fix cvc validation

.gitignore

@@ -0,0 +1,2 @@
+.stack-work
+.hie-yaml

spec/CreditCardSpec.hs

@@ -72,6 +72,29 @@ wrongNumbers =
   , "353011133330000"
   , "3566002028360505" ]
 
+correctCvc :: [Text]
+correctCvc =
+  [ "311"
+  , "3211"
+  , "9999"
+  , "0000"
+  , "000"
+  , "1234"
+  , "111"
+  ]
+
+wrongCvc :: [Text]
+wrongCvc =
+  [ "31111"
+  , "a31"
+  , "zzz"
+  , "00O"
+  , "000O"
+  , "OOO"
+  , "11111"
+  , "11"
+  ]
+
 checkNumbers :: [Text] -> CreditCardType -> Spec
 checkNumbers ns t = describe (show t) $ do
   for_ ns $ \n -> it (T.unpack n) $ do
@@ -94,3 +117,7 @@ spec = describe "Credit card number validation" $ do
     (parseExpirationDate . formatExpiryDate) d == Just d
   prop "JSON instances isomorphism" $ \(cc :: CreditCard) ->
     (decode . encode) cc == Just cc
+  it "Wrong CVC" $ for_ wrongCvc $ \cvc -> do
+    parseCreditCardSecurity cvc `shouldBe` Nothing
+  it "Correct CVC" $ for_ correctCvc $ \cvc -> do
+    parseCreditCardSecurity cvc `shouldBe` Just (CreditCardSecurity cvc)

src/Data/CreditCard.hs

@@ -54,7 +54,6 @@ import Control.Lens hiding (elements)
 import Control.Monad (guard)
 import Data.Aeson as Aeson
 import Data.Aeson.Inflections (defaultFieldLabelModifier)
-import Data.Aeson.Types (withText)
 import Data.Char (isDigit)
 import Data.Digit
 import Data.Either (isRight)
@@ -245,7 +244,7 @@ parseCreditCardSecurity txt
   | otherwise = Nothing
   where
     isValid = and
-      [ T.length txt == 3
+      [ (3, 4) `inRange` T.length txt
       , T.all isDigit txt ]
 
 data CreditCard = CreditCard

stack.yaml.lock

@@ -0,0 +1,45 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages:
+- completed:
+    name: aeson-inflections
+    version: 0.1.0.0
+    git: https://github.com/typeable/aeson-inflections
+    pantry-tree:
+      size: 305
+      sha256: 306e91dd974dae0170d0b7cf7b74769782b4d4342575a2e39d82224ac69d6dad
+    commit: 66ac49cc1e468f36bf9d6c78b73bdabcfca0855d
+  original:
+    git: https://github.com/typeable/aeson-inflections
+    commit: 66ac49cc1e468f36bf9d6c78b73bdabcfca0855d
+- completed:
+    name: digit
+    version: 0.1.0.0
+    git: https://github.com/typeable/digit.git
+    pantry-tree:
+      size: 314
+      sha256: 41a3214a12218a1cf85baa3dc33292491b662c32218ba88ce0f0e27478e1d78c
+    commit: e03f087c90c9228a9ae52a0e516eba22589eef94
+  original:
+    git: https://github.com/typeable/digit.git
+    commit: e03f087c90c9228a9ae52a0e516eba22589eef94
+- completed:
+    name: missing-lens
+    version: 0.1.0.0
+    git: https://github.com/typeable/missing-lens.git
+    pantry-tree:
+      size: 221
+      sha256: ab572e39921e6f367dbc4b0a8df29fa170dc4ab015e407c4dfe03d84d07665ec
+    commit: 328659fdda8fd7ec509abfab6298775062fc2926
+  original:
+    git: https://github.com/typeable/missing-lens.git
+    commit: 328659fdda8fd7ec509abfab6298775062fc2926
+snapshots:
+- completed:
+    size: 616897
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/19/0.yaml
+    sha256: bbf2be02f17940bac1f87cb462d4fb0c3355de6dcfc53d84f4f9ad3ee2164f65
+  original: lts-19.0