Migration script to populate the returned letters.

migrations/versions/0311_populate_returned_letters.py

@@ -0,0 +1,30 @@
+"""
+
+Revision ID: 0311_populate_returned_letters
+Revises: 0310_returned_letters_table
+Create Date: 2019-12-09 12:13:49.432993
+
+"""
+from alembic import op
+
+from app.dao.returned_letters_dao import insert_or_update_returned_letters
+
+revision = '0311_populate_returned_letters'
+down_revision = '0310_returned_letters_table'
+
+
+def upgrade():
+    conn = op.get_bind()
+    sql = """
+        select id, service_id, reference 
+        from notification_history 
+        where notification_type = 'letter'
+        and notification_status = 'returned-letter'"""
+    results = conn.execute(sql)
+    returned_letters = results.fetchall()
+    references = [x.reference for x in returned_letters]
+    insert_or_update_returned_letters(references)
+
+
+def downgrade():
+    pass