Issue warning when stocks are lower than required

src/Schedule.hs

@@ -3,28 +3,33 @@ module Schedule (
     schedule
   ) where
 
-import Data.Map (elems, mergeWithKey)
+import Data.Map ((!), elems, mergeWithKey)
 import Data.Time (Day, addDays)
-import Medicine (Pharmacy)
+import Medicine (Medicine(..), Pharmacy)
 import Timeline (State(..))
 import YAML ((.:), Value(..), YAML(..))
 
 data Schedule = Schedule {
       daysLeft :: Integer
-    , provisionDate :: Day
+    , provisionDate :: Maybe Day
   }
 
 instance YAML Schedule where
-  toYAML (Schedule {daysLeft, provisionDate}) = Object [
+  toYAML (Schedule {daysLeft, provisionDate = Nothing}) = Object [
+        "Warning" .: "Stock lower than the minimum security amount defined. Go now !"
+      , "Days left" .: daysLeft
+    ]
+  toYAML (Schedule {daysLeft, provisionDate = Just day}) = Object [
         "Days left" .: daysLeft
-      , "Provision on" .: provisionDate
+      , "Provision on" .: day
     ]
 
 schedule :: Pharmacy -> State -> Schedule
-schedule _ (State {day, stock, consumptionRate}) =
-  Schedule {daysLeft , provisionDate = daysLeft `addDays` day}
+schedule pharmacy (State {day, stock, consumptionRate}) =
+  Schedule {daysLeft , provisionDate = if daysLeft > 0 then Just $ daysLeft `addDays` day else Nothing}
   where
-    daysLeftByMedicine =
-      mergeWithKey (\_ a b -> Just $ a / b) id id stock consumptionRate
+    stockInDays medicineName stockLeft rate =
+      Just $ (stockLeft - minStock (pharmacy ! medicineName)) / rate
+    daysLeftByMedicine = mergeWithKey stockInDays id id stock consumptionRate
     daysLeft = truncate . minimum $ elems daysLeftByMedicine