add CLI helpers, switch to bottle-sqlalchemy

groove/db/__init__.py

@@ -1 +1,2 @@
 from groove.db.schema import metadata, track, playlist, entry
+from groove.db.helpers import windowed_query

groove/db/helpers.py

@@ -0,0 +1,20 @@
+def windowed_query(query, column, window_size):
+    """"
+    Break a Query into chunks on a given column.
+
+    see: https://github.com/sqlalchemy/sqlalchemy/wiki/RangeQuery-and-WindowedRangeQuery
+    """
+    single_entity = query.is_single_entity
+    query = query.add_columns(column).order_by(column)
+    last_id = None
+
+    while True:
+        sub_query = query
+        if last_id is not None:
+            sub_query = sub_query.filter(column > last_id)
+        chunk = sub_query.limit(window_size).all()
+        if not chunk:
+            break
+        last_id = chunk[-1][-1]
+        for row in chunk:
+            yield row

groove/db/manager.py

@@ -0,0 +1,43 @@
+import os
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from . import metadata
+
+
+class DatabaseManager:
+    """
+    A context manager for working with sqllite database.
+    """
+
+    def __init__(self):
+        self._engine = None
+        self._session = None
+
+    @property
+    def engine(self):
+        if not self._engine:
+            self._engine = create_engine(f"sqlite:///{os.environ.get('DATABASE_PATH')}", future=True)
+        return self._engine
+
+    @property
+    def session(self):
+        if not self._session:
+            Session = sessionmaker(bind=self.engine, future=True)
+            self._session = Session()
+        return self._session
+
+    def import_from_filesystem(self):
+        pass
+
+    def __enter__(self):
+        metadata.create_all(bind=self.engine)
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        if self.session:
+            self.session.close()
+
+
+database_manager = DatabaseManager