From 6a86b45ddc52e6826faba6a58ed940704992413e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C3=A9vin=20Chalet?= <kevinchalet@gmail.com>
Date: Thu, 13 Oct 2022 19:23:30 +0200
Subject: [PATCH] Add StackExchange support

---
 ...ctClientWebIntegrationHandlers.Userinfo.cs | 54 +++++++++++++++++++
 .../OpenIddictClientWebIntegrationHandlers.cs | 10 +++-
 ...penIddictClientWebIntegrationProviders.xml | 14 +++++
 3 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Userinfo.cs b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Userinfo.cs
index f8dc287b..e8e7955f 100644
--- a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Userinfo.cs
+++ b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Userinfo.cs
@@ -8,6 +8,7 @@ using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Text.Json;
 using static OpenIddict.Client.OpenIddictClientHandlers.Userinfo;
+using static OpenIddict.Client.SystemNetHttp.OpenIddictClientSystemNetHttpHandlers.Userinfo;
 using static OpenIddict.Client.WebIntegration.OpenIddictClientWebIntegrationConstants;
 
 namespace OpenIddict.Client.WebIntegration;
@@ -17,11 +18,59 @@ public static partial class OpenIddictClientWebIntegrationHandlers
     public static class Userinfo
     {
         public static ImmutableArray<OpenIddictClientHandlerDescriptor> DefaultHandlers { get; } = ImmutableArray.Create(
+            /*
+             * Userinfo request preparation:
+             */
+            AttachAccessTokenParameter.Descriptor,
+
             /*
              * Userinfo response extraction:
              */
             UnwrapUserinfoResponse.Descriptor);
 
+        /// <summary>
+        /// Contains the logic responsible for attaching the access token
+        /// parameter to the request for the providers that require it.
+        /// </summary>
+        public class AttachAccessTokenParameter : IOpenIddictClientHandler<PrepareUserinfoRequestContext>
+        {
+            /// <summary>
+            /// Gets the default descriptor definition assigned to this handler.
+            /// </summary>
+            public static OpenIddictClientHandlerDescriptor Descriptor { get; }
+                = OpenIddictClientHandlerDescriptor.CreateBuilder<PrepareUserinfoRequestContext>()
+                    .UseSingletonHandler<AttachAccessTokenParameter>()
+                    .SetOrder(AttachBearerAccessToken.Descriptor.Order + 250)
+                    .SetType(OpenIddictClientHandlerType.BuiltIn)
+                    .Build();
+
+            /// <inheritdoc/>
+            public ValueTask HandleAsync(PrepareUserinfoRequestContext context)
+            {
+                if (context is null)
+                {
+                    throw new ArgumentNullException(nameof(context));
+                }
+
+                // This handler only applies to System.Net.Http requests. If the HTTP request cannot be resolved,
+                // this may indicate that the request was incorrectly processed by another client stack.
+                var request = context.Transaction.GetHttpRequestMessage() ??
+                    throw new InvalidOperationException(SR.GetResourceString(SR.ID0173));
+
+                // By default, OpenIddict sends the access token as part of the Authorization header
+                // using the Bearer authentication scheme. Some providers don't support this method
+                // and require sending the access token as part of the userinfo request payload.
+
+                if (context.Registration.ProviderName is Providers.StackExchange)
+                {
+                    context.Request.AccessToken = request.Headers.Authorization?.Parameter;
+                    request.Headers.Authorization = null;
+                }
+
+                return default;
+            }
+        }
+
         /// <summary>
         /// Contains the logic responsible for extracting the userinfo response
         /// from nested JSON nodes (e.g "data") for the providers that require it.
@@ -55,6 +104,11 @@ public static partial class OpenIddictClientWebIntegrationHandlers
 
                 context.Response = context.Registration.ProviderName switch
                 {
+                    // StackExchange returns an "items" array containing a single element.
+                    Providers.StackExchange => (JsonElement) context.Response["items"]
+                        is { ValueKind: JsonValueKind.Array } element && element.GetArrayLength() is 1 ?
+                        new(element[0]) : throw new InvalidOperationException(SR.FormatID0334("items")),
+
                     // Twitter returns a nested "data" object.
                     Providers.Twitter => (JsonElement) context.Response["data"]
                         is { ValueKind: JsonValueKind.Object } element ?
diff --git a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.cs b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.cs
index dfc6b803..0756ba75 100644
--- a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.cs
+++ b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.cs
@@ -148,7 +148,15 @@ public static partial class OpenIddictClientWebIntegrationHandlers
 
             Debug.Assert(context.UserinfoRequest is not null, SR.GetResourceString(SR.ID4008));
 
-            if (context.Registration.ProviderName is Providers.Twitter)
+            if (context.Registration.ProviderName is Providers.StackExchange)
+            {
+                var options = context.Registration.GetStackExchangeOptions();
+
+                context.UserinfoRequest["key"] = options.ApplicationKey;
+                context.UserinfoRequest["site"] = options.Site;
+            }
+
+            else if (context.Registration.ProviderName is Providers.Twitter)
             {
                 var options = context.Registration.GetTwitterOptions();
 
diff --git a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml
index be271390..6ba621ff 100644
--- a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml
+++ b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml
@@ -58,6 +58,20 @@
     </Environment>
   </Provider>
 
+  <Provider Name="StackExchange" Documentation="https://api.stackexchange.com/docs/authentication">
+    <Environment Issuer="https://api.stackexchange.com/">
+      <Configuration AuthorizationEndpoint="https://stackoverflow.com/oauth"
+                     TokenEndpoint="https://stackoverflow.com/oauth/access_token/json"
+                     UserinfoEndpoint="https://api.stackexchange.com/2.3/me" />
+    </Environment>
+
+    <Setting PropertyName="ApplicationKey" ParameterName="key" Type="String" Required="true"
+             Description="The application key used to communicate with the StackExchange API" />
+
+    <Setting PropertyName="Site" ParameterName="site" Type="String" Required="true" DefaultValue="stackoverflow"
+             Description="The site specified in userinfo requests (by default, 'stackoverflow')" />
+  </Provider>
+
   <Provider Name="Twitter" Documentation="https://developer.twitter.com/en/docs/authentication/oauth-2-0/authorization-code">
     <Environment Issuer="https://twitter.com/">
       <Configuration AuthorizationEndpoint="https://twitter.com/i/oauth2/authorize"