Program.cs

using System.Text;
using FluentValidation;
using MassTransit;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.EntityFrameworkCore;
using Microsoft.IdentityModel.Tokens;
using Microsoft.OpenApi.Models;
using OpenTelemetry.Metrics;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
using Serilog;
using Serilog.Events;
using TradeTrac.OrderService.API.Controllers;
using TradeTrac.OrderService.API.Middleware;
using TradeTrac.OrderService.Application.Behaviours;
using TradeTrac.OrderService.Application.Commands;
using TradeTrac.OrderService.Application.Queries;
using TradeTrac.OrderService.Domain.Repositories;
using TradeTrac.OrderService.Infrastructure.Messaging;
using TradeTrac.OrderService.Infrastructure.Persistence;
using TradeTrac.OrderService.Infrastructure.Persistence.Repositories;

// ── Bootstrap Serilog immediately so startup errors are captured ──────────────
Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
    .MinimumLevel.Override("System", LogEventLevel.Warning)
    .Enrich.FromLogContext()
    .Enrich.WithProperty("Service", "OrderService")
    .WriteTo.Console(outputTemplate:
        "[{Timestamp:HH:mm:ss} {Level:u3}] {SourceContext}: {Message:lj}{NewLine}{Exception}")
    .CreateBootstrapLogger();

try
{
    var builder = WebApplication.CreateBuilder(args);

    // ── Serilog ───────────────────────────────────────────────────────────────
    builder.Host.UseSerilog((ctx, services, cfg) => cfg
        .ReadFrom.Configuration(ctx.Configuration)
        .ReadFrom.Services(services)
        .MinimumLevel.Override("Microsoft.EntityFrameworkCore.Database.Command", LogEventLevel.Warning)
        .Enrich.FromLogContext()
        .Enrich.WithProperty("Service", "OrderService")
        .WriteTo.Console(outputTemplate:
            "[{Timestamp:HH:mm:ss} {Level:u3}] {SourceContext}: {Message:lj}{NewLine}{Exception}"));

    // ── Configuration binding ─────────────────────────────────────────────────
    var jwtSection = builder.Configuration.GetSection("Jwt");
    builder.Services.Configure<JwtOptions>(jwtSection);
    var jwtOptions = jwtSection.Get<JwtOptions>()!;

    var connStr = builder.Configuration.GetConnectionString("Orders")
        ?? throw new InvalidOperationException("ConnectionStrings:Orders is required.");
    var rabbitHost = builder.Configuration["RabbitMQ:Host"] ?? "localhost";
    var rabbitUser = builder.Configuration["RabbitMQ:Username"] ?? "guest";
    var rabbitPass = builder.Configuration["RabbitMQ:Password"] ?? "guest";
    var otelEndpoint = builder.Configuration["Otel:Endpoint"] ?? "http://localhost:4317";

    // ── EF Core ───────────────────────────────────────────────────────────────
    builder.Services.AddDbContext<OrdersDbContext>(opts =>
        opts.UseNpgsql(connStr, pg =>
        {
            pg.EnableRetryOnFailure(3, TimeSpan.FromSeconds(5), null);
            pg.CommandTimeout(30);
            pg.MigrationsHistoryTable("__ef_migrations", "public");
        })
        .UseSnakeCaseNamingConvention());

    // ── Repository + Unit of Work ─────────────────────────────────────────────
    builder.Services.AddScoped<IOrderRepository, OrderRepository>();
    builder.Services.AddScoped<IUnitOfWork>(sp => sp.GetRequiredService<OrdersDbContext>());
    builder.Services.AddScoped<IOutboxService, OutboxService>();

    // Register the connection string for Dapper query handlers
    builder.Services.AddSingleton(connStr);

    // ── MediatR (CQRS) ────────────────────────────────────────────────────────
    builder.Services.AddMediatR(cfg =>
    {
        cfg.RegisterServicesFromAssemblyContaining<PlaceOrderCommand>();
        cfg.AddOpenBehavior(typeof(LoggingBehaviour<,>));
        cfg.AddOpenBehavior(typeof(ValidationBehaviour<,>));
    });

    // ── FluentValidation ─────────────────────────────────────────────────────
    builder.Services.AddValidatorsFromAssemblyContaining<PlaceOrderCommand>();

    // ── MassTransit → RabbitMQ ────────────────────────────────────────────────
    builder.Services.AddMassTransit(mt =>
    {
        mt.UsingRabbitMq((ctx, cfg) =>
        {
            cfg.Host(rabbitHost, h =>
            {
                h.Username(rabbitUser);
                h.Password(rabbitPass);
            });

            // Publisher confirms — don't consider a message delivered until RabbitMQ confirms
            cfg.PublisherConfirmation = true;
            cfg.ConfigureEndpoints(ctx);
        });
    });

    // ── Background workers ────────────────────────────────────────────────────
    builder.Services.AddHostedService<OutboxPublisherWorker>();

    // ── JWT Authentication ────────────────────────────────────────────────────
    builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
        .AddJwtBearer(opts =>
        {
            opts.TokenValidationParameters = new TokenValidationParameters
            {
                ValidateIssuer = true,
                ValidateAudience = true,
                ValidateLifetime = true,
                ValidateIssuerSigningKey = true,
                ValidIssuer = jwtOptions.Issuer,
                ValidAudience = jwtOptions.Audience,
                IssuerSigningKey = new SymmetricSecurityKey(
                    Encoding.UTF8.GetBytes(jwtOptions.Key))
            };
        });

    builder.Services.AddAuthorization(opts =>
    {
        opts.AddPolicy("InternalService", p => p.RequireRole("InternalService"));
    });

    // ── OpenTelemetry ─────────────────────────────────────────────────────────
    builder.Services.AddOpenTelemetry()
        .ConfigureResource(r => r.AddService("OrderService", serviceVersion: "1.0.0"))
        .WithTracing(tracing => tracing
            .AddAspNetCoreInstrumentation(opts =>
            {
                opts.Filter = ctx => ctx.Request.Path.Value?.StartsWith("/health") != true;
            })
            .AddEntityFrameworkCoreInstrumentation()
            .AddHttpClientInstrumentation()
            .AddSource("MassTransit")
            .AddOtlpExporter(o => o.Endpoint = new Uri(otelEndpoint)))
        .WithMetrics(metrics => metrics
            .AddAspNetCoreInstrumentation()
            .AddRuntimeInstrumentation()
            .AddOtlpExporter(o => o.Endpoint = new Uri(otelEndpoint)));

    // ── Health Checks ─────────────────────────────────────────────────────────
    builder.Services.AddHealthChecks()
        .AddNpgsql(connStr, name: "postgres", tags: ["db", "ready"])
        .AddRabbitMQ(
            rabbitConnectionString: $"amqp://{rabbitUser}:{rabbitPass}@{rabbitHost}",
            name: "rabbitmq",
            tags: ["mq", "ready"]);

    // ── Swagger / OpenAPI ─────────────────────────────────────────────────────
    builder.Services.AddEndpointsApiExplorer();
    builder.Services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo
        {
            Title = "TradeTrac — Order Service",
            Version = "v1",
            Description = "Trade order management API. DDD + Clean Architecture + CQRS."
        });
        c.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme
        {
            In = ParameterLocation.Header,
            Description = "Enter: Bearer {token}",
            Name = "Authorization",
            Type = SecuritySchemeType.ApiKey,
            Scheme = "Bearer"
        });
        c.AddSecurityRequirement(new OpenApiSecurityRequirement
        {
            {
                new OpenApiSecurityScheme
                {
                    Reference = new OpenApiReference { Type = ReferenceType.SecurityScheme, Id = "Bearer" }
                },
                Array.Empty<string>()
            }
        });
    });

    builder.Services.AddControllers();

    // ── Build ─────────────────────────────────────────────────────────────────
    var app = builder.Build();

    // ── Auto-migrate on startup ───────────────────────────────────────────────
    using (var scope = app.Services.CreateScope())
    {
        var db = scope.ServiceProvider.GetRequiredService<OrdersDbContext>();
        Log.Information("Running database migrations…");
        await db.Database.MigrateAsync();
        Log.Information("Migrations complete.");
    }

    // ── Middleware pipeline ───────────────────────────────────────────────────
    app.UseMiddleware<ExceptionHandlingMiddleware>();
    app.UseSerilogRequestLogging(opts =>
    {
        opts.MessageTemplate = "HTTP {RequestMethod} {RequestPath} → {StatusCode} ({Elapsed:0.0}ms)";
        opts.GetLevel = (ctx, elapsed, ex) => ex != null
            ? LogEventLevel.Error
            : ctx.Response.StatusCode >= 400
                ? LogEventLevel.Warning
                : LogEventLevel.Information;
    });

    if (app.Environment.IsDevelopment())
    {
        app.UseSwagger();
        app.UseSwaggerUI();
    }

    app.UseAuthentication();
    app.UseAuthorization();
    app.MapControllers();

    app.MapHealthChecks("/health");
    app.MapHealthChecks("/health/ready", new()
    {
        Predicate = check => check.Tags.Contains("ready")
    });
    app.MapHealthChecks("/health/live", new()
    {
        Predicate = _ => false // liveness = just the process is up
    });

    Log.Information("Order Service starting on {Urls}", app.Urls);
    await app.RunAsync();
}
catch (Exception ex)
{
    Log.Fatal(ex, "Order Service failed to start.");
    return 1;
}
finally
{
    await Log.CloseAndFlushAsync();
}

return 0;