source: ChapterX.API/Program.cs@ 99c1e45

using ChapterX.Application;
using ChapterX.Infrastructure;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;
using System.Reflection;
using System.Text;

var builder = WebApplication.CreateBuilder(args);

var jwtKey = builder.Configuration["Jwt:Key"];
if (string.IsNullOrWhiteSpace(jwtKey))
    throw new InvalidOperationException("Jwt:Key is not configured. Set it via environment variable DOTNET_Jwt__Key before starting the application.");

builder.Services.AddCors(options =>
{
    options.AddPolicy("Frontend", policy =>
        policy.WithOrigins("http://localhost:5173", "https://localhost:5173")
              .AllowAnyHeader()
              .AllowAnyMethod()
              .AllowCredentials());
});

builder.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.ReferenceHandler = System.Text.Json.Serialization.ReferenceHandler.IgnoreCycles;
    });
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen(options =>
{
    options.CustomSchemaIds(type => type.FullName);
    options.AddSecurityDefinition("Bearer", new Microsoft.OpenApi.Models.OpenApiSecurityScheme
    {
        Name = "Authorization",
        Type = Microsoft.OpenApi.Models.SecuritySchemeType.Http,
        Scheme = "Bearer",
        BearerFormat = "JWT",
        In = Microsoft.OpenApi.Models.ParameterLocation.Header,
        Description = "Enter your JWT token"
    });
    options.AddSecurityRequirement(new Microsoft.OpenApi.Models.OpenApiSecurityRequirement
    {
        {
            new Microsoft.OpenApi.Models.OpenApiSecurityScheme
            {
                Reference = new Microsoft.OpenApi.Models.OpenApiReference
                {
                    Type = Microsoft.OpenApi.Models.ReferenceType.SecurityScheme,
                    Id = "Bearer"
                }
            },
            Array.Empty<string>()
        }
    });
});

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = true,
            ValidateIssuerSigningKey = true,
            ValidIssuer = builder.Configuration["Jwt:Issuer"],
            ValidAudience = builder.Configuration["Jwt:Audience"],
            IssuerSigningKey = new SymmetricSecurityKey(
                Encoding.UTF8.GetBytes(builder.Configuration["Jwt:Key"]!))
        };
    });
builder.Services.AddAuthorization();

builder.Services.AddApplication();
builder.Services.AddInfrastructure(builder.Configuration);

var app = builder.Build();

app.UseExceptionHandler(err => err.Run(async ctx =>
{
    var ex = ctx.Features.Get<Microsoft.AspNetCore.Diagnostics.IExceptionHandlerFeature>()?.Error;
    ctx.Response.ContentType = "application/json";

    var logger = ctx.RequestServices.GetRequiredService<ILogger<Program>>();

    string message;
    int status;

    if (ex is UnauthorizedAccessException)
    {
        status = 401;
        message = ex.Message;
    }
    else if (ex is InvalidOperationException)
    {
        status = 400;
        message = ex.Message;
    }
    else if (ex is Microsoft.EntityFrameworkCore.DbUpdateException dbEx)
    {
        status = 400;
        var inner = dbEx.InnerException?.Message ?? "";
        if (inner.Contains("email_format"))
            message = "Invalid email format.";
        else if (inner.Contains("unique") || inner.Contains("duplicate") || inner.Contains("23505"))
            message = "A user with this email or username already exists.";
        else
        {
            logger.LogError(dbEx, "Unhandled database error");
            message = "A database error occurred. Please try again.";
        }
    }
    else
    {
        logger.LogError(ex, "Unhandled exception");
        status = 500;
        message = "An unexpected error occurred.";
    }

    ctx.Response.StatusCode = status;
    await ctx.Response.WriteAsJsonAsync(new { message });
}));

app.UseCors("Frontend");

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

app.UseAuthentication();
app.UseAuthorization();
try
{
    app.MapControllers();
}
catch (ReflectionTypeLoadException ex)
{
    Console.Error.WriteLine("ReflectionTypeLoadException while mapping controllers:");
    foreach (var loaderEx in ex.LoaderExceptions ?? [])
    {
        Console.Error.WriteLine(loaderEx.ToString());
    }

    throw;
}

app.Run();