Add database migration functionality

- Added _migrate_db() for database migrations.
- Checks current database version for updates.
- Replaced 'response' with 'responses' in dictionary.

devchat/store.py

@@ -3,7 +3,8 @@
 from typing import List, Dict, Any, Optional
 from xml.etree.ElementTree import ParseError
 import networkx as nx
-from tinydb import TinyDB, where
+from tinydb import TinyDB, where, Query
+from tinydb.table import Table
 from devchat.chat import Chat
 from devchat.prompt import Prompt
 from devchat.utils import get_logger
@@ -37,11 +38,34 @@ def __init__(self, store_dir: str, chat: Chat):
             self._graph = nx.DiGraph()
 
         self._db = TinyDB(self._db_path)
+        self._db_meta = self._migrate_db()
         self._topics_table = self._db.table('topics')
 
-        if not self._topics_table or self._topics_table.all() == []:
+        if not self._topics_table or not self._topics_table.all():
             self._initialize_topics_table()
 
+    def _migrate_db(self) -> Table:
+        """
+        Migrate the database to the latest version.
+        """
+        metadata = self._db.table('metadata')
+
+        result = metadata.get(where('version').exists())
+        if not result or result['version'].startswith('0.1.'):
+            def replace_response():
+                def transform(doc):
+                    if '_new_messages' not in doc or 'response' not in doc['_new_messages']:
+                        logger.error("Prompt %s does not match '_new_messages.response'",
+                                     doc['_hash'])
+                    doc['_new_messages']['responses'] = doc['_new_messages'].pop('response')
+                return transform
+
+            logger.info("Migrating database from %s to 0.2.0", result)
+            self._db.update(replace_response(),
+                            Query()._new_messages.response.exists())  # pylint: disable=W0212
+            metadata.insert({'version': '0.2.0'})
+        return metadata
+
     def _initialize_topics_table(self):
         roots = [node for node in self._graph.nodes() if self._graph.out_degree(node) == 0]
         for root in roots: