Add part5

intro/part5/src/Api.elm

@@ -0,0 +1,53 @@
+module Api exposing (addServerError, decodeErrors, url)
+
+import Http
+import Json.Decode as Decode exposing (Decoder, decodeString, field, string)
+import Json.Decode.Pipeline as Pipeline exposing (optional)
+import Url.Builder
+
+
+
+-- URL
+
+
+{-| Get a URL to the Conduit API.
+-}
+url : List String -> String
+url paths =
+    -- NOTE: Url.Builder takes care of percent-encoding special URL characters.
+    -- See https://package.elm-lang.org/packages/elm/url/latest/Url#percentEncode
+    Url.Builder.relative ("api" :: paths) []
+
+
+
+-- ERRORS
+
+
+addServerError : List String -> List String
+addServerError list =
+    "Server error" :: list
+
+
+{-| Many API endpoints include an "errors" field in their BadStatus responses.
+-}
+decodeErrors : Http.Error -> List String
+decodeErrors error =
+    case error of
+        Http.BadStatus response ->
+            response.body
+                |> decodeString (field "errors" errorsDecoder)
+                |> Result.withDefault [ "Server error" ]
+
+        err ->
+            [ "Server error" ]
+
+
+errorsDecoder : Decoder (List String)
+errorsDecoder =
+    Decode.keyValuePairs (Decode.list Decode.string)
+        |> Decode.map (List.concatMap fromPair)
+
+
+fromPair : ( String, List String ) -> List String
+fromPair ( field, errors ) =
+    List.map (\error -> field ++ " " ++ error) errors