1 files changed, 132 insertions, 19 deletions

diff --git a/app/assets/javascripts/fly_out_nav.js b/app/assets/javascripts/fly_out_nav.js
index 56744a440e7..1b61392aae3 100644
--- a/app/assets/javascripts/fly_out_nav.js
+++ b/app/assets/javascripts/fly_out_nav.js
@@ -1,6 +1,24 @@
 import Cookies from 'js-cookie';
 import bp from './breakpoints';
 
+const HIDE_INTERVAL_TIMEOUT = 300;
+const IS_OVER_CLASS = 'is-over';
+const IS_ABOVE_CLASS = 'is-above';
+const IS_SHOWING_FLY_OUT_CLASS = 'is-showing-fly-out';
+let currentOpenMenu = null;
+let menuCornerLocs;
+let timeoutId;
+
+export const mousePos = [];
+
+export const setOpenMenu = (menu = null) => { currentOpenMenu = menu; };
+
+export const slope = (a, b) => (b.y - a.y) / (b.x - a.x);
+
+let headerHeight = 50;
+
+export const getHeaderHeight = () => headerHeight;
+
 export const canShowActiveSubItems = (el) => {
   const isHiddenByMedia = bp.getBreakpointSize() === 'sm' || bp.getBreakpointSize() === 'md';
 
@@ -10,8 +28,28 @@ export const canShowActiveSubItems = (el) => {
 
   return true;
 };
+
 export const canShowSubItems = () => bp.getBreakpointSize() === 'sm' || bp.getBreakpointSize() === 'md' || bp.getBreakpointSize() === 'lg';
 
+export const getHideSubItemsInterval = () => {
+  if (!currentOpenMenu) return 0;
+
+  const currentMousePos = mousePos[mousePos.length - 1];
+  const prevMousePos = mousePos[0];
+  const currentMousePosY = currentMousePos.y;
+  const [menuTop, menuBottom] = menuCornerLocs;
+
+  if (currentMousePosY < menuTop.y ||
+    currentMousePosY > menuBottom.y) return 0;
+
+  if (slope(prevMousePos, menuBottom) < slope(currentMousePos, menuBottom) &&
+    slope(prevMousePos, menuTop) > slope(currentMousePos, menuTop)) {
+    return HIDE_INTERVAL_TIMEOUT;
+  }
+
+  return 0;
+};
+
 export const calculateTop = (boundingRect, outerHeight) => {
   const windowHeight = window.innerHeight;
   const bottomOverflow = windowHeight - (boundingRect.top + outerHeight);
@@ -20,45 +58,120 @@ export const calculateTop = (boundingRect, outerHeight) => {
     boundingRect.top;
 };
 
-export const showSubLevelItems = (el) => {
-  const subItems = el.querySelector('.sidebar-sub-level-items');
+export const hideMenu = (el) => {
+  if (!el) return;
 
-  if (!subItems || !canShowSubItems() || !canShowActiveSubItems(el)) return;
+  const parentEl = el.parentNode;
 
-  subItems.style.display = 'block';
-  el.classList.add('is-showing-fly-out');
-  el.classList.add('is-over');
+  el.style.display = ''; // eslint-disable-line no-param-reassign
+  el.style.transform = ''; // eslint-disable-line no-param-reassign
+  el.classList.remove(IS_ABOVE_CLASS);
+  parentEl.classList.remove(IS_OVER_CLASS);
+  parentEl.classList.remove(IS_SHOWING_FLY_OUT_CLASS);
+
+  setOpenMenu();
+};
 
+export const moveSubItemsToPosition = (el, subItems) => {
   const boundingRect = el.getBoundingClientRect();
   const top = calculateTop(boundingRect, subItems.offsetHeight);
   const isAbove = top < boundingRect.top;
 
   subItems.classList.add('fly-out-list');
-  subItems.style.transform = `translate3d(0, ${Math.floor(top)}px, 0)`;
+  subItems.style.transform = `translate3d(0, ${Math.floor(top) - headerHeight}px, 0)`; // eslint-disable-line no-param-reassign
+
+  const subItemsRect = subItems.getBoundingClientRect();
+
+  menuCornerLocs = [
+    {
+      x: subItemsRect.left, // left position of the sub items
+      y: subItemsRect.top, // top position of the sub items
+    },
+    {
+      x: subItemsRect.left, // left position of the sub items
+      y: subItemsRect.top + subItemsRect.height, // bottom position of the sub items
+    },
+  ];
 
   if (isAbove) {
-    subItems.classList.add('is-above');
+    subItems.classList.add(IS_ABOVE_CLASS);
   }
 };
 
-export const hideSubLevelItems = (el) => {
+export const showSubLevelItems = (el) => {
+  const subItems = el.querySelector('.sidebar-sub-level-items');
+
+  if (!canShowSubItems() || !canShowActiveSubItems(el)) return;
+
+  el.classList.add(IS_OVER_CLASS);
+
+  if (!subItems) return;
+
+  subItems.style.display = 'block';
+  el.classList.add(IS_SHOWING_FLY_OUT_CLASS);
+
+  setOpenMenu(subItems);
+  moveSubItemsToPosition(el, subItems);
+};
+
+export const mouseEnterTopItems = (el) => {
+  clearTimeout(timeoutId);
+
+  timeoutId = setTimeout(() => {
+    if (currentOpenMenu) hideMenu(currentOpenMenu);
+
+    showSubLevelItems(el);
+  }, getHideSubItemsInterval());
+};
+
+export const mouseLeaveTopItem = (el) => {
   const subItems = el.querySelector('.sidebar-sub-level-items');
 
-  if (!subItems || !canShowSubItems() || !canShowActiveSubItems(el)) return;
+  if (!canShowSubItems() || !canShowActiveSubItems(el) ||
+    (subItems && subItems === currentOpenMenu)) return;
+
+  el.classList.remove(IS_OVER_CLASS);
+};
+
+export const documentMouseMove = (e) => {
+  mousePos.push({
+    x: e.clientX,
+    y: e.clientY,
+  });
 
-  el.classList.remove('is-showing-fly-out');
-  el.classList.remove('is-over');
-  subItems.style.display = '';
-  subItems.style.transform = '';
-  subItems.classList.remove('is-above');
+  if (mousePos.length > 6) mousePos.shift();
 };
 
 export default () => {
-  const items = [...document.querySelectorAll('.sidebar-top-level-items > li')]
-    .filter(el => el.querySelector('.sidebar-sub-level-items'));
+  const sidebar = document.querySelector('.sidebar-top-level-items');
+
+  if (!sidebar) return;
+
+  const items = [...sidebar.querySelectorAll('.sidebar-top-level-items > li')];
+
+  sidebar.addEventListener('mouseleave', () => {
+    clearTimeout(timeoutId);
+
+    timeoutId = setTimeout(() => {
+      if (currentOpenMenu) hideMenu(currentOpenMenu);
+    }, getHideSubItemsInterval());
+  });
+
+  headerHeight = document.querySelector('.nav-sidebar').offsetTop;
 
   items.forEach((el) => {
-    el.addEventListener('mouseenter', e => showSubLevelItems(e.currentTarget));
-    el.addEventListener('mouseleave', e => hideSubLevelItems(e.currentTarget));
+    const subItems = el.querySelector('.sidebar-sub-level-items');
+
+    if (subItems) {
+      subItems.addEventListener('mouseleave', () => {
+        clearTimeout(timeoutId);
+        hideMenu(currentOpenMenu);
+      });
+    }
+
+    el.addEventListener('mouseenter', e => mouseEnterTopItems(e.currentTarget));
+    el.addEventListener('mouseleave', e => mouseLeaveTopItem(e.currentTarget));
   });
+
+  document.addEventListener('mousemove', documentMouseMove);
 };