Implement basic scheduling

src/Main.hs

@@ -1,12 +1,15 @@
+{-# LANGUAGE NamedFieldPuns #-}
 module Main where
 
 import CLI (Invocation(..), invoked)
 import CSV (Row, parse)
-import Data.Time (UTCTime(..), getCurrentTime)
+import Data.List (minimum)
+import Data.Map (elems, mergeWithKey)
+import Data.Time (UTCTime(..), getCurrentTime, addDays)
 import Event (Event)
 import Medicine (Medicine, Pharmacy, pharmacy)
 import System.Exit (exitFailure, exitSuccess)
-import Timeline (State, currentState)
+import Timeline (State(..), currentState)
 
 readCSV :: Row a => FilePath -> IO [a]
 readCSV filePath = do
@@ -22,10 +25,20 @@ getCurrentState =
   <*> (pharmacy <$> readCSV "medicine.csv")
   <*> readCSV "timeline.csv"
 
+schedule :: State -> String
+schedule (State {day, stock, consumptionRate}) = unlines [
+      "Days left: " ++ show deltaDays
+    , "Provision on: " ++ show (deltaDays `addDays` day )
+  ]
+  where
+    daysLeftByMedicine =
+      mergeWithKey (\k a b -> Just $ a / b) id id stock consumptionRate
+    deltaDays = truncate . minimum $ elems daysLeftByMedicine
+
 main :: IO ()
 main = do
   invocation <- invoked
   case invocation of
     Inventory -> show <$> getCurrentState >>= putStrLn
-    Schedule -> putStrLn "schedule"
+    Schedule -> schedule <$> getCurrentState >>= putStrLn
     Version version -> putStrLn version >> exitSuccess

src/Timeline.hs

@@ -1,6 +1,6 @@
 {-# LANGUAGE NamedFieldPuns #-}
 module Timeline (
-      State
+      State(..)
     , currentState
   ) where