feat: Extension to configure oauth implicit flow

.gitignore

@@ -397,5 +397,5 @@ FodyWeavers.xsd
 # JetBrains Rider
 *.sln.iml
 
-.DS_Store
 .idea/
+.DS_Store

src/OpenApi.Extensions/Extensions/OpenApiOptionsExtensions.cs

@@ -7,7 +7,9 @@
 using Microsoft.AspNetCore.OpenApi;
 using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Models;
+using OpenApi.Extensions.Options;
 using OpenApi.Extensions.Transformers;
+using OpenApi.Extensions.Transformers.Documents;
 using OpenApi.Extensions.Transformers.Operations;
 
 namespace OpenApi.Extensions.Extensions;
@@ -29,6 +31,21 @@ public static OpenApiOptions AddDescription(this OpenApiOptions options, string
         return options;
     }
 
+    /// <summary>
+    /// Adds a document transformer to configure OAuth2 Implicit Flow.
+    /// </summary>
+    /// <param name="options">The OpenAPI options to configure.</param>
+    /// <param name="configure"></param>
+    /// <returns>The updated <see cref="OpenApiOptions"/> instance.</returns>
+    public static OpenApiOptions AddOAuth2ImplicitFlow(this OpenApiOptions options, Action<ImplicitFlowOptions> configure)
+    {
+        var opt = new ImplicitFlowOptions();
+        configure(opt);
+
+        options.AddDocumentTransformer(new OAuth2ImplicitFlowDocumentTransformation(opt.SecurityScheme, opt.TokenEndpoint, opt.AuthorizationEndpoint, opt.Description, opt.Scopes));
+        return options;
+    }
+
     /// <summary>
     /// Adds the given status code and description to all operations
     /// </summary>
@@ -489,13 +506,6 @@ private static string FormatJson<T>(T obj, JsonSerializerOptions? jsonSerializer
         return formatToJson;
     }
 
-    private static bool ShouldTransform<T>(OpenApiSchemaTransformerContext context)
-    {
-        var jsonType = context.JsonTypeInfo.Type;
-        var type = Nullable.GetUnderlyingType(jsonType) ?? jsonType;
-        return type == typeof(T);
-    }
-
     private static string GetTypeName<T>()
     {
         if (typeof(T) == typeof(string))
@@ -505,4 +515,11 @@ private static string GetTypeName<T>()
 
         return typeof(T).Name;
     }
+
+    private static bool ShouldTransform<T>(OpenApiSchemaTransformerContext context)
+    {
+        var jsonType = context.JsonTypeInfo.Type;
+        var type = Nullable.GetUnderlyingType(jsonType) ?? jsonType;
+        return type == typeof(T);
+    }
 }

src/OpenApi.Extensions/Options/ImplicitFlowOptions.cs

@@ -0,0 +1,10 @@
+namespace OpenApi.Extensions.Options;
+
+public class ImplicitFlowOptions
+{
+    public string AuthorizationEndpoint { get; set; } = null!;
+    public string Description { get; set; } = null!;
+    public string[] Scopes { get; set; } = [];
+    public string SecurityScheme { get; set; } = null!;
+    public string TokenEndpoint { get; set; } = null!;
+}

src/OpenApi.Extensions/Transformers/Documents/OAuth2ImplicitFlowDocumentTransformation.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.OpenApi;
+using Microsoft.OpenApi.Models;
+
+namespace OpenApi.Extensions.Transformers.Documents;
+
+public class OAuth2ImplicitFlowDocumentTransformation : IOpenApiDocumentTransformer
+{
+    private readonly string _authorizationEndpoint;
+    private readonly string _description;
+    private readonly string[] _scopes;
+    private readonly string _securityScheme;
+    private readonly string _tokenEndpoint;
+
+    public OAuth2ImplicitFlowDocumentTransformation(string securityScheme,
+        string tokenEndpoint,
+        string authorizationEndpoint,
+        string description,
+        params string[] scopes)
+    {
+        _securityScheme = securityScheme;
+        _tokenEndpoint = tokenEndpoint;
+        _authorizationEndpoint = authorizationEndpoint;
+        _description = description;
+        _scopes = scopes;
+    }
+
+    public Task TransformAsync(OpenApiDocument document, OpenApiDocumentTransformerContext context, CancellationToken cancellationToken)
+    {
+        document.Components ??= new OpenApiComponents();
+        document.Components.SecuritySchemes[_securityScheme] =
+            new OpenApiSecurityScheme
+            {
+                Type = SecuritySchemeType.OAuth2,
+                Description = _description,
+                Flows = new OpenApiOAuthFlows
+                {
+                    Implicit = new OpenApiOAuthFlow
+                    {
+                        AuthorizationUrl = new Uri(_authorizationEndpoint),
+                        TokenUrl = new Uri(_tokenEndpoint),
+                        Scopes = _scopes.ToDictionary(
+                            s => s,
+                            s => s)
+                    }
+                }
+            };
+
+        document.SecurityRequirements.Add(
+            new OpenApiSecurityRequirement
+            {
+                {
+                    new OpenApiSecurityScheme
+                    {
+                        Reference = new OpenApiReference
+                        {
+                            Type = ReferenceType
+                                .SecurityScheme,
+                            Id = _securityScheme,
+                        }
+                    },
+                    _scopes
+                }
+            });
+
+        return Task.CompletedTask;
+    }
+}