Initial changes for VAT Registration Number capture

app/controllers/purchaser/RegistrationNumberController.scala

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2025 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package controllers.purchaser
+
+import controllers.actions.*
+import forms.purchaser.RegistrationNumberFormProvider
+import models.{Mode, NormalMode}
+import models.purchaser.{NameOfPurchaser, WhoIsMakingThePurchase, PurchaserConfirmIdentity}
+import navigation.Navigator
+import pages.purchaser.{NameOfPurchaserPage, PurchaserConfirmIdentityPage, RegistrationNumberPage, WhoIsMakingThePurchasePage}
+import play.api.i18n.{I18nSupport, MessagesApi}
+import play.api.mvc.{Action, AnyContent, MessagesControllerComponents}
+import repositories.SessionRepository
+import services.purchaser.PurchaserService
+import uk.gov.hmrc.play.bootstrap.frontend.controller.FrontendBaseController
+import views.html.purchaser.RegistrationNumberView
+
+import javax.inject.Inject
+import scala.concurrent.{ExecutionContext, Future}
+
+class RegistrationNumberController @Inject()(
+                                        override val messagesApi: MessagesApi,
+                                        sessionRepository: SessionRepository,
+                                        navigator: Navigator,
+                                        identify: IdentifierAction,
+                                        getData: DataRetrievalAction,
+                                        requireData: DataRequiredAction,
+                                        formProvider: RegistrationNumberFormProvider,
+                                        val controllerComponents: MessagesControllerComponents,
+                                        view: RegistrationNumberView,
+                                        purchaserService: PurchaserService
+                                    )(implicit ec: ExecutionContext) extends FrontendBaseController with I18nSupport {
+
+  val form = formProvider()
+
+  def onPageLoad(mode: Mode): Action[AnyContent] = (identify andThen getData andThen requireData) {
+    implicit request =>
+      val purchaserFullName: Option[String] = request.userAnswers.get(NameOfPurchaserPage).map(_.fullName)
+      // val isPurchaserVATRegistered: Option[String] = Some("VATRegistrationNumber")
+       val isPurchaserVATRegistered: Option[PurchaserConfirmIdentity] = request.userAnswers.get(PurchaserConfirmIdentityPage)
+
+        purchaserService.checkPurchaserTypeAndCompanyDetails(
+        purchaserType = WhoIsMakingThePurchase.Company,
+        userAnswers = request.userAnswers,
+        continueRoute = {
+          (purchaserFullName) match {
+            case Some(purchaserFullName) if isPurchaserVATRegistered.contains(PurchaserConfirmIdentity.VatRegistrationNumber) =>
+              val preparedForm = request.userAnswers.get(RegistrationNumberPage) match {
+                case None => form
+                case Some(value) => form.fill(value)
+              }
+              Ok(view(preparedForm, mode, purchaserFullName))
+            case None => Redirect(controllers.purchaser.routes.NameOfPurchaserController.onPageLoad(NormalMode))
+            case _ =>
+              //TODO update to more relevant path i.e. back to pr-5b
+              Redirect(controllers.routes.GenericErrorController.onPageLoad())
+          }
+        }
+      )
+  }
+
+  def onSubmit(mode: Mode): Action[AnyContent] = (identify andThen getData andThen requireData).async {
+    implicit request =>
+
+      val purchaserFullName: Option[String] = request.userAnswers.get(NameOfPurchaserPage).map(_.fullName)
+
+      purchaserFullName match  {
+        case Some(purchaserFullName) =>
+          form.bindFromRequest().fold(
+            formWithErrors =>
+              Future.successful(BadRequest(view(formWithErrors, mode, purchaserFullName))),
+
+            value =>
+              for {
+                updatedAnswers <- Future.fromTry(request.userAnswers.set(RegistrationNumberPage, value))
+                _ <- sessionRepository.set(updatedAnswers)
+              } yield Redirect(navigator.nextPage(RegistrationNumberPage, mode, updatedAnswers))
+          )
+        case _ =>
+          Future.successful(Redirect(controllers.purchaser.routes.NameOfPurchaserController.onPageLoad(mode)))
+        }
+       }
+  }
+

app/forms/mappings/Constraints.scala

@@ -178,4 +178,51 @@ trait Constraints {
       checkSum(s"${errorKey}.invalid")
     )
   }
+
+  protected def vatCheckF16Validation(errorKey: String): Constraint[String] = {
+
+    def vatF16Check(errorKey: String): Constraint[String] = {
+
+      def validateVAT(raw: String): Boolean = Try {
+        // ---- Normalization requested: drop "GB" and spaces ----
+        val normalized = {
+          val up = Option(raw).getOrElse("").trim.toUpperCase
+          val noGb = if (up.startsWith("GB")) up.drop(2) else up
+          noGb.replaceAll("\\s+", "")
+        }
+        val bodyDigits       = normalized.substring(0, 7)
+        val checkDigitsValue = normalized.substring(7, 9).toInt
+
+        val weights = Array(8, 7, 6, 5, 4, 3, 2)
+        val sum = bodyDigits
+          .map(_.asDigit)
+          .zip(weights)
+          .map { case (digit, weight) => digit * weight }
+          .sum
+
+        val check1 = 97 - Math.floorMod(sum, 97)
+        val check2 = 97 - Math.floorMod(sum + 55, 97)
+
+        checkDigitsValue >= 0 &&
+          checkDigitsValue <= 97 &&
+          (checkDigitsValue == check1 || checkDigitsValue == check2)
+      } match {
+        case Success(isValid) => isValid
+        case Failure(_)       => false
+      }
+
+      Constraint[String] { str =>
+        // Only returns Valid/Invalid; no extra format/length checks here
+        if (validateVAT(str)) Valid else Invalid(errorKey)
+      }
+    }
+
+    firstError(
+      regexp("^[0-9]*$", s"${errorKey}.regex.invalid"),
+      minLength(9, s"${errorKey}.length"),
+      maxLength(9, s"${errorKey}.length"),
+      vatF16Check(s"${errorKey}.invalid")
+    )
+  }
+
 }

app/forms/purchaser/RegistrationNumberFormProvider.scala

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2025 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package forms.purchaser
+
+import forms.mappings.Mappings
+import play.api.data.Form
+import play.api.data.validation.Constraints.minLength
+import forms.mappings.Constraints
+import javax.inject.Inject
+
+class RegistrationNumberFormProvider @Inject() extends Mappings with Constraints{
+
+  private val RegistrationNumberPattern = "^[0-9]*$"
+
+  def apply(): Form[String] =
+    Form(
+      "registrationNumber" -> text("purchaser.registrationNumber.error.required")
+        .verifying(vatCheckF16Validation("purchaser.registrationNumber.error"))
+
+    )
+}

app/navigation/Navigator.scala

@@ -62,7 +62,7 @@ class Navigator @Inject()() {
 
   private def isPurchaserSection(page: Page): Boolean = page match {
 
-    case WhoIsMakingThePurchasePage | NameOfPurchaserPage | DoesPurchaserHaveNIPage | PurchaserNationalInsurancePage | PurchaserFormOfIdIndividualPage | AddPurchaserPhoneNumberPage | PurchaserDateOfBirthPage | EnterPurchaserPhoneNumberPage | PurchaserPartnershipUtrPage | PurchaserCorporationTaxUTRPage => true
+    case WhoIsMakingThePurchasePage | NameOfPurchaserPage | DoesPurchaserHaveNIPage | PurchaserNationalInsurancePage | PurchaserFormOfIdIndividualPage | AddPurchaserPhoneNumberPage | PurchaserDateOfBirthPage | EnterPurchaserPhoneNumberPage | PurchaserPartnershipUtrPage | PurchaserCorporationTaxUTRPage | RegistrationNumberPage => true
 
     case _ => false
   }
@@ -88,6 +88,8 @@ class Navigator @Inject()() {
       _ => controllers.purchaser.routes.PurchaserPartnershipUtrController.onPageLoad(NormalMode)
     case PurchaserCorporationTaxUTRPage => //TODO: to be updated to 'type of business' (DTR-1679 pr-9 - sprint 5)
      _ => controllers.purchaser.routes.PurchaserCorporationTaxUTRController.onPageLoad(NormalMode)
+    case RegistrationNumberPage => //TODO update post pr-9 page implementation in future sprints
+      _ => controllers.routes.ReturnTaskListController.onPageLoad()
     case _ => _ => routes.IndexController.onPageLoad()
   }
 

app/pages/purchaser/RegistrationNumberPage.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2025 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package pages.purchaser
+
+import pages.QuestionPage
+import play.api.libs.json.JsPath
+
+case object RegistrationNumberPage extends QuestionPage[String] {
+
+  override def path: JsPath = JsPath \ "purchaserCurrent" \ toString
+
+  override def toString: String = "registrationNumber"
+}

app/services/purchaser/PurchaserService.scala

@@ -116,8 +116,7 @@ class PurchaserService {
         case PurchaserConfirmIdentity.CorporationTaxUTR =>
           controllers.purchaser.routes.PurchaserCorporationTaxUTRController.onPageLoad(NormalMode)
         case PurchaserConfirmIdentity.VatRegistrationNumber =>
-          // TODO: redirect to Vat Reg Num page
-          controllers.purchaser.routes.NameOfPurchaserController.onPageLoad(NormalMode)
+          controllers.purchaser.routes.RegistrationNumberController.onPageLoad(NormalMode)
         case PurchaserConfirmIdentity.AnotherFormOfID =>
           // TODO: redirect to Another Form ID page
           controllers.purchaser.routes.NameOfPurchaserController.onPageLoad(NormalMode)

app/viewmodels/checkAnswers/purchaser/RegistrationNumberSummary.scala

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2025 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package viewmodels.checkAnswers.purchaser
+
+import controllers.routes
+import models.{CheckMode, UserAnswers}
+import pages.purchaser.RegistrationNumberPage
+import play.api.i18n.Messages
+import play.twirl.api.HtmlFormat
+import uk.gov.hmrc.govukfrontend.views.viewmodels.summarylist.SummaryListRow
+import viewmodels.govuk.summarylist.*
+import viewmodels.implicits.*
+
+object RegistrationNumberSummary  {
+
+  def row(answers: UserAnswers)(implicit messages: Messages): Option[SummaryListRow] =
+    answers.get(RegistrationNumberPage).map {
+      answer =>
+
+        SummaryListRowViewModel(
+          key     = "purchaser.registrationNumber.checkYourAnswersLabel",
+          value   = ValueViewModel(HtmlFormat.escape(answer).toString),
+          actions = Seq(
+            ActionItemViewModel("site.change", controllers.purchaser.routes.RegistrationNumberController.onPageLoad(CheckMode).url)
+              .withVisuallyHiddenText(messages("purchaser.registrationNumber.change.hidden"))
+          )
+        )
+    }
+}

app/views/purchaser/RegistrationNumberView.scala.html

@@ -0,0 +1,52 @@
+@*
+ * Copyright 2025 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *@
+
+@import viewmodels.InputWidth._
+@import viewmodels.LabelSize.Large
+
+@this(
+    layout: templates.Layout,
+    formHelper: FormWithCSRF,
+    govukErrorSummary: GovukErrorSummary,
+    govukInput: GovukInput,
+    govukButton: GovukButton
+)
+
+@(form: Form[_], mode: Mode, purchaserName: String)(implicit request: Request[_], messages: Messages)
+
+@layout(pageTitle = title(form, messages("purchaser.registrationNumber.title"))) {
+
+    @formHelper(action = controllers.purchaser.routes.RegistrationNumberController.onSubmit(mode)) {
+
+        @if(form.errors.nonEmpty) {
+            @govukErrorSummary(ErrorSummaryViewModel(form))
+        }
+        <span class="govuk-caption-l">@messages("purchaser.registrationNumber.caption")</span>
+
+        @govukInput(
+            InputViewModel(
+                field = form("registrationNumber"),
+                label = LabelViewModel(messages("purchaser.registrationNumber.heading",purchaserName)).asPageHeading(size = Large)
+            )
+            .withWidth(Full)
+            .withHint(HintViewModel(HtmlContent(Html(messages("purchaser.registrationNumber.hint",purchaserName)))))
+        )
+
+        @govukButton(
+            ButtonViewModel(messages("site.save.continue"))
+        )
+    }
+}

conf/app.routes

@@ -185,6 +185,11 @@ POST       /about-the-purchaser/partnership-utr
 GET        /about-the-purchaser/partnership-utr/change                                controllers.purchaser.PurchaserPartnershipUtrController.onPageLoad(mode: Mode = CheckMode)
 POST       /about-the-purchaser/partnership-utr/change                                controllers.purchaser.PurchaserPartnershipUtrController.onSubmit(mode: Mode = CheckMode)
 
+GET        /about-the-purchaser/vat-registration-number                        controllers.purchaser.RegistrationNumberController.onPageLoad(mode: Mode = NormalMode)
+POST       /about-the-purchaser/vat-registration-number                        controllers.purchaser.RegistrationNumberController.onSubmit(mode: Mode = NormalMode)
+GET        /about-the-purchaser/vat-registration-number/change                  controllers.purchaser.RegistrationNumberController.onPageLoad(mode: Mode = CheckMode)
+POST       /about-the-purchaser/vat-registration-number/change                 controllers.purchaser.RegistrationNumberController.onSubmit(mode: Mode = CheckMode)
+
 GET        /about-the-purchaser/corporation-tax-utr                        controllers.purchaser.PurchaserCorporationTaxUTRController.onPageLoad(mode: Mode = NormalMode)
 POST       /about-the-purchaser/corporation-tax-utr                        controllers.purchaser.PurchaserCorporationTaxUTRController.onSubmit(mode: Mode = NormalMode)
 GET        /about-the-purchaser/corporation-tax-utr/change                 controllers.purchaser.PurchaserCorporationTaxUTRController.onPageLoad(mode: Mode = CheckMode)

conf/messages.en

@@ -550,4 +550,17 @@ purchaser.purchaserCorporationTaxUTR.error.required = Enter Corporation Tax Uniq
 purchaser.purchaserCorporationTaxUTR.error.length = Corporation Tax Unique Taxpayer Reference (UTR) must be 10 characters
 purchaser.purchaserCorporationTaxUTR.error.regex.invalid = Enter a valid UTR
 purchaser.purchaserCorporationTaxUTR.error.invalid = Enter a valid UTR
-purchaser.purchaserCorporationTaxUTR.change.hidden = Corporation Tax Unique Taxpayer Reference (UTR)
+purchaser.purchaserCorporationTaxUTR.change.hidden = Corporation Tax Unique Taxpayer Reference (UTR)
+
+purchaser.registrationNumber.title = What is the purchaser’s VAT registration number? - About the purchaser
+purchaser.registrationNumber.caption = About the purchaser
+purchaser.registrationNumber.heading = What is {0}’s VAT registration number?
+purchaser.registrationNumber.checkYourAnswersLabel = registrationNumber
+purchaser.registrationNumber.error.required = Enter VAT Registration Number
+purchaser.registrationNumber.error.length = Registration Number must be 9 digits
+purchaser.registrationNumber.error.invalid =  Registration Number must be 9 digits
+purchaser.registrationNumber.change.hidden = registrationNumber
+purchaser.registrationNumber.error.regex.error = Numeric only
+purchaser.registrationNumber.error.regex.invalid = Numeric only
+purchaser.registrationNumber.error.invalid = Registration Number is invalid
+purchaser.registrationNumber.hint = This is 9 numbers, sometimes with ‘GB’ at the start, for example 123456789 or GB123456789. You can find it on {0}’s VAT registration certificate