import { GlBreakpointInstance as bp } from '@gitlab/ui/dist/utils';
import { SIDEBAR_COLLAPSED_CLASS } from './contextual_sidebar';

const HIDE_INTERVAL_TIMEOUT = 300;
const COLLAPSED_PANEL_WIDTH = 48;
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;
let sidebar;

export const mousePos = [];

export const setSidebar = (el) => {
  sidebar = el;
};
export const getOpenMenu = () => currentOpenMenu;
export const setOpenMenu = (menu = null) => {
  currentOpenMenu = menu;
};

export const slope = (a, b) => (b.y - a.y) / (b.x - a.x);

export const getHeaderHeight = () => sidebar?.offsetTop || 0;

export const isSidebarCollapsed = () =>
  sidebar && sidebar.classList.contains(SIDEBAR_COLLAPSED_CLASS);

export const canShowActiveSubItems = (el) => {
  if (el.classList.contains('active') && !isSidebarCollapsed()) {
    return false;
  }

  return true;
};

export const canShowSubItems = () => ['md', 'lg', 'xl'].includes(bp.getBreakpointSize());

export const getHideSubItemsInterval = () => {
  if (!currentOpenMenu || !mousePos.length) 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);

  return bottomOverflow < 0
    ? boundingRect.top - outerHeight + boundingRect.height
    : boundingRect.top;
};

export const hideMenu = (el) => {
  if (!el) return;

  const parentEl = el.parentNode;

  el.style.display = '';
  el.style.transform = '';
  el.classList.remove(IS_ABOVE_CLASS);
  el.classList.remove('fly-out-list');
  parentEl.classList.remove(IS_OVER_CLASS);
  parentEl.classList.remove(IS_SHOWING_FLY_OUT_CLASS);

  setOpenMenu();
};

export const moveSubItemsToPosition = (el, subItems) => {
  const hasSubItems = subItems.parentNode.querySelector('.has-sub-items');
  const header = subItems.querySelector('.fly-out-top-item');
  const boundingRect = el.getBoundingClientRect();
  const left = sidebar ? sidebar.offsetWidth : COLLAPSED_PANEL_WIDTH;
  let top = calculateTop(boundingRect, subItems.offsetHeight);
  const isAbove = top < boundingRect.top;
  if (hasSubItems) {
    top = isAbove ? top : top - header.offsetHeight;
  } else {
    top = boundingRect.top;
  }

  subItems.classList.add('fly-out-list');
  subItems.style.transform = `translate3d(${left}px, ${Math.floor(top) - getHeaderHeight()}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_CLASS);
  }
};

export const showSubLevelItems = (el) => {
  const subItems = el.querySelector('.sidebar-sub-level-items');
  const isIconOnly = subItems && subItems.classList.contains('is-fly-out-only');

  if (!canShowSubItems() || !canShowActiveSubItems(el)) return;

  el.classList.add(IS_OVER_CLASS);

  if (!subItems || (!isSidebarCollapsed() && isIconOnly)) return;

  subItems.style.display = 'block';
  el.classList.add(IS_SHOWING_FLY_OUT_CLASS);

  setOpenMenu(subItems);
  moveSubItemsToPosition(el, subItems);
};

export const mouseEnterTopItems = (el, timeout = getHideSubItemsInterval()) => {
  clearTimeout(timeoutId);

  timeoutId = setTimeout(() => {
    if (currentOpenMenu) hideMenu(currentOpenMenu);

    showSubLevelItems(el);
  }, timeout);
};

export const mouseLeaveTopItem = (el) => {
  const subItems = el.querySelector('.sidebar-sub-level-items');

  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,
  });

  if (mousePos.length > 6) mousePos.shift();
};

export const subItemsMouseLeave = (relatedTarget) => {
  clearTimeout(timeoutId);

  if (relatedTarget && !relatedTarget.closest(`.${IS_OVER_CLASS}`)) {
    hideMenu(currentOpenMenu);
  }
};

export default () => {
  sidebar = document.querySelector('.nav-sidebar');

  if (!sidebar) return;

  const items = [...sidebar.querySelectorAll('.sidebar-top-level-items > li')];

  const topItems = sidebar.querySelector('.sidebar-top-level-items');
  if (topItems) {
    sidebar.querySelector('.sidebar-top-level-items').addEventListener('mouseleave', () => {
      clearTimeout(timeoutId);

      timeoutId = setTimeout(() => {
        if (currentOpenMenu) hideMenu(currentOpenMenu);
      }, getHideSubItemsInterval());
    });
  }

  items.forEach((el) => {
    const subItems = el.querySelector('.sidebar-sub-level-items');

    if (subItems) {
      subItems.addEventListener('mouseleave', (e) => subItemsMouseLeave(e.relatedTarget));
    }

    el.addEventListener('mouseenter', (e) => mouseEnterTopItems(e.currentTarget));
    el.addEventListener('mouseleave', (e) => mouseLeaveTopItem(e.currentTarget));
  });

  document.addEventListener('mousemove', documentMouseMove);
};