start implementing property layering

owrx/property/__init__.py

@@ -119,3 +119,25 @@ class PropertyManager(object):
             if p.getValue() is None:
                 p.setValue(other_pm[key])
         return self
+
+
+class PropertyLayers(object):
+    def __init__(self):
+        self.layers = []
+
+    def addLayer(self, priority: int, pm: PropertyManager):
+        """
+        highest priority = 0
+        """
+        self.layers.append({"priority": priority, "props": pm})
+
+    def removeLayer(self, pm: PropertyManager):
+        for layer in self.layers:
+            if layer["props"] == pm:
+                self.layers.remove(layer)
+
+    def __getitem__(self, item):
+        layers = [la["props"] for la in sorted(self.layers, key=lambda l: l["priority"])]
+        for m in layers:
+            if item in m:
+                return m[item]

test/property/test_property_overlay.py

@@ -0,0 +1,43 @@
+from unittest import TestCase
+from unittest.mock import Mock
+from owrx.property import PropertyManager, PropertyLayers
+
+
+class TestPropertyMock(TestCase):
+    def testLayer(self):
+        om = PropertyLayers()
+        pm = PropertyManager()
+        pm["testkey"] = "testvalue"
+        om.addLayer(1, pm)
+        self.assertEqual(om["testkey"], "testvalue")
+
+    def testHighPriority(self):
+        om = PropertyLayers()
+        low_pm = PropertyManager()
+        high_pm = PropertyManager()
+        low_pm["testkey"] = "low value"
+        high_pm["testkey"] = "high value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        self.assertEqual(om["testkey"], "high value")
+
+    def testPriorityFallback(self):
+        om = PropertyLayers()
+        low_pm = PropertyManager()
+        high_pm = PropertyManager()
+        low_pm["testkey"] = "low value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        self.assertEqual(om["testkey"], "low value")
+
+    def testLayerRemoval(self):
+        om = PropertyLayers()
+        low_pm = PropertyManager()
+        high_pm = PropertyManager()
+        low_pm["testkey"] = "low value"
+        high_pm["testkey"] = "high value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        self.assertEqual(om["testkey"], "high value")
+        om.removeLayer(high_pm)
+        self.assertEqual(om["testkey"], "low value")