Add check digit calculation

Author: jmarin

validation/src/main/scala/hmda/validation/engine/lar/ULIValidation.scala

@@ -0,0 +1,59 @@
+package hmda.validation.engine.lar
+
+//See https://www.consumerfinance.gov/eregulations/1003-C/2015-26607_20180101#1003-C-1
+
+object ULIValidation {
+
+  val conversionTable = Map(
+    "a" -> 10,
+    "b" -> 11,
+    "c" -> 12,
+    "d" -> 13,
+    "e" -> 14,
+    "f" -> 15,
+    "g" -> 16,
+    "h" -> 17,
+    "i" -> 18,
+    "j" -> 19,
+    "k" -> 20,
+    "l" -> 21,
+    "m" -> 22,
+    "n" -> 23,
+    "o" -> 24,
+    "p" -> 25,
+    "q" -> 26,
+    "r" -> 27,
+    "s" -> 28,
+    "t" -> 29,
+    "u" -> 30,
+    "v" -> 31,
+    "w" -> 32,
+    "x" -> 33,
+    "y" -> 34,
+    "z" -> 35
+  )
+
+  private def convert(uli: String): String = uli
+    .map(_.toLower)
+    .map { c =>
+      if (!c.isDigit)
+        conversionTable(c.toString).toString
+      else
+        c
+    }.mkString("") + "00"
+
+  private def calculateMod(i: BigInt): BigInt = {
+    i % 97
+  }
+
+  private def calculateCheckDigit(i: BigInt) = {
+    98 - i
+  }
+
+  def checkDigit(uli: String): String = {
+    val checkDigit =
+      calculateCheckDigit(calculateMod(BigInt(convert(uli))))
+    uli + checkDigit.toString
+  }
+
+}

validation/src/test/scala/hmda/validation/engine/lar/ULIValidationSpec.scala

@@ -0,0 +1,13 @@
+package hmda.validation.engine.lar
+
+import org.scalatest.{ MustMatchers, WordSpec }
+
+class ULIValidationSpec extends WordSpec with MustMatchers {
+
+  "A ULI Validation" must {
+    "Produce valid check digit" in {
+      val uli = "10Bx939c5543TqA1144M999143X"
+      ULIValidation.checkDigit(uli) mustBe "10Bx939c5543TqA1144M999143X38"
+    }
+  }
+}