Inform user about CorruptDatabaseBackup.dbfix/inform_on_db_moved

Prior to this commit, the user gets no feedback what-so-ever of what is
going on when a corrupted database gets renamed. Which we should assume
can be a quite horrifying experience.

This adds a friendly message about what has happened, and suggests what
to do.

GitHub issue #6212, named "More useful error message for corrupted
databases", might still be relevant for the "more useful" part.

By reusing the design and making the dual-alternative of HomeFragment
into instead one of three container views, the code changes stay small
and complexity low. Easy to merge, and easy to revert once some code for
a better implementation actually gets available.

The date parsing, used when logging detection of a corrupt database, is
copied verbatim from CrashReportWriter.java which presumably should make
it reasonable enough.

4 files changed, 60 insertions, 1 deletions

diff --git a/app/src/main/java/de/danoeh/antennapod/ui/screen/home/HomeFragment.java b/app/src/main/java/de/danoeh/antennapod/ui/screen/home/HomeFragment.java
index 0b6132ef0..cfd0082b4 100644
--- a/app/src/main/java/de/danoeh/antennapod/ui/screen/home/HomeFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/ui/screen/home/HomeFragment.java
@@ -44,8 +44,11 @@ import org.greenrobot.eventbus.EventBus;
 import org.greenrobot.eventbus.Subscribe;
 import org.greenrobot.eventbus.ThreadMode;
 
+import java.io.File;
+import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * Shows unread or recently published episodes
@@ -178,11 +181,34 @@ public class HomeFragment extends Fragment implements Toolbar.OnMenuItemClickLis
         if (disposable != null) {
             disposable.dispose();
         }
+        boolean hasCorruptBackup = false;
+        try {
+            // These needs to correspond with where the database is move in:
+            // storage/database/src/main/java/de/danoeh/antennapod/storage/database/PodDBAdapter.java
+            File backupFolder = getContext().getExternalFilesDir(null);
+            File backupFile = new File(backupFolder, "CorruptedDatabaseBackup.db");
+            hasCorruptBackup = backupFile.exists();
+            if (hasCorruptBackup) {
+                Log.d(TAG, "There is a " + backupFile.getName() + " file, last modified: "
+                        + new SimpleDateFormat("dd-MM-yyyy HH:mm:ss", Locale.getDefault())
+                        .format(backupFile.lastModified()));
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+        final boolean hasCorruptBackupFinal = hasCorruptBackup;
+
         disposable = Observable.fromCallable(() -> DBReader.getTotalEpisodeCount(FeedItemFilter.unfiltered()))
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .subscribe(numEpisodes -> {
-                    viewBinding.welcomeContainer.setVisibility(numEpisodes == 0 ? View.VISIBLE : View.GONE);
+                    if (hasCorruptBackupFinal) {
+                        viewBinding.welcomeContainer.setVisibility(View.GONE);
+                        viewBinding.dbMovedContainer.setVisibility(numEpisodes == 0 ? View.VISIBLE : View.GONE);
+                    } else {
+                        viewBinding.welcomeContainer.setVisibility(numEpisodes == 0 ? View.VISIBLE : View.GONE);
+                        viewBinding.dbMovedContainer.setVisibility(View.GONE);
+                    }
                     viewBinding.homeContainer.setVisibility(numEpisodes == 0 ? View.GONE : View.VISIBLE);
                     viewBinding.swipeRefresh.setVisibility(numEpisodes == 0 ? View.GONE : View.VISIBLE);
                     if (numEpisodes == 0) {
diff --git a/app/src/main/res/layout/home_fragment.xml b/app/src/main/res/layout/home_fragment.xml
index 3ef602334..d0c80ed32 100644
--- a/app/src/main/res/layout/home_fragment.xml
+++ b/app/src/main/res/layout/home_fragment.xml
@@ -65,6 +65,35 @@
 
     </LinearLayout>
 
+    <LinearLayout
+        android:id="@+id/dbMovedContainer"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:visibility="gone"
+        android:paddingHorizontal="32dp">
+
+        <TextView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/home_dbmoved_title"
+            android:layout_marginBottom="8dp"
+            android:layout_gravity="center_horizontal"
+            android:textAlignment="center"
+            android:textColor="?android:attr/textColorPrimary"
+            android:textSize="20sp" />
+
+        <TextView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/home_dbmoved_text"
+            android:layout_gravity="center_horizontal"
+            android:textAlignment="center"
+            android:textColor="?android:attr/textColorPrimary"
+            android:textSize="14sp" />
+
+    </LinearLayout>
+
     <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
         android:id="@+id/swipeRefresh"
         android:layout_width="match_parent"
diff --git a/storage/database/src/main/java/de/danoeh/antennapod/storage/database/PodDBAdapter.java b/storage/database/src/main/java/de/danoeh/antennapod/storage/database/PodDBAdapter.java
index 8f8d03927..641699d29 100644
--- a/storage/database/src/main/java/de/danoeh/antennapod/storage/database/PodDBAdapter.java
+++ b/storage/database/src/main/java/de/danoeh/antennapod/storage/database/PodDBAdapter.java
@@ -1473,6 +1473,8 @@ public class PodDBAdapter {
             Log.e(TAG, "Database corrupted: " + db.getPath());
 
             File dbPath = new File(db.getPath());
+            // These needs to correspond with where the user is notified, in:
+            // app/src/main/java/de/danoeh/antennapod/ui/screen/home/HomeFragment.java
             File backupFolder = PodDBAdapter.context.getExternalFilesDir(null);
             File backupFile = new File(backupFolder, "CorruptedDatabaseBackup.db");
             try {
diff --git a/ui/i18n/src/main/res/values/strings.xml b/ui/i18n/src/main/res/values/strings.xml
index ae6b3b743..07e442629 100644
--- a/ui/i18n/src/main/res/values/strings.xml
+++ b/ui/i18n/src/main/res/values/strings.xml
@@ -67,6 +67,8 @@
     <string name="home_downloads_empty_text">You can download any episode to listen to it offline.</string>
     <string name="home_welcome_title">Welcome to AntennaPod!</string>
     <string name="home_welcome_text">You are not subscribed to any podcasts yet. Open the side menu to add a podcast.</string>
+    <string name="home_dbmoved_title">Stay calm!</string>
+    <string name="home_dbmoved_text">AntennaPod encountered an error with the database and renamed it CorruptedDatabaseBackup.db. Visit https://antennapod.org/documentation/bugs-first-aid/database-error for instructions on ways to recover. https://forum.antennapod.org is open for support, or for venting that this bug bit you.</string>
     <string name="notification_permission_text">AntennaPod needs your permission to show notifications. By default, AntennaPod only shows notifications while something is being downloaded or when something goes wrong.</string>
     <string name="notification_permission_denied">You denied the permission.</string>
     <string name="notification_permission_deny_warning">If you disable notifications and something goes wrong, you might be unable to find out why it went wrong.</string>