using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.ScadaBridge.AuditLog;
using ZB.MOM.WW.ScadaBridge.ClusterInfrastructure;
using ZB.MOM.WW.ScadaBridge.Communication;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Observability;
using ZB.MOM.WW.ScadaBridge.DataConnectionLayer;
using ZB.MOM.WW.ScadaBridge.ExternalSystemGateway;
using ZB.MOM.WW.ScadaBridge.HealthMonitoring;
using ZB.MOM.WW.ScadaBridge.Host.Actors;
using ZB.MOM.WW.ScadaBridge.Host.Health;
using ZB.MOM.WW.ScadaBridge.NotificationService;
using ZB.MOM.WW.ScadaBridge.SiteEventLogging;
using ZB.MOM.WW.ScadaBridge.SiteRuntime;
using ZB.MOM.WW.ScadaBridge.StoreAndForward;
using ZB.MOM.WW.Telemetry;

namespace ZB.MOM.WW.ScadaBridge.Host;

/// <summary>
/// Extracted site-role DI registrations so both Program.cs and tests
/// use the same composition root.
/// </summary>
public static class SiteServiceRegistration
{
    /// <summary>Registers all DI services required for the site role.</summary>
    /// <param name="services">The service collection to register into.</param>
    /// <param name="config">Application configuration for options binding.</param>
    public static void Configure(IServiceCollection services, IConfiguration config)
    {
        // Shared components
        services.AddClusterInfrastructure();
        services.AddCommunication();
        services.AddSiteHealthMonitoring();
        services.AddExternalSystemGateway();
        // AddNotificationService() is intentionally NOT registered on the site path.
        // Sites no longer deliver notifications over SMTP — a buffered notification is
        // forwarded to the central cluster (via NotificationForwarder / SiteCommunicationActor),
        // and central owns SMTP delivery through the Notification Outbox. The SMTP machinery
        // (OAuth2TokenService, ISmtpClientWrapper) has no consumer on a site node.

        // Health report transport: sends SiteHealthReport to SiteCommunicationActor via Akka
        services.AddSingleton<ISiteIdentityProvider, SiteIdentityProvider>();
        services.AddSingleton<IHealthReportTransport, AkkaHealthReportTransport>();

        // Site-only components — AddSiteRuntime registers SiteStorageService with SQLite path
        // and site-local repository implementations (IExternalSystemRepository, INotificationRepository)
        var siteDbPath = config["ScadaBridge:Database:SiteDbPath"] ?? "site.db";
        services.AddSiteRuntime($"Data Source={siteDbPath}");
        services.AddDataConnectionLayer();
        // Adapter that surfaces the site id to
        // StoreAndForwardService through DI WITHOUT introducing a
        // StoreAndForward → HealthMonitoring project-reference cycle. Must be
        // registered BEFORE AddStoreAndForward so the S&F factory resolves a
        // non-empty SiteId at construction time (otherwise the S&F service is
        // a singleton and the empty-string value would be cached for the
        // lifetime of the process).
        services.AddSingleton<ZB.MOM.WW.ScadaBridge.StoreAndForward.IStoreAndForwardSiteContext, StoreAndForwardSiteContext>();
        services.AddStoreAndForward();
        services.AddSiteEventLogging();

        // Site Event Logging — bridge ISiteEventLogger.FailedWriteCount
        // into the site health report as a point-in-time SiteEventLogWriteFailures field.
        // Must come AFTER both AddSiteHealthMonitoring (registers ISiteHealthCollector) and
        // AddSiteEventLogging (registers ISiteEventLogger). The outer Func<IServiceProvider, …>
        // is evaluated once at hosted-service resolution time (root IServiceProvider is available);
        // the inner Func<long> is called on every poll tick and reads FailedWriteCount from the
        // already-resolved ISiteEventLogger singleton.
        services.AddSiteEventLogHealthMetricsBridge(
            sp => () => sp.GetRequiredService<ISiteEventLogger>().FailedWriteCount);

        // Audit Log — site-side hot-path writer + telemetry collaborators.
        // The SiteAuditTelemetryActor itself is registered by AkkaHostedService
        // in the site-role block; this call wires every DI dependency it (and
        // ScriptRuntimeContext) reaches for.
        services.AddAuditLog(config);

        // Bridge FallbackAuditWriter primary
        // failures into the site health report payload as
        // SiteAuditWriteFailures. Must come AFTER both AddSiteHealthMonitoring
        // (registers ISiteHealthCollector) and AddAuditLog (registers the
        // NoOp default this call replaces).
        services.AddAuditLogHealthMetricsBridge();

        // Akka.NET bootstrap via hosted service
        services.AddSingleton<AkkaHostedService>();
        services.AddHostedService(sp => sp.GetRequiredService<AkkaHostedService>());

        // Bridge the AkkaHostedService-owned ActorSystem to DI as a SINGLETON via
        // GetOrCreateActorSystem(). The shared ZB.MOM.WW.Health Akka checks resolve ActorSystem
        // from DI, per probe, inside a child scope. ActorSystem is IDisposable, so a TRANSIENT
        // (or scoped) bridge is captured-and-disposed by each probe's scope — disposing the live
        // system mid-flight (CoordinatedShutdown/ActorSystemTerminateReason) and tearing down the
        // node. A singleton is resolved from the root and never disposed by a child scope; routing
        // through GetOrCreateActorSystem (instead of a plain singleton factory over .ActorSystem)
        // means the first resolve CREATES the system rather than caching a null if a probe wins
        // the startup race.
        services.AddSingleton<Akka.Actor.ActorSystem>(sp =>
            sp.GetRequiredService<AkkaHostedService>().GetOrCreateActorSystem());

        // Cluster node status provider for health reports
        services.AddSingleton<IClusterNodeProvider>(sp =>
        {
            var akkaService = sp.GetRequiredService<AkkaHostedService>();
            var nodeOptions = sp.GetRequiredService<Microsoft.Extensions.Options.IOptions<NodeOptions>>().Value;
            var siteRole = $"site-{nodeOptions.SiteId}";
            return new AkkaClusterNodeProvider(akkaService, siteRole);
        });

        // The EventLogPurgeService runs on every
        // site host node but consults this optional gate each tick and early-exits on
        // the standby. Register it to delegate to IClusterNodeProvider.SelfIsPrimary
        // (the canonical "this node is the oldest Up member (singleton host)" check) so purge
        // runs ONLY on the active node — no duplicated cluster logic. Non-clustered test hosts that
        // never call SiteServiceRegistration leave it unregistered, so the purge defaults
        // to always-run (the pre-fix behaviour, preserved).
        services.AddSingleton<SiteEventLogActiveNodeCheck>(sp =>
        {
            var nodeProvider = sp.GetRequiredService<IClusterNodeProvider>();
            return () => nodeProvider.SelfIsPrimary;
        });

        // Options binding
        BindSharedOptions(services, config);

        // Bind + eagerly validate the site-pipeline options. The validators live with their
        // owner component projects (SiteRuntime / StoreAndForward / SiteEventLogging) per the
        // "options classes owned by component projects" convention, but these three sections
        // are bound HERE in the Host (not in a component SCE), so both the ValidateOnStart()
        // chain and the TryAddEnumerable validator registration happen here. A bad section
        // fails fast at host build with a clear, key-naming message instead of crashing an
        // actor / hosted service later with an opaque ArgumentOutOfRangeException.
        services.AddOptions<SiteRuntimeOptions>()
            .Bind(config.GetSection("ScadaBridge:SiteRuntime"))
            .ValidateOnStart();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IValidateOptions<SiteRuntimeOptions>, SiteRuntimeOptionsValidator>());

        services.Configure<DataConnectionOptions>(config.GetSection("ScadaBridge:DataConnection"));

        services.AddOptions<StoreAndForwardOptions>()
            .Bind(config.GetSection("ScadaBridge:StoreAndForward"))
            .ValidateOnStart();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IValidateOptions<StoreAndForwardOptions>, StoreAndForwardOptionsValidator>());

        services.AddOptions<SiteEventLogOptions>()
            .Bind(config.GetSection("ScadaBridge:SiteEventLog"))
            .ValidateOnStart();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IValidateOptions<SiteEventLogOptions>, SiteEventLogOptionsValidator>());
    }

    /// <summary>Binds shared options sections (Node, Cluster, Database, Communication, etc.) used by both site and central roles.</summary>
    /// <param name="services">The service collection to bind options into.</param>
    /// <param name="config">Application configuration supplying the option values.</param>
    public static void BindSharedOptions(IServiceCollection services, IConfiguration config)
    {
        // Bind + eagerly validate: an empty NodeName would stamp the SourceNode audit
        // column NULL, so fail the host at boot with a key-naming message instead of
        // silently degrading the audit trail (arch-review 08r2 NF4).
        services.AddOptions<NodeOptions>().Bind(config.GetSection("ScadaBridge:Node")).ValidateOnStart();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IValidateOptions<NodeOptions>, NodeOptionsValidator>());
        // Bind + eagerly validate: ClusterOptionsValidator is registered (TryAddEnumerable)
        // by the ClusterInfrastructure module, so chaining ValidateOnStart() here makes a bad
        // ScadaBridge:Cluster section fail fast at host build instead of lazily on first resolve.
        services.AddOptions<ClusterOptions>().Bind(config.GetSection("ScadaBridge:Cluster")).ValidateOnStart();
        // Bind + eagerly validate: a present-but-blank connection setting fails fast
        // here rather than opaquely at first DB use (arch-review 08r2 NF4).
        services.AddOptions<DatabaseOptions>().Bind(config.GetSection("ScadaBridge:Database")).ValidateOnStart();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IValidateOptions<DatabaseOptions>, DatabaseOptionsValidator>());
        services.Configure<CommunicationOptions>(config.GetSection("ScadaBridge:Communication"));
        // Bind + eagerly validate: HealthMonitoringOptionsValidator is registered (TryAddEnumerable)
        // by the HealthMonitoring module, so chaining ValidateOnStart() here makes a bad
        // ScadaBridge:HealthMonitoring section fail fast at host build instead of lazily on first resolve.
        services.AddOptions<HealthMonitoringOptions>().Bind(config.GetSection("ScadaBridge:HealthMonitoring")).ValidateOnStart();
        services.Configure<NotificationOptions>(config.GetSection("ScadaBridge:Notification"));
        // Bind + eagerly validate: an unrecognised MinimumLevel would silently fall back
        // to Information; fail fast at boot so the operator's intended floor is honoured
        // (arch-review 08r2 NF4).
        services.AddOptions<LoggingOptions>().Bind(config.GetSection("ScadaBridge:Logging")).ValidateOnStart();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IValidateOptions<LoggingOptions>, LoggingOptionsValidator>());

        // Audit Log — exposes ScadaBridge:Node:NodeName to downstream audit
        // writers so they can stamp the SourceNode column. Registered here in
        // shared bootstrap because every node (central + site) needs it.
        services.AddSingleton<INodeIdentityProvider, NodeIdentityProvider>();

        // Observability — shared ZB.MOM.WW.Telemetry. Registered in shared bootstrap so
        // BOTH the central and site composition roots wire the OTel Resource (the
        // service.name/site.id/node.role identity triple) + standard instrumentation +
        // the always-on Prometheus exporter. Mount the /metrics scrape endpoint per role
        // with app.MapZbMetrics(). The same `?? "central"` SiteId default Program.cs uses
        // is applied here so the Resource attribute matches the log-enricher value.
        // The application meter is named so OTel observes its instruments; emit points are
        // wired by follow-on tasks (the instruments are no-op until a listener attaches).
        services.AddZbTelemetry(o =>
        {
            o.ServiceName = "scadabridge";
            o.SiteId = config["ScadaBridge:Node:SiteId"] ?? "central";
            o.NodeRole = config["ScadaBridge:Node:Role"];
            o.Meters = [ScadaBridgeTelemetry.MeterName];
            if (Enum.TryParse<ZbExporter>(config["ScadaBridge:Telemetry:Exporter"], ignoreCase: true, out var exporter))
                o.Exporter = exporter;
            var otlp = config["ScadaBridge:Telemetry:OtlpEndpoint"];
            if (!string.IsNullOrWhiteSpace(otlp))
                o.OtlpEndpoint = otlp;
        });
    }
}