Integrate RevenueCat billing SDK with KMP architecture

androidApp/src/main/kotlin/com/rickyhu/hushtimer/HushTimerApplication.kt

@@ -1,6 +1,7 @@
 package com.rickyhu.hushtimer
 
 import android.app.Application
+import com.rickyhu.hushtimer.billing.data.initializeBilling
 import com.rickyhu.hushtimer.di.initKoin
 import org.koin.android.ext.koin.androidContext
 
@@ -10,5 +11,6 @@ class HushTimerApplication : Application() {
         initKoin {
             androidContext(this@HushTimerApplication)
         }
+        initializeBilling()
     }
 }

composeApp/build.gradle.kts

@@ -94,6 +94,8 @@ kotlin {
             implementation(libs.multiplatform.settings)
             implementation(libs.multiplatform.settings.coroutines)
             implementation(libs.multiplatform.settings.observable)
+            implementation(libs.purchases.kmp.core)
+            implementation(libs.purchases.kmp.result)
             implementation(libs.room.runtime)
             implementation(libs.semantic.versioning)
             implementation(libs.sqlite.bundled)
@@ -182,6 +184,8 @@ buildkonfig {
     // Uses CONFIGCAT_KEY_TEST by default, which must be available
     defaultConfigs {
         buildConfigField(STRING, "CONFIGCAT_SDK_KEY", getSecret("CONFIGCAT_KEY_TEST"))
+        buildConfigField(STRING, "REVENUECAT_APPLE_API_KEY", getSecret("REVENUECAT_APPLE_API_KEY", ""))
+        buildConfigField(STRING, "REVENUECAT_GOOGLE_API_KEY", getSecret("REVENUECAT_GOOGLE_API_KEY", ""))
     }
 
     // B. ANDROID VARIANTS (Auto-detected by the plugin)

composeApp/src/androidMain/kotlin/com/rickyhu/hushtimer/billing/data/BillingInitializer.android.kt

@@ -0,0 +1,8 @@
+package com.rickyhu.hushtimer.billing.data
+
+import com.revenuecat.purchases.kmp.Purchases
+import com.rickyhu.hushtimer.BuildKonfig
+
+internal actual fun initializeBilling() {
+    Purchases.configure(apiKey = BuildKonfig.REVENUECAT_GOOGLE_API_KEY)
+}

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/billing/data/BillingInitializer.kt

@@ -0,0 +1,3 @@
+package com.rickyhu.hushtimer.billing.data
+
+internal expect fun initializeBilling()

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/billing/data/RevenueCatBillingService.kt

@@ -0,0 +1,67 @@
+package com.rickyhu.hushtimer.billing.data
+
+import com.revenuecat.purchases.kmp.Purchases
+import com.rickyhu.hushtimer.billing.domain.BillingService
+import com.rickyhu.hushtimer.billing.domain.BillingState
+import com.rickyhu.hushtimer.billing.domain.EntitlementInfo
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
+
+internal class RevenueCatBillingService : BillingService {
+    private val _billingState = MutableStateFlow<BillingState>(BillingState.Loading)
+
+    override fun observeBillingState(): Flow<BillingState> = _billingState.asStateFlow()
+
+    override suspend fun refreshCustomerInfo() {
+        try {
+            val purchases = Purchases.sharedInstance
+            val customerInfo = purchases.awaitCustomerInfo()
+
+            val activeEntitlements =
+                customerInfo.entitlements.active.map { (id, entitlement) ->
+                    EntitlementInfo(
+                        id = id,
+                        isActive = entitlement.isActive,
+                        expiresAtEpochMillis = entitlement.expirationDate?.toEpochMilliseconds(),
+                    )
+                }
+
+            val isPro = customerInfo.entitlements.active.containsKey(PRO_ENTITLEMENT_ID)
+
+            _billingState.value = BillingState.Ready(isPro = isPro, activeEntitlements = activeEntitlements)
+        } catch (e: Exception) {
+            _billingState.value = BillingState.Error(e.message ?: "Failed to refresh customer info")
+        }
+    }
+
+    override suspend fun purchase(packageId: String): Result<Unit> =
+        try {
+            val purchases = Purchases.sharedInstance
+            val offerings = purchases.awaitOfferings()
+            val currentOffering = offerings.current ?: return Result.failure(Exception("No current offering"))
+            val packageToPurchase =
+                currentOffering.availablePackages.find { it.identifier == packageId }
+                    ?: return Result.failure(Exception("Package not found: $packageId"))
+
+            purchases.awaitPurchase(packageToPurchase)
+            refreshCustomerInfo()
+            Result.success(Unit)
+        } catch (e: Exception) {
+            Result.failure(e)
+        }
+
+    override suspend fun restorePurchases(): Result<Unit> =
+        try {
+            val purchases = Purchases.sharedInstance
+            purchases.awaitRestorePurchases()
+            refreshCustomerInfo()
+            Result.success(Unit)
+        } catch (e: Exception) {
+            Result.failure(e)
+        }
+
+    companion object {
+        private const val PRO_ENTITLEMENT_ID = "pro"
+    }
+}

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/billing/domain/BillingService.kt

@@ -0,0 +1,13 @@
+package com.rickyhu.hushtimer.billing.domain
+
+import kotlinx.coroutines.flow.Flow
+
+interface BillingService {
+    fun observeBillingState(): Flow<BillingState>
+
+    suspend fun refreshCustomerInfo()
+
+    suspend fun purchase(packageId: String): Result<Unit>
+
+    suspend fun restorePurchases(): Result<Unit>
+}

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/billing/domain/BillingState.kt

@@ -0,0 +1,14 @@
+package com.rickyhu.hushtimer.billing.domain
+
+sealed interface BillingState {
+    data object Loading : BillingState
+
+    data class Ready(
+        val isPro: Boolean,
+        val activeEntitlements: List<EntitlementInfo>,
+    ) : BillingState
+
+    data object Unavailable : BillingState
+
+    data class Error(val message: String) : BillingState
+}

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/billing/domain/EntitlementInfo.kt

@@ -0,0 +1,7 @@
+package com.rickyhu.hushtimer.billing.domain
+
+data class EntitlementInfo(
+    val id: String,
+    val isActive: Boolean,
+    val expiresAtEpochMillis: Long?,
+)

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/billing/presentation/BillingViewModel.kt

@@ -0,0 +1,37 @@
+package com.rickyhu.hushtimer.billing.presentation
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.rickyhu.hushtimer.billing.domain.BillingService
+import com.rickyhu.hushtimer.billing.domain.BillingState
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
+
+class BillingViewModel(
+    private val billingService: BillingService,
+) : ViewModel() {
+    val billingState: StateFlow<BillingState> =
+        billingService
+            .observeBillingState()
+            .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), BillingState.Loading)
+
+    init {
+        viewModelScope.launch {
+            billingService.refreshCustomerInfo()
+        }
+    }
+
+    fun purchase(packageId: String) {
+        viewModelScope.launch {
+            billingService.purchase(packageId)
+        }
+    }
+
+    fun restorePurchases() {
+        viewModelScope.launch {
+            billingService.restorePurchases()
+        }
+    }
+}

composeApp/src/commonMain/kotlin/com/rickyhu/hushtimer/di/Modules.kt

@@ -4,6 +4,9 @@ import androidx.sqlite.driver.bundled.BundledSQLiteDriver
 import com.configcat.ConfigCatClient
 import com.configcat.log.LogLevel
 import com.rickyhu.hushtimer.BuildKonfig
+import com.rickyhu.hushtimer.billing.data.RevenueCatBillingService
+import com.rickyhu.hushtimer.billing.domain.BillingService
+import com.rickyhu.hushtimer.billing.presentation.BillingViewModel
 import com.rickyhu.hushtimer.config.data.ConfigRepositoryImpl
 import com.rickyhu.hushtimer.config.domain.ConfigRepository
 import com.rickyhu.hushtimer.core.data.DatabaseFactory
@@ -55,6 +58,9 @@ val sharedModule =
         singleOf(::SettingsRepositoryImpl).bind<SettingsRepository>()
         singleOf(::ConfigRepositoryImpl).bind<ConfigRepository>()
 
+        // Billing
+        singleOf(::RevenueCatBillingService).bind<BillingService>()
+
         // Timer engine
         single { TimerEngine(CoroutineScope(SupervisorJob() + Dispatchers.Default)) }
 
@@ -63,4 +69,5 @@ val sharedModule =
         viewModelOf(::SessionViewModel)
         viewModelOf(::SettingsViewModel)
         viewModelOf(::VersionCheckViewModel)
+        viewModelOf(::BillingViewModel)
     }

composeApp/src/iosMain/kotlin/com/rickyhu/hushtimer/billing/data/BillingInitializer.ios.kt

@@ -0,0 +1,8 @@
+package com.rickyhu.hushtimer.billing.data
+
+import com.revenuecat.purchases.kmp.Purchases
+import com.rickyhu.hushtimer.BuildKonfig
+
+internal actual fun initializeBilling() {
+    Purchases.configure(apiKey = BuildKonfig.REVENUECAT_APPLE_API_KEY)
+}

composeApp/src/iosMain/kotlin/main.kt

@@ -2,6 +2,7 @@
 
 import androidx.compose.ui.window.ComposeUIViewController
 import com.rickyhu.hushtimer.App
+import com.rickyhu.hushtimer.billing.data.initializeBilling
 import com.rickyhu.hushtimer.di.initKoin
 import platform.UIKit.UIViewController
 
@@ -10,5 +11,6 @@ fun MainViewController(): UIViewController =
     ComposeUIViewController(
         configure = {
             initKoin()
+            initializeBilling()
         },
     ) { App() }

composeApp/src/jvmMain/kotlin/com/rickyhu/hushtimer/billing/data/BillingInitializer.jvm.kt

@@ -0,0 +1,5 @@
+package com.rickyhu.hushtimer.billing.data
+
+internal actual fun initializeBilling() {
+    // No-op: RevenueCat doesn't support Desktop
+}

composeApp/src/jvmMain/kotlin/com/rickyhu/hushtimer/billing/data/NoOpBillingService.kt

@@ -0,0 +1,20 @@
+package com.rickyhu.hushtimer.billing.data
+
+import com.rickyhu.hushtimer.billing.domain.BillingService
+import com.rickyhu.hushtimer.billing.domain.BillingState
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+
+internal class NoOpBillingService : BillingService {
+    override fun observeBillingState(): Flow<BillingState> = flowOf(BillingState.Unavailable)
+
+    override suspend fun refreshCustomerInfo() {
+        // No-op
+    }
+
+    override suspend fun purchase(packageId: String): Result<Unit> =
+        Result.failure(UnsupportedOperationException("Billing not available on Desktop"))
+
+    override suspend fun restorePurchases(): Result<Unit> =
+        Result.failure(UnsupportedOperationException("Billing not available on Desktop"))
+}

composeApp/src/jvmMain/kotlin/com/rickyhu/hushtimer/di/Modules.jvm.kt

@@ -1,5 +1,7 @@
 package com.rickyhu.hushtimer.di
 
+import com.rickyhu.hushtimer.billing.data.NoOpBillingService
+import com.rickyhu.hushtimer.billing.domain.BillingService
 import com.rickyhu.hushtimer.core.data.DatabaseFactory
 import com.rickyhu.hushtimer.core.domain.AppVersion
 import com.rickyhu.hushtimer.core.domain.AppVersionImpl
@@ -34,4 +36,7 @@ actual val platformModule: Module
 
             // Scramble repository - JVM implementation
             single<ScrambleRepository> { ScrambleRepositoryImpl() }
+
+            // Billing - Desktop no-op
+            single<BillingService> { NoOpBillingService() }
         }

gradle/libs.versions.toml

@@ -26,6 +26,7 @@ ksp = "2.3.4"
 material-kolor = "4.1.1"
 multiplatform-settings = "1.3.0"
 navigation-compose = "2.9.2"
+purchases-kmp = "2.4.0+17.30.0"
 room = "2.8.4"
 semver = "3.0.0"
 sqlite = "2.6.2"
@@ -66,6 +67,8 @@ multiplatform-settings = { module = "com.russhwolf:multiplatform-settings", vers
 multiplatform-settings-coroutines = { module = "com.russhwolf:multiplatform-settings-coroutines", version.ref = "multiplatform-settings" }
 multiplatform-settings-observable = { module = "com.russhwolf:multiplatform-settings-make-observable", version.ref = "multiplatform-settings" }
 jetbrains-compose-navigation = { group = "org.jetbrains.androidx.navigation", name = "navigation-compose", version.ref= "navigation-compose"}
+purchases-kmp-core = { module = "com.revenuecat.purchases:purchases-kmp-core", version.ref = "purchases-kmp" }
+purchases-kmp-result = { module = "com.revenuecat.purchases:purchases-kmp-result", version.ref = "purchases-kmp" }
 koin-android = { module = "io.insert-koin:koin-android", version.ref = "koin" }
 koin-androidx-compose = { module = "io.insert-koin:koin-androidx-compose", version.ref = "koin" }
 koin-core = { module = "io.insert-koin:koin-core", version.ref = "koin" }