step3/api/QuestionsApi/Program.cs

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.AspNetCore.Diagnostics;
using Microsoft.IdentityModel.Tokens;
using Microsoft.OpenApi.Models;
using QuestionsApi.Services;
using MongoDB.Bson;
using System.Text;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();

builder.Services.AddSingleton<MongoDatabaseProvider>();
builder.Services.AddSingleton<QuestionStore>();
builder.Services.AddSingleton<QuestionAttemptStore>();
builder.Services.AddSingleton<AnswerStatisticsStore>();
builder.Services.AddSingleton<RatingStore>();
builder.Services.AddSingleton<QuestionMediaStore>();
builder.Services.AddSingleton<QuestionReportStore>();
builder.Services.AddSingleton<ExamSimulationStore>();
builder.Services.AddSingleton<CcsStore>();
builder.Services.AddSingleton<CcsRatingStore>();
builder.Services.AddSingleton<CcsCaseReportStore>();
builder.Services.AddSingleton<AppFeedbackStore>();
builder.Services.AddSingleton<ServiceMetrics>();
builder.Services.AddHostedService<AnswerStatisticsMaintenanceService>();

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "Questions API", Version = "v1" });
    c.AddSecurityDefinition("bearerAuth", new OpenApiSecurityScheme
    {
        Type = SecuritySchemeType.Http,
        Scheme = "bearer",
        BearerFormat = "JWT",
        Description = "Paste your access token here (no 'Bearer ' prefix needed)."
    });
    c.AddSecurityRequirement(new OpenApiSecurityRequirement
    {
        {
            new OpenApiSecurityScheme
            {
                Reference = new OpenApiReference
                { Type = ReferenceType.SecurityScheme, Id = "bearerAuth" }
            },
            Array.Empty<string>()
        }
    });
});

var cfg = builder.Configuration;
var jwtKey = cfg["Jwt:Key"] ?? throw new Exception("Jwt:Key missing");
var issuer = cfg["Jwt:Issuer"] ?? "promiscuity";
var aud = cfg["Jwt:Audience"] ?? issuer;

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(o =>
    {
        o.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidIssuer = issuer,
            ValidateAudience = true,
            ValidAudience = aud,
            ValidateIssuerSigningKey = true,
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(jwtKey)),
            ValidateLifetime = true,
            ClockSkew = TimeSpan.FromSeconds(30)
        };
    });

builder.Services.AddAuthorization();

var app = builder.Build();

app.Use(async (context, next) =>
{
    var started = System.Diagnostics.Stopwatch.StartNew();
    try
    {
        await next();
    }
    finally
    {
        context.RequestServices.GetRequiredService<ServiceMetrics>().HttpRequest(started.Elapsed);
    }
});

app.UseExceptionHandler(errorApp =>
{
    errorApp.Run(async context =>
    {
        var feature = context.Features.Get<IExceptionHandlerFeature>();
        var exception = feature?.Error;
        var logger = context.RequestServices.GetRequiredService<ILoggerFactory>().CreateLogger("GlobalException");
        var traceId = context.TraceIdentifier;

        if (exception is not null)
        {
            logger.LogError(
                exception,
                "Unhandled exception for {Method} {Path}. TraceId={TraceId}",
                context.Request.Method,
                context.Request.Path,
                traceId
            );
        }

        context.Response.StatusCode = StatusCodes.Status500InternalServerError;
        context.Response.ContentType = "application/problem+json";

        await context.Response.WriteAsJsonAsync(new
        {
            type = "https://httpstatuses.com/500",
            title = "Internal Server Error",
            status = 500,
            detail = exception?.Message ?? "An unexpected server error occurred.",
            traceId
        });
    });
});

app.MapGet("/healthz", () => Results.Ok("ok"));
app.MapGet("/readyz", async (MongoDatabaseProvider mongo) =>
{
    await mongo.Database.RunCommandAsync<BsonDocument>(new BsonDocument("ping", 1));
    return Results.Ok("ready");
});
app.MapGet("/metrics", (ServiceMetrics metrics) => Results.Text(metrics.RenderPrometheus(), "text/plain; version=0.0.4"));
app.UseSwagger();
app.UseSwaggerUI(o =>
{
    o.SwaggerEndpoint("/swagger/v1/swagger.json", "Questions API v1");
    o.RoutePrefix = "swagger";
});
app.UseAuthentication();
app.UseAuthorization();
app.MapControllers();
app.Run();