LinkActivity, ViewModel and Navigator

link/src/main/AndroidManifest.xml

@@ -2,6 +2,13 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
 
     <application>
+        <activity
+            android:name="com.stripe.android.link.LinkActivity"
+            android:autoRemoveFromRecents="true"
+            android:configChanges="orientation|keyboard|keyboardHidden|screenLayout|screenSize|smallestScreenSize"
+            android:launchMode="singleTop"
+            android:theme="@style/StripeTransparentTheme" />
+
         <activity
             android:name="com.stripe.android.link.LinkForegroundActivity"
             android:autoRemoveFromRecents="true"

link/src/main/java/com/stripe/android/link/LinkActivity.kt

@@ -0,0 +1,71 @@
+package com.stripe.android.link
+
+import android.os.Bundle
+import androidx.activity.compose.setContent
+import androidx.activity.viewModels
+import androidx.annotation.VisibleForTesting
+import androidx.appcompat.app.AppCompatActivity
+import androidx.compose.runtime.LaunchedEffect
+import androidx.lifecycle.ViewModelProvider
+import androidx.navigation.NavHostController
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.rememberNavController
+import com.stripe.android.link.ui.cardedit.CardEditScreen
+import com.stripe.android.link.ui.paymentmenthod.PaymentMethodScreen
+import com.stripe.android.link.ui.signup.SignUpScreen
+import com.stripe.android.link.ui.verification.VerificationScreen
+import com.stripe.android.link.ui.wallet.WalletScreen
+
+internal class LinkActivity : AppCompatActivity() {
+    @VisibleForTesting
+    internal var viewModelFactory: ViewModelProvider.Factory = LinkActivityViewModel.Factory()
+    private val viewModel: LinkActivityViewModel by viewModels { viewModelFactory }
+
+    @VisibleForTesting
+    internal lateinit var navController: NavHostController
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        setContent {
+            navController = rememberNavController()
+
+            LaunchedEffect("LinkEffects") {
+                viewModel.effect.collect { effect ->
+                    when (effect) {
+                        LinkEffect.GoBack -> navController.popBackStack()
+                        is LinkEffect.NavigateTo -> {
+                            navController.navigate(effect.screen.route)
+                        }
+                    }
+                }
+            }
+
+            NavHost(
+                navController = navController,
+                startDestination = LinkScreen.SignUp.route
+            ) {
+                composable(LinkScreen.SignUp.route) {
+                    SignUpScreen()
+                }
+
+                composable(LinkScreen.Verification.route) {
+                    VerificationScreen()
+                }
+
+                composable(LinkScreen.Wallet.route) {
+                    WalletScreen()
+                }
+
+                composable(LinkScreen.CardEdit.route) {
+                    CardEditScreen()
+                }
+
+                composable(LinkScreen.PaymentMethod.route) {
+                    PaymentMethodScreen()
+                }
+            }
+        }
+    }
+}

link/src/main/java/com/stripe/android/link/LinkActivityViewModel.kt

@@ -0,0 +1,45 @@
+package com.stripe.android.link
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+
+internal class LinkActivityViewModel : LinkViewModel<LinkState, LinkAction, LinkResult, LinkEffect>(
+    initialState = LinkState,
+) {
+    override fun actionToResult(action: LinkAction): Flow<LinkResult> {
+        return when (action) {
+            LinkAction.BackPressed -> handleBackPressed()
+            LinkAction.WalletClicked -> handleWalletClicked()
+        }
+    }
+
+    private fun handleBackPressed(): Flow<LinkResult> {
+        return flowOf(LinkResult.SendEffect(LinkEffect.GoBack))
+    }
+
+    private fun handleWalletClicked(): Flow<LinkResult> {
+        return flowOf(
+            value = LinkResult.SendEffect(
+                effect = LinkEffect.NavigateTo(
+                    screen = LinkScreen.Wallet
+                )
+            )
+        )
+    }
+
+    override fun resultToState(currentState: LinkState, result: LinkResult) = currentState
+
+    override fun resultToEffect(result: LinkResult): LinkEffect? {
+        return when (result) {
+            is LinkResult.SendEffect -> result.effect
+        }
+    }
+
+    internal class Factory : ViewModelProvider.Factory {
+        override fun <T : ViewModel> create(modelClass: Class<T>): T {
+            return LinkActivityViewModel() as T
+        }
+    }
+}

link/src/main/java/com/stripe/android/link/LinkScreen.kt

@@ -1,9 +1,9 @@
 package com.stripe.android.link
 
-internal sealed interface LinkScreen {
-    data object Verification : LinkScreen
-    data object Wallet : LinkScreen
-    data object PaymentMethod : LinkScreen
-    data object CardEdit : LinkScreen
-    data object SignUp : LinkScreen
+internal sealed class LinkScreen(val route: String) {
+    data object Verification : LinkScreen("verification")
+    data object Wallet : LinkScreen("wallet")
+    data object PaymentMethod : LinkScreen("paymentMethod")
+    data object CardEdit : LinkScreen("cardEdit")
+    data object SignUp : LinkScreen("signUp")
 }

link/src/main/java/com/stripe/android/link/LinkState.kt

@@ -0,0 +1,17 @@
+package com.stripe.android.link
+
+internal object LinkState
+
+internal sealed interface LinkAction {
+    data object BackPressed : LinkAction
+    data object WalletClicked : LinkAction
+}
+
+internal sealed interface LinkResult {
+    data class SendEffect(val effect: LinkEffect) : LinkResult
+}
+
+internal sealed interface LinkEffect {
+    data object GoBack : LinkEffect
+    data class NavigateTo(val screen: LinkScreen) : LinkEffect
+}

link/src/main/java/com/stripe/android/link/LinkViewModel.kt

@@ -0,0 +1,52 @@
+package com.stripe.android.link
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.flatMapConcat
+import kotlinx.coroutines.flow.receiveAsFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+
+// This will be used as a base for all Link screen viewmodels to create a consistent architecture
+// There should be no more logic here besides updating state and sending effects
+internal abstract class LinkViewModel<State, Action, Result, Effect>(
+    initialState: State,
+) : ViewModel() {
+    private val actionChannel = Channel<Action>(Channel.UNLIMITED)
+
+    private val _state = MutableStateFlow(initialState)
+    val state: StateFlow<State> = _state
+
+    private val _effect = MutableSharedFlow<Effect>()
+    val effect: Flow<Effect> = _effect
+
+    init {
+        viewModelScope.launch {
+            actionChannel.receiveAsFlow()
+                .flatMapConcat(::actionToResult)
+                .collect { result ->
+                    _state.update { currentState ->
+                        resultToState(currentState, result)
+                    }
+                    resultToEffect(result)?.let { newEffect ->
+                        _effect.emit(newEffect)
+                    }
+                }
+        }
+    }
+
+    fun handleAction(action: Action) {
+        actionChannel.trySend(action)
+    }
+
+    protected abstract fun actionToResult(action: Action): Flow<Result>
+
+    protected abstract fun resultToState(currentState: State, result: Result): State
+
+    protected abstract fun resultToEffect(result: Result): Effect?
+}

link/src/test/java/com/stripe/android/link/LinkActivityTest.kt

@@ -0,0 +1,88 @@
+package com.stripe.android.link
+
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule
+import androidx.compose.ui.test.junit4.createAndroidComposeRule
+import androidx.navigation.NavHostController
+import androidx.test.core.app.ApplicationProvider
+import com.stripe.android.link.utils.InjectableActivityScenario
+import com.stripe.android.link.utils.injectableActivityScenario
+import com.stripe.android.link.utils.viewModelFactoryFor
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.test.resetMain
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.verify
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import kotlin.test.AfterTest
+
+@RunWith(RobolectricTestRunner::class)
+@Config(sdk = [Build.VERSION_CODES.Q])
+internal class LinkActivityTest {
+
+    @get:Rule
+    val rule = InstantTaskExecutorRule()
+
+    @get:Rule
+    val composeTestRule = createAndroidComposeRule<LinkActivity>()
+
+    private val navHostController: NavHostController = mock()
+
+    private val context = ApplicationProvider.getApplicationContext<Context>()
+
+    @AfterTest
+    fun cleanup() {
+        Dispatchers.resetMain()
+    }
+
+    @Test
+    fun `test that navigator pops back on back pressed`() {
+        val vm = LinkActivityViewModel()
+        val scenario = activityScenario(viewModel = vm)
+        scenario.launchTest {
+            vm.handleAction(LinkAction.BackPressed)
+
+            composeTestRule.waitForIdle()
+
+            verify(navHostController).popBackStack()
+        }
+    }
+
+    @Test
+    fun `test that navigator navigates to wallet on wallet clicked`() {
+        val vm = LinkActivityViewModel()
+        val scenario = activityScenario(viewModel = vm)
+        scenario.launchTest {
+            vm.handleAction(LinkAction.WalletClicked)
+
+            composeTestRule.waitForIdle()
+
+            verify(navHostController).navigate(LinkScreen.Wallet.route)
+        }
+    }
+
+    private fun InjectableActivityScenario<LinkActivity>.launchTest(
+        startIntent: Intent = Intent(context, LinkActivity::class.java),
+        block: (LinkActivity) -> Unit
+    ) {
+        launch(startIntent).onActivity { activity ->
+            activity.navController = navHostController
+            block(activity)
+        }
+    }
+
+    private fun activityScenario(
+        viewModel: LinkActivityViewModel = LinkActivityViewModel(),
+    ): InjectableActivityScenario<LinkActivity> {
+        return injectableActivityScenario {
+            injectActivity {
+                viewModelFactory = viewModelFactoryFor(viewModel)
+            }
+        }
+    }
+}

link/src/test/java/com/stripe/android/link/LinkActivityViewModelTest.kt

@@ -0,0 +1,45 @@
+package com.stripe.android.link
+
+import app.cash.turbine.test
+import com.google.common.truth.Truth
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.test.setMain
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+
+@RunWith(RobolectricTestRunner::class)
+internal class LinkActivityViewModelTest {
+    private val dispatcher = UnconfinedTestDispatcher()
+    private val vm = LinkActivityViewModel()
+
+    @Before
+    fun setUp() {
+        Dispatchers.setMain(dispatcher)
+    }
+
+    @After
+    fun tearDown() {
+        Dispatchers.resetMain()
+    }
+
+    @Test
+    fun `test that viewmodel has correct initial state`() = runTest(dispatcher) {
+        vm.state.test {
+            Truth.assertThat(awaitItem()).isEqualTo(LinkState)
+        }
+    }
+
+    @Test
+    fun `test that correct effect is emitted on back pressed`() = runTest(dispatcher) {
+        vm.effect.test {
+            vm.handleAction(LinkAction.BackPressed)
+            Truth.assertThat(awaitItem()).isEqualTo(LinkEffect.GoBack)
+        }
+    }
+}