Merge changes I84c9b9af,I387740d8 into main

* changes:
  Migrates Snackbar manager to expose a StateFlow
  Migrates Schedule to Flow

Author: JoseAlcerreca

mobile/src/main/java/com/google/samples/apps/iosched/ui/SnackbarMessageFragmentExtensions.kt

@@ -85,14 +85,14 @@ fun Fragment.setUpSnackbar(
     setupSnackbarManager(snackbarMessageManager, fadingSnackbar, actionClickListener)
 }
 
-private fun Fragment.setupSnackbarManager(
+fun Fragment.setupSnackbarManager(
     snackbarMessageManager: SnackbarMessageManager,
     fadingSnackbar: FadingSnackbar,
     actionClickListener: () -> Unit
 ) {
-    snackbarMessageManager.observeNextMessage().observe(
-        viewLifecycleOwner,
-        EventObserver { message ->
+    viewLifecycleOwner.lifecycleScope.launchWhenStarted {
+        snackbarMessageManager.currentSnackbar.collect { message ->
+            if (message == null) { return@collect }
             val messageText = HtmlCompat.fromHtml(
                 requireContext().getString(message.messageId, message.session?.title),
                 FROM_HTML_MODE_LEGACY
@@ -107,8 +107,10 @@ private fun Fragment.setupSnackbarManager(
                 },
                 // When the snackbar is dismissed, ping the snackbar message manager in case there
                 // are pending messages.
-                dismissListener = { snackbarMessageManager.loadNextMessage() }
+                dismissListener = {
+                    snackbarMessageManager.removeMessageAndLoadNext(message)
+                }
             )
         }
-    )
+    }
 }

mobile/src/main/java/com/google/samples/apps/iosched/ui/messages/SnackbarMessageManager.kt

@@ -17,12 +17,13 @@
 package com.google.samples.apps.iosched.ui.messages
 
 import androidx.annotation.VisibleForTesting
-import androidx.lifecycle.MutableLiveData
 import com.google.samples.apps.iosched.R
 import com.google.samples.apps.iosched.shared.data.prefs.PreferenceStorage
-import com.google.samples.apps.iosched.shared.result.Event
 import com.google.samples.apps.iosched.ui.SnackbarMessage
 import com.google.samples.apps.iosched.ui.messages.SnackbarMessageManager.Companion.MAX_ITEMS
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import timber.log.Timber
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -47,48 +48,46 @@ open class SnackbarMessageManager @Inject constructor(
         const val MAX_ITEMS = 10
     }
 
-    private val messages = mutableListOf<Event<SnackbarMessage>>()
+    private val messages = mutableListOf<SnackbarMessage>()
 
-    private val result = MutableLiveData<Event<SnackbarMessage>>()
+    private val _currentSnackbar = MutableStateFlow<SnackbarMessage?>(null)
+    val currentSnackbar: StateFlow<SnackbarMessage?> = _currentSnackbar
 
     fun addMessage(msg: SnackbarMessage) {
-        if (isSnackbarShouldBeIgnored(msg)) {
+        if (shouldSnackbarBeIgnored(msg)) {
             return
         }
-        // If the new message is about the same change as a pending one, keep the new one. (rare)
-        val sameRequestId = messages.filter {
-            it.peekContent().requestChangeId == msg.requestChangeId && !it.hasBeenHandled
-        }
-        if (sameRequestId.isNotEmpty()) {
-            messages.removeAll(sameRequestId)
-        }
-
-        // If the new message is about a change that was already notified, ignore it.
-        val alreadyHandledWithSameId = messages.filter {
-            it.peekContent().requestChangeId == msg.requestChangeId && it.hasBeenHandled
+        // Limit amount of pending messages
+        if (messages.size > MAX_ITEMS) {
+            Timber.e("Too many Snackbar messages. Message id: ${msg.messageId}")
+            return
         }
-
-        // Only add the message if it hasn't been handled before
-        if (alreadyHandledWithSameId.isEmpty()) {
-            messages.add(Event(msg))
-            loadNextMessage()
+        // If the new message is about the same change as a pending one, keep the old one. (rare)
+        val sameRequestId = messages.find {
+            it.requestChangeId == msg.requestChangeId
         }
-
-        // Remove old messages
-        if (messages.size > MAX_ITEMS) {
-            messages.retainAll(messages.drop(messages.size - MAX_ITEMS))
+        if (sameRequestId == null) {
+            messages.add(msg)
         }
+        loadNext()
     }
 
-    fun loadNextMessage() {
-        result.postValue(messages.firstOrNull { !it.hasBeenHandled })
+    private fun loadNext() {
+        if (_currentSnackbar.value == null) {
+            _currentSnackbar.value = messages.firstOrNull()
+        }
     }
 
-    fun observeNextMessage(): MutableLiveData<Event<SnackbarMessage>> {
-        return result
+    fun removeMessageAndLoadNext(shownMsg: SnackbarMessage?) {
+        messages.removeAll { it == shownMsg }
+        if (_currentSnackbar.value == shownMsg) {
+            _currentSnackbar.value = null
+        }
+        loadNext()
     }
 
-    private fun isSnackbarShouldBeIgnored(msg: SnackbarMessage): Boolean {
+    private fun shouldSnackbarBeIgnored(msg: SnackbarMessage): Boolean {
+        // TODO: This should call a suspend fun (migrate to datastore)
         return preferenceStorage.observableSnackbarIsStopped.value == true &&
             msg.actionId == R.string.dont_show
     }

mobile/src/main/java/com/google/samples/apps/iosched/ui/schedule/ScheduleFragment.kt

@@ -24,7 +24,7 @@ import android.widget.Toast
 import androidx.core.view.updatePaddingRelative
 import androidx.fragment.app.activityViewModels
 import androidx.fragment.app.viewModels
-import androidx.lifecycle.Observer
+import androidx.lifecycle.lifecycleScope
 import androidx.navigation.fragment.findNavController
 import androidx.recyclerview.widget.DefaultItemAnimator
 import androidx.recyclerview.widget.LinearLayoutManager
@@ -47,8 +47,12 @@ import com.google.samples.apps.iosched.ui.messages.SnackbarMessageManager
 import com.google.samples.apps.iosched.ui.prefs.SnackbarPreferenceViewModel
 import com.google.samples.apps.iosched.ui.schedule.ScheduleFragmentDirections.Companion.toSearch
 import com.google.samples.apps.iosched.ui.schedule.ScheduleFragmentDirections.Companion.toSessionDetail
+import com.google.samples.apps.iosched.ui.schedule.ScheduleNavigationAction.NavigateToSession
+import com.google.samples.apps.iosched.ui.schedule.ScheduleNavigationAction.NavigateToSignInDialogAction
+import com.google.samples.apps.iosched.ui.schedule.ScheduleNavigationAction.NavigateToSignOutDialogAction
+import com.google.samples.apps.iosched.ui.schedule.ScheduleNavigationAction.ShowScheduleUiHints
 import com.google.samples.apps.iosched.ui.sessioncommon.SessionsAdapter
-import com.google.samples.apps.iosched.ui.setUpSnackbar
+import com.google.samples.apps.iosched.ui.setupSnackbarManager
 import com.google.samples.apps.iosched.ui.signin.NotificationsPreferenceDialogFragment
 import com.google.samples.apps.iosched.ui.signin.NotificationsPreferenceDialogFragment.Companion.DIALOG_NOTIFICATIONS_PREFERENCE
 import com.google.samples.apps.iosched.ui.signin.SignInDialogFragment
@@ -62,6 +66,7 @@ import com.google.samples.apps.iosched.widget.BubbleDecoration
 import com.google.samples.apps.iosched.widget.FadingSnackbar
 import com.google.samples.apps.iosched.widget.JumpSmoothScroller
 import dagger.hilt.android.AndroidEntryPoint
+import kotlinx.coroutines.flow.collect
 import javax.inject.Inject
 import javax.inject.Named
 
@@ -115,7 +120,7 @@ class ScheduleFragment : MainNavigationFragment() {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         binding = FragmentScheduleBinding.inflate(inflater, container, false).apply {
             lifecycleOwner = viewLifecycleOwner
             viewModel = scheduleViewModel
@@ -146,8 +151,8 @@ class ScheduleFragment : MainNavigationFragment() {
         }
 
         // Snackbar configuration
-        setUpSnackbar(
-            scheduleViewModel.snackBarMessage, snackbar, snackbarMessageManager,
+        setupSnackbarManager(
+            snackbarMessageManager, snackbar,
             actionClickListener = {
                 snackbarPrefsViewModel.onStopClicked()
             }
@@ -193,18 +198,14 @@ class ScheduleFragment : MainNavigationFragment() {
         dayIndicatorRecyclerView.adapter = dayIndicatorAdapter
 
         // Start observing ViewModels
-        scheduleViewModel.scheduleUiData.observe(
-            viewLifecycleOwner,
-            Observer {
-                it ?: return@Observer
-                updateScheduleUi(it)
-            }
-        )
+        viewLifecycleOwner.lifecycleScope.launchWhenStarted {
+            scheduleViewModel.scheduleUiData.collect { updateScheduleUi(it) }
+        }
 
         // During conference, scroll to current event.
-        scheduleViewModel.scrollToEvent.observe(
-            viewLifecycleOwner,
-            EventObserver { scrollEvent ->
+
+        viewLifecycleOwner.lifecycleScope.launchWhenStarted {
+            scheduleViewModel.scrollToEvent.collect { scrollEvent ->
                 if (scrollEvent.targetPosition != -1) {
                     scheduleRecyclerView.run {
                         post {
@@ -219,36 +220,19 @@ class ScheduleFragment : MainNavigationFragment() {
                     }
                 }
             }
-        )
-
-        scheduleViewModel.navigateToSessionAction.observe(
-            viewLifecycleOwner,
-            EventObserver { sessionId ->
-                openSessionDetail(sessionId)
-            }
-        )
-
-        scheduleViewModel.navigateToSignInDialogAction.observe(
-            viewLifecycleOwner,
-            EventObserver {
-                openSignInDialog()
-            }
-        )
-
-        scheduleViewModel.navigateToSignOutDialogAction.observe(
-            viewLifecycleOwner,
-            EventObserver {
-                openSignOutDialog()
-            }
-        )
-        scheduleViewModel.scheduleUiHintsShown.observe(
-            viewLifecycleOwner,
-            EventObserver {
-                if (!it) {
-                    openScheduleUiHintsDialog()
+        }
+        viewLifecycleOwner.lifecycleScope.launchWhenStarted {
+            scheduleViewModel.navigationActions.collect {
+                when (it) {
+                    is NavigateToSession -> openSessionDetail(it.sessionId)
+                    is NavigateToSignInDialogAction -> openSignInDialog()
+                    is NavigateToSignOutDialogAction -> openSignOutDialog()
+                    is ShowScheduleUiHints -> openScheduleUiHintsDialog()
                 }
             }
-        )
+        }
+
+        // TODO: Migrate to StateFlow
         scheduleViewModel.shouldShowNotificationsPrefAction.observe(
             viewLifecycleOwner,
             EventObserver {
@@ -259,13 +243,11 @@ class ScheduleFragment : MainNavigationFragment() {
         )
 
         // Show an error message
-        scheduleViewModel.errorMessage.observe(
-            viewLifecycleOwner,
-            EventObserver { errorMsg ->
-                // TODO: Change once there's a way to show errors to the user
-                Toast.makeText(this.context, errorMsg, Toast.LENGTH_LONG).show()
+        viewLifecycleOwner.lifecycleScope.launchWhenStarted {
+            scheduleViewModel.errorMessage.collect { errorMsg ->
+                Toast.makeText(context, errorMsg, Toast.LENGTH_LONG).show()
             }
-        )
+        }
 
         if (savedInstanceState == null) {
             // VM outlives the UI, so reset this flag when a new Schedule page is shown

mobile/src/main/java/com/google/samples/apps/iosched/ui/schedule/ScheduleNavigationAction.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.iosched.ui.schedule
+
+import com.google.samples.apps.iosched.model.SessionId
+
+sealed class ScheduleNavigationAction {
+    object NavigateToSignInDialogAction : ScheduleNavigationAction()
+    object NavigateToSignOutDialogAction : ScheduleNavigationAction()
+    class NavigateToSession(val sessionId: SessionId) : ScheduleNavigationAction()
+    object ShowScheduleUiHints : ScheduleNavigationAction()
+}