Add hasSufficientBillingDetailsForAutomaticTax validator (MOBILESDK-4697)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Committed-By-Agent: claude

Author: cttsai-stripe

paymentsheet/src/main/java/com/stripe/android/common/validation/BillingDetailsValidation.kt

@@ -0,0 +1,30 @@
+package com.stripe.android.common.validation
+
+import com.stripe.android.model.PaymentMethod
+import com.stripe.android.ui.core.elements.automaticTaxRequiredFields
+import com.stripe.android.uicore.elements.IdentifierSpec
+
+/**
+ * Does this saved payment method's billing address have what Stripe Tax needs to compute
+ * automatic tax for its country? See automaticTaxRequiredFields for the per-country field set.
+ */
+internal fun PaymentMethod.hasSufficientBillingDetailsForAutomaticTax(): Boolean {
+    val address = billingDetails?.address ?: return false
+    // Saved-PM billing details come from the API and are not guaranteed uppercase, unlike the
+    // CountryConfig-sourced value the CardBillingAddressElement form passes. Uppercase before the
+    // map lookup; do not "simplify" this away.
+    val country = address.country?.uppercase()
+    if (country.isNullOrBlank()) return false
+
+    return automaticTaxRequiredFields(country).all { field ->
+        when (field) {
+            IdentifierSpec.Line1 -> !address.line1.isNullOrBlank()
+            IdentifierSpec.City -> !address.city.isNullOrBlank()
+            IdentifierSpec.State -> !address.state.isNullOrBlank()
+            IdentifierSpec.PostalCode -> !address.postalCode.isNullOrBlank()
+            // additionalAutomaticTaxFieldsByCountry only emits the four specs above today. If that
+            // map ever adds another (e.g. Line2), add its case here — else it silently over-filters.
+            else -> false
+        }
+    }
+}

paymentsheet/src/test/java/com/stripe/android/common/validation/BillingDetailsValidationTest.kt

@@ -0,0 +1,72 @@
+package com.stripe.android.common.validation
+
+import com.google.common.truth.Truth.assertThat
+import com.stripe.android.model.Address
+import com.stripe.android.model.PaymentMethod
+import com.stripe.android.testing.PaymentMethodFactory
+import kotlin.test.Test
+
+class BillingDetailsValidationTest {
+
+    private fun card(
+        line1: String? = "123 Main St",
+        city: String? = "San Francisco",
+        state: String? = "CA",
+        postalCode: String? = "94111",
+        country: String? = "US",
+        hasAddress: Boolean = true,
+    ): PaymentMethod = PaymentMethodFactory.card(id = "pm_test").copy(
+        billingDetails = PaymentMethod.BillingDetails(
+            address = if (hasAddress) {
+                Address(
+                    line1 = line1,
+                    city = city,
+                    state = state,
+                    postalCode = postalCode,
+                    country = country,
+                )
+            } else {
+                null
+            },
+        ),
+    )
+
+    @Test
+    fun `null address is insufficient`() {
+        assertThat(card(hasAddress = false).hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+    }
+
+    @Test
+    fun `missing country is insufficient`() {
+        assertThat(card(country = null).hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+    }
+
+    @Test
+    fun `country with no additional tax requirement needs only the country`() {
+        val pm = card(country = "FR", line1 = null, city = null, state = null, postalCode = null)
+        assertThat(pm.hasSufficientBillingDetailsForAutomaticTax()).isTrue()
+    }
+
+    @Test
+    fun `CA GB IN require postal code only`() {
+        assertThat(card(country = "CA", postalCode = null).hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+        assertThat(card(country = "CA", postalCode = "K1A0B1").hasSufficientBillingDetailsForAutomaticTax()).isTrue()
+        assertThat(card(country = "GB", postalCode = null).hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+        assertThat(card(country = "IN", postalCode = null).hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+    }
+
+    @Test
+    fun `PR requires line1, city, and postal code but not state`() {
+        val missingCity = card(country = "PR", city = null)
+        assertThat(missingCity.hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+
+        val completeWithoutState = card(country = "PR", state = null)
+        assertThat(completeWithoutState.hasSufficientBillingDetailsForAutomaticTax()).isTrue()
+    }
+
+    @Test
+    fun `US requires line1, city, state, and postal code`() {
+        assertThat(card(country = "US", state = null).hasSufficientBillingDetailsForAutomaticTax()).isFalse()
+        assertThat(card(country = "US").hasSufficientBillingDetailsForAutomaticTax()).isTrue()
+    }
+}