example-spa-elm-app/frontend/src/Body.elm

module Body exposing (Msg(..), Model(..), init, update, view, handleRoute, subscriptions)

import Element

import Page.Landing
import Page.Products
import Page.Resources
import Page.About
import Page.Contact
import Page.Term
import Page.NotFound

type Msg
    = MsgLanding    Page.Landing.Msg
    | MsgProducts   Page.Products.Msg
    | MsgResources  Page.Resources.Msg
    | MsgAbout      Page.About.Msg
    | MsgContact    Page.Contact.Msg
    | MsgTerm       Page.Term.Msg
    | MsgNotFound   Page.NotFound.Msg

type Model
    = ModelLanding   Page.Landing.Model
    | ModelProducts  Page.Products.Model
    | ModelResources Page.Resources.Model
    | ModelAbout     Page.About.Model
    | ModelContact   Page.Contact.Model
    | ModelTerm      Page.Term.Model
    | ModelNotFound  Page.NotFound.Model

init : () -> (Model, Cmd Msg)
init flags =
    let
        (landingModel, landingCmd) = Page.Landing.init ()
    in
    (ModelLanding landingModel, Cmd.map MsgLanding landingCmd)

subscriptions : Model -> Sub Msg
subscriptions model =
    case model of
        ModelLanding m      -> Page.Landing.subscriptions m      |> Sub.map MsgLanding
        ModelProducts m     -> Page.Products.subscriptions m     |> Sub.map MsgProducts
        ModelResources m    -> Page.Resources.subscriptions m    |> Sub.map MsgResources
        ModelAbout m        -> Page.About.subscriptions m        |> Sub.map MsgAbout
        ModelContact m      -> Page.Contact.subscriptions m      |> Sub.map MsgContact
        ModelTerm m         -> Page.Term.subscriptions m         |> Sub.map MsgTerm
        ModelNotFound m     -> Page.NotFound.subscriptions m     |> Sub.map MsgNotFound

handleRoute : String -> (Model, Cmd Msg)
handleRoute path =
    case path of
        "/" ->
            let
                (landingModel, landingCmd) = Page.Landing.init ()
            in
            (ModelLanding landingModel, Cmd.map MsgLanding landingCmd)

        "/Products" ->
            let
                (productsModel, productsCmd) = Page.Products.init ()
            in
            (ModelProducts productsModel, Cmd.map MsgProducts productsCmd)

        "/Resources" ->
            let
                (resourcesModel, resourcesCmd) = Page.Resources.init ()
            in
            (ModelResources resourcesModel, Cmd.map MsgResources resourcesCmd)

        "/About" ->
            let
                (aboutModel, aboutCmd) = Page.About.init ()
            in
            (ModelAbout aboutModel, Cmd.map MsgAbout aboutCmd)

        "/Contact" ->
            let
                (contactModel, contactCmd) = Page.Contact.init ()
            in
            (ModelContact contactModel, Cmd.map MsgContact contactCmd)

        "/Term" ->
            let
                (termModel, termCmd) = Page.Term.init ()
            in
            (ModelTerm termModel, Cmd.map MsgTerm termCmd)

        _ ->
            let
                (notFoundModel, notFoundCmd) = Page.NotFound.init ()
            in
            (ModelNotFound notFoundModel, Cmd.map MsgNotFound notFoundCmd)
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

        (MsgTerm msg, ModelTerm m) ->
            updatePage msg m Page.Term.update MsgTerm ModelTerm

        _ ->
            (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
            ModelTerm m         -> Page.Term.view m         |> Element.map MsgTerm
            ModelNotFound m     -> Page.NotFound.view m     |> Element.map MsgNotFound
    in
        Element.el [Element.centerY ,Element.centerX] content