From 5e0eaf419ea02e687adad949dd4c3ad6b9553e0b Mon Sep 17 00:00:00 2001
From: Eike Kettner <eike.kettner@posteo.de>
Date: Sun, 18 Oct 2020 21:32:37 +0200
Subject: [PATCH] Fix browser back button to restore scroll state

Removes the url parameter that was used to identify the card to scroll
to and instead use the id from the internal model.
---
 modules/webapp/src/main/elm/App/Data.elm      |  2 +-
 modules/webapp/src/main/elm/App/Update.elm    |  7 ++++---
 modules/webapp/src/main/elm/App/View.elm      | 11 +++++-----
 .../src/main/elm/Comp/ItemDetail/Update.elm   |  2 +-
 .../src/main/elm/Comp/ItemDetail/View.elm     |  2 +-
 modules/webapp/src/main/elm/Page.elm          | 20 ++++++-------------
 .../webapp/src/main/elm/Page/Home/Data.elm    |  4 +++-
 .../webapp/src/main/elm/Page/Home/Update.elm  | 17 +++++++---------
 .../webapp/src/main/elm/Page/Home/View.elm    |  2 +-
 .../webapp/src/main/elm/Page/Login/Update.elm |  2 +-
 .../webapp/src/main/elm/Page/Upload/View.elm  |  2 +-
 11 files changed, 32 insertions(+), 39 deletions(-)

diff --git a/modules/webapp/src/main/elm/App/Data.elm b/modules/webapp/src/main/elm/App/Data.elm
index c461fadc..28fbd8d4 100644
--- a/modules/webapp/src/main/elm/App/Data.elm
+++ b/modules/webapp/src/main/elm/App/Data.elm
@@ -160,7 +160,7 @@ checkPage flags page =
 defaultPage : Flags -> Page
 defaultPage flags =
     if isSignedIn flags then
-        HomePage Nothing
+        HomePage
 
     else
         LoginPage Nothing
diff --git a/modules/webapp/src/main/elm/App/Update.elm b/modules/webapp/src/main/elm/App/Update.elm
index dfdf5316..e261463b 100644
--- a/modules/webapp/src/main/elm/App/Update.elm
+++ b/modules/webapp/src/main/elm/App/Update.elm
@@ -31,6 +31,7 @@ import Page.UserSettings.Data
 import Page.UserSettings.Update
 import Ports
 import Url
+import Util.Maybe
 import Util.Update
 
 
@@ -312,8 +313,8 @@ updateHome lmsg model =
     let
         mid =
             case model.page of
-                HomePage x ->
-                    x
+                HomePage ->
+                    Util.Maybe.fromString model.itemDetailModel.detail.item.id
 
                 _ ->
                     Nothing
@@ -348,7 +349,7 @@ initPage model_ page =
             { model_ | page = page }
     in
     case page of
-        HomePage _ ->
+        HomePage ->
             Util.Update.andThen2
                 [ updateHome Page.Home.Data.Init
                 , updateQueue Page.Queue.Data.StopRefresh
diff --git a/modules/webapp/src/main/elm/App/View.elm b/modules/webapp/src/main/elm/App/View.elm
index afd850d7..2223a342 100644
--- a/modules/webapp/src/main/elm/App/View.elm
+++ b/modules/webapp/src/main/elm/App/View.elm
@@ -16,6 +16,7 @@ import Page.Queue.View
 import Page.Register.View
 import Page.Upload.View
 import Page.UserSettings.View
+import Util.Maybe
 
 
 view : Model -> Html Msg
@@ -65,7 +66,7 @@ defaultLayout model =
             [ div [ class "ui fluid container" ]
                 [ a
                     [ class "header item narrow-item"
-                    , Page.href (HomePage Nothing)
+                    , Page.href HomePage
                     ]
                     [ img
                         [ class "image"
@@ -84,7 +85,7 @@ defaultLayout model =
             , id "main-content"
             ]
             [ case model.page of
-                HomePage _ ->
+                HomePage ->
                     viewHome model
 
                 LoginPage _ ->
@@ -180,8 +181,8 @@ viewHome model =
     let
         mid =
             case model.page of
-                HomePage x ->
-                    x
+                HomePage ->
+                    Util.Maybe.fromString model.itemDetailModel.detail.item.id
 
                 _ ->
                     Nothing
@@ -218,7 +219,7 @@ loginInfo model =
                             ]
                         ]
                         [ menuEntry model
-                            (HomePage Nothing)
+                            HomePage
                             [ img
                                 [ class "image icon"
                                 , src (model.flags.config.docspellAssetPath ++ "/img/logo-mc-96.png")
diff --git a/modules/webapp/src/main/elm/Comp/ItemDetail/Update.elm b/modules/webapp/src/main/elm/Comp/ItemDetail/Update.elm
index f6a8f5a9..5fddccca 100644
--- a/modules/webapp/src/main/elm/Comp/ItemDetail/Update.elm
+++ b/modules/webapp/src/main/elm/Comp/ItemDetail/Update.elm
@@ -632,7 +632,7 @@ update key flags inav settings msg model =
                         noSub ( model, Page.set key (ItemDetailPage id) )
 
                     Nothing ->
-                        noSub ( model, Page.set key (HomePage Nothing) )
+                        noSub ( model, Page.set key HomePage )
 
             else
                 noSub ( model, Cmd.none )
diff --git a/modules/webapp/src/main/elm/Comp/ItemDetail/View.elm b/modules/webapp/src/main/elm/Comp/ItemDetail/View.elm
index 131c1c8f..ba2b76b9 100644
--- a/modules/webapp/src/main/elm/Comp/ItemDetail/View.elm
+++ b/modules/webapp/src/main/elm/Comp/ItemDetail/View.elm
@@ -110,7 +110,7 @@ renderDetailMenu settings inav model =
               )
             ]
         ]
-        [ a [ class "item", Page.href (HomePage (Just model.item.id)) ]
+        [ a [ class "item", Page.href HomePage ]
             [ i [ class "arrow left icon" ] []
             ]
         , a
diff --git a/modules/webapp/src/main/elm/Page.elm b/modules/webapp/src/main/elm/Page.elm
index 7308e1a2..286d35bf 100644
--- a/modules/webapp/src/main/elm/Page.elm
+++ b/modules/webapp/src/main/elm/Page.elm
@@ -24,7 +24,7 @@ import Util.Maybe
 
 
 type Page
-    = HomePage (Maybe String)
+    = HomePage
     | LoginPage (Maybe Page)
     | ManageDataPage
     | CollectiveSettingPage
@@ -39,7 +39,7 @@ type Page
 isSecured : Page -> Bool
 isSecured page =
     case page of
-        HomePage _ ->
+        HomePage ->
             True
 
         LoginPage _ ->
@@ -88,7 +88,7 @@ loginPage p =
 pageName : Page -> String
 pageName page =
     case page of
-        HomePage _ ->
+        HomePage ->
             "Home"
 
         LoginPage _ ->
@@ -147,10 +147,7 @@ uploadId page =
 pageToString : Page -> String
 pageToString page =
     case page of
-        HomePage (Just id) ->
-            "/app/home?item=" ++ id
-
-        HomePage Nothing ->
+        HomePage ->
             "/app/home"
 
         LoginPage referer ->
@@ -232,8 +229,8 @@ parser =
     oneOf
         [ Parser.map HomePage
             (oneOf
-                [ Parser.top <?> itemQuery
-                , s pathPrefix </> s "home" <?> itemQuery
+                [ Parser.top
+                , s pathPrefix </> s "home"
                 ]
             )
         , Parser.map LoginPage (s pathPrefix </> s "login" <?> pageQuery)
@@ -271,8 +268,3 @@ pageQuery =
     in
     Query.string "r"
         |> Query.map parsePage
-
-
-itemQuery : Query.Parser (Maybe String)
-itemQuery =
-    Query.string "item"
diff --git a/modules/webapp/src/main/elm/Page/Home/Data.elm b/modules/webapp/src/main/elm/Page/Home/Data.elm
index eda1efbf..cb671eb5 100644
--- a/modules/webapp/src/main/elm/Page/Home/Data.elm
+++ b/modules/webapp/src/main/elm/Page/Home/Data.elm
@@ -41,6 +41,7 @@ type alias Model =
     , searchTypeForm : SearchType
     , contentOnlySearch : Maybe String
     , dragDropData : DD.DragDropData
+    , scrollToCard : Maybe String
     }
 
 
@@ -70,6 +71,7 @@ init flags =
     , contentOnlySearch = Nothing
     , dragDropData =
         DD.DragDropData DD.init Nothing
+    , scrollToCard = Nothing
     }
 
 
@@ -98,7 +100,7 @@ type Msg
     | KeyUpMsg (Maybe KeyCode)
     | SetContentOnly String
     | ScrollResult (Result Dom.Error ())
-    | ClearItemDetailId (Maybe String)
+    | ClearItemDetailId
 
 
 type SearchType
diff --git a/modules/webapp/src/main/elm/Page/Home/Update.elm b/modules/webapp/src/main/elm/Page/Home/Update.elm
index 2382929a..edb3d70b 100644
--- a/modules/webapp/src/main/elm/Page/Home/Update.elm
+++ b/modules/webapp/src/main/elm/Page/Home/Update.elm
@@ -243,18 +243,12 @@ update mId key flags settings msg model =
         ScrollResult _ ->
             let
                 cmd =
-                    Process.sleep 800 |> Task.perform (always (ClearItemDetailId mId))
+                    Process.sleep 800 |> Task.perform (always ClearItemDetailId)
             in
             withSub ( model, cmd )
 
-        ClearItemDetailId id ->
-            -- if user clicks quickly away (e.g. on another item), the
-            -- deferred command should be ignored
-            if mId == id then
-                noSub ( model, Page.set key (HomePage Nothing) )
-
-            else
-                noSub ( model, Cmd.none )
+        ClearItemDetailId ->
+            noSub ( { model | scrollToCard = Nothing }, Cmd.none )
 
 
 
@@ -269,7 +263,10 @@ scrollToCard mId model =
     in
     case mId of
         Just id ->
-            ( model, Task.attempt ScrollResult (scroll id), Sub.none )
+            ( { model | scrollToCard = mId }
+            , Task.attempt ScrollResult (scroll id)
+            , Sub.none
+            )
 
         Nothing ->
             ( model, Cmd.none, Sub.none )
diff --git a/modules/webapp/src/main/elm/Page/Home/View.elm b/modules/webapp/src/main/elm/Page/Home/View.elm
index 69f0b2d4..32653c43 100644
--- a/modules/webapp/src/main/elm/Page/Home/View.elm
+++ b/modules/webapp/src/main/elm/Page/Home/View.elm
@@ -82,7 +82,7 @@ view current flags settings model =
             ]
             [ viewSearchBar flags model
             , Html.map ItemCardListMsg
-                (Comp.ItemCardList.view current settings model.itemListModel)
+                (Comp.ItemCardList.view model.scrollToCard settings model.itemListModel)
             ]
         , div
             [ classList
diff --git a/modules/webapp/src/main/elm/Page/Login/Update.elm b/modules/webapp/src/main/elm/Page/Login/Update.elm
index 54145cd8..539d2f02 100644
--- a/modules/webapp/src/main/elm/Page/Login/Update.elm
+++ b/modules/webapp/src/main/elm/Page/Login/Update.elm
@@ -25,7 +25,7 @@ update referrer flags msg model =
         AuthResp (Ok lr) ->
             let
                 gotoRef =
-                    Maybe.withDefault (HomePage Nothing) referrer |> Page.goto
+                    Maybe.withDefault HomePage referrer |> Page.goto
             in
             if lr.success then
                 ( { model | result = Just lr, password = "" }, Cmd.batch [ setAccount lr, gotoRef ], Just lr )
diff --git a/modules/webapp/src/main/elm/Page/Upload/View.elm b/modules/webapp/src/main/elm/Page/Upload/View.elm
index f45873da..a297fb28 100644
--- a/modules/webapp/src/main/elm/Page/Upload/View.elm
+++ b/modules/webapp/src/main/elm/Page/Upload/View.elm
@@ -77,7 +77,7 @@ renderSuccessMsg public _ =
                   else
                     p []
                         [ text "Your files have been successfully uploaded. They are now being processed. Check the "
-                        , a [ class "ui link", Page.href (HomePage Nothing) ]
+                        , a [ class "ui link", Page.href HomePage ]
                             [ text "Items page"
                             ]
                         , text " later where the files will arrive eventually. Or go to the "