Introduced RetainedInstanceStore to keep data during configuration ch…

…ange

libraries/core/src/androidTest/kotlin/com/bumble/appyx/core/node/RetainedInstanceStoreTest.kt

@@ -0,0 +1,62 @@
+package com.bumble.appyx.core.node
+
+import androidx.lifecycle.Lifecycle
+import com.bumble.appyx.core.AppyxTestScenario
+import com.bumble.appyx.core.modality.BuildContext
+import com.bumble.appyx.core.store.RetainedInstanceStore
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import kotlin.reflect.KClass
+
+class RetainedInstanceStoreTest {
+    private val stubRetainedInstanceStore = StubRetainedInstanceStore()
+
+    @get:Rule
+    val rule = AppyxTestScenario { buildContext ->
+        TestParentNode(buildContext, stubRetainedInstanceStore)
+    }
+
+    @Test
+    fun WHEN_activity_finished_THEN_retained_instance_store_content_is_removed() {
+        rule.start()
+
+        rule.activityScenario.moveToState(Lifecycle.State.DESTROYED)
+
+        assertTrue(stubRetainedInstanceStore.removeAllCalled)
+    }
+
+    @Test
+    fun WHEN_activity_recreated_THEN_retained_instance_store_content_is_not_removed() {
+        rule.start()
+
+        rule.activityScenario.recreate()
+
+        assertFalse(stubRetainedInstanceStore.removeAllCalled)
+    }
+
+    class TestParentNode(
+        buildContext: BuildContext,
+        retainedInstanceStore: RetainedInstanceStore,
+    ) : Node(
+        buildContext = buildContext,
+        retainedInstanceStore = retainedInstanceStore,
+    )
+
+    class StubRetainedInstanceStore : RetainedInstanceStore {
+        var removeAllCalled: Boolean = false
+
+        override fun <T : Any> get(
+            nodeId: String,
+            clazz: KClass<*>,
+            disposer: (T) -> Unit,
+            factory: () -> T
+        ): T = RetainedInstanceStore.get(nodeId, clazz, disposer, factory)
+
+        override fun removeAll(nodeId: String) {
+            removeAllCalled = true
+            RetainedInstanceStore.removeAll(nodeId)
+        }
+    }
+}

libraries/core/src/main/kotlin/com/bumble/appyx/core/integrationpoint/ActivityIntegrationPoint.kt

@@ -23,6 +23,9 @@ open class ActivityIntegrationPoint(
     override val permissionRequester: PermissionRequester
         get() = permissionRequestBoundary
 
+    override val isChangingConfigurations: Boolean
+        get() = activity.isChangingConfigurations
+
     fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
         activityBoundary.onActivityResult(requestCode, resultCode, data)
     }

libraries/core/src/main/kotlin/com/bumble/appyx/core/integrationpoint/IntegrationPoint.kt

@@ -18,6 +18,8 @@ abstract class IntegrationPoint(
 
     abstract val permissionRequester: PermissionRequester
 
+    abstract val isChangingConfigurations: Boolean
+
     fun onSaveInstanceState(outState: Bundle) {
         requestCodeRegistry.onSaveInstanceState(outState)
     }

libraries/core/src/main/kotlin/com/bumble/appyx/core/integrationpoint/IntegrationPointStub.kt

@@ -18,6 +18,9 @@ class IntegrationPointStub : IntegrationPoint(savedInstanceState = null) {
     override val permissionRequester: PermissionRequester
         get() = error(ERROR)
 
+    override val isChangingConfigurations: Boolean
+        get() = false
+
     override fun handleUpNavigation() {
         error(ERROR)
     }

libraries/core/src/main/kotlin/com/bumble/appyx/core/modality/BuildContext.kt

@@ -1,16 +1,20 @@
 package com.bumble.appyx.core.modality
 
+import com.bumble.appyx.core.state.MutableSavedStateMap
+import com.bumble.appyx.core.state.SavedStateMap
 import com.bumble.appyx.utils.customisations.NodeCustomisation
 import com.bumble.appyx.utils.customisations.NodeCustomisationDirectory
 import com.bumble.appyx.utils.customisations.NodeCustomisationDirectoryImpl
-import com.bumble.appyx.core.state.SavedStateMap
+import java.util.UUID
 
 data class BuildContext(
     val ancestryInfo: AncestryInfo,
     val savedStateMap: SavedStateMap?,
     val customisations: NodeCustomisationDirectory,
 ) {
     companion object {
+        private const val IDENTIFIER_KEY = "build.context.identifier"
+
         fun root(
             savedStateMap: SavedStateMap?,
             customisations: NodeCustomisationDirectory = NodeCustomisationDirectoryImpl()
@@ -22,6 +26,18 @@ data class BuildContext(
             )
     }
 
-    fun <T : NodeCustomisation> getOrDefault(defaultCustomisation: T) : T =
+    val identifier: String by lazy {
+        if (savedStateMap == null) {
+            UUID.randomUUID().toString()
+        } else {
+            savedStateMap[IDENTIFIER_KEY] as String? ?: error("onSaveInstanceState() was not called")
+        }
+    }
+
+    fun <T : NodeCustomisation> getOrDefault(defaultCustomisation: T): T =
         customisations.getRecursivelyOrDefault(defaultCustomisation)
+
+    fun onSaveInstanceState(state: MutableSavedStateMap) {
+        state[IDENTIFIER_KEY] = identifier
+    }
 }

libraries/core/src/main/kotlin/com/bumble/appyx/core/node/Node.kt

@@ -2,6 +2,7 @@ package com.bumble.appyx.core.node
 
 import androidx.activity.compose.LocalOnBackPressedDispatcherOwner
 import androidx.annotation.CallSuper
+import androidx.annotation.VisibleForTesting
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.DisposableEffect
@@ -35,17 +36,24 @@ import com.bumble.appyx.core.plugin.plugins
 import com.bumble.appyx.core.state.MutableSavedStateMap
 import com.bumble.appyx.core.state.MutableSavedStateMapImpl
 import com.bumble.appyx.core.state.SavedStateMap
+import com.bumble.appyx.core.store.RetainedInstanceStore
 import kotlinx.coroutines.withContext
-import java.util.UUID
 
 @Suppress("TooManyFunctions")
 @Stable
-open class Node(
-    buildContext: BuildContext,
+open class Node @VisibleForTesting internal constructor(
+    val buildContext: BuildContext,
     val view: NodeView = EmptyNodeView,
+    private val retainedInstanceStore: RetainedInstanceStore,
     plugins: List<Plugin> = emptyList()
 ) : NodeLifecycle, NodeView by view, RequestCodeClient {
 
+    constructor(
+        buildContext: BuildContext,
+        view: NodeView = EmptyNodeView,
+        plugins: List<Plugin> = emptyList()
+    ) : this(buildContext, view, RetainedInstanceStore, plugins)
+
     @Suppress("LeakingThis") // Implemented in the same way as in androidx.Fragment
     private val nodeLifecycle = NodeLifecycleImpl(this)
 
@@ -77,7 +85,8 @@ open class Node(
 
     private var wasBuilt = false
 
-    val id = getNodeId(buildContext)
+    val id: String
+        get() = buildContext.identifier
 
     override val requestCodeClientId: String = id
 
@@ -92,14 +101,6 @@ open class Node(
         })
     }
 
-    private fun getNodeId(buildContext: BuildContext): String {
-        val state = buildContext.savedStateMap ?: return UUID.randomUUID().toString()
-
-        return state[NODE_ID_KEY] as String? ?: error(
-            "super.onSaveInstanceState() was not called for the node: ${this::class.qualifiedName}"
-        )
-    }
-
     @Deprecated(
         replaceWith = ReplaceWith("executeAction(action)"),
         message = "Will be removed in 1.1"
@@ -182,6 +183,9 @@ open class Node(
         }
         nodeLifecycle.updateLifecycleState(state)
         if (state == Lifecycle.State.DESTROYED) {
+            if (!integrationPoint.isChangingConfigurations) {
+                retainedInstanceStore.removeAll(id)
+            }
             plugins<Destroyable>().forEach { it.destroy() }
         }
     }
@@ -197,7 +201,7 @@ open class Node(
 
     @CallSuper
     protected open fun onSaveInstanceState(state: MutableSavedStateMap) {
-        state[NODE_ID_KEY] = id
+        buildContext.onSaveInstanceState(state)
     }
 
     fun finish() {
@@ -231,8 +235,6 @@ open class Node(
         plugins<UpNavigationHandler>().any { it.handleUpNavigation() }
 
     companion object {
-        private const val NODE_ID_KEY = "node.id"
-
         // BackPressHandler is correct when only one of its properties is implemented.
         private fun BackPressHandler.isCorrect(): Boolean {
             val listIsOverriddenOrPluginIgnored = onBackPressedCallback == null

libraries/core/src/main/kotlin/com/bumble/appyx/core/store/RetainedInstanceStore.kt

@@ -0,0 +1,37 @@
+package com.bumble.appyx.core.store
+
+import kotlin.reflect.KClass
+
+/**
+ * A simple storage to preserve any objects during configuration change events.
+ * `factory` function will be invoked immediately on the same thread
+ * only if an object of the same class within the same Node does not exist.
+ *
+ * The framework will manage the lifecycle of provided objects
+ * and invoke `disposer` function to destroy objects properly.
+ *
+ * Sample usage:
+ * ```kotlin
+ * val feature = RetainedInstanceStore.get(
+ *     owner = buildContext.identifier,
+ *     factory = { FeatureImpl() },
+ *     disposer = { feature.dispose() }
+ * }
+ * ```
+ * or
+ *  * ```kotlin
+ *  * val feature = buildContext.getRetainedInstance(
+ *  *     factory = { FeatureImpl() },
+ *  *     disposer = { feature.dispose() }
+ *  * }
+ *  * ```
+ */
+interface RetainedInstanceStore {
+
+    fun <T : Any> get(nodeId: String, clazz: KClass<*>, disposer: (T) -> Unit, factory: () -> T): T
+
+    fun removeAll(nodeId: String)
+
+    companion object : RetainedInstanceStore by RetainedInstanceStoreImpl()
+
+}

libraries/core/src/main/kotlin/com/bumble/appyx/core/store/RetainedInstanceStoreExt.kt

@@ -0,0 +1,16 @@
+package com.bumble.appyx.core.store
+
+import com.bumble.appyx.core.modality.BuildContext
+
+inline fun <reified T : Any> RetainedInstanceStore.get(
+    nodeId: String,
+    noinline disposer: (T) -> Unit = {},
+    noinline factory: () -> T
+): T =
+    get(nodeId, T::class, disposer, factory)
+
+inline fun <reified T : Any> BuildContext.getRetainedInstance(
+    noinline disposer: (T) -> Unit = {},
+    noinline factory: () -> T
+) =
+    RetainedInstanceStore.get(identifier, disposer, factory)

libraries/core/src/main/kotlin/com/bumble/appyx/core/store/RetainedInstanceStoreImpl.kt

@@ -0,0 +1,28 @@
+package com.bumble.appyx.core.store
+
+import kotlin.reflect.KClass
+
+internal class RetainedInstanceStoreImpl : RetainedInstanceStore {
+
+    private val map: MutableMap<String, MutableMap<KClass<*>, ValueHolder<*>>> = HashMap()
+
+    @Suppress("UNCHECKED_CAST")
+    override fun <T : Any> get(nodeId: String, clazz: KClass<*>, disposer: (T) -> Unit, factory: () -> T): T =
+        map
+            .getOrPut(nodeId) { HashMap() }
+            .getOrPut(clazz) { ValueHolder(factory(), disposer) }
+            .value as T
+
+    override fun removeAll(nodeId: String) {
+        map.remove(nodeId)?.values?.forEach { it.dispose() }
+    }
+
+    private class ValueHolder<T : Any>(
+        val value: T,
+        private val disposer: (T) -> Unit
+    ) {
+        fun dispose() {
+            disposer(value)
+        }
+    }
+}