Clock.hs

Clock.hs

module Clock (addDelta, fromHourMin, toString) where

import           Text.Printf

newtype Clock = Clock Int
  deriving Eq

instance Semigroup Clock where
  Clock a <> Clock b = mkClock $ a + b

mkClock :: Int -> Clock
mkClock minutes = Clock $ minutes `mod` (24 * 60)

fromHourMin :: Int -> Int -> Clock
fromHourMin hours minutes = mkClock $ hours * 60 + minutes

toString :: Clock -> String
toString (Clock m) = printf "%02d:%02d" (m `div` 60) (m `mod` 60)

addDelta :: Int -> Int -> Clock -> Clock
addDelta hours minutes clock =
  clock <> fromHourMin hours minutes