Fix confirm dialog database change

Gdrive setup basically working again
Moved basicconfig behind login
Database setup separated from other setup
Config page is using ajax (flask >2 and slow computers)

cps/db.py

@@ -524,19 +524,44 @@ class CalibreDB():
         return cc_classes
 
     @classmethod
-    def setup_db(cls, config, app_db_path):
+    def check_valid_db(cls, config_calibre_dir, app_db_path):
+        if not config_calibre_dir:
+            return False
+        dbpath = os.path.join(config_calibre_dir, "metadata.db")
+        if not os.path.exists(dbpath):
+            return False
+        try:
+            check_engine = create_engine('sqlite://',
+                          echo=False,
+                          isolation_level="SERIALIZABLE",
+                          connect_args={'check_same_thread': False},
+                          poolclass=StaticPool)
+            with check_engine.begin() as connection:
+                connection.execute(text("attach database '{}' as calibre;".format(dbpath)))
+                connection.execute(text("attach database '{}' as app_settings;".format(app_db_path)))
+            check_engine.connect()
+        except Exception:
+            return False
+        return True
+
+    @classmethod
+    def update_config(cls, config):
         cls.config = config
+
+    @classmethod
+    def setup_db(cls, config_calibre_dir, app_db_path):
+        # cls.config = config
         cls.dispose()
 
         # toDo: if db changed -> delete shelfs, delete download books, delete read boks, kobo sync??
 
-        if not config.config_calibre_dir:
-            config.invalidate()
+        if not config_calibre_dir:
+            cls.config.invalidate()
             return False
 
-        dbpath = os.path.join(config.config_calibre_dir, "metadata.db")
+        dbpath = os.path.join(config_calibre_dir, "metadata.db")
         if not os.path.exists(dbpath):
-            config.invalidate()
+            cls.config.invalidate()
             return False
 
         try:
@@ -552,10 +577,10 @@ class CalibreDB():
             conn = cls.engine.connect()
             # conn.text_factory = lambda b: b.decode(errors = 'ignore') possible fix for #1302
         except Exception as ex:
-            config.invalidate(ex)
+            cls.config.invalidate(ex)
             return False
 
-        config.db_configured = True
+        cls.config.db_configured = True
 
         if not cc_classes:
             try:
@@ -828,7 +853,8 @@ class CalibreDB():
     def reconnect_db(self, config, app_db_path):
         self.dispose()
         self.engine.dispose()
-        self.setup_db(config, app_db_path)
+        self.setup_db(config.config_calibre_dir, app_db_path)
+        self.update_config(config)
 
 
 def lcase(s):