Closes #7645: Disable push service when migrating

app/src/main/java/org/mozilla/fenix/components/BackgroundServices.kt

@@ -87,7 +87,7 @@ class BackgroundServices(
             syncPeriodInMinutes = 240L) // four hours
     }
 
-    private val pushService by lazy { FirebasePush() }
+    val pushService by lazy { FirebasePush() }
 
     val push by lazy { makePushConfig()?.let { makePush(it) } }
 

app/src/migration/java/org/mozilla/fenix/MigratingFenixApplication.kt

@@ -29,6 +29,14 @@ class MigratingFenixApplication : FenixApplication() {
 
     val migrationStore by lazy { MigrationStore() }
 
+    val migrationPushSubscriber by lazy {
+        MigrationPushSubscriber(
+            this,
+            components.backgroundServices.pushService,
+            migrationStore
+        )
+    }
+
     override fun setupInMainProcessOnly() {
         // These migrations need to run before regular initialization happens.
         migrateBlocking()
@@ -37,6 +45,7 @@ class MigratingFenixApplication : FenixApplication() {
         super.setupInMainProcessOnly()
 
         // The rest of the migrations can happen now.
+        migrationPushSubscriber.start()
         migrator.startMigrationIfNeeded(migrationStore, MigrationService::class.java)
     }
 

app/src/migration/java/org/mozilla/fenix/MigrationPushSubscriber.kt

@@ -0,0 +1,38 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix
+
+import android.content.Context
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.collect
+import mozilla.components.concept.push.PushService
+import mozilla.components.lib.state.ext.flowScoped
+import mozilla.components.support.migration.state.MigrationProgress
+import mozilla.components.support.migration.state.MigrationStore
+
+/**
+ * Migration-aware subscriber that disables the push service during an active migration
+ * and re-enables when complete.
+ */
+class MigrationPushSubscriber(
+    private val context: Context,
+    private val service: PushService,
+    private val store: MigrationStore
+) {
+    @UseExperimental(ExperimentalCoroutinesApi::class)
+    fun start() {
+        // Stop the service if it is already started.
+        service.stop()
+
+        // Observe for migration completed.
+        store.flowScoped { flow ->
+            flow.collect { state ->
+                if (state.progress == MigrationProgress.COMPLETED) {
+                    service.start(context)
+                }
+            }
+        }
+    }
+}