Rename more stuff

intro/part4/src/Views/User/Follow.elm

@@ -0,0 +1,41 @@
+module Views.User.Follow exposing (State, button)
+
+{-| The Follow button.
+
+This API accepts a "toggle follow" message and the current state of whether
+the user is already being followed. It's very lightweight!
+
+It would be overkill to give something this simple its own Model, Msg, and
+update. That would make it way more work to use than it needed to be,
+and for no benefit.
+
+-}
+
+import Data.User as User exposing (Username)
+import Html exposing (Html, i, text)
+import Html.Attributes exposing (class)
+import Html.Events exposing (onClick)
+
+
+type alias State record =
+    { record | following : Bool, username : Username }
+
+
+button : (Username -> msg) -> State record -> Html msg
+button toggleFollow { following, username } =
+    let
+        ( prefix, secondaryClass ) =
+            if following then
+                ( "Unfollow", "btn-secondary" )
+            else
+                ( "Follow", "btn-outline-secondary" )
+
+        classes =
+            [ "btn", "btn-sm", secondaryClass, "action-btn" ]
+                |> String.join " "
+                |> class
+    in
+    Html.button [ classes, onClick (toggleFollow username) ]
+        [ i [ class "ion-plus-round" ] []
+        , text (" " ++ prefix ++ " " ++ User.usernameToString username)
+        ]