Re-add part3

advanced/part3/src/Avatar.elm

@@ -0,0 +1,56 @@
+module Avatar exposing (Avatar, decoder, encode, src, toMaybeString)
+
+import Asset
+import Html exposing (Attribute)
+import Html.Attributes
+import Json.Decode as Decode exposing (Decoder)
+import Json.Encode as Encode exposing (Value)
+
+
+
+-- TYPES
+
+
+type Avatar
+    = Avatar (Maybe String)
+
+
+
+-- CREATE
+
+
+decoder : Decoder Avatar
+decoder =
+    Decode.map Avatar (Decode.nullable Decode.string)
+
+
+
+-- TRANSFORM
+
+
+encode : Avatar -> Value
+encode (Avatar maybeUrl) =
+    case maybeUrl of
+        Just url ->
+            Encode.string url
+
+        Nothing ->
+            Encode.null
+
+
+src : Avatar -> Attribute msg
+src (Avatar maybeUrl) =
+    case maybeUrl of
+        Nothing ->
+            Asset.src Asset.defaultAvatar
+
+        Just "" ->
+            Asset.src Asset.defaultAvatar
+
+        Just url ->
+            Html.Attributes.src url
+
+
+toMaybeString : Avatar -> Maybe String
+toMaybeString (Avatar maybeUrl) =
+    maybeUrl