From f1f8aa0a89921f442b1983cec15804df2670a927 Mon Sep 17 00:00:00 2001
From: Peter Makowski <me+git@petermakowski.io>
Date: Fri, 5 Jan 2024 14:07:42 +0100
Subject: [PATCH] feat: adjust contextual dropdown vert position

---
 .../ContextualMenu/ContextualMenu.stories.mdx |  3 +-
 .../ContextualMenu/ContextualMenu.tsx         | 44 ++++++++++++++++++-
 .../ContextualMenuDropdown.tsx                | 26 +++++++++--
 3 files changed, 67 insertions(+), 6 deletions(-)

diff --git a/src/components/ContextualMenu/ContextualMenu.stories.mdx b/src/components/ContextualMenu/ContextualMenu.stories.mdx
index 690f580d0..8c036aea5 100644
--- a/src/components/ContextualMenu/ContextualMenu.stories.mdx
+++ b/src/components/ContextualMenu/ContextualMenu.stories.mdx
@@ -1,5 +1,5 @@
 import { ArgsTable, Canvas, Meta, Story } from "@storybook/addon-docs";
-
+import Button from "../Button";
 import ContextualMenu from "./ContextualMenu";
 
 <Meta
@@ -37,6 +37,7 @@ export const ScrollTemplate = (args) => (
         voluptas odit aspernatur alias molestias facere.
       </p>
     )}
+    <ContextualMenu {...args} />
   </div>
 );
 
diff --git a/src/components/ContextualMenu/ContextualMenu.tsx b/src/components/ContextualMenu/ContextualMenu.tsx
index 536c17862..b1f80ce90 100644
--- a/src/components/ContextualMenu/ContextualMenu.tsx
+++ b/src/components/ContextualMenu/ContextualMenu.tsx
@@ -110,6 +110,23 @@ export type Props<L> = PropsWithSpread<
   HTMLProps<HTMLSpanElement>
 >;
 
+const getClosestScrollableParent = (
+  node: HTMLElement | null
+): HTMLElement | null => {
+  let currentNode = node;
+  while (currentNode && currentNode !== document.body) {
+    const { overflowY, overflowX } = window.getComputedStyle(currentNode);
+    if (
+      ["auto", "scroll", "overlay"].includes(overflowY) &&
+      ["auto", "scroll", "overlay"].includes(overflowX)
+    ) {
+      return currentNode;
+    }
+    currentNode = currentNode.parentElement;
+  }
+  return document.body;
+};
+
 /**
  * Get the node to use for positioning the menu.
  * @param wrapper - The component's wrapping element.
@@ -191,11 +208,35 @@ const ContextualMenu = <L,>({
   const wrapper = useRef<HTMLDivElement | null>(null);
   const [positionCoords, setPositionCoords] = useState<DOMRect>();
   const [adjustedPosition, setAdjustedPosition] = useState(position);
+  const [verticalPosition, setVerticalPosition] = useState<"top" | "bottom">(
+    "bottom"
+  );
   const hasToggle = hasToggleIcon || toggleLabel;
 
+  const updateVerticalPosition = useCallback(() => {
+    const parent = getPositionNode(wrapper.current, positionNode);
+    if (!parent) {
+      return null;
+    }
+    const rect = parent.getBoundingClientRect();
+    const scrollableParent = getClosestScrollableParent(parent);
+    if (!scrollableParent) {
+      return null;
+    }
+    const scrollableParentRect = scrollableParent.getBoundingClientRect();
+    const spaceBelow = scrollableParentRect.height - rect.bottom;
+    const spaceAbove = rect.top;
+    const dropdownHeight = rect.height;
+
+    setVerticalPosition(
+      spaceBelow >= dropdownHeight || spaceBelow > spaceAbove ? "bottom" : "top"
+    );
+  }, [wrapper, positionNode]);
+
   useEffect(() => {
     setAdjustedPosition(position);
-  }, [position, autoAdjust]);
+    updateVerticalPosition();
+  }, [position, autoAdjust, updateVerticalPosition]);
 
   // Update the coordinates of the position node.
   const updatePositionCoords = useCallback(() => {
@@ -338,6 +379,7 @@ const ContextualMenu = <L,>({
         <Portal>
           <ContextualMenuDropdown<L>
             adjustedPosition={adjustedPosition}
+            verticalPosition={verticalPosition}
             autoAdjust={autoAdjust}
             handleClose={closePortal}
             constrainPanelWidth={constrainPanelWidth}
diff --git a/src/components/ContextualMenu/ContextualMenuDropdown/ContextualMenuDropdown.tsx b/src/components/ContextualMenu/ContextualMenuDropdown/ContextualMenuDropdown.tsx
index 5c71191f3..202fd28ec 100644
--- a/src/components/ContextualMenu/ContextualMenuDropdown/ContextualMenuDropdown.tsx
+++ b/src/components/ContextualMenu/ContextualMenuDropdown/ContextualMenuDropdown.tsx
@@ -24,6 +24,7 @@ export enum Label {
 export type MenuLink<L = null> = string | ButtonProps<L> | ButtonProps<L>[];
 
 export type Position = "left" | "center" | "right";
+type VerticalPosition = "top" | "bottom";
 
 /**
  * The props for the ContextualMenuDropdown component.
@@ -31,6 +32,7 @@ export type Position = "left" | "center" | "right";
  */
 export type Props<L = null> = {
   adjustedPosition?: Position;
+  verticalPosition: VerticalPosition;
   autoAdjust?: boolean;
   handleClose?: (evt?: MouseEvent) => void;
   constrainPanelWidth?: boolean;
@@ -55,6 +57,7 @@ export type Props<L = null> = {
  */
 const getPositionStyle = (
   position: Position,
+  verticalPosition: VerticalPosition,
   positionCoords: Props["positionCoords"],
   constrainPanelWidth: Props["constrainPanelWidth"]
 ): React.CSSProperties => {
@@ -62,7 +65,10 @@ const getPositionStyle = (
     return null;
   }
   const { height, left, top, width } = positionCoords;
-  const topPos = top + height + (window.scrollY || 0);
+  const topPos =
+    verticalPosition === "bottom"
+      ? top + height + (window.scrollY || 0)
+      : top + (window.scrollY || 0);
   let leftPos = left;
 
   switch (position) {
@@ -173,6 +179,7 @@ const ContextualMenuDropdown = <L,>({
   links,
   position,
   positionCoords,
+  verticalPosition,
   positionNode,
   scrollOverflow,
   setAdjustedPosition,
@@ -182,16 +189,26 @@ const ContextualMenuDropdown = <L,>({
   const dropdown = useRef();
 
   const [positionStyle, setPositionStyle] = useState(
-    getPositionStyle(adjustedPosition, positionCoords, constrainPanelWidth)
+    getPositionStyle(
+      adjustedPosition,
+      verticalPosition,
+      positionCoords,
+      constrainPanelWidth
+    )
   );
   const [maxHeight, setMaxHeight] = useState<number>();
 
   // Update the styles to position the menu.
   const updatePositionStyle = useCallback(() => {
     setPositionStyle(
-      getPositionStyle(adjustedPosition, positionCoords, constrainPanelWidth)
+      getPositionStyle(
+        adjustedPosition,
+        verticalPosition,
+        positionCoords,
+        constrainPanelWidth
+      )
     );
-  }, [adjustedPosition, positionCoords, constrainPanelWidth]);
+  }, [adjustedPosition, positionCoords, verticalPosition, constrainPanelWidth]);
 
   // Update the position when the window fitment info changes.
   const onUpdateWindowFitment = useCallback(
@@ -237,6 +254,7 @@ const ContextualMenuDropdown = <L,>({
           ...(scrollOverflow
             ? { maxHeight, minHeight: "2rem", overflowX: "auto" }
             : {}),
+          ...(verticalPosition === "top" ? { bottom: "0" } : {}),
         }}
         {...props}
       >