Add more defaults, add Data.Status

src/Data/Status.elm

@@ -0,0 +1,167 @@
+module Data.Status exposing
+    ( Status(..)
+    , cons
+    , fromResult
+    , map
+    , map2
+    , map3
+    , mapError
+    , sequence
+    , traverse
+    , withDefault
+    )
+
+-- STATUS
+
+
+type Status err result
+    = NotAsked
+    | Failure err (List err)
+    | Loading
+    | Success result
+
+
+
+-- MAP ERROR
+
+
+mapError : (x -> y) -> Status x a -> Status y a
+mapError func status =
+    case status of
+        NotAsked ->
+            NotAsked
+
+        Failure err errors ->
+            Failure (func err) (List.map func errors)
+
+        Loading ->
+            Loading
+
+        Success a ->
+            Success a
+
+
+
+-- MAPPING
+
+
+map : (a -> b) -> Status x a -> Status x b
+map func status =
+    case status of
+        NotAsked ->
+            NotAsked
+
+        Failure err errors ->
+            Failure err errors
+
+        Loading ->
+            Loading
+
+        Success a ->
+            Success (func a)
+
+
+map2 : (a -> b -> result) -> Status x a -> Status x b -> Status x result
+map2 func aStatus bStatus =
+    case ( aStatus, bStatus ) of
+        ( Success a, Success b ) ->
+            Success (func a b)
+
+        _ ->
+            case toErrors aStatus ++ toErrors bStatus of
+                [] ->
+                    Loading
+
+                err :: errors ->
+                    Failure err errors
+
+
+map3 : (a -> b -> c -> result) -> Status x a -> Status x b -> Status x c -> Status x result
+map3 func aStatus bStatus cStatus =
+    case ( aStatus, bStatus, cStatus ) of
+        ( Success a, Success b, Success c ) ->
+            Success (func a b c)
+
+        _ ->
+            case toErrors aStatus ++ toErrors bStatus ++ toErrors cStatus of
+                [] ->
+                    Loading
+
+                err :: errors ->
+                    Failure err errors
+
+
+
+-- CONS
+
+
+cons : Status a b -> Status a (List b) -> Status a (List b)
+cons aStatus bStatus =
+    case ( aStatus, bStatus ) of
+        ( Success a, Success b ) ->
+            Success (a :: b)
+
+        ( Failure _ _, Success b ) ->
+            Success b
+
+        _ ->
+            case toErrors aStatus ++ toErrors bStatus of
+                [] ->
+                    Loading
+
+                err :: errors ->
+                    Failure err errors
+
+
+toErrors : Status x a -> List x
+toErrors status =
+    case status of
+        NotAsked ->
+            []
+
+        Failure e es ->
+            e :: es
+
+        Loading ->
+            []
+
+        Success _ ->
+            []
+
+
+traverse : (a -> Status err b) -> List a -> Status err (List b)
+traverse func list =
+    sequence (List.map func list)
+
+
+sequence : List (Status err a) -> Status err (List a)
+sequence status =
+    List.foldr (map2 (::)) (Success []) status
+
+
+
+-- FROM RESULT
+
+
+fromResult : Result err a -> Status err a
+fromResult result =
+    case result of
+        Ok x ->
+            Success x
+
+        Err err ->
+            Failure err []
+
+
+
+-- UNWRAP
+
+
+withDefault : a -> Status err a -> a
+withDefault default status =
+    case status of
+        Success s ->
+            s
+
+        _ ->
+            default

src/Main.elm

@@ -48,11 +48,12 @@ type Page
 
 init : flags -> Url -> Navigation.Key -> ( Model, Cmd Msg )
 init _ url key =
-    onNavigation
-        { route = Route.fromUrl url
-        , page = Loading
-        , key = key
-        }
+    Debug.log "init" <|
+        onNavigation
+            { route = Route.fromUrl url
+            , page = Loading
+            , key = key
+            }
 
 
 
@@ -104,16 +105,24 @@ mapPage model toPage toMsg ( page, cmds ) =
     )
 
 
+{-| Map a Route (a parsed url) to a Page and initialize the modules Model.
+
+This is the place you fetch data to render the page.
+
+-}
 onNavigation : Model -> ( Model, Cmd Msg )
 onNavigation model =
     case model.route of
         Route.Root ->
             mapPage model Home HomeMsg <|
                 Page.Home.init
 
-        Route.Article _ ->
+        Route.Article (Just id) ->
             mapPage model Article ArticleMsg <|
-                Page.Article.init
+                Page.Article.init id
+
+        Route.Article Nothing ->
+            ( model, Cmd.none )
 
         Route.NotFound ->
             ( model, Cmd.none )

src/Page/Article.elm

@@ -6,37 +6,44 @@ module Page.Article exposing
     , view
     )
 
+import Data.Id as Id exposing (Id)
+import Data.Status as Status exposing (Status)
 import Html exposing (..)
 import Html.Attributes exposing (..)
 import Html.Events exposing (..)
+import Http
 
 
 
 -- MODEL
 
 
 type alias Model =
-    ()
+    { data : Status Http.Error String }
 
 
-init : ( Model, Cmd Msg )
-init =
-    ( (), Cmd.none )
+init : Id Id.Article -> ( Model, Cmd Msg )
+init articleId =
+    ( { data = Status.NotAsked }
+    , Cmd.none
+    )
 
 
 
 -- UPDATE
 
 
 type Msg
-    = NoOp
+    = GotData (Result Http.Error String)
 
 
 update : Msg -> Model -> ( Model, Cmd Msg )
 update msg model =
     case msg of
-        NoOp ->
-            ( model, Cmd.none )
+        GotData data ->
+            ( { model | data = Status.fromResult data }
+            , Cmd.none
+            )
 
 
 
@@ -47,7 +54,23 @@ view : Model -> { title : String, page : List (Html Msg) }
 view model =
     { title = "Article"
     , page =
-        [ header [] [ h1 [] [ text "Article page" ] ]
-        , main_ [] []
+        [ header [] [ h1 [] [ text "Article" ] ]
+        , main_ [] (viewPage model)
         ]
     }
+
+
+viewPage : Model -> List (Html Msg)
+viewPage model =
+    case model.data of
+        Status.NotAsked ->
+            [ text "not asked" ]
+
+        Status.Loading ->
+            [ text "loading" ]
+
+        Status.Failure err _ ->
+            [ text "error" ]
+
+        Status.Success data ->
+            [ text data ]

src/Page/Home.elm

@@ -6,37 +6,43 @@ module Page.Home exposing
     , view
     )
 
+import Data.Status as Status exposing (Status)
 import Html exposing (..)
 import Html.Attributes exposing (..)
 import Html.Events exposing (..)
+import Http
 
 
 
 -- MODEL
 
 
 type alias Model =
-    ()
+    { data : Status Http.Error String }
 
 
 init : ( Model, Cmd Msg )
 init =
-    ( (), Cmd.none )
+    ( { data = Status.NotAsked }
+    , Cmd.none
+    )
 
 
 
 -- UPDATE
 
 
 type Msg
-    = NoOp
+    = GotData (Result Http.Error String)
 
 
 update : Msg -> Model -> ( Model, Cmd Msg )
 update msg model =
     case msg of
-        NoOp ->
-            ( model, Cmd.none )
+        GotData data ->
+            ( { model | data = Status.fromResult data }
+            , Cmd.none
+            )
 
 
 
@@ -48,6 +54,22 @@ view model =
     { title = "Home"
     , page =
         [ header [] [ h1 [] [ text "Homepage" ] ]
-        , main_ [] []
+        , main_ [] (viewPage model)
         ]
     }
+
+
+viewPage : Model -> List (Html Msg)
+viewPage model =
+    case model.data of
+        Status.NotAsked ->
+            [ text "not asked" ]
+
+        Status.Loading ->
+            [ text "loading" ]
+
+        Status.Failure err _ ->
+            [ text "error" ]
+
+        Status.Success data ->
+            [ text data ]