import { Arr, Optional, Type } from '@ephox/katamari';

import { HTMLElementFullTagNameMap } from '../../alien/DomTypes';
import * as Traverse from '../search/Traverse';
import { SugarElement } from './SugarElement';
import * as SugarHead from './SugarHead';
import * as SugarNode from './SugarNode';

export type RootNode = SugarElement<Document | ShadowRoot>;

/**
 * Is the element a ShadowRoot?
 *
 * Note: this is insufficient to test if any element is a shadow root, but it is sufficient to differentiate between
 * a Document and a ShadowRoot.
 */
export const isShadowRoot = (dos: SugarElement<Node>): dos is SugarElement<ShadowRoot> =>
  SugarNode.isDocumentFragment(dos) && Type.isNonNullable((dos.dom as ShadowRoot).host);

export const getRootNode: (e: SugarElement<Node>) => RootNode = (e) =>
  SugarElement.fromDom(e.dom.getRootNode()) as RootNode;

/** Create an element, using the actual document. */
export const createElement: {
  <K extends keyof HTMLElementFullTagNameMap>(dos: RootNode, tag: K): SugarElement<HTMLElementFullTagNameMap[K]>;
  (dos: RootNode, tag: string): SugarElement<HTMLElement>;
} = (dos: RootNode, tag: string) =>
  SugarElement.fromTag(tag, Traverse.documentOrOwner(dos).dom);

/** Where style tags need to go. ShadowRoot or document head */
export const getStyleContainer = (dos: RootNode): SugarElement<HTMLHeadElement | ShadowRoot> =>
  isShadowRoot(dos) ? dos : SugarHead.getHead(Traverse.documentOrOwner(dos));

/** Where content needs to go. ShadowRoot or document body */
export const getContentContainer = (dos: RootNode): SugarElement<HTMLElement | ShadowRoot> =>
  // Can't use SugarBody.body without causing a circular module reference (since SugarBody.inBody uses SugarShadowDom)
  isShadowRoot(dos) ? dos : SugarElement.fromDom(Traverse.documentOrOwner(dos).dom.body);

/** Is this element either a ShadowRoot or a descendent of a ShadowRoot. */
export const isInShadowRoot = (e: SugarElement<Node>): boolean =>
  getShadowRoot(e).isSome();

/** If this element is in a ShadowRoot, return it. */
export const getShadowRoot = (e: SugarElement<Node>): Optional<SugarElement<ShadowRoot>> => {
  const r = getRootNode(e);
  return isShadowRoot(r) ? Optional.some(r) : Optional.none();
};

/** Return the host of a ShadowRoot.
 *
 * This function will throw if Shadow DOM is unsupported in the browser, or if the host is null.
 * If you actually have a ShadowRoot, this shouldn't happen.
 */
export const getShadowHost = (e: SugarElement<ShadowRoot>): SugarElement<Element> =>
  SugarElement.fromDom(e.dom.host);

/**
 * When Events bubble up through a ShadowRoot, the browser changes the target to be the shadow host.
 * This function gets the "original" event target if possible.
 * This only works if the shadow tree is open - if the shadow tree is closed, event.target is returned.
 * See: https://developers.google.com/web/fundamentals/web-components/shadowdom#events
 */
export const getOriginalEventTarget = (event: Event): Optional<EventTarget> => {
  if (Type.isNonNullable(event.target)) {
    const el = SugarElement.fromDom(event.target as Node);
    if (SugarNode.isElement(el) && isOpenShadowHost(el)) {
      // When target element is inside Shadow DOM we need to take first element from composedPath
      // otherwise we'll get Shadow Root parent, not actual target element.
      if (event.composed && event.composedPath) {
        const composedPath = event.composedPath();
        if (composedPath) {
          return Arr.head(composedPath);
        }
      }
    }
  }
  return Optional.from(event.target);
};

export const isOpenShadowRoot = (sr: SugarElement<ShadowRoot>): boolean =>
  sr.dom.mode === 'open';

export const isClosedShadowRoot = (sr: SugarElement<ShadowRoot>): boolean =>
  sr.dom.mode === 'closed';

/** Return true if the element is a host of an open shadow root.
 *  Return false if the element is a host of a closed shadow root, or if the element is not a host.
 */
export const isOpenShadowHost = (element: SugarElement<Element>): boolean =>
  Type.isNonNullable(element.dom.shadowRoot);
