Prepare for selecting languages

UI language is stored in user settings for authenticated users;
otherwise is only stored in the current model (not persisted).

modules/webapp/src/main/elm/App/Data.elm

@@ -2,6 +2,7 @@ module App.Data exposing
     ( Model
     , Msg(..)
     , defaultPage
+    , getUiLanguage
     , init
     )
 
@@ -24,6 +25,7 @@ import Page.Queue.Data
 import Page.Register.Data
 import Page.Upload.Data
 import Page.UserSettings.Data
+import UiLanguage exposing (UiLanguage)
 import Url exposing (Url)
 
 
@@ -48,6 +50,8 @@ type alias Model =
     , uiSettings : UiSettings
     , sidebarVisible : Bool
     , anonymousTheme : UiTheme
+    , anonymousUiLang : UiLanguage
+    , langMenuOpen : Bool
     }
 
 
@@ -97,6 +101,8 @@ init key url flags_ settings =
       , uiSettings = settings
       , sidebarVisible = settings.sideMenuVisible
       , anonymousTheme = Data.UiTheme.Light
+      , anonymousUiLang = UiLanguage.English
+      , langMenuOpen = False
       }
     , Cmd.batch
         [ Cmd.map UserSettingsMsg uc
@@ -152,8 +158,20 @@ type Msg
     | GetUiSettings UiSettings
     | ToggleSidebar
     | ToggleDarkMode
+    | ToggleLangMenu
+    | SetLanguage UiLanguage
 
 
 defaultPage : Flags -> Page
 defaultPage flags =
     HomePage
+
+
+getUiLanguage : Model -> UiLanguage
+getUiLanguage model =
+    case model.flags.account of
+        Just _ ->
+            model.uiSettings.uiLang
+
+        Nothing ->
+            model.anonymousUiLang

modules/webapp/src/main/elm/App/Update.elm

@@ -84,6 +84,15 @@ updateWithSub msg model =
                     , Sub.none
                     )
 
+        ToggleLangMenu ->
+            ( { model | langMenuOpen = not model.langMenuOpen }
+            , Cmd.none
+            , Sub.none
+            )
+
+        SetLanguage lang ->
+            ( { model | anonymousUiLang = lang, langMenuOpen = False }, Cmd.none, Sub.none )
+
         HomeMsg lm ->
             updateHome lm model
 

modules/webapp/src/main/elm/App/View2.elm

@@ -7,6 +7,7 @@ import Data.Flags
 import Html exposing (..)
 import Html.Attributes exposing (..)
 import Html.Events exposing (onClick)
+import Messages
 import Page exposing (Page(..))
 import Page.CollectiveSettings.View2 as CollectiveSettings
 import Page.Home.Data
@@ -20,6 +21,7 @@ import Page.Register.View2 as Register
 import Page.Upload.View2 as Upload
 import Page.UserSettings.View2 as UserSettings
 import Styles as S
+import UiLanguage
 
 
 view : Model -> List (Html Msg)
@@ -64,13 +66,18 @@ topNavUser auth model =
 
 topNavAnon : Model -> Html Msg
 topNavAnon model =
+    let
+        texts =
+            Messages.get <| App.Data.getUiLanguage model
+    in
     nav
         [ id "top-nav"
         , class styleTopNav
         ]
         [ headerNavItem model
         , div [ class "flex flex-grow justify-end" ]
-            [ a
+            [ langMenu model
+            , a
                 [ href "#"
                 , onClick ToggleDarkMode
                 , class dropdownLink
@@ -100,6 +107,10 @@ headerNavItem model =
 
 mainContent : Model -> Html Msg
 mainContent model =
+    let
+        texts =
+            Messages.get <| App.Data.getUiLanguage model
+    in
     div
         [ id "main"
         , class styleMain
@@ -151,6 +162,45 @@ styleMain =
     "mt-12 flex md:flex-row flex-col w-full h-screen-12 overflow-y-hidden bg-white dark:bg-bluegray-800 text-gray-800 dark:text-bluegray-300 antialiased"
 
 
+langMenu : Model -> Html Msg
+langMenu model =
+    let
+        texts =
+            Messages.get <| App.Data.getUiLanguage model
+
+        langItem lang =
+            let
+                langMsg =
+                    Messages.get lang
+            in
+            a
+                [ classList
+                    [ ( dropdownItem, True )
+                    , ( "bg-gray-200 dark:bg-bluegray-700", lang == texts.lang )
+                    ]
+                , onClick (SetLanguage lang)
+                , href "#"
+                ]
+                [ i [ langMsg |> .flagIcon |> class ] []
+                , span [ class "ml-2" ] [ text langMsg.label ]
+                ]
+    in
+    div [ class "relative" ]
+        [ a
+            [ class dropdownLink
+            , onClick ToggleLangMenu
+            , href "#"
+            ]
+            [ i [ class texts.flagIcon ] []
+            ]
+        , div
+            [ class dropdownMenu
+            , classList [ ( "hidden", not model.langMenuOpen ) ]
+            ]
+            (List.map langItem UiLanguage.all)
+        ]
+
+
 dataMenu : AuthResult -> Model -> Html Msg
 dataMenu _ model =
     div [ class "relative" ]