--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/py/params.py	Thu Nov 29 23:50:40 2012 +0800
@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+import collections
+import json
+import config
+
+_FIELD_DEFAULTS = {
+    'fridge_setpoint': 16,
+    'fridge_difference': 0.2,
+    'overshoot_delay': 720, # 12 minutes
+    'overshoot_factor': 1, # ºC
+    }
+
+class Params(dict):
+    class Error(Exception):
+        pass
+
+    def __init__(self):
+        self.update(_FIELD_DEFAULTS)
+
+    def __getattr__(self, k):
+        return self[k]
+
+    def __setattr__(self, k, v):
+        # fail if we set a bad value
+        self[k]
+        self[k] = v
+
+    def load(self, f = None):
+        if not f:
+            f = file(config.PARAMS_FILE, 'r')
+        u = json.load(f)
+        for k in u:
+            if k not in self:
+                raise self.Error("Unknown parameter %s=%s in file '%s'" % (str(k), str(u[k]), getattr(f, 'name', '???')))
+        self.update(u)
+
+    def save(self, f = None):
+        if not f:
+            f = file(config.PARAMS_FILE, 'w')
+        json.dump(self, f, sort_keys=True, indent=4)
+        f.flush()