feat: computing cvc mask based on card brand

example/src/main/java/com/basistheory/android/example/view/card/CardFragment.kt

@@ -25,6 +25,8 @@ class CardFragment : Fragment() {
         binding.lifecycleOwner = this
         binding.viewModel = viewModel
 
+        binding.cvc.cardNumberElement = binding.cardNumber
+
         binding.tokenizeButton.setOnClickListener { tokenize() }
         binding.autofillButton.setOnClickListener { autofill() }
 

lib/src/main/java/com/basistheory/android/service/CardBrandEnricher.kt

@@ -2,7 +2,7 @@ package com.basistheory.android.service
 
 import com.basistheory.android.constants.CardBrands
 
-internal class CardBrandEnricher {
+class CardBrandEnricher {
 
     object CardMasks {
         const val MASK_4_8_12GAPS_19LENGTH = "#### #### #### #######"
@@ -21,18 +21,21 @@ internal class CardBrandEnricher {
         var identifierRanges: List<Pair<String, String?>>,
         var validLengths: IntArray,
         var cvcMask: String,
-        var cardMask: String
-    )
-
-    class CardResult(
-        var cardDetails: CardDetails?,
+        var cardMask: String,
         var cardLength: Int = -1,
         var identifierLength: Int = -1,
     ) {
-        val complete: Boolean
-            get() = cardDetails?.validLengths?.contains(cardLength) ?: false
+        val isComplete: Boolean
+            get() = validLengths.contains(cardLength)
     }
 
+    class CardMetadata(
+        val brand: String?,
+        val cvcMask: String?,
+        val cardMask: String?,
+        val isComplete: Boolean
+    )
+
     private val cardBrands = listOf(
         CardDetails(
             CardBrands.VISA.label,
@@ -205,10 +208,10 @@ internal class CardBrandEnricher {
         )
     )
 
-    fun evaluateCard(number: String?): CardResult {
-        if (number.isNullOrBlank()) return CardResult(null)
+    fun evaluateCard(number: String?): CardMetadata? {
+        if (number.isNullOrBlank()) return null
 
-        var bestMatch = CardResult(null)
+        var bestMatch: CardDetails? = null
 
         cardBrands.forEach { cardDetails ->
             cardDetails.identifierRanges.forEach { range ->
@@ -222,19 +225,32 @@ internal class CardBrandEnricher {
             }
         }
 
-        return bestMatch
+        return with(bestMatch) {
+            CardMetadata(
+                this?.brand,
+                this?.cvcMask,
+                this?.cardMask,
+                this?.isComplete ?: false
+            )
+        }
     }
 
     private fun chooseBestMatch(
-        currentBestMatch: CardResult,
+        currentBestMatch: CardDetails?,
         cardDetails: CardDetails,
         identifierMatch: String,
         number: String
-    ): CardResult =
-        if (currentBestMatch.identifierLength < identifierMatch.length) CardResult(
-            cardDetails,
-            number.length,
-            identifierMatch.length
-        )
+    ): CardDetails? =
+        if ((currentBestMatch?.identifierLength ?: -1) < identifierMatch.length) with(cardDetails) {
+            CardDetails(
+                this.brand,
+                this.identifierRanges,
+                this.validLengths,
+                this.cvcMask,
+                this.cardMask,
+                number.length,
+                identifierMatch.length
+            )
+        }
         else currentBestMatch
 }

lib/src/main/java/com/basistheory/android/view/CardNumberElement.kt

@@ -16,6 +16,9 @@ class CardNumberElement @JvmOverloads constructor(
     defStyleAttr: Int = 0
 ) : TextElement(context, attrs, defStyleAttr) {
 
+    var cardMetadata: CardBrandEnricher.CardMetadata? = null
+        private set
+
     private val cardBrandEnricher: CardBrandEnricher = CardBrandEnricher()
 
     init {
@@ -26,9 +29,10 @@ class CardNumberElement @JvmOverloads constructor(
     }
 
     override fun beforeTextChanged(value: String?): String? {
-        val cardResult = cardBrandEnricher.evaluateCard(getDigitsOnly(value))
-        if (cardResult.cardDetails?.cardMask != null)
-            mask = ElementMask(cardResult.cardDetails!!.cardMask)
+        cardMetadata = cardBrandEnricher.evaluateCard(getDigitsOnly(value))
+
+        if (cardMetadata?.cardMask != null)
+            mask = ElementMask(cardMetadata!!.cardMask!!)
 
         return value
     }
@@ -39,8 +43,7 @@ class CardNumberElement @JvmOverloads constructor(
         isEmpty: Boolean,
         isValid: Boolean
     ): ChangeEvent {
-        val cardResult = cardBrandEnricher.evaluateCard(getDigitsOnly(value))
-        val eventDetails = cardResult.cardDetails?.brand?.let { brand ->
+        val eventDetails = this.cardMetadata?.brand?.let { brand ->
             mutableListOf(
                 EventDetails(
                     "cardBrand",
@@ -50,7 +53,7 @@ class CardNumberElement @JvmOverloads constructor(
         } ?: mutableListOf()
 
         return ChangeEvent(
-            cardResult.complete,
+            cardMetadata?.isComplete ?: false,
             isEmpty,
             isValid,
             eventDetails

lib/src/main/java/com/basistheory/android/view/CardVerificationCodeElement.kt

@@ -9,7 +9,20 @@ import com.basistheory.android.view.validation.RegexValidator
 class CardVerificationCodeElement @JvmOverloads constructor(
     context: Context,
     attrs: AttributeSet? = null,
-    defStyleAttr: Int = 0) : TextElement(context, attrs, defStyleAttr) {
+    defStyleAttr: Int = 0
+) : TextElement(context, attrs, defStyleAttr) {
+
+    var cardNumberElement: CardNumberElement? = null
+        set(value) {
+            if (value != null && cardNumberElement !== value) {
+                field = value
+                super.mask =
+                    cardNumberElement?.cardMetadata?.cvcMask?.let { ElementMask(it) } ?: defaultMask
+                field?.addChangeEventListener { updateMask() }
+            } else {
+                field = value
+            }
+        }
 
     init {
         super.keyboardType = KeyboardType.NUMBER
@@ -24,4 +37,9 @@ class CardVerificationCodeElement @JvmOverloads constructor(
             listOf(digit, digit, digit)
         )
     }
+
+    private fun updateMask() {
+        super.mask =
+            cardNumberElement?.cardMetadata?.cvcMask?.let { ElementMask(it) } ?: defaultMask
+    }
 }

lib/src/main/java/com/basistheory/android/view/TextElement.kt

@@ -25,7 +25,6 @@ import com.basistheory.android.view.mask.ElementMask
 import com.basistheory.android.view.transform.ElementTransform
 import com.basistheory.android.view.validation.ElementValidator
 
-
 open class TextElement @JvmOverloads constructor(
     context: Context,
     attrs: AttributeSet? = null,

lib/src/test/java/com/basistheory/android/service/CardBrandEnricherTests.kt

@@ -37,40 +37,36 @@ class CardBrandEnricherTests {
         expectedBrand: String,
         expectedCardMask: String
     ) {
-        with(cardBrandEnricher.evaluateCard(cardNumber).cardDetails) {
+        with(cardBrandEnricher.evaluateCard(cardNumber)) {
             expectThat(this?.brand).isEqualTo(expectedBrand)
             expectThat(this?.cardMask).isEqualTo(expectedCardMask)
         }
     }
 
     @Test
     fun `should pick best match based on identifier length`() {
-        expectThat(cardBrandEnricher.evaluateCard("4011784867543859").cardDetails?.brand).isEqualTo(
+        expectThat(cardBrandEnricher.evaluateCard("4011784867543859")?.brand).isEqualTo(
             "elo"
         )
     }
 
     @Test
-    fun `should set complete for best match card lengths`() {
+    fun `should set isComplete for best match card lengths`() {
         // discover valid lengths are 16 or 19
         val sixteenDigitsDiscoverCardNumber = "6582937163058334"
 
-        expectThat(cardBrandEnricher.evaluateCard(sixteenDigitsDiscoverCardNumber).complete).isTrue()
-        expectThat(cardBrandEnricher.evaluateCard("${sixteenDigitsDiscoverCardNumber}1").complete).isFalse()
-        expectThat(cardBrandEnricher.evaluateCard("${sixteenDigitsDiscoverCardNumber}12").complete).isFalse()
-        expectThat(cardBrandEnricher.evaluateCard("${sixteenDigitsDiscoverCardNumber}123").complete).isTrue()
+        expectThat(cardBrandEnricher.evaluateCard(sixteenDigitsDiscoverCardNumber)?.isComplete).isTrue()
+        expectThat(cardBrandEnricher.evaluateCard("${sixteenDigitsDiscoverCardNumber}1")?.isComplete).isFalse()
+        expectThat(cardBrandEnricher.evaluateCard("${sixteenDigitsDiscoverCardNumber}12")?.isComplete).isFalse()
+        expectThat(cardBrandEnricher.evaluateCard("${sixteenDigitsDiscoverCardNumber}123")?.isComplete).isTrue()
     }
 
     @Test
     fun `should handle null or empty card number`() {
         val nullCard = cardBrandEnricher.evaluateCard(null)
-
-        expectThat(nullCard.cardDetails).isNull()
-        expectThat(nullCard.complete).isFalse()
+        expectThat(nullCard).isNull()
 
         val emptyCard = cardBrandEnricher.evaluateCard("")
-
-        expectThat(emptyCard.cardDetails).isNull()
-        expectThat(emptyCard.complete).isFalse()
+        expectThat(emptyCard).isNull()
     }
 }

lib/src/test/java/com/basistheory/android/view/CardVerificationCodeElementTests.kt

@@ -2,7 +2,13 @@ package com.basistheory.android.view
 
 import android.app.Activity
 import com.basistheory.android.event.ChangeEvent
+import io.mockk.impl.annotations.RelaxedMockK
+import io.mockk.impl.annotations.SpyK
+import io.mockk.junit4.MockKRule
+import io.mockk.spyk
+import io.mockk.verify
 import org.junit.Before
+import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.Robolectric
@@ -17,10 +23,13 @@ import strikt.assertions.single
 class CardVerificationCodeElementTests {
     private lateinit var cvcElement: CardVerificationCodeElement
 
+    private lateinit var cardNumberElement: CardNumberElement
+
     @Before
     fun setUp() {
         val activity = Robolectric.buildActivity(Activity::class.java).get()
         cvcElement = CardVerificationCodeElement(activity)
+        cardNumberElement = CardNumberElement(activity)
     }
 
     @Test
@@ -33,11 +42,26 @@ class CardVerificationCodeElementTests {
     }
 
     @Test
-    fun `applies mask when setting the value`() {
+    fun `applies default mask when setting the value and no card number element is attached`() {
+        cvcElement.cardNumberElement = null
+
         cvcElement.setText("1a2b3c")
         expectThat(cvcElement.getText()).isEqualTo("123")
     }
 
+    @Test
+    fun `updates mask depending on card brand`() {
+        cvcElement.cardNumberElement = cardNumberElement
+
+        cardNumberElement.setText("42")
+        cvcElement.setText("1a2b3c4d5e")
+        expectThat(cvcElement.getText()).isEqualTo("123")
+
+        cardNumberElement.setText("34")
+        cvcElement.setText("1a2b3c4d5e")
+        expectThat(cvcElement.getText()).isEqualTo("1234")
+    }
+
     @Test
     fun `ChangeEvent is computed properly for incomplete cvc values`() {
         val changeEvents = mutableListOf<ChangeEvent>()
@@ -63,4 +87,13 @@ class CardVerificationCodeElementTests {
             get { isComplete }.isTrue()
         }
     }
+
+    @Test
+    fun `setting card number element multiple times does not duplicate listeners`() {
+        val cardNumberElement = spyk(CardNumberElement(Robolectric.buildActivity(Activity::class.java).get()))
+        cvcElement.cardNumberElement = cardNumberElement
+        cvcElement.cardNumberElement = cardNumberElement
+
+        verify(exactly = 1) { cardNumberElement.addChangeEventListener(any()) }
+    }
 }