New Style Generator (#8)

1 files changed, 52 insertions, 0 deletions

diff --git a/style-generator/src/Decoder/Generic.elm b/style-generator/src/Decoder/Generic.elm
new file mode 100644
index 0000000..b81167e
--- /dev/null
+++ b/style-generator/src/Decoder/Generic.elm
@@ -0,0 +1,52 @@
+module Decoder.Generic exposing (combine, pair, resultToDecoder, subdecode, tail, withDefault)
+
+import Json.Decode as D exposing (Decoder)
+
+
+withDefault : a -> Decoder a -> Decoder a
+withDefault fallback decoder =
+    D.oneOf
+        [ decoder
+        , D.succeed fallback
+        ]
+
+
+combine : List (Decoder a) -> Decoder (List a)
+combine =
+    List.foldr (D.map2 (::)) (D.succeed [])
+
+
+subdecode : Decoder a -> D.Value -> Decoder a
+subdecode d v =
+    D.decodeValue d v |> resultToDecoder
+
+
+tail : Decoder a -> Decoder (List a)
+tail itemDecoder =
+    D.list D.value
+        |> D.andThen
+            (\l ->
+                case l of
+                    [] ->
+                        D.fail "Can't get tail of empty"
+
+                    head :: t ->
+                        List.map (subdecode itemDecoder) t |> combine
+            )
+
+
+pair : Decoder a -> Decoder b -> Decoder ( a, b )
+pair aDecoder bDecoder =
+    D.map2 Tuple.pair
+        (D.index 0 aDecoder)
+        (D.index 1 bDecoder)
+
+
+resultToDecoder : Result D.Error a -> Decoder a
+resultToDecoder res =
+    case res of
+        Ok a ->
+            D.succeed a
+
+        Err e ->
+            D.fail (D.errorToString e)