basic food property calculation

cookbook/helper/food_property_helper.py

@@ -0,0 +1,29 @@
+from cookbook.models import FoodPropertyType
+
+
+def calculate_recipe_properties(recipe):
+    ingredients = []
+    computed_properties = {}
+
+    for s in recipe.steps.all():
+        ingredients += s.ingredients.all()
+
+    for fpt in FoodPropertyType.objects.filter(space=recipe.space).all():  # TODO is this safe or should I require the request context?
+        computed_properties[fpt.id] = {'name': fpt.name, 'food_values': {}, 'total_value': 0}
+
+    # TODO unit conversion support
+
+    for i in ingredients:
+        for p in i.food.foodproperty_set.all():
+            computed_properties[p.property_type.id]['total_value'] += (i.amount / p.food_amount) * p.property_amount
+            computed_properties[p.property_type.id]['food_values'][i.food.id] = add_or_create(computed_properties[p.property_type.id]['food_values'], i.food.id, (i.amount / p.food_amount) * p.property_amount)
+
+    return computed_properties
+
+# small dict helper to add to existing key or create new, probably a better way of doing this
+def add_or_create(d, key, value):
+    if key in d:
+        d[key] += value
+    else:
+        d[key] = value
+    return d