[db] Rework AppDao#clearAll() method to fix critical bug

This is a breaking change.

The new method is in FDroidDatabase and called clearAllAppData(). It now also resets repository timestamps, so we will not try to apply a diff when we should use a full index.

libs/database/src/dbTest/java/org/fdroid/database/FDroidDatabaseTest.kt

@@ -0,0 +1,44 @@
+package org.fdroid.database
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.fdroid.test.TestRepoUtils
+import org.junit.Test
+import org.junit.runner.RunWith
+import kotlin.test.assertEquals
+import kotlin.test.assertNotEquals
+
+@RunWith(AndroidJUnit4::class)
+internal class FDroidDatabaseTest : AppTest() {
+
+    @Test
+    fun testClearAllAppData() {
+        // insert three apps in two repos
+        val repoId2 = repoDao.insertOrReplace(TestRepoUtils.getRandomRepo())
+        val repoId1 = repoDao.insertOrReplace(TestRepoUtils.getRandomRepo())
+        appDao.insert(repoId1, packageName1, app1, locales)
+        appDao.insert(repoId2, packageName2, app2, locales)
+        appDao.insert(repoId2, packageName3, app3, locales)
+
+        // assert that both repos and all three apps made it into the DB
+        assertEquals(2, repoDao.getRepositories().size)
+        assertEquals(3, appDao.countApps())
+
+        // assert that repo timestamps are recent, not reset
+        repoDao.getRepositories().forEach { repo ->
+            assertNotEquals(-1, repo.timestamp)
+        }
+
+        // clear all app data
+        db.clearAllAppData()
+
+        // assert that both repos survived, but all apps are gone
+        assertEquals(2, repoDao.getRepositories().size)
+        assertEquals(0, appDao.countApps())
+
+        // assert that repo timestamps got reset
+        repoDao.getRepositories().forEach { repo ->
+            assertEquals(-1, repo.timestamp)
+        }
+    }
+
+}

libs/database/src/main/java/org/fdroid/database/AppDao.kt

@@ -111,11 +111,6 @@ public interface AppDao {
     public fun getNumberOfAppsInCategory(category: String): Int
 
     public fun getNumberOfAppsInRepository(repoId: Long): Int
-
-    /**
-     * Removes all apps and associated data from all repositories.
-     */
-    public fun clearAll()
 }
 
 public enum class AppListSortOrder {
@@ -598,5 +593,5 @@ internal interface AppDaoInt : AppDao {
     fun countLocalizedFileLists(): Int
 
     @Query("DELETE FROM ${AppMetadata.TABLE}")
-    override fun clearAll()
+    fun clearAll()
 }

libs/database/src/main/java/org/fdroid/database/FDroidDatabase.kt

@@ -69,6 +69,13 @@ internal abstract class FDroidDatabaseInt internal constructor() : RoomDatabase(
     fun afterUpdatingRepo(repoId: Long) {
         getAppDao().updateCompatibility(repoId)
     }
+
+    override fun clearAllAppData() {
+        runInTransaction {
+            getAppDao().clearAll()
+            getRepositoryDao().resetTimestamps()
+        }
+    }
 }
 
 /**
@@ -93,4 +100,11 @@ public interface FDroidDatabase {
      * Please run as little code as possible to keep the time the database is blocked minimal.
      */
     public fun runInTransaction(body: Runnable)
+
+    /**
+     * Removes all apps and associated data (such as versions) from all repositories.
+     * The repository data and app preferences are kept as-is.
+     * Only the timestamp of the last repo update gets reset, so we won't try to apply diffs.
+     */
+    public fun clearAllAppData()
 }

libs/database/src/main/java/org/fdroid/database/RepositoryDao.kt

@@ -378,6 +378,13 @@ internal interface RepositoryDaoInt : RepositoryDao {
     @Query("DELETE FROM ${ReleaseChannel.TABLE} WHERE repoId = :repoId AND id = :id")
     fun deleteReleaseChannel(repoId: Long, id: String)
 
+    /**
+     * Resets timestamps for *all* repos in the database.
+     * This will cause
+     */
+    @Query("UPDATE ${CoreRepository.TABLE} SET timestamp = -1")
+    fun resetTimestamps()
+
     /**
      * Use when replacing an existing repo with a full index.
      * This removes all existing index data associated with this repo from the database,