Store and check uid validity

app/src/main/java/eu/faircode/email/Core.java

@@ -985,6 +985,19 @@ class Core {
 
             db.folder().setFolderSyncState(folder.id, "syncing");
 
+            // Check uid validity
+            try {
+                long uidv = ifolder.getUIDValidity();
+                if (folder.uidv != null && folder.uidv.equals(uidv)) {
+                    Log.w(folder.name + " uid validity changed from " + folder.uidv + " to " + uidv);
+                    db.message().deleteLocalMessages(folder.id);
+                }
+                folder.uidv = uidv;
+                db.folder().setFolderUidValidity(folder.id, uidv);
+            } catch (MessagingException ex) {
+                Log.w(ex);
+            }
+
             // Get reference times
             Calendar cal_sync = Calendar.getInstance();
             cal_sync.add(Calendar.DAY_OF_MONTH, -sync_days);

app/src/main/java/eu/faircode/email/DB.java

@@ -57,7 +57,7 @@ import io.requery.android.database.sqlite.RequerySQLiteOpenHelperFactory;
 // https://developer.android.com/topic/libraries/architecture/room.html
 
 @Database(
-        version = 96,
+        version = 97,
         entities = {
                 EntityIdentity.class,
                 EntityAccount.class,
@@ -977,6 +977,13 @@ public abstract class DB extends RoomDatabase {
                                 " (SELECT COUNT(attachment.id) FROM attachment WHERE attachment.message = message.id)");
                     }
                 })
+                .addMigrations(new Migration(96, 97) {
+                    @Override
+                    public void migrate(@NonNull SupportSQLiteDatabase db) {
+                        Log.i("DB migration from version " + startVersion + " to " + endVersion);
+                        db.execSQL("ALTER TABLE `folder` ADD COLUMN `uidv` INTEGER");
+                    }
+                })
                 .build();
     }
 

app/src/main/java/eu/faircode/email/DaoFolder.java

@@ -278,6 +278,9 @@ public interface DaoFolder {
     @Query("UPDATE folder SET keep_days = :days WHERE id = :id")
     int setFolderKeep(long id, int days);
 
+    @Query("UPDATE folder SET uidv = :uidv WHERE id = :id")
+    int setFolderUidValidity(long id, Long uidv);
+
     @Query("UPDATE folder SET last_sync = :last_sync WHERE id = :id")
     int setFolderSync(long id, long last_sync);
 

app/src/main/java/eu/faircode/email/EntityFolder.java

@@ -64,6 +64,7 @@ public class EntityFolder extends EntityOrder implements Serializable {
     public Long id;
     public Long account; // Outbox = null
     public Long parent;
+    public Long uidv; // UIDValidity
     @NonNull
     public String name;
     @NonNull
@@ -287,6 +288,7 @@ public class EntityFolder extends EntityOrder implements Serializable {
             EntityFolder other = (EntityFolder) obj;
             return (this.id.equals(other.id) &&
                     Objects.equals(this.account, other.account) &&
+                    Objects.equals(this.uidv, other.uidv) &&
                     this.name.equals(other.name) &&
                     this.type.equals(other.type) &&
                     this.synchronize.equals(other.synchronize) &&