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

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"/>, and runs until stopped.
///     Phase 1 scope: bootstrap-only — the OPC UA transport layer that serves endpoints stays in
///     the legacy Host until the Phase 2 cutover.
/// </summary>
public sealed class OpcUaServerService(
    NodeBootstrap bootstrap,
    DriverHost driverHost,
    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);

        // Phase 1: no drivers are wired up at bootstrap — Galaxy still lives in legacy Host.
        // Phase 2 will register drivers here based on the fetched generation.

        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 driverHost.DisposeAsync();
    }
}