From 12a547c7aafa413cedf673a05d7d66b102084cf3 Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Sat, 16 Nov 2024 00:22:29 +0000
Subject: [PATCH] drag time graphs left/right

---
 frontend/src/Main.elm | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/frontend/src/Main.elm b/frontend/src/Main.elm
index 8d0056a..49a9661 100644
--- a/frontend/src/Main.elm
+++ b/frontend/src/Main.elm
@@ -144,6 +144,7 @@ type alias Model =
     { centre: Coord
     , zoom: FineZoomLevel
     , drag: Drag
+    , timeDrag: Drag
     , startTime : Int
     , duration : Int
     , track: TrackState }
@@ -155,7 +156,7 @@ init _ url navKey =
                 Just (Timeline (Just s) (Just d)) -> (s, d)
                 _ -> (10,10)
     in
-        ((Model (toCoord 51.60 -0.01) (FineZoomLevel (13*8)) None start duration Empty),
+        ((Model (toCoord 51.60 -0.01) (FineZoomLevel (13*8)) None None start duration Empty),
              (fetchTrack start duration))
 
 -- SUBSCRIPTIONS
@@ -182,6 +183,9 @@ type Msg
   | MapDrag (Int, Int)
   | MapDragFinish (Int, Int)
   | TimeScale (Float)
+  | TimeDragStart (Int, Int)
+  | TimeDrag (Int, Int)
+  | TimeDragFinish (Int, Int)
   | Loaded (Result Http.Error (List Point))
   | NewUrlRequest
   | UrlChanged
@@ -214,6 +218,18 @@ newModel msg model =
                ,     duration = len
                }
 
+        TimeDragStart (x,y) ->
+            { model | timeDrag = Dragging (x,y) (x,y) }
+
+        TimeDrag (x,y) ->
+            { model | timeDrag = dragTo model.timeDrag (x,y) }
+
+        TimeDragFinish (x,y) ->
+            { model | timeDrag = None,
+                  startTime =
+                  let (delta, _) = dragDelta model.timeDrag
+                  in model.startTime + delta * model.duration // portalWidth
+            }
         Loaded result ->
             case result of
                 Ok trk -> { model | track = Present trk }
@@ -366,7 +382,10 @@ ifTrack : Model -> (List Point ->  Html msg) ->  Html msg
 ifTrack model content =
     case model.track of
         Present t ->
-            let points = Point.subseq t (toFloat model.startTime) (toFloat model.duration)
+            let (dt, _) = dragDelta model.timeDrag
+                dpix = dt * model.duration // portalWidth
+                start = toFloat (model.startTime + dpix)
+                points = Point.subseq t start (toFloat model.duration)
             in  content points
         Failure f -> Debug.log f (div [] [ Html.text "failure", Html.text f])
         Loading -> div [] [Html.text "loading"]
@@ -420,6 +439,7 @@ viewDiv : Model -> Html Msg
 viewDiv model =
     let coord = translate model.centre (pixelsToCoord (toZoom model.zoom) (dragDelta model.drag))
         canvasV = canvas coord (toZoom model.zoom) portalWidth portalHeight model
+        epos e = Tuple.mapBoth floor floor e.pointer.clientPos
     in div [ style "display" "flex"
            , style "column-gap" "15px"
            ]
@@ -440,6 +460,9 @@ viewDiv model =
               ]
         , div [ style "display" "flex"
               , Html.Events.custom "wheel" timeWheelDecoder
+              , Pointer.onUp (\e -> TimeDragFinish (epos e))
+              , Pointer.onMove (\e -> TimeDrag (epos e))
+              , Pointer.onDown (\e -> TimeDragStart (epos e))
               , style "flex-direction" "column"
               , style "row-gap" "10px"
               ]