1 files changed, 52 insertions, 0 deletions
diff --git a/mapping.py b/mapping.py
new file mode 100644
index 0000000..a01652f
--- /dev/null
+++ b/mapping.py
@@ -0,0 +1,52 @@
+import enum
+import os
+
+# A mapping defines how to convert part of a row to a dictionary for
+# an API response, and how to insert data from a received dictionary
+# back into the row.  In other words it allows you to quickly select
+# and rename a lot of fields.  This module deals with parsing them.
+# They are used in database and the path is chosen in myconfig.
+
+class Direction(enum.Flag):
+	TO = enum.auto()
+	FROM = enum.auto()
+
+Direction.BOTH = Direction.TO|Direction.FROM
+
+_direction_symbols = [("<", Direction.TO), (">", Direction.FROM)]
+
+def load_mappings(path):
+	mappings = {}
+	for fn in os.listdir(path):
+		with open(os.path.join(path, fn)) as f:
+			mapping = []
+			for l in f:
+				l = l.strip()
+				if l == "" or l.startswith("#"):
+					continue
+				cols = l.split()
+				dictname = cols.pop(0)
+				if cols:
+					direction = Direction(0)
+					dirstring = cols.pop(0)
+					for sym, val in _direction_symbols:
+						if sym in dirstring:
+							direction |= val
+				else:
+					direction = Direction.BOTH
+				if cols:
+					tablename = cols.pop(0)
+				else:
+					tablename = dictname
+				mapping.append((dictname, direction, tablename))
+			mappings[fn] = mapping
+	return mappings
+
+def map_to(row, mapping):
+	return {dictname: getattr(row, tablename) for dictname, direction, tablename in mapping if direction & direction.TO}
+
+def map_from(row, mapping, data):
+	for dictname, direction, tablename in mapping:
+			if direction & direction.FROM:
+				setattr(row, tablename, data[dictname])
+