Replace retry with exponential backoff with arrow schedule

Also clean up the code related to play purchase verification

15 files changed, 72 insertions, 98 deletions

diff --git a/android/app/build.gradle.kts b/android/app/build.gradle.kts
index 798667ff3f..8e523ecb39 100644
--- a/android/app/build.gradle.kts
+++ b/android/app/build.gradle.kts
@@ -329,6 +329,7 @@ dependencies {
     implementation(Dependencies.AndroidX.lifecycleViewmodelKtx)
     implementation(Dependencies.AndroidX.lifecycleRuntimeCompose)
     implementation(Dependencies.Arrow.core)
+    implementation(Dependencies.Arrow.resilience)
     implementation(Dependencies.Compose.constrainLayout)
     implementation(Dependencies.Compose.foundation)
     implementation(Dependencies.Compose.material3)
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/constant/PaymentConstant.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/constant/PaymentConstant.kt
index 1cf1c32b2c..ba2413d4fc 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/constant/PaymentConstant.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/constant/PaymentConstant.kt
@@ -1,5 +1,7 @@
 package net.mullvad.mullvadvpn.constant
 
+import kotlin.time.Duration.Companion.seconds
+
 const val VERIFICATION_MAX_ATTEMPTS = 4
-const val VERIFICATION_INITIAL_BACK_OFF_MILLISECONDS = 3000L
-const val VERIFICATION_BACK_OFF_FACTOR = 3L
+val VERIFICATION_INITIAL_BACK_OFF_DURATION = 3.seconds
+const val VERIFICATION_BACK_OFF_FACTOR = 3.toDouble()
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/usecase/PaymentUseCase.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/usecase/PaymentUseCase.kt
index fbd662f95e..23f6c797b0 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/usecase/PaymentUseCase.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/usecase/PaymentUseCase.kt
@@ -1,20 +1,24 @@
 package net.mullvad.mullvadvpn.usecase
 
 import android.app.Activity
+import arrow.core.Either
+import arrow.core.right
+import arrow.resilience.Schedule
+import arrow.resilience.retryEither
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.transform
 import net.mullvad.mullvadvpn.constant.VERIFICATION_BACK_OFF_FACTOR
-import net.mullvad.mullvadvpn.constant.VERIFICATION_INITIAL_BACK_OFF_MILLISECONDS
+import net.mullvad.mullvadvpn.constant.VERIFICATION_INITIAL_BACK_OFF_DURATION
 import net.mullvad.mullvadvpn.constant.VERIFICATION_MAX_ATTEMPTS
 import net.mullvad.mullvadvpn.lib.payment.PaymentRepository
 import net.mullvad.mullvadvpn.lib.payment.model.PaymentAvailability
 import net.mullvad.mullvadvpn.lib.payment.model.ProductId
 import net.mullvad.mullvadvpn.lib.payment.model.PurchaseResult
+import net.mullvad.mullvadvpn.lib.payment.model.VerificationError
 import net.mullvad.mullvadvpn.lib.payment.model.VerificationResult
-import net.mullvad.mullvadvpn.util.retryWithExponentialBackOff
 
 interface PaymentUseCase {
     val paymentAvailability: Flow<PaymentAvailability?>
@@ -26,7 +30,7 @@ interface PaymentUseCase {
 
     suspend fun resetPurchaseResult()
 
-    suspend fun verifyPurchases(onSuccessfulVerification: () -> Unit = {})
+    suspend fun verifyPurchases(): Either<VerificationError, VerificationResult>
 }
 
 class PlayPaymentUseCase(private val paymentRepository: PaymentRepository) : PaymentUseCase {
@@ -60,24 +64,19 @@ class PlayPaymentUseCase(private val paymentRepository: PaymentRepository) : Pay
     }
 
     @Suppress("ensure every public functions method is named 'invoke' with operator modifier")
-    override suspend fun verifyPurchases(onSuccessfulVerification: () -> Unit) {
-        paymentRepository
-            .verifyPurchases()
-            .retryWithExponentialBackOff(
-                maxAttempts = VERIFICATION_MAX_ATTEMPTS,
-                initialBackOffDelay = VERIFICATION_INITIAL_BACK_OFF_MILLISECONDS,
-                backOffDelayFactor = VERIFICATION_BACK_OFF_FACTOR
-            ) {
-                it is VerificationResult.Error
-            }
-            .collect {
+    override suspend fun verifyPurchases() =
+        Schedule.exponential<VerificationError>(
+                VERIFICATION_INITIAL_BACK_OFF_DURATION,
+                VERIFICATION_BACK_OFF_FACTOR
+            )
+            .and(Schedule.recurs(VERIFICATION_MAX_ATTEMPTS.toLong()))
+            .retryEither { paymentRepository.verifyPurchases() }
+            .onRight {
                 if (it == VerificationResult.Success) {
                     // Update the payment availability after a successful verification.
                     queryPaymentAvailability()
-                    onSuccessfulVerification()
                 }
             }
-    }
 
     private fun PurchaseResult?.shouldDelayLoading() =
         this is PurchaseResult.FetchingProducts || this is PurchaseResult.VerificationStarted
@@ -107,7 +106,5 @@ class EmptyPaymentUseCase : PaymentUseCase {
     }
 
     @Suppress("ensure every public functions method is named 'invoke' with operator modifier")
-    override suspend fun verifyPurchases(onSuccessfulVerification: () -> Unit) {
-        // No op
-    }
+    override suspend fun verifyPurchases() = VerificationResult.NothingToVerify.right()
 }
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/FlowUtils.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/FlowUtils.kt
index fbe44a5fea..13561aa7f8 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/FlowUtils.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/FlowUtils.kt
@@ -3,11 +3,7 @@
 package net.mullvad.mullvadvpn.util
 
 import kotlinx.coroutines.Deferred
-import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.catch
-import kotlinx.coroutines.flow.map
-import kotlinx.coroutines.flow.retryWhen
 
 inline fun <T1, T2, T3, T4, T5, T6, R> combine(
     flow: Flow<T1>,
@@ -90,34 +86,3 @@ fun <T> Deferred<T>.getOrDefault(default: T) =
     } catch (e: IllegalStateException) {
         default
     }
-
-@Suppress("UNCHECKED_CAST")
-suspend inline fun <T> Flow<T>.retryWithExponentialBackOff(
-    maxAttempts: Int,
-    initialBackOffDelay: Long,
-    backOffDelayFactor: Long,
-    crossinline predicate: (T) -> Boolean,
-): Flow<T> =
-    map {
-            if (predicate(it)) {
-                throw ExceptionWrapper(it as Any)
-            }
-            it
-        }
-        .retryWhen { _, attempt ->
-            if (attempt >= maxAttempts) {
-                return@retryWhen false
-            }
-            val backOffDelay = initialBackOffDelay * backOffDelayFactor.pow(attempt.toInt())
-            delay(backOffDelay)
-            true
-        }
-        .catch {
-            if (it is ExceptionWrapper) {
-                this.emit(it.item as T)
-            } else {
-                throw it
-            }
-        }
-
-class ExceptionWrapper(val item: Any) : Throwable()
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/VerificationResultExtensions.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/VerificationResultExtensions.kt
new file mode 100644
index 0000000000..d4484d50e6
--- /dev/null
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/util/VerificationResultExtensions.kt
@@ -0,0 +1,8 @@
+package net.mullvad.mullvadvpn.util
+
+import arrow.core.Either
+import net.mullvad.mullvadvpn.lib.payment.model.VerificationError
+import net.mullvad.mullvadvpn.lib.payment.model.VerificationResult
+
+fun Either<VerificationError, VerificationResult>.isSuccess() =
+    getOrNull() == VerificationResult.Success
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/AccountViewModel.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/AccountViewModel.kt
index a42003d6e2..7c2635b63a 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/AccountViewModel.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/AccountViewModel.kt
@@ -24,6 +24,7 @@ import net.mullvad.mullvadvpn.lib.payment.model.ProductId
 import net.mullvad.mullvadvpn.lib.shared.AccountRepository
 import net.mullvad.mullvadvpn.lib.shared.DeviceRepository
 import net.mullvad.mullvadvpn.usecase.PaymentUseCase
+import net.mullvad.mullvadvpn.util.isSuccess
 import net.mullvad.mullvadvpn.util.toPaymentState
 import org.joda.time.DateTime
 
@@ -90,8 +91,9 @@ class AccountViewModel(
 
     private fun verifyPurchases() {
         viewModelScope.launch {
-            paymentUseCase.verifyPurchases()
-            updateAccountExpiry()
+            if (paymentUseCase.verifyPurchases().isSuccess()) {
+                updateAccountExpiry()
+            }
         }
     }
 
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/ConnectViewModel.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/ConnectViewModel.kt
index b41a175dad..037c3243ab 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/ConnectViewModel.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/ConnectViewModel.kt
@@ -32,6 +32,7 @@ import net.mullvad.mullvadvpn.usecase.PaymentUseCase
 import net.mullvad.mullvadvpn.usecase.SelectedLocationTitleUseCase
 import net.mullvad.mullvadvpn.util.combine
 import net.mullvad.mullvadvpn.util.daysFromNow
+import net.mullvad.mullvadvpn.util.isSuccess
 import net.mullvad.mullvadvpn.util.toInAddress
 import net.mullvad.mullvadvpn.util.toOutAddress
 
@@ -114,8 +115,8 @@ class ConnectViewModel(
 
     init {
         viewModelScope.launch {
-            paymentUseCase.verifyPurchases {
-                viewModelScope.launch { accountRepository.getAccountData() }
+            if (paymentUseCase.verifyPurchases().isSuccess()) {
+                accountRepository.getAccountData()
             }
         }
         viewModelScope.launch { deviceRepository.updateDevice() }
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/OutOfTimeViewModel.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/OutOfTimeViewModel.kt
index 7784181466..d279792853 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/OutOfTimeViewModel.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/OutOfTimeViewModel.kt
@@ -20,6 +20,7 @@ import net.mullvad.mullvadvpn.lib.shared.ConnectionProxy
 import net.mullvad.mullvadvpn.lib.shared.DeviceRepository
 import net.mullvad.mullvadvpn.usecase.OutOfTimeUseCase
 import net.mullvad.mullvadvpn.usecase.PaymentUseCase
+import net.mullvad.mullvadvpn.util.isSuccess
 import net.mullvad.mullvadvpn.util.toPaymentState
 
 class OutOfTimeViewModel(
@@ -76,8 +77,9 @@ class OutOfTimeViewModel(
 
     private fun verifyPurchases() {
         viewModelScope.launch {
-            paymentUseCase.verifyPurchases()
-            updateAccountExpiry()
+            if (paymentUseCase.verifyPurchases().isSuccess()) {
+                updateAccountExpiry()
+            }
         }
     }
 
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/WelcomeViewModel.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/WelcomeViewModel.kt
index 4b61468f8e..9322ef9ce4 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/WelcomeViewModel.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/WelcomeViewModel.kt
@@ -21,6 +21,7 @@ import net.mullvad.mullvadvpn.lib.shared.AccountRepository
 import net.mullvad.mullvadvpn.lib.shared.ConnectionProxy
 import net.mullvad.mullvadvpn.lib.shared.DeviceRepository
 import net.mullvad.mullvadvpn.usecase.PaymentUseCase
+import net.mullvad.mullvadvpn.util.isSuccess
 import net.mullvad.mullvadvpn.util.toPaymentState
 
 class WelcomeViewModel(
@@ -79,8 +80,9 @@ class WelcomeViewModel(
 
     private fun verifyPurchases() {
         viewModelScope.launch {
-            paymentUseCase.verifyPurchases()
-            updateAccountExpiry()
+            if (paymentUseCase.verifyPurchases().isSuccess()) {
+                updateAccountExpiry()
+            }
         }
     }
 
diff --git a/android/buildSrc/src/main/kotlin/Dependencies.kt b/android/buildSrc/src/main/kotlin/Dependencies.kt
index a31859e5e5..26b1a03753 100644
--- a/android/buildSrc/src/main/kotlin/Dependencies.kt
+++ b/android/buildSrc/src/main/kotlin/Dependencies.kt
@@ -46,6 +46,7 @@ object Dependencies {
         const val core = "io.arrow-kt:arrow-core:${Versions.Arrow.base}"
         const val optics = "io.arrow-kt:arrow-optics:${Versions.Arrow.base}"
         const val opticsKsp = "io.arrow-kt:arrow-optics-ksp-plugin:${Versions.Arrow.base}"
+        const val resilience = "io.arrow-kt:arrow-resilience:${Versions.Arrow.base}"
     }
 
     object Compose {
diff --git a/android/lib/billing/src/main/kotlin/net/mullvad/mullvadvpn/lib/billing/BillingPaymentRepository.kt b/android/lib/billing/src/main/kotlin/net/mullvad/mullvadvpn/lib/billing/BillingPaymentRepository.kt
index 8b3ad66171..b526a10032 100644
--- a/android/lib/billing/src/main/kotlin/net/mullvad/mullvadvpn/lib/billing/BillingPaymentRepository.kt
+++ b/android/lib/billing/src/main/kotlin/net/mullvad/mullvadvpn/lib/billing/BillingPaymentRepository.kt
@@ -1,6 +1,9 @@
 package net.mullvad.mullvadvpn.lib.billing
 
 import android.app.Activity
+import arrow.core.Either
+import arrow.core.raise.either
+import arrow.core.raise.ensure
 import com.android.billingclient.api.BillingClient.BillingResponseCode
 import com.android.billingclient.api.Purchase
 import kotlinx.coroutines.flow.Flow
@@ -22,6 +25,7 @@ import net.mullvad.mullvadvpn.lib.payment.ProductIds
 import net.mullvad.mullvadvpn.lib.payment.model.PaymentAvailability
 import net.mullvad.mullvadvpn.lib.payment.model.ProductId
 import net.mullvad.mullvadvpn.lib.payment.model.PurchaseResult
+import net.mullvad.mullvadvpn.lib.payment.model.VerificationError
 import net.mullvad.mullvadvpn.lib.payment.model.VerificationResult
 
 class BillingPaymentRepository(
@@ -129,28 +133,19 @@ class BillingPaymentRepository(
         }
     }
 
-    override fun verifyPurchases(): Flow<VerificationResult> = flow {
-        emit(VerificationResult.FetchingUnfinishedPurchases)
+    override suspend fun verifyPurchases(): Either<VerificationError, VerificationResult> = either {
         val purchasesResult = billingRepository.queryPurchases()
-        when (purchasesResult.responseCode()) {
-            BillingResponseCode.OK -> {
-                val purchases = purchasesResult.nonPendingPurchases()
-                if (purchases.isNotEmpty()) {
-                    emit(VerificationResult.VerificationStarted)
-                    emit(
-                        verifyPurchase(purchases.first())
-                            .fold(
-                                { VerificationResult.Error.VerificationError(null) },
-                                { VerificationResult.Success }
-                            )
-                    )
-                } else {
-                    emit(VerificationResult.NothingToVerify)
-                }
-            }
-            else ->
-                emit(VerificationResult.Error.BillingError(purchasesResult.toBillingException()))
+        ensure(purchasesResult.responseCode() == BillingResponseCode.OK) {
+            VerificationError.BillingError(purchasesResult.toBillingException())
+        }
+        val purchases = purchasesResult.nonPendingPurchases()
+        if (purchases.isEmpty()) {
+            return@either VerificationResult.NothingToVerify
         }
+        verifyPurchase(purchases.first())
+            .mapLeft { VerificationError.PlayVerificationError }
+            .map { VerificationResult.Success }
+            .bind()
     }
 
     private suspend fun initialisePurchase() = playPurchaseRepository.initializePlayPurchase()
diff --git a/android/lib/payment/build.gradle.kts b/android/lib/payment/build.gradle.kts
index 23f945b4f9..892ce21c75 100644
--- a/android/lib/payment/build.gradle.kts
+++ b/android/lib/payment/build.gradle.kts
@@ -39,6 +39,7 @@ android {
 }
 
 dependencies {
+    implementation(Dependencies.Arrow.core)
     implementation(Dependencies.Kotlin.stdlib)
     implementation(Dependencies.KotlinX.coroutinesAndroid)
 }
diff --git a/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/PaymentRepository.kt b/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/PaymentRepository.kt
index 73fd0c061d..0f076eab74 100644
--- a/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/PaymentRepository.kt
+++ b/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/PaymentRepository.kt
@@ -1,10 +1,12 @@
 package net.mullvad.mullvadvpn.lib.payment
 
 import android.app.Activity
+import arrow.core.Either
 import kotlinx.coroutines.flow.Flow
 import net.mullvad.mullvadvpn.lib.payment.model.PaymentAvailability
 import net.mullvad.mullvadvpn.lib.payment.model.ProductId
 import net.mullvad.mullvadvpn.lib.payment.model.PurchaseResult
+import net.mullvad.mullvadvpn.lib.payment.model.VerificationError
 import net.mullvad.mullvadvpn.lib.payment.model.VerificationResult
 
 interface PaymentRepository {
@@ -14,7 +16,7 @@ interface PaymentRepository {
         activityProvider: () -> Activity
     ): Flow<PurchaseResult>
 
-    fun verifyPurchases(): Flow<VerificationResult>
+    suspend fun verifyPurchases(): Either<VerificationError, VerificationResult>
 
     fun queryPaymentAvailability(): Flow<PaymentAvailability>
 }
diff --git a/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationError.kt b/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationError.kt
new file mode 100644
index 0000000000..51cf8d1d28
--- /dev/null
+++ b/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationError.kt
@@ -0,0 +1,7 @@
+package net.mullvad.mullvadvpn.lib.payment.model
+
+sealed interface VerificationError {
+    data class BillingError(val exception: Throwable) : VerificationError
+
+    data object PlayVerificationError : VerificationError
+}
diff --git a/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationResult.kt b/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationResult.kt
index 725ea0af68..8cf971194d 100644
--- a/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationResult.kt
+++ b/android/lib/payment/src/main/kotlin/net/mullvad/mullvadvpn/lib/payment/model/VerificationResult.kt
@@ -1,19 +1,7 @@
 package net.mullvad.mullvadvpn.lib.payment.model
 
-sealed interface VerificationResult {
-    data object FetchingUnfinishedPurchases : VerificationResult
-
-    data object VerificationStarted : VerificationResult
-
-    // No verification was needed as there is no purchases to verify
+interface VerificationResult {
     data object NothingToVerify : VerificationResult
 
     data object Success : VerificationResult
-
-    // Generic error, add more cases as needed
-    sealed interface Error : VerificationResult {
-        data class BillingError(val exception: Throwable?) : Error
-
-        data class VerificationError(val exception: Throwable?) : Error
-    }
 }