using HealthChecks.UI.Client;
using Microsoft.AspNetCore.Diagnostics.HealthChecks;
using ZB.MOM.WW.ScadaBridge.AuditLog;
using ZB.MOM.WW.ScadaBridge.CentralUI;
using ZB.MOM.WW.ScadaBridge.ClusterInfrastructure;
using ZB.MOM.WW.ScadaBridge.Communication;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase;
using ZB.MOM.WW.ScadaBridge.DeploymentManager;
using ZB.MOM.WW.ScadaBridge.ExternalSystemGateway;
using ZB.MOM.WW.ScadaBridge.HealthMonitoring;
using ZB.MOM.WW.ScadaBridge.Host;
using ZB.MOM.WW.ScadaBridge.Host.Actors;
using ZB.MOM.WW.ScadaBridge.Host.Health;
using ZB.MOM.WW.ScadaBridge.InboundAPI;
using ZB.MOM.WW.ScadaBridge.InboundAPI.Middleware;
using ZB.MOM.WW.ScadaBridge.ManagementService;
using ZB.MOM.WW.ScadaBridge.NotificationOutbox;
using ZB.MOM.WW.ScadaBridge.NotificationService;
using ZB.MOM.WW.ScadaBridge.Security;
using ZB.MOM.WW.ScadaBridge.SiteCallAudit;
using ZB.MOM.WW.ScadaBridge.TemplateEngine;
using ZB.MOM.WW.ScadaBridge.Transport;
using Serilog;

// SCADABRIDGE_CONFIG determines which role-specific config to load (Central or Site)
// DOTNET_ENVIRONMENT/ASPNETCORE_ENVIRONMENT stay as "Development" for dev tooling (static assets, EF migrations, etc.)
var scadabridgeConfig = Environment.GetEnvironmentVariable("SCADABRIDGE_CONFIG")
    ?? Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT")
    ?? "Production";

var configuration = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json", optional: false)
    .AddJsonFile($"appsettings.{scadabridgeConfig}.json", optional: true)
    .AddEnvironmentVariables()
    .AddCommandLine(args)
    .Build();

// WP-11: Full startup validation — fail fast before any DI or actor system setup
StartupValidator.Validate(configuration);

// Read node options for Serilog enrichment
var nodeRole = configuration["ScadaBridge:Node:Role"]!;
var nodeHostname = configuration["ScadaBridge:Node:NodeHostname"] ?? "unknown";
var siteId = configuration["ScadaBridge:Node:SiteId"] ?? "central";

// WP-14: Serilog structured logging.
// Host-011: minimum level is driven by ScadaBridge:Logging:MinimumLevel (LoggingOptions).
// Host-014: console and file sinks are defined in the `Serilog` configuration
// section (appsettings.json) and applied via ReadFrom.Configuration inside the
// factory — the sink set, output template, file path and rolling interval are all
// configuration-driven per REQ-HOST-8, not hard-coded here.
Log.Logger = ZB.MOM.WW.ScadaBridge.Host.LoggerConfigurationFactory
    .Build(configuration, nodeRole, siteId, nodeHostname)
    .CreateLogger();

try
{
    Log.Information("Starting ScadaBridge host as {Role} on {Hostname}", nodeRole, nodeHostname);

    if (nodeRole.Equals("Central", StringComparison.OrdinalIgnoreCase))
    {
        var builder = WebApplication.CreateBuilder(args);
        builder.Configuration.AddConfiguration(configuration);

        // WP-14: Serilog
        builder.Host.UseSerilog();

        // WP-17: Windows Service support (no-op when not running as a Windows Service)
        builder.Host.UseWindowsService();

        // Shared components
        builder.Services.AddClusterInfrastructure();
        builder.Services.AddCommunication();
        builder.Services.AddHealthMonitoring();
        builder.Services.AddCentralHealthAggregation();
        builder.Services.AddExternalSystemGateway();
        builder.Services.AddNotificationService();

        // Central-only components
        // Notification Outbox: central owns SMTP delivery; the Email adapter reuses the
        // AddNotificationService() SMTP machinery above. AddNotificationOutbox binds
        // NotificationOutboxOptions via BindConfiguration, so no explicit Configure is needed.
        builder.Services.AddNotificationOutbox();
        // Transport (#24) — central-only bundle export/import pipeline. Binds
        // TransportOptions from ScadaBridge:Transport via BindConfiguration; no
        // explicit Configure needed.
        builder.Services.AddTransport();
        // Audit Log (#23) — central node owns the AuditLogIngestActor singleton +
        // IAuditLogRepository. The site writer chain is still registered (lazy
        // singletons) but is never resolved on a central node.
        builder.Services.AddAuditLog(builder.Configuration);
        // #23 M6-T5 Bundle D — central-only hosted service that rolls
        // pf_AuditLog_Month forward monthly. Depends on IPartitionMaintenance
        // (registered below by AddConfigurationDatabase).
        builder.Services.AddAuditLogCentralMaintenance(builder.Configuration);
        // Site Call Audit (#22) — central node owns the SiteCallAuditActor
        // singleton (M3 Bundle F). The extension itself currently registers
        // nothing — actor Props are constructed inline in AkkaHostedService —
        // but the call is here for symmetry with the other audit composition
        // roots so future per-actor DI lands without touching Program.cs.
        builder.Services.AddSiteCallAudit();
        builder.Services.AddTemplateEngine();
        builder.Services.AddDeploymentManager();
        builder.Services.AddSecurity();
        builder.Services.AddCentralUI();
        builder.Services.AddInboundAPI();
        builder.Services.AddManagementService();

        var configDbConnectionString = configuration["ScadaBridge:Database:ConfigurationDb"]
            ?? throw new InvalidOperationException("ScadaBridge:Database:ConfigurationDb connection string is required for Central role.");
        builder.Services.AddConfigurationDatabase(configDbConnectionString);

        // WP-12: Health checks for readiness gating
        builder.Services.AddHealthChecks()
            .AddCheck<DatabaseHealthCheck>("database")
            .AddCheck<AkkaClusterHealthCheck>("akka-cluster")
            .AddCheck<ActiveNodeHealthCheck>("active-node");

        // WP-13: Akka.NET bootstrap via hosted service
        builder.Services.AddSingleton<AkkaHostedService>();
        builder.Services.AddHostedService(sp => sp.GetRequiredService<AkkaHostedService>());

        // InboundAPI-022: register the production IActiveNodeGate implementation so
        // standby-node gating is actually enforced (the InboundApiEndpointFilter
        // consults IActiveNodeGate and defaults to "allow" when none is registered,
        // which leaves the design's "central cluster only (active node)" guarantee
        // unenforced in deployed binaries). The gate is backed by the same Akka
        // cluster-leadership check as ActiveNodeHealthCheck above, so the inbound
        // API and the /health/active endpoint Traefik routes against agree on
        // which node is active.
        builder.Services.AddSingleton<ZB.MOM.WW.ScadaBridge.InboundAPI.IActiveNodeGate, ActiveNodeGate>();

        // Cluster node status provider scoped to the Central role — feeds the
        // CentralHealthReportLoop so the central cluster appears on /monitoring/health.
        builder.Services.AddSingleton<IClusterNodeProvider>(sp =>
        {
            var akkaService = sp.GetRequiredService<AkkaHostedService>();
            return new AkkaClusterNodeProvider(akkaService, "Central");
        });

        // Options binding
        SiteServiceRegistration.BindSharedOptions(builder.Services, builder.Configuration);
        builder.Services.Configure<SecurityOptions>(builder.Configuration.GetSection("ScadaBridge:Security"));
        builder.Services.Configure<InboundApiOptions>(builder.Configuration.GetSection("ScadaBridge:InboundApi"));
        builder.Services.Configure<DeploymentManagerOptions>(
            builder.Configuration.GetSection(ZB.MOM.WW.ScadaBridge.DeploymentManager.ServiceCollectionExtensions.OptionsSection));

        var app = builder.Build();

        // Apply or validate database migrations (skip when running in test harness)
        if (!string.Equals(configuration["ScadaBridge:Database:SkipMigrations"], "true", StringComparison.OrdinalIgnoreCase))
        {
            var isDevelopment = app.Environment.IsDevelopment()
                || string.Equals(Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT"), "Development", StringComparison.OrdinalIgnoreCase);
            var migrationLogger = app.Services
                .GetRequiredService<ILoggerFactory>()
                .CreateLogger(typeof(MigrationHelper).FullName!);

            // Host-010: tolerate a database that is briefly unreachable at boot
            // (e.g. app and DB containers starting together) with a bounded
            // exponential backoff before failing fatally.
            // Host-015: only connection-class (transient) faults are retried — a
            // schema-version mismatch is permanent and must fail fast on attempt 1.
            // Host-019: thread the host's ApplicationStopping token into both the
            // migration call itself and the inter-attempt Task.Delay so a SIGTERM
            // during the bounded-retry window (~2 min worst-case) tears down
            // cleanly instead of being ignored until the loop exhausts.
            await StartupRetry.ExecuteWithRetryAsync(
                "database-migration",
                async ct =>
                {
                    using var scope = app.Services.CreateScope();
                    var dbContext = scope.ServiceProvider.GetRequiredService<ScadaBridgeDbContext>();
                    await MigrationHelper.ApplyOrValidateMigrationsAsync(dbContext, isDevelopment, migrationLogger, ct);
                },
                maxAttempts: 8,
                initialDelay: TimeSpan.FromSeconds(2),
                migrationLogger,
                isTransient: StartupRetry.IsTransientDatabaseFault,
                cancellationToken: app.Lifetime.ApplicationStopping);
        }

        // Middleware pipeline
        app.UseWebSockets();
        app.UseRouting();
        app.UseAuthentication();
        app.UseAuthorization();
        app.UseAntiforgery();

        // Audit Log #23 (M4 Bundle D, T8): emit one InboundRequest/InboundAuthFailure
        // audit row per call into the inbound API. Placed AFTER UseAuthentication/
        // UseAuthorization so any HttpContext.User the framework populates is in
        // place, and scoped to the /api/ prefix so it never observes the Central UI,
        // Management API, SignalR hubs, or health endpoints. The endpoint handler
        // is responsible for stashing the resolved API key name on
        // HttpContext.Items (see AuditWriteMiddleware.AuditActorItemKey) AFTER its
        // in-handler API key validation succeeds.
        // InboundAPI-025: scope the audit middleware to the inbound API method
        // route (/api/{methodName}) and explicitly exclude the management/audit
        // sub-trees that share the /api prefix. Without these exclusions the
        // middleware would emit a spurious ApiInbound audit row for every
        // /api/audit/query and /api/audit/export call (and would treat audit-log
        // reads as inbound script invocations — recursive write-on-read). The
        // POST-only filter rules out the GET routes on /api/audit, /api/centralui,
        // /api/script-analysis even if a future route is added under those
        // prefixes with the same verb; the explicit prefix excludes still belt-
        // and-brace POST-y additions there.
        app.UseWhen(
            ctx => ctx.Request.Path.StartsWithSegments("/api")
                && !ctx.Request.Path.StartsWithSegments("/api/audit")
                && !ctx.Request.Path.StartsWithSegments("/api/centralui")
                && !ctx.Request.Path.StartsWithSegments("/api/script-analysis")
                && !ctx.Request.Path.StartsWithSegments("/api/management")
                && HttpMethods.IsPost(ctx.Request.Method),
            branch => branch.UseAuditWriteMiddleware());

        // WP-12: Map readiness endpoint — returns 503 until ready, 200 when ready.
        // REQ-HOST-4a defines readiness as cluster membership + DB connectivity,
        // explicitly NOT cluster leadership. The leader-only "active-node" check is
        // excluded here so a fully operational standby central node reports ready;
        // leadership is reported separately on /health/active.
        app.MapHealthChecks("/health/ready", new HealthCheckOptions
        {
            Predicate = check => check.Name != "active-node",
            ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
        });

        // Active node endpoint — returns 200 only on the cluster leader; used by Traefik for routing
        app.MapHealthChecks("/health/active", new HealthCheckOptions
        {
            Predicate = check => check.Name == "active-node",
            ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
        });

        app.MapStaticAssets();
        app.MapCentralUI<ZB.MOM.WW.ScadaBridge.Host.Components.App>();
        app.MapInboundAPI();
        app.MapManagementAPI();
        // Audit Log #23 (M8): CLI-facing /api/audit/{query,export} routes. Same
        // Basic-Auth + LDAP mechanism as /management; gated on the OperationalAudit
        // / AuditExport role sets.
        app.MapAuditAPI();
        app.MapHub<ZB.MOM.WW.ScadaBridge.ManagementService.DebugStreamHub>("/hubs/debug-stream");

        // Compile and register all Inbound API method scripts at startup
        using (var scope = app.Services.CreateScope())
        {
            var apiRepo = scope.ServiceProvider.GetRequiredService<ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories.IInboundApiRepository>();
            var executor = app.Services.GetRequiredService<ZB.MOM.WW.ScadaBridge.InboundAPI.InboundScriptExecutor>();
            var methods = await apiRepo.GetAllApiMethodsAsync();
            foreach (var method in methods)
            {
                executor.CompileAndRegister(method);
            }
        }

        await app.RunAsync();
    }
    else if (nodeRole.Equals("Site", StringComparison.OrdinalIgnoreCase))
    {
        var builder = WebApplication.CreateBuilder(args);
        builder.Configuration.AddConfiguration(configuration);

        // WP-14: Serilog
        builder.Host.UseSerilog();

        // WP-17: Windows Service support (no-op when not running as a Windows Service)
        builder.Host.UseWindowsService();

        // Read GrpcPort from config (NodeOptions already has default 8083)
        var grpcPort = configuration.GetValue<int>("ScadaBridge:Node:GrpcPort", 8083);

        // Configure Kestrel for HTTP/2 only on the gRPC port
        builder.WebHost.ConfigureKestrel(options =>
        {
            options.ListenAnyIP(grpcPort, listenOptions =>
            {
                listenOptions.Protocols = Microsoft.AspNetCore.Server.Kestrel.Core.HttpProtocols.Http2;
            });
        });

        // gRPC server registration
        builder.Services.AddGrpc();
        builder.Services.AddSingleton<ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamGrpcServer>();

        // Existing site service registrations
        SiteServiceRegistration.Configure(builder.Services, builder.Configuration);

        var app = builder.Build();

        // Map gRPC service — resolves the singleton SiteStreamGrpcServer from DI
        app.MapGrpcService<ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamGrpcServer>();

        // Host-017 / REQ-HOST-7: site-shutdown ordering. ApplicationStopping
        // fires BEFORE IHostedService.StopAsync runs, so the gRPC server
        // refuses new streams (Unavailable) and cancels every active stream
        // here — clients observe a clean Cancelled and reconnect — and only
        // THEN does AkkaHostedService run CoordinatedShutdown and tear down
        // actors. Without this hand-off, in-flight streams go silent and only
        // time out via gRPC keepalive (~25 s), violating the documented
        // four-step sequence.
        var siteLifetime = app.Services.GetRequiredService<Microsoft.Extensions.Hosting.IHostApplicationLifetime>();
        var siteGrpcServer = app.Services.GetRequiredService<ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamGrpcServer>();
        siteLifetime.ApplicationStopping.Register(() => siteGrpcServer.CancelAllStreams());

        await app.RunAsync();
    }
    else
    {
        throw new InvalidOperationException($"Unknown role: {nodeRole}. Must be 'Central' or 'Site'.");
    }
}
catch (Exception ex)
{
    Log.Fatal(ex, "ScadaBridge host terminated unexpectedly");
    throw;
}
finally
{
    await Log.CloseAndFlushAsync();
}

/// <summary>
/// Exposes the auto-generated Program class for test infrastructure (e.g. WebApplicationFactory).
/// </summary>
public partial class Program { }