I think we've now hit what one might consider to be a good baseline

README.md

@@ -15,13 +15,12 @@ make serve
 
 Now open `http://localhost:8000` in your browser.
 
-# Viewing
-
-Open index.html in your browser.
-
 # TODO
 
  - [x] Add Makefile
+ - [ ] Determine if `src/Body.elm` or pages in `sr/Page` should have subscription functions
+ - [ ] use actix backend that maps most root requests to serve `actix_file::Files`
+ - [ ] Submit to slack for feedback...
  - [ ] Refactor into router page
  - [ ] Handle back-navigation
  - [ ] Add `default.nix`

src/Body.elm

@@ -0,0 +1,66 @@
+module Body exposing (Msg(..), Model(..), init, update, view)
+
+import Element
+
+import Page.About
+import Page.Contact
+import Page.Landing
+import Page.Products
+import Page.Resources
+
+type Msg
+    = MsgLanding    Page.Landing.Msg
+    | MsgProducts   Page.Products.Msg
+    | MsgResources  Page.Resources.Msg
+    | MsgAbout      Page.About.Msg
+    | MsgContact    Page.Contact.Msg
+
+type Model
+    = ModelLanding   Page.Landing.Model
+    | ModelProducts  Page.Products.Model
+    | ModelResources Page.Resources.Model
+    | ModelAbout     Page.About.Model
+    | ModelContact   Page.Contact.Model
+
+init : () -> Model
+init flags = ModelLanding (Page.Landing.init flags)
+
+update : Msg -> Model -> (Model, Cmd Msg)
+update bodyMsg bodyModel =
+    let
+        updatePage msg model updateFn wrapMsg toBodyModel =
+            let
+                (newModel, cmd) = updateFn msg model
+            in
+                (toBodyModel newModel, Cmd.map wrapMsg cmd)
+    in
+    case (bodyMsg, bodyModel) of
+        (MsgLanding msg, ModelLanding m) ->
+            updatePage msg m Page.Landing.update MsgLanding ModelLanding
+
+        (MsgProducts msg, ModelProducts m) ->
+            updatePage msg m Page.Products.update MsgProducts ModelProducts
+
+        (MsgResources msg, ModelResources m) ->
+            updatePage msg m Page.Resources.update MsgResources ModelResources
+
+        (MsgAbout msg, ModelAbout m) ->
+            updatePage msg m Page.About.update MsgAbout ModelAbout
+
+        (MsgContact msg, ModelContact m) ->
+            updatePage msg m Page.Contact.update MsgContact ModelContact
+
+        _ ->
+            (bodyModel, Cmd.none)
+
+view : Model -> Element.Element Msg
+view model =
+    let
+        content = case model of
+            ModelLanding m   -> Page.Landing.view m     |> Element.map MsgLanding
+            ModelProducts m -> Page.Products.view m     |> Element.map MsgProducts
+            ModelResources m -> Page.Resources.view m   |> Element.map MsgResources
+            ModelAbout m     -> Page.About.view m       |> Element.map MsgAbout
+            ModelContact m   -> Page.Contact.view m     |> Element.map MsgContact
+    in
+        Element.el [Element.centerY ,Element.centerX] content

src/Header.elm

@@ -1,18 +1,17 @@
-module Header exposing (Model, Msg(..), view, init)
+module Header exposing (Model, Msg, view, init, update)
 import Element exposing (Element)
 import Element.Events
 import Element.Border
 
 type alias Model = {}
-type Msg
-    = ClickedProducts
-    | ClickedResources
-    | ClickedAbout
-    | ClickedContact
+type alias Msg = {}
 
 init : () -> Model
 init flags = {}
 
+update : Msg -> Model -> (Model, Cmd Msg)
+update msg model = (model, Cmd.none)
+
 view : Model -> Element Msg
 view model =
     let

src/Main.elm

@@ -1,35 +1,35 @@
 module Main exposing (main)
 
+-- external imports
 import Browser
 import Url
 import Html exposing (Html)
 import Element exposing (Element, el, text, column)
 import String exposing (right)
 import Browser.Navigation
-
-import Page.Landing
-import Header
+import Browser exposing (UrlRequest)
 import Html exposing (header)
 
+-- internal imports
+import Body
+import Header
 
--- MODEL
-type Page
-    = Landing Page.Landing.Model
-    | Products
-    | Resources
-    | About
-    | Contact
+type Msg
+    = Header        Header.Msg
+    | Body          Body.Msg
+    | UrlChanged    Url.Url
+    | UrlRequest    Browser.UrlRequest
 
 type alias Model =
     { key : Browser.Navigation.Key
     , url : Url.Url
-    , page : Page
+    , page : Body.Model
     , header : Header.Model}
 
 init : () -> Url.Url -> Browser.Navigation.Key -> ( Model, Cmd Msg )
 init flags url key =
     let
-        page = Landing (Page.Landing.init flags)
+        page = Body.init flags
         header = Header.init flags
         model =
             { key = key
@@ -40,85 +40,49 @@ init flags url key =
     in
         (model, Cmd.none)
 
-toPage : Header.Msg -> Page
-toPage msg =
-    case msg of
-        Header.ClickedProducts -> Products
-        Header.ClickedResources -> Resources
-        Header.ClickedAbout -> About
-        Header.ClickedContact -> Contact
-
--- TODO : move this function to Router.elm
-toUrl : Url.Url -> Header.Msg -> Url.Url
-toUrl baseUrl msg =
-    case msg of
-        Header.ClickedProducts -> {baseUrl | path = "/products"}
-        Header.ClickedResources -> {baseUrl | path = "/resources"}
-        Header.ClickedAbout -> {baseUrl | path = "/about"}
-        Header.ClickedContact -> {baseUrl | path = "/contact"}
-
--- UPDATE
-type Msg
-    = NoOp
-    | Header Header.Msg
-    | LandingPage Page.Landing.Msg
-    | UrlChanged Url.Url
-    | UrlRequest Browser.UrlRequest
-
-
 update : Msg -> Model -> (Model, Cmd Msg)
 update msg model =
     case msg of
-        Header headerMsg ->
+        Body bodyMsg ->
             let
-                newUrl = toUrl model.url headerMsg
-                newModel = { model | page = toPage headerMsg }
+                (newPage, cmd) = Body.update bodyMsg model.page
             in
-                (newModel, Browser.Navigation.pushUrl model.key (Url.toString newUrl))
-        UrlChanged url ->
-                (model, Browser.Navigation.pushUrl model.key (Url.toString url))
+                ( {model | page = newPage}, cmd |> Cmd.map Body )
+        UrlChanged url  ->
+            ( {model | url = url}, Cmd.none )
+        UrlRequest (Browser.Internal url) ->
+            ( model, Browser.Navigation.pushUrl model.key (Url.toString url) )
         _ -> (model, Cmd.none)
 
 subscriptions : Model -> Sub Msg
 subscriptions _ =
   Sub.none
 
-viewBody : Model -> Element.Element Msg
-viewBody model =
-    let
-        content = case model.page of
-            Landing m -> Page.Landing.view m |> Element.map LandingPage
-            Products -> Element.text "Products"
-            Resources -> Element.text "Resources"
-            About -> Element.text "About"
-            Contact -> Element.text "Contact"
-    in
-        Element.el [Element.centerY ,Element.centerX] content
-
--- VIEW
 
 view : Model -> Browser.Document Msg
 view model =
     let
+        header = Header.view model.header |> Element.map Header
+        body = Body.view model.page |> Element.map Body
         page =
             Element.column
                 [ Element.width Element.fill
                 , Element.height Element.fill
                 , Element.centerX]
-                [ Header.view model.header |> Element.map Header
-                , viewBody model]
+                [ header
+                , body]
     in
         { title = "Example Spa Elm App"
         , body  = [ Element.layout [] page ]}
 
--- MAIN
-
 main =
     Browser.application {
-        init   = init
-       ,view   = view
-       ,update = update
-       ,subscriptions = subscriptions
-       ,onUrlChange = UrlChanged
-       ,onUrlRequest = UrlRequest
+        init            = init
+       ,view            = view
+       ,update          = update
+       ,subscriptions   = subscriptions
+       -- when a link is clicked, first UrlRequest is issued
+       ,onUrlRequest    = UrlRequest
+       -- then UrlChanged is issued
+       ,onUrlChange     = UrlChanged
        }

src/Page/About.elm

@@ -0,0 +1,16 @@
+module Page.About exposing (Model, Msg, view, init, update)
+import Element exposing (Element)
+
+type alias Model = {}
+type alias Msg = {}
+
+init : () -> Model
+init flags = {}
+
+update : Msg -> Model -> (Model, Cmd Msg)
+update msg model = (model, Cmd.none)
+
+view : Model -> Element Msg
+view model =
+    Element.el []
+        <| Element.text "About"

src/Page/Contact.elm

@@ -0,0 +1,16 @@
+module Page.Contact exposing (Model, Msg, view, init, update)
+import Element exposing (Element)
+
+type alias Model = {}
+type alias Msg = {}
+
+init : () -> Model
+init flags = {}
+
+update : Msg -> Model -> (Model, Cmd Msg)
+update msg model = (model, Cmd.none)
+
+view : Model -> Element Msg
+view model =
+    Element.el []
+        <| Element.text "Contact"

src/Page/Landing.elm

@@ -1,4 +1,4 @@
-module Page.Landing exposing (Model, Msg, view, init)
+module Page.Landing exposing (Model, Msg, view, init, update)
 import Element exposing (Element)
 
 type alias Model = {}
@@ -7,6 +7,9 @@ type alias Msg = {}
 init : () -> Model
 init flags = {}
 
+update : Msg -> Model -> (Model, Cmd Msg)
+update msg model = (model, Cmd.none)
+
 view : Model -> Element Msg
 view model =
     Element.el []

src/Page/Products.elm

@@ -0,0 +1,16 @@
+module Page.Products exposing (Model, Msg, view, init, update)
+import Element exposing (Element)
+
+type alias Model = {}
+type alias Msg = {}
+
+init : () -> Model
+init flags = {}
+
+update : Msg -> Model -> (Model, Cmd Msg)
+update msg model = (model, Cmd.none)
+
+view : Model -> Element Msg
+view model =
+    Element.el []
+        <| Element.text "Products"

src/Page/Resources.elm

@@ -0,0 +1,16 @@
+module Page.Resources exposing (Model, Msg, view, init, update)
+import Element exposing (Element)
+
+type alias Model = {}
+type alias Msg = {}
+
+init : () -> Model
+init flags = {}
+
+update : Msg -> Model -> (Model, Cmd Msg)
+update msg model = (model, Cmd.none)
+
+view : Model -> Element Msg
+view model =
+    Element.el []
+        <| Element.text "Resources"