Add subscription extension methods and sample code (#8)

* ✨ Add SubscriptionExtensions.kt

* 👨‍🏭 Add user subscription to demonstrate composite subscription

komposable-architecture/src/main/java/com/toggl/komposable/extensions/SubscriptionExtensions.kt

@@ -0,0 +1,21 @@
+package com.toggl.komposable.extensions
+
+import com.toggl.komposable.architecture.Subscription
+import com.toggl.komposable.internal.CompositeSubscription
+
+/**
+ * @param subscriptions      List of subscriptions which should be merged
+ * @return A [CompositeSubscription] of a given subscriptions
+ * @see CompositeSubscription
+ */
+fun <State, Action : Any> mergeSubscriptions(vararg subscriptions: Subscription<State, Action>): Subscription<State, Action> =
+    CompositeSubscription(subscriptions.toList())
+
+/**
+ * @receiver First subscription
+ * @param subscription      Second subscription that will be merged with the receiver
+ * @return A [CompositeSubscription] of a given subscriptions
+ * @see CompositeSubscription
+ */
+infix fun <State, Action : Any> Subscription<State, Action>.mergeWith(subscription: Subscription<State, Action>): Subscription<State, Action> =
+    mergeSubscriptions(this, subscription)

todo-sample/src/main/java/com/toggl/komposable/sample/todo/AppAction.kt

@@ -1,11 +1,13 @@
 package com.toggl.komposable.sample.todo
 
+import com.toggl.komposable.sample.todo.data.Identity
 import com.toggl.komposable.sample.todo.edit.EditAction
 import com.toggl.komposable.sample.todo.list.ListAction
 
 sealed class AppAction {
     class List(override val action: ListAction) : AppAction(), ActionWrapper<ListAction>
     class Edit(override val action: EditAction) : AppAction(), ActionWrapper<EditAction>
+    data class IdentityUpdated(val newIdentity: Identity) : AppAction()
     object BackPressed : AppAction()
 }
 

todo-sample/src/main/java/com/toggl/komposable/sample/todo/AppState.kt

@@ -4,11 +4,13 @@ import com.toggl.komposable.architecture.Effect
 import com.toggl.komposable.architecture.Mutable
 import com.toggl.komposable.extensions.mutateWithoutEffects
 import com.toggl.komposable.sample.todo.data.EditableTodoItem
+import com.toggl.komposable.sample.todo.data.Identity
 import com.toggl.komposable.sample.todo.data.TodoItem
 
 data class AppState(
     val todoList: List<TodoItem> = emptyList(),
     val editableTodo: EditableTodoItem = EditableTodoItem(title = "", description = ""),
+    val identity: Identity = Identity.Unknown,
     override val backStack: BackStack = listOf(AppDestination.List)
 ) : BackStackAwareState<AppState> {
     override fun changeBackStack(backStack: BackStack): AppState =

todo-sample/src/main/java/com/toggl/komposable/sample/todo/AuthReducer.kt

@@ -0,0 +1,18 @@
+package com.toggl.komposable.sample.todo
+
+import com.toggl.komposable.architecture.Effect
+import com.toggl.komposable.architecture.Mutable
+import com.toggl.komposable.architecture.Reducer
+import com.toggl.komposable.extensions.mutateWithoutEffects
+import com.toggl.komposable.extensions.noEffect
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class AuthReducer @Inject constructor() : Reducer<AppState, AppAction> {
+    override fun reduce(state: Mutable<AppState>, action: AppAction): List<Effect<AppAction>> =
+        when (action) {
+            is AppAction.IdentityUpdated -> state.mutateWithoutEffects { copy(identity = action.newIdentity) }
+            else -> noEffect()
+        }
+}

todo-sample/src/main/java/com/toggl/komposable/sample/todo/TodoModule.kt

@@ -7,9 +7,11 @@ import com.toggl.komposable.architecture.Reducer
 import com.toggl.komposable.architecture.Store
 import com.toggl.komposable.extensions.combine
 import com.toggl.komposable.extensions.createStore
+import com.toggl.komposable.extensions.mergeWith
 import com.toggl.komposable.extensions.pullback
 import com.toggl.komposable.sample.todo.data.AppDatabase
 import com.toggl.komposable.sample.todo.data.TodoDao
+import com.toggl.komposable.sample.todo.data.UserSubscription
 import com.toggl.komposable.sample.todo.edit.EditAction
 import com.toggl.komposable.sample.todo.edit.EditReducer
 import com.toggl.komposable.sample.todo.edit.EditState
@@ -35,11 +37,13 @@ class TodoModule {
     @Provides
     fun appReducer(
         navigationReducer: NavigationReducer,
+        authReducer: AuthReducer,
         listReducer: ListReducer,
         editReducer: EditReducer
     ): Reducer<AppState, AppAction> =
         combine(
             navigationReducer,
+            authReducer,
             listReducer.pullback(
                 mapToLocalState = { appState -> ListState(appState.todoList, appState.backStack) },
                 mapToLocalAction = AppAction::unwrap,
@@ -59,13 +63,14 @@ class TodoModule {
     fun appStore(
         reducer: Reducer<AppState, AppAction>,
         listSubscription: ListSubscription,
+        userSubscription: UserSubscription,
         dispatcherProvider: DispatcherProvider,
         application: Application
     ): Store<AppState, AppAction> =
         createStore(
             initialState = AppState(),
             reducer = reducer,
-            subscription = listSubscription,
+            subscription = listSubscription mergeWith userSubscription,
             dispatcherProvider = dispatcherProvider,
             storeScopeProvider = application as StoreScopeProvider
         )

todo-sample/src/main/java/com/toggl/komposable/sample/todo/TodoScaffold.kt

@@ -2,6 +2,8 @@ package com.toggl.komposable.sample.todo
 
 import androidx.activity.OnBackPressedCallback
 import androidx.appcompat.app.AppCompatActivity
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.BottomAppBar
 import androidx.compose.material.FabPosition
@@ -13,10 +15,13 @@ import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.rounded.Check
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.DefaultLifecycleObserver
 import androidx.lifecycle.LifecycleOwner
+import com.toggl.komposable.sample.todo.data.Identity
 import com.toggl.komposable.sample.todo.edit.EditAction
 import com.toggl.komposable.sample.todo.list.AddTodoFab
 import kotlinx.coroutines.ExperimentalCoroutinesApi
@@ -43,18 +48,7 @@ fun TodoScaffold() {
         floatingActionButton = { if (currentDestination == AppDestination.List) AddTodoFab() },
         floatingActionButtonPosition = FabPosition.Center,
         isFloatingActionButtonDocked = true,
-        bottomBar = {
-            BottomAppBar(cutoutShape = RoundedCornerShape(100)) {
-                if (currentDestination == AppDestination.Add) {
-                    OutlinedButton(
-                        onClick = { appStore.dispatch(AppAction.Edit(EditAction.SaveTapped)) }
-                    ) {
-                        Icon(Icons.Rounded.Check, contentDescription = null)
-                        Text(text = "Save")
-                    }
-                }
-            }
-        }
+        bottomBar = { TodoBottomAppBar(appStore, currentDestination) }
     ) {
         AppNavigationHost(
             backStack = backStack
@@ -81,3 +75,28 @@ fun AppCompatActivity.handleBackPressesEmitting(callback: () -> Unit) {
         }
     )
 }
+
+@Composable
+private fun TodoBottomAppBar(appStore: AppStoreViewModel, currentDestination: AppDestination) {
+
+    val identity by appStore.state
+        .map { it.identity }
+        .collectAsStateWhenStarted(initial = Identity.Unknown)
+
+    BottomAppBar(cutoutShape = RoundedCornerShape(100)) {
+        if (currentDestination == AppDestination.Add) {
+            OutlinedButton(
+                onClick = { appStore.dispatch(AppAction.Edit(EditAction.SaveTapped)) }
+            ) {
+                Icon(Icons.Rounded.Check, contentDescription = null)
+                Text(text = "Save")
+            }
+        }
+        Spacer(modifier = Modifier.weight(1f))
+        val identityText = when (identity) {
+            Identity.Unknown -> "Loading..."
+            is Identity.User -> (identity as Identity.User).username
+        }
+        Text(text = identityText, modifier = Modifier.padding(end = 12.dp))
+    }
+}

todo-sample/src/main/java/com/toggl/komposable/sample/todo/data/AccountManager.kt

@@ -0,0 +1,21 @@
+package com.toggl.komposable.sample.todo.data
+
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class AccountManager @Inject constructor() {
+    fun getLoggedInUser(): Flow<Identity> = flow {
+        emit(Identity.Unknown)
+        delay(3000)
+        emit(Identity.User("John Balance", "[email protected]"))
+    }
+}
+
+sealed class Identity {
+    object Unknown : Identity()
+    data class User(val username: String, val email: String) : Identity()
+}

todo-sample/src/main/java/com/toggl/komposable/sample/todo/data/UserSubscription.kt

@@ -0,0 +1,15 @@
+package com.toggl.komposable.sample.todo.data
+
+import com.toggl.komposable.architecture.Subscription
+import com.toggl.komposable.sample.todo.AppAction
+import com.toggl.komposable.sample.todo.AppState
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class UserSubscription @Inject constructor(private val accountManager: AccountManager) : Subscription<AppState, AppAction> {
+    override fun subscribe(state: Flow<AppState>): Flow<AppAction> =
+        accountManager.getLoggedInUser().map { AppAction.IdentityUpdated(it) }
+}

todo-sample/src/main/java/com/toggl/komposable/sample/todo/list/ListSubscription.kt

@@ -10,7 +10,7 @@ import javax.inject.Inject
 import javax.inject.Singleton
 
 @Singleton
-class ListSubscription @Inject constructor(val todoDao: TodoDao) : Subscription<AppState, AppAction> {
+class ListSubscription @Inject constructor(private val todoDao: TodoDao) : Subscription<AppState, AppAction> {
     override fun subscribe(state: Flow<AppState>): Flow<AppAction> =
         todoDao.getAll().map { AppAction.List(ListAction.ListUpdated(it)) }
 }