booking-microservices/BuildingBlocks/OpenApi/Extensions.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using Scalar.AspNetCore;

namespace BuildingBlocks.OpenApi
{
    public static class Extensions
    {
        // ref: https://github.com/dotnet/eShop/blob/main/src/eShop.ServiceDefaults/OpenApi.Extensions.cs
        public static IServiceCollection AddAspnetOpenApi(this IServiceCollection services)
        {
            string[] versions = ["v1"];

            foreach (var description in versions)
            {
                services.AddOpenApi(
                    description,
                    options =>
                    {
                        options.AddDocumentTransformer<SecuritySchemeDocumentTransformer>();
                    });
            }

            return services;
        }

        public static IApplicationBuilder UseAspnetOpenApi(this WebApplication app)
        {
            app.MapOpenApi();

            app.UseSwaggerUI(
                options =>
                {
                    var descriptions = app.DescribeApiVersions();

                    // build a swagger endpoint for each discovered API version
                    foreach (var description in descriptions)
                    {
                        var openApiUrl = $"/openapi/{description.GroupName}.json";
                        var name = description.GroupName.ToUpperInvariant();
                        options.SwaggerEndpoint(openApiUrl, name);
                    }
                });

            // Add scalar ui
            app.MapScalarApiReference(
                redocOptions =>
                {
                    redocOptions.WithOpenApiRoutePattern("/openapi/{documentName}.json");
                });

            return app;
        }
    }
}