EonaCat.DoxaApi/DoxaApi/Middleware/ApiDocsMiddleware.cs

using System.Reflection;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
using EonaCat.DoxaApi.Generation;
using EonaCat.DoxaApi.Interop;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.Extensions.DependencyInjection;

namespace EonaCat.DoxaApi.Middleware
{
    public static class DoxaApiMiddlewareExtensions
    {
        private static readonly JsonSerializerOptions _writeOptions = new()
        {
            WriteIndented = true,
            DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull
        };

        public static IApplicationBuilder UseDoxaApi(this IApplicationBuilder app, Action<DoxaApiOptions>? configure = null)
        {

            var options = app.ApplicationServices.GetService<DoxaApiOptions>() ?? new DoxaApiOptions();
            configure?.Invoke(options);

            var prefix = "/" + options.RoutePrefix.Trim('/');

            app.Map(prefix + "/doxaApi.json", specApp =>
            {
                specApp.Run(async context =>
                {
                    var document = GenerateDocument(context, options);
                    context.Response.ContentType = "application/json; charset=utf-8";
                    await JsonSerializer.SerializeAsync(context.Response.Body, document, _writeOptions);
                });
            });

            app.Map(prefix + "/openapi.json", oaApp =>
            {
                oaApp.Run(async context =>
                {
                    var document = GenerateDocument(context, options);
                    var openApi = OpenApiExporter.Export(document);
                    context.Response.ContentType = "application/json; charset=utf-8";
                    await context.Response.WriteAsync(
                        openApi.ToJsonString(_writeOptions), Encoding.UTF8);
                });
            });

            app.Map(prefix + "/swagger.json", swApp =>
            {
                swApp.Run(async context =>
                {
                    var document = GenerateDocument(context, options);
                    var swagger = SwaggerExporter.Export(document);
                    context.Response.ContentType = "application/json; charset=utf-8";
                    await context.Response.WriteAsync(
                        swagger.ToJsonString(_writeOptions), Encoding.UTF8);
                });
            });

            app.Map(prefix + "/import", importApp =>
            {
                importApp.Run(async context =>
                {
                    if (!HttpMethods.IsPost(context.Request.Method))
                    {
                        context.Response.StatusCode = 405;
                        context.Response.Headers["Allow"] = "POST";
                        await context.Response.WriteAsync("Method Not Allowed - use POST with a JSON body.");
                        return;
                    }

                    if (context.Request.ContentLength == 0 || context.Request.Body is null)
                    {
                        context.Response.StatusCode = 400;
                        await context.Response.WriteAsync("Request body is empty.");
                        return;
                    }

                    try
                    {
                        var imported = await OpenApiImporter.ImportAsync(context.Request.Body);
                        context.Response.ContentType = "application/json; charset=utf-8";
                        await JsonSerializer.SerializeAsync(context.Response.Body, imported, _writeOptions);
                    }
                    catch (NotSupportedException ex)
                    {
                        context.Response.StatusCode = 400;
                        await context.Response.WriteAsync($"Unsupported spec format: {ex.Message}");
                    }
                    catch (Exception ex)
                    {
                        context.Response.StatusCode = 400;
                        await context.Response.WriteAsync($"Failed to parse spec: {ex.Message}");
                    }
                });
            });

            app.Map(prefix, uiApp =>
            {
                uiApp.Run(async context =>
                {
                    var requestPath = context.Request.Path.Value ?? "";
                    var assetName = requestPath.Trim('/');
                    if (string.IsNullOrEmpty(assetName) || assetName == options.RoutePrefix.Trim('/'))
                    {
                        assetName = "index.html";
                    }

                    var asset = EmbeddedAssetLoader.Load(assetName);
                    if (asset is null)
                    {
                        context.Response.StatusCode = 404;
                        await context.Response.WriteAsync("Not found");
                        return;
                    }

                    context.Response.ContentType = asset.Value.ContentType;

                    if (assetName == "index.html")
                    {
                        var html = Encoding.UTF8.GetString(asset.Value.Bytes);
                        html = html.Replace("__DOXA_API_TITLE__", options.Title)
                                   .Replace("__DOXA_API_ACCENT__", options.AccentColor)
                                   .Replace("__DOXA_API_THEME__", options.Theme)
                                   .Replace("__DOXA_API_BASE__", prefix + "/")
                                   .Replace("__DOXA_API_SPEC_PATH__", prefix + "/doxaApi.json");
                        await context.Response.WriteAsync(html, Encoding.UTF8);
                        return;
                    }

                    await context.Response.Body.WriteAsync(asset.Value.Bytes);
                });
            });

            return app;
        }

        private static Models.ApiDocument GenerateDocument(HttpContext context, DoxaApiOptions options)
        {
            var provider = context.RequestServices.GetRequiredService<IActionDescriptorCollectionProvider>();
            var actions = provider.ActionDescriptors.Items;
            return new ApiDocumentGenerator(actions, options).Generate();
        }
    }

    internal static class EmbeddedAssetLoader
    {
        private static readonly Assembly _assembly = typeof(EmbeddedAssetLoader).Assembly;
        private static readonly string _prefix = "EonaCat.DoxaApi.UI.Assets.";

        public static (byte[] Bytes, string ContentType)? Load(string assetName)
        {
            var resourceName = _prefix + assetName.Replace('/', '.');
            using var stream = _assembly.GetManifestResourceStream(resourceName);
            if (stream is null)
            {
                return null;
            }

            using var ms = new MemoryStream();
            stream.CopyTo(ms);

            var contentType = Path.GetExtension(assetName) switch
            {
                ".html" => "text/html; charset=utf-8",
                ".css" => "text/css; charset=utf-8",
                ".js" => "application/javascript; charset=utf-8",
                ".svg" => "image/svg+xml",
                ".png" => "image/png",
                ".ico" => "image/x-icon",
                _ => "application/octet-stream"
            };

            return (ms.ToArray(), contentType);
        }
    }
}