jblite/db.py

   1 """Base database object support."""
   2
   3 from table import Record
   4
   5
   6 class Database(object):
   7
   8     entry_class = None
   9     table_map = None
  10
  11     def __init__(self):
  12         self.tables = {}
  13
  14     def lookup(self, key, entry_id):
  15         """Creates an entry object.
  16
  17         Finds a record table based upon the entry table.  (This
  18         contains all data for an entry.)  This is then wrapped in an
  19         Entry object which provides logic for displaying or otherwise
  20         using the data.
  21
  22         """
  23         # Lookup data in entry table.
  24         data = self.tables[key].lookup_by_id(entry_id)  # 1 row only
  25         # Lookup child data using the entry_id as a foreign key.
  26         children = self._lookup_children(self.table_map[key], data['id'])
  27         record = Record(data, children)
  28         return self.entry_class(record)
  29
  30     def _lookup_children(self, children_map, fk):
  31         children = {}
  32         for child_table in children_map:
  33             grandchild_map = children_map[child_table]
  34             rows = self._lookup_by_fk(child_table,
  35                                       children_map[child_table], fk)
  36             if len(rows) > 0:
  37                 children[child_table] = rows
  38         return children
  39
  40     def _lookup_by_fk(self, table_name, children_map, fk):
  41         """Looks up data from a table and related 'child' tables.
  42
  43         table_name: name of the table to query.
  44         children_map: a dictionary of child table mappings, or None if
  45             no children are present.
  46         fk: foreign key used in table query.
  47
  48         """
  49         rows = self.tables[table_name].lookup_by_fk(fk)
  50         results = []
  51         for row in rows:
  52             children = self._lookup_children(children_map, row['id'])
  53             record = Record(row, children)
  54             results.append(record)
  55         return results