Solve 'Can Santa save Christmas?' kata

Author: borisskert

src/SaveChristmas.hs

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+module SaveChristmas (determineTime) where
+
+-- https://www.codewars.com/kata/5857e8bb9948644aa1000246/train/haskell
+
+import Data.Maybe (fromJust, mapMaybe)
+import Data.Time (DiffTime, defaultTimeLocale, diffTimeToPicoseconds, parseTimeM)
+
+determineTime :: [String] -> Bool
+determineTime arr = needed <= oneDay
+  where
+    needed = sum . map diffTimeToPicoseconds . mapMaybe readDiffTime $ arr :: Integer
+    oneDay = readPicoseconds "24:00:00"
+
+readPicoseconds :: String -> Integer
+readPicoseconds = diffTimeToPicoseconds . fromJust . readDiffTime
+
+readDiffTime :: String -> Maybe DiffTime
+readDiffTime = parseTimeM True defaultTimeLocale "%H:%M:%S"

test/SaveChristmasSpec.hs

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+module SaveChristmasSpec where
+
+import SaveChristmas (determineTime)
+import Test.Hspec
+
+spec :: Spec
+spec = do
+  describe "Fixed Tests" $ do
+    mapM_
+      (uncurry fixedTest)
+      [ (["01:00:00", "02:30:00"], True),
+        (["01:00:00", "02:30:00", "22:00:00"], False),
+        (["12:00:00", "12:00:00"], True),
+        ([], True)
+      ]
+
+fixedTest :: [String] -> Bool -> Spec
+fixedTest arr expected = it (show arr) $ determineTime arr `shouldBe` expected