Use AuthServer requested in the CredentialOffer (#342)

Signed-off-by: Johannes Tuerk <johannes.tuerk@lissi.id>

Author: JoTiTu

src/WalletFramework.Oid4Vc/Oid4Vci/CredOffer/GrantTypes/PreAuthorizedCode.cs

@@ -3,6 +3,7 @@
 using Newtonsoft.Json.Linq;
 using WalletFramework.Core.Functional;
 using WalletFramework.Core.Json;
+using WalletFramework.Oid4Vc.Oid4Vci.Authorization.Models;
 using static WalletFramework.Oid4Vc.Oid4Vci.CredOffer.GrantTypes.TransactionCode;
 
 namespace WalletFramework.Oid4Vc.Oid4Vci.CredOffer.GrantTypes;
@@ -24,11 +25,18 @@ public record PreAuthorizedCode
     /// </summary>
     [JsonProperty("tx_code")]
     public Option<TransactionCode> TransactionCode { get; }
+    
+    /// <summary>
+    ///     Specifying whether the user must send a Transaction Code along with the Token Request in a Pre-Authorized Code Flow.
+    /// </summary>
+    [JsonProperty("authorization_server")]
+    public Option<AuthorizationServerId> AuthorizationServer { get; }
 
-    private PreAuthorizedCode(string value, Option<TransactionCode> transactionCode)
+    private PreAuthorizedCode(string value, Option<TransactionCode> transactionCode, Option<AuthorizationServerId> authorizationServer)
     {
         Value = value;
         TransactionCode = transactionCode;
+        AuthorizationServer = authorizationServer;
     }
 
     public static Option<PreAuthorizedCode> OptionalPreAuthorizedCode(JToken preAuthCode)
@@ -38,12 +46,17 @@ public static Option<PreAuthorizedCode> OptionalPreAuthorizedCode(JToken preAuth
             .ToOption()
             .OnSome(OptionalTransactionCode);
 
+        var authorizationServer = preAuthCode
+            .GetByKey("authorization_server")
+            .OnSuccess(AuthorizationServerId.ValidAuthorizationServerId)
+            .ToOption();
+        
         return preAuthCode
             .GetByKey("pre-authorized_code")
             .OnSuccess(token =>
             {
                 var value = token.ToString();
-                return new PreAuthorizedCode(value, transactionCode);
+                return new PreAuthorizedCode(value, transactionCode, authorizationServer);
             })
             .ToOption();
     }

src/WalletFramework.Oid4Vc/Oid4Vci/Implementations/Oid4VciClientService.cs

@@ -711,9 +711,7 @@ from server in code.AuthorizationServer
             var getAuthServerResponse = await _httpClient.GetAsync(authServerUrl);
 
             if (!getAuthServerResponse.IsSuccessStatusCode)
-                throw new HttpRequestException(
-                    $"Failed to get authorization server metadata. Status Code is: {getAuthServerResponse.StatusCode}"
-                );
+                continue;
 
             var content = await getAuthServerResponse.Content.ReadAsStringAsync();
 
@@ -724,28 +722,37 @@ from server in code.AuthorizationServer
             authorizationServerMetadatas.Add(authServer);
         }
 
-        if (authorizationServerMetadatas.Count == 1)
-            return authorizationServerMetadatas.First();
-
         return credentialOffer.Match(
             Some: offer =>
             {
                 var credentialOfferAuthCodeGrantType = from grants in offer.Grants 
                     from code in grants.AuthorizationCode
                     select code;
 
-                return credentialOfferAuthCodeGrantType.Match(
-                    Some: code => authorizationServerMetadatas.Find(authServer => authServer.SupportsAuthCodeFlow) ??
-                            throw new InvalidOperationException("No suitable Authorization Server found"),
+                return  credentialOfferAuthCodeGrantType.Match(
+                    Some: code => code.AuthorizationServer.Match(
+                        Some: requestedAuthServer => 
+                            authorizationServerMetadatas.Find(authServer => 
+                                authServer.Issuer == requestedAuthServer.ToString())
+                            ?? throw new InvalidOperationException("No suitable Authorization Server found"),
+                        None: () => authorizationServerMetadatas.Find(authServer => authServer.SupportsAuthCodeFlow) ??
+                              throw new InvalidOperationException("No suitable Authorization Server found")),
                     None: () =>
                     {
                         var credentialOfferPreAuthGrantType = from grants in offer.Grants 
-                            from code in grants.AuthorizationCode
+                            from code in grants.PreAuthorizedCode
                             select code;
 
                         return credentialOfferPreAuthGrantType.Match(
-                            Some: preAuth => authorizationServerMetadatas.Find(authServer => authServer.SupportsPreAuthFlow)
-                                             ?? throw new InvalidOperationException("No suitable Authorization Server found"),
+                            Some: preAuth =>
+                            {
+                                return preAuth.AuthorizationServer.Match(
+                                    Some: requestedAuthServer => 
+                                        authorizationServerMetadatas.Find(authServer =>
+                                            authServer.Issuer == requestedAuthServer.ToString()) 
+                                        ?? throw new InvalidOperationException("No suitable Authorization Server found"),
+                                    None: () => authorizationServerMetadatas.Find(authServer => authServer.SupportsPreAuthFlow));
+                            },
                             None: () => authorizationServerMetadatas.First());
                     });
             },