[ACL-96] Add cancel payment endpoint (#218)

src/TrueLayer/Payments/IPaymentsApi.cs

@@ -120,5 +120,17 @@ Task<ApiResponse<ListPaymentRefundsResponse>> ListPaymentRefunds(string paymentI
         Task<ApiResponse<RefundUnion>> GetPaymentRefund(string paymentId,
             string refundId,
             CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Cancel a payment.
+        /// </summary>
+        /// <param name="paymentId">The payment identifier</param>
+        /// <param name="idempotencyKey">
+        /// An idempotency key to allow safe retrying without the operation being performed multiple times.
+        /// The value should be unique for each operation, e.g. a UUID, with the same key being sent on a retry of the same request.
+        /// </param>
+        /// <param name="cancellationToken">The cancellation token to cancel the operation</param>
+        /// <returns>HTTP 202 Accepted if successful, otherwise problem details.</returns>
+        Task<ApiResponse> CancelPayment(string paymentId, string idempotencyKey, CancellationToken cancellationToken = default);
     }
 }

src/TrueLayer/Payments/PaymentsApi.cs

@@ -198,5 +198,26 @@ public async Task<ApiResponse<RefundUnion>> GetPaymentRefund(string paymentId,
                 cancellationToken: cancellationToken
             );
         }
+
+        public async Task<ApiResponse> CancelPayment(string paymentId, string idempotencyKey, CancellationToken cancellationToken = default)
+        {
+            paymentId.NotNullOrWhiteSpace(nameof(paymentId));
+            idempotencyKey.NotNullOrWhiteSpace(nameof(idempotencyKey));
+
+            ApiResponse<GetAuthTokenResponse> authResponse = await _auth.GetAuthToken(
+                new GetAuthTokenRequest("payments"), cancellationToken);
+
+            if (!authResponse.IsSuccessful)
+            {
+                return new ApiResponse(authResponse.StatusCode, authResponse.TraceId);
+            }
+
+            return await _apiClient.PostAsync(
+                _baseUri.Append(paymentId).Append("/actions/cancel"),
+                idempotencyKey: idempotencyKey,
+                accessToken: authResponse.Data!.AccessToken,
+                signingKey: _options.Payments!.SigningKey,
+                cancellationToken: cancellationToken);
+        }
     }
 }

test/TrueLayer.AcceptanceTests/PaymentTests.cs

@@ -227,6 +227,32 @@ public async Task Can_create_and_list_payment_refunds()
         listPaymentRefundsResponse.Data!.Items.Count.ShouldBe(1);
     }
 
+    [Fact]
+    public async Task Can_cancel_a_payment()
+    {
+        // arrange
+        var paymentRequest = CreateTestPaymentRequest();
+        var payment = await _fixture.Client.Payments.CreatePayment(
+            paymentRequest, idempotencyKey: Guid.NewGuid().ToString());
+
+        payment.IsSuccessful.ShouldBeTrue();
+        var paymentId = payment.Data.AsT0.Id;
+
+        // act
+        var cancelPaymentResponse = await _fixture.Client.Payments.CancelPayment(
+            paymentId,
+            idempotencyKey: Guid.NewGuid().ToString());
+
+        var getPaymentResponse = await _fixture.Client.Payments.GetPayment(paymentId);
+
+        // assert
+        cancelPaymentResponse.IsSuccessful.ShouldBeTrue();
+        cancelPaymentResponse.StatusCode.ShouldBe(HttpStatusCode.Accepted);
+        getPaymentResponse.IsSuccessful.ShouldBeTrue();
+        getPaymentResponse.Data.AsT5.ShouldNotBeNull();
+        getPaymentResponse.Data.AsT5.FailureReason.ShouldBe("canceled");
+    }
+
     private static void AssertSchemeSelection(
         PaymentsSchemeSelectionUnion? actualSchemeSelection,
         PaymentsSchemeSelectionUnion? expectedSchemeSelection,