NejCommon.NET/Controllers/TypedResultsPolyfill.cs

using System.Diagnostics.Eventing.Reader;
using System.Runtime.CompilerServices;
using Microsoft.AspNetCore.Http.HttpResults;
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;

namespace NejCommon.Controllers
{
    public class TypedResultsMetadataProvider : IOperationFilter
    {
        public void Apply(OpenApiOperation operation, OperationFilterContext context)
        {
            var responseType = context.MethodInfo.ReturnType;
            //Console.WriteLine(context.MethodInfo.DeclaringType.Name);
            //Console.WriteLine(context.MethodInfo.Name);
            //Console.WriteLine(responseType);
            var t = IsSubclassOfRawGeneric(typeof(Microsoft.AspNetCore.Http.HttpResults.Results<,>), responseType);
            if (t == null)
            {
                return;
            }

            var parArg = t.GetGenericArguments();
            if (operation.Responses.ContainsKey("200"))
                operation.Responses.Remove("200");

            foreach (var arg in parArg)
            {
                if (arg == typeof(NotFound))
                {
                    operation.Responses.Add("404", new OpenApiResponse { Description = "Not found" });
                }
                else if (arg == typeof(Ok))
                {
                    operation.Responses.Add("200", new OpenApiResponse { Description = "Success" });
                }
                else if (IsSubclassOfRawGeneric(typeof(Ok<>), arg) != null)
                {

                    var okArg = IsSubclassOfRawGeneric(typeof(Ok<>), arg).GetGenericArguments()[0];
                    // Console.WriteLine("Adding: " + okArg);

                    //get or generate the schema
                    var schema = context.SchemaGenerator.GenerateSchema(okArg, context.SchemaRepository);
                    operation.Responses.Add("200", new OpenApiResponse { Description = "Success", Content = { { "application/json", new OpenApiMediaType { Schema = schema } } } });

                }
                else if (arg == typeof(CreatedAtRoute))
                {
                    operation.Responses.Add("201", new OpenApiResponse { Description = "Success" });
                }
                else if (IsSubclassOfRawGeneric(typeof(CreatedAtRoute<>), arg) != null)
                {
                    if (operation.Responses.ContainsKey("201"))
                        operation.Responses.Remove("201");

                    var okArg = IsSubclassOfRawGeneric(typeof(CreatedAtRoute<>), arg).GetGenericArguments()[0];
                    // Console.WriteLine("Adding: " + okArg);

                    //get or generate the schema
                    var schema = context.SchemaGenerator.GenerateSchema(okArg, context.SchemaRepository);
                    operation.Responses.Add("201", new OpenApiResponse { Description = "Success", Content = { { "application/json", new OpenApiMediaType { Schema = schema } } } });
                }
                else if (arg == typeof(BadRequest))
                {
                    operation.Responses.Add("400", new OpenApiResponse { Description = "There was an error" });
                }
                else if (IsSubclassOfRawGeneric(typeof(BadRequest<>), arg) != null)
                {
                    if (operation.Responses.ContainsKey("400"))
                        operation.Responses.Remove("400");

                    var okArg = IsSubclassOfRawGeneric(typeof(BadRequest<>), arg).GetGenericArguments()[0];
                    // Console.WriteLine("Adding: " + okArg);

                    //get or generate the schema
                    var schema = context.SchemaGenerator.GenerateSchema(okArg, context.SchemaRepository);
                    operation.Responses.Add("400", new OpenApiResponse { Description = "There was an error", Content = { { "application/json", new OpenApiMediaType { Schema = schema } } } });
                }
                else if (arg == typeof(FileStreamHttpResult)){
                    operation.Responses.Add("200", new OpenApiResponse { Description = "Success", Content = { { "application/octet-stream", new OpenApiMediaType { Schema = new OpenApiSchema { Type = "string", Format = "binary" } } } } });
                }
                else
                {
                    Console.WriteLine("Unknown type: " + arg);
                }
            }
        }

        static Type? IsSubclassOfRawGeneric(Type generic, Type toCheck)
        {
            while (toCheck != null && toCheck != typeof(object))
            {
                //if Task is used, we need to check the underlying type
                var realTypeNoTask = toCheck.IsGenericType && toCheck.GetGenericTypeDefinition() == typeof(Task<>) ? toCheck.GetGenericArguments()[0] : toCheck;
                var cur = realTypeNoTask.IsGenericType ? realTypeNoTask.GetGenericTypeDefinition() : realTypeNoTask;
                //Console.WriteLine(cur);
                if (generic == cur)
                {
                    return realTypeNoTask;
                }
                toCheck = toCheck.BaseType;
            }
            return null;
        }
    }
}