Introduce ITSA tax identifier

src/main/scala/uk/gov/hmrc/domain/Itsa.scala

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2021 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 uk.gov.hmrc.domain
+
+import play.api.libs.json.{Reads, Writes}
+
+case class Itsa(itsa: String) extends TaxIdentifier with SimpleName {
+  require(Itsa.isValid(itsa), s"$itsa is not a valid itsa.")
+  override def toString = itsa
+
+  private val LengthWithoutSuffix: Int = 8
+
+  def value = itsa
+
+  val name = "itsa"
+
+  def formatted = value.grouped(2).mkString(" ")
+
+  def withoutSuffix = value.take(LengthWithoutSuffix)
+}
+
+object Itsa extends (String => Itsa) {
+  implicit val itsaWrite: Writes[Itsa] = new SimpleObjectWrites[Itsa](_.value)
+  implicit val itsaRead: Reads[Itsa] = new SimpleObjectReads[Itsa]("itsa", Itsa.apply)
+
+  // TODO Review the regular expression pattern for ITSA
+  private val validItsaFormat = "^[a-zA-Z0-9_]*$"
+
+  def isValid(itsa: String) = itsa != null && itsa.matches(validItsaFormat)
+}

src/main/scala/uk/gov/hmrc/domain/taxIds.scala

@@ -41,6 +41,7 @@ case class TaxIds(values: Set[TaxIds.TaxIdWithName]) {
   lazy val org = as[Org]
   lazy val agentBusinessUtr = as[AgentBusinessUtr]
   lazy val psaId = as[PsaId]
+  lazy val itsa = as[Itsa]
 }
 
 object TaxIds {
@@ -89,7 +90,8 @@ object TaxIds {
     SerialisableTaxId("agentbusinessutr", AgentBusinessUtr.apply),
     SerialisableTaxId("psaid", PsaId.apply),
     SerialisableTaxId("HMRC-OBTDS-ORG", HmrcObtdsOrg.apply),
-    SerialisableTaxId("HMRC-MTD-VAT", HmrcMtdVat.apply)
+    SerialisableTaxId("HMRC-MTD-VAT", HmrcMtdVat.apply),
+    SerialisableTaxId("itsa", Itsa.apply),
   )
 }
 

src/test/scala/uk/gov/hmrc/domain/ItsaSpec.scala

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2021 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 uk.gov.hmrc.domain
+
+import org.scalatest.{Matchers, WordSpec}
+
+class ItsaSpec extends WordSpec with Matchers {
+  import Itsa.isValid
+
+  "The validation of an itsa" should {
+    "pass with valid alphanumerics" in {
+      isValid("AB123456C") shouldBe true
+    }
+    // TODO add more test cases here ...
+  }
+}