Refactor Gigasecond.add to Speak Date Instead of String

exercises/gigasecond/Gigasecond.example

@@ -2,120 +2,13 @@ module Gigasecond exposing (add)
 
 import Date
 import Time
-import String
 
 
-add : String -> Result String String
+add : Date.Date -> Date.Date
-add x =
+add =
-    x
+    Date.toTime >> (+) gigasecond >> Date.fromTime
-        |> Date.fromString
-        |> Result.map (add' gigasecond)
-        |> Result.map format
-
-
-add' : Time.Time -> Date.Date -> Date.Date
-add' t d =
-    d
-        |> Date.toTime
-        |> flip (+) t
-        |> Date.fromTime
 
 
 gigasecond : Time.Time
 gigasecond =
     10 ^ 12
-
-
-format : Date.Date -> String
-format date =
-    let
-        date =
-            toGMT date
-    in
-        --toString date
-        [ Date.year date
-            |> toString
-        , "-"
-        , Date.month date
-            |> monthToInt
-            |> Maybe.withDefault 1
-            |> toString
-            |> String.pad 2 '0'
-        , "-"
-        , Date.day date
-            |> toString
-            |> String.pad 2 '0'
-        , "T"
-        , Date.hour date
-            |> toString
-            |> String.pad 2 '0'
-        , ":"
-        , Date.minute date
-            |> toString
-            |> String.pad 2 '0'
-        , ":"
-        , Date.second date
-            |> toString
-            |> String.pad 2 '0'
-        ]
-            |> String.concat
-
-
-monthToInt : Date.Month -> Maybe Int
-monthToInt n =
-    case n of
-        Date.Jan ->
-            Just 1
-
-        Date.Feb ->
-            Just 2
-
-        Date.Mar ->
-            Just 3
-
-        Date.Apr ->
-            Just 4
-
-        Date.May ->
-            Just 5
-
-        Date.Jun ->
-            Just 6
-
-        Date.Jul ->
-            Just 7
-
-        Date.Aug ->
-            Just 8
-
-        Date.Sep ->
-            Just 9
-
-        Date.Oct ->
-            Just 10
-
-        Date.Nov ->
-            Just 11
-
-        Date.Dec ->
-            Just 12
-
-
-toGMT : Date.Date -> Date.Date
-toGMT date =
-    let
-        tzOffset =
-            date
-                |> toString
-                |> String.split " "
-                |> List.drop 5
-                |> List.head
-                |> Maybe.withDefault "GMT-0000"
-                |> String.dropLeft 3
-                |> String.toInt
-                |> Result.withDefault 0
-                |> flip (//) 100
-                |> toFloat
-                |> (*) -Time.hour
-    in
-        add' tzOffset date

exercises/gigasecond/GigasecondTests.elm

@@ -4,6 +4,7 @@ import Test.Runner.Node exposing (run)
 import Json.Encode exposing (Value)
 import Test exposing (..)
 import Expect
+import Date
 import Gigasecond exposing (add)
 
 
@@ -13,23 +14,33 @@ tests =
         [ describe "add"
             [ test "2011-04-25" <|
                 \() ->
-                    Expect.equal (Ok "2043-01-01T01:46:40") (Gigasecond.add "2011-04-25")
+                    Expect.equal (actual "2011-04-25") (expected "2043-01-01T01:46:40")
             , test "1977-06-13" <|
                 \() ->
-                    Expect.equal (Ok "2009-02-19T01:46:40") (Gigasecond.add "1977-06-13")
+                    Expect.equal (actual "1977-06-13") (expected "2009-02-19T01:46:40")
             , test "1959-07-19" <|
                 \() ->
-                    Expect.equal (Ok "1991-03-27T01:46:40") (Gigasecond.add "1959-07-19")
+                    Expect.equal (actual "1959-07-19") (expected "1991-03-27T01:46:40")
             , test "full time specified" <|
                 \() ->
-                    Expect.equal (Ok "2046-10-02T23:46:40") (Gigasecond.add "2015-01-24T22:00:00")
+                    Expect.equal (actual "2015-01-24T22:00:00") (expected "2046-10-02T23:46:40")
             , test "full time with day roll-over" <|
                 \() ->
-                    Expect.equal (Ok "2046-10-03T01:46:39") (Gigasecond.add "2015-01-24T23:59:59")
+                    Expect.equal (actual "2015-01-24T23:59:59") (expected "2046-10-03T01:46:39")
             ]
         ]
 
 
+actual : String -> Result String Date.Date
+actual =
+    Date.fromString >> Result.map Gigasecond.add
+
+
+expected : String -> Result String Date.Date
+expected =
+    Date.fromString
+
+
 main : Program Value
 main =
     run emit tests