary>
public sealed class OpcUaServerService(
    NodeBootstrap bootstrap,
    DriverHost driverHost,
    OpcUaApplicationHost applicationHost,
    ILogger<OpcUaServerService> logger) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        logger.LogInformation("OtOpcUa.Server starting");

        var result = await bootstrap.LoadCurrentGenerationAsync(stoppingToken);
        logger.LogInformation("Bootstrap complete: source={Source} generation={Gen}", result.Source, result.GenerationId);

        // PR 17: stand up the OPC UA server + drive discovery per registered driver. Driver
        // registration itself (RegisterAsync on DriverHost) happens during an earlier DI
        // extension once the central config DB query + per-driver factory land; for now the
        // server comes up with whatever drivers are in DriverHost at start time.
        await applicationHost.StartAsync(stoppingToken);

        logger.LogInformation("OtOpcUa.Server running. Hosted drivers: {Count}", driverHost.RegisteredDriverIds.Count);

        try
        {
            await Task.Delay(Timeout.InfiniteTimeSpan, stoppingToken);
        }
        catch (OperationCanceledException)
        {
            logger.LogInformation("OtOpcUa.Server stopping");
        }
    }

    public override async Task StopAsync(CancellationToken cancellationToken)
    {
        await base.StopAsync(cancellationToken);
        await applicationHost.DisposeAsync();
        await driverHost.DisposeAsync();
    }
}