/**
 * Copyright (c) Paymium.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root of this projects source tree.
 */

// import { useEvent } from '@tamagui/use-event';
import * as React from 'react';

import type { FocusScopeProps } from './FocusScopeProps';
import { useComposedRefs } from '@crossed/core';
import { useEvent } from '../useEvent';

const AUTOFOCUS_ON_MOUNT = 'focusScope.autoFocusOnMount';
const AUTOFOCUS_ON_UNMOUNT = 'focusScope.autoFocusOnUnmount';
const EVENT_OPTIONS = { bubbles: false, cancelable: true };

type FocusableTarget = HTMLElement | { focus(): void };

/* -------------------------------------------------------------------------------------------------
 * FocusScope
 * -----------------------------------------------------------------------------------------------*/

type FocusScopeElement = HTMLDivElement;

const FocusScope = React.forwardRef<FocusScopeElement, FocusScopeProps>(
  function FocusScope(props, forwardedRef) {
    const childProps = useFocusScope(props, forwardedRef);

    if (typeof props.children === 'function') {
      return <>{props.children(childProps)}</>;
    }

    return React.cloneElement(
      React.Children.only(props.children) as any,
      childProps
    );
  }
);

/* -------------------------------------------------------------------------------------------------
 * useFocusScope
 * -----------------------------------------------------------------------------------------------*/

export function useFocusScope(
  props: FocusScopeProps,
  forwardedRef: React.ForwardedRef<FocusScopeElement>
) {
  const {
    loop = false,
    enabled = true,
    trapped = false,
    onMountAutoFocus: onMountAutoFocusProp,
    onUnmountAutoFocus: onUnmountAutoFocusProp,
    forceUnmount,
    children: _children,
    ...scopeProps
  } = props;
  const [container, setContainer] = React.useState<HTMLElement | null>(null);
  const onMountAutoFocus = useEvent(onMountAutoFocusProp);
  const onUnmountAutoFocus = useEvent(onUnmountAutoFocusProp);
  const lastFocusedElementRef = React.useRef<HTMLElement | null>(null);
  const composedRefs = useComposedRefs(forwardedRef, (node) =>
    setContainer(node)
  );

  const focusScope = React.useRef({
    paused: false,
    pause() {
      this.paused = true;
    },
    resume() {
      this.paused = false;
    },
  }).current;

  // Takes care of trapping focus if focus is moved outside programmatically for example
  React.useEffect(() => {
    if (!enabled) return;
    if (!trapped) return;
    function handleFocusIn(event: FocusEvent) {
      if (focusScope.paused || !container) return;
      const target = event.target as HTMLElement | null;
      if (container.contains(target)) {
        lastFocusedElementRef.current = target;
      } else {
        focus(lastFocusedElementRef.current, { select: true });
      }
    }

    function handleFocusOut(event: FocusEvent) {
      if (focusScope.paused || !container) return;
      if (!container.contains(event.relatedTarget as HTMLElement | null)) {
        focus(lastFocusedElementRef.current, { select: true });
      }
    }

    document.addEventListener('focusin', handleFocusIn);
    document.addEventListener('focusout', handleFocusOut);
    return () => {
      document.removeEventListener('focusin', handleFocusIn);
      document.removeEventListener('focusout', handleFocusOut);
    };
  }, [trapped, forceUnmount, container, focusScope.paused]);

  React.useEffect(() => {
    if (!enabled) return;
    if (!container) return;
    if (forceUnmount) return;

    focusScopesStack.add(focusScope);
    const previouslyFocusedElement =
      document.activeElement as HTMLElement | null;
    const hasFocusedCandidate = container.contains(previouslyFocusedElement);

    if (!hasFocusedCandidate) {
      const mountEvent = new CustomEvent(AUTOFOCUS_ON_MOUNT, EVENT_OPTIONS);
      container.addEventListener(AUTOFOCUS_ON_MOUNT, onMountAutoFocus);
      container.dispatchEvent(mountEvent);
      if (!mountEvent.defaultPrevented) {
        focusFirst(removeLinks(getTabbableCandidates(container)), {
          select: true,
        });
        if (document.activeElement === previouslyFocusedElement) {
          focus(container);
        }
      }
    }

    return () => {
      container.removeEventListener(AUTOFOCUS_ON_MOUNT, onMountAutoFocus);

      const unmountEvent = new CustomEvent(AUTOFOCUS_ON_UNMOUNT, EVENT_OPTIONS);
      container.addEventListener(AUTOFOCUS_ON_UNMOUNT, onUnmountAutoFocus);
      container.dispatchEvent(unmountEvent);
      if (!unmountEvent.defaultPrevented) {
        focus(previouslyFocusedElement ?? document.body, { select: true });
      }
      // we need to remove the listener after we `dispatchEvent`
      container.removeEventListener(AUTOFOCUS_ON_UNMOUNT, onUnmountAutoFocus);

      focusScopesStack.remove(focusScope);
    };
  }, [
    enabled,
    container,
    forceUnmount,
    onMountAutoFocus,
    onUnmountAutoFocus,
    focusScope,
  ]);

  // Takes care of looping focus (when tabbing whilst at the edges)
  const handleKeyDown = React.useCallback(
    (event: React.KeyboardEvent) => {
      if (!trapped) return;
      if (!loop) return;
      if (focusScope.paused) return;

      const isTabKey =
        event.key === 'Tab' &&
        !event.altKey &&
        !event.ctrlKey &&
        !event.metaKey;
      const focusedElement = document.activeElement as HTMLElement | null;

      if (isTabKey && focusedElement) {
        const container = event.currentTarget as HTMLElement;
        const [first, last] = getTabbableEdges(container);
        const hasTabbableElementsInside = first && last;

        // we can only wrap focus if we have tabbable edges
        if (!hasTabbableElementsInside) {
          if (focusedElement === container) event.preventDefault();
        } else {
          if (!event.shiftKey && focusedElement === last) {
            event.preventDefault();
            if (loop) focus(first, { select: true });
          } else if (event.shiftKey && focusedElement === first) {
            event.preventDefault();
            if (loop) focus(last, { select: true });
          }
        }
      }
    },
    [loop, trapped, focusScope.paused]
  );

  return {
    tabIndex: -1,
    ...scopeProps,
    ref: composedRefs,
    onKeyDown: handleKeyDown,
  };
}

/* -------------------------------------------------------------------------------------------------
 * Utils
 * -----------------------------------------------------------------------------------------------*/

/**
 * Attempts focusing the first element in a list of candidates.
 * Stops when focus has actually moved.
 */
function focusFirst(candidates: HTMLElement[], { select = false } = {}) {
  const previouslyFocusedElement = document.activeElement;
  for (const candidate of candidates) {
    focus(candidate, { select });
    if (document.activeElement !== previouslyFocusedElement) return;
  }
}

/**
 * Returns the first and last tabbable elements inside a container.
 */
function getTabbableEdges(container: HTMLElement) {
  const candidates = getTabbableCandidates(container);
  const first = findVisible(candidates, container);
  const last = findVisible(candidates.reverse(), container);
  return [first, last] as const;
}

/**
 * Returns a list of potential tabbable candidates.
 *
 * NOTE: This is only a close approximation. For example it doesn't take into account cases like when
 * elements are not visible. This cannot be worked out easily by just reading a property, but rather
 * necessitate runtime knowledge (computed styles, etc). We deal with these cases separately.
 *
 * See: https://developer.mozilla.org/en-US/docs/Web/API/TreeWalker
 * Credit: https://github.com/discord/focus-layers/blob/master/src/util/wrapFocus.tsx#L1
 */
function getTabbableCandidates(container: HTMLElement) {
  const nodes: HTMLElement[] = [];
  const walker = document.createTreeWalker(container, NodeFilter.SHOW_ELEMENT, {
    acceptNode: (node: any) => {
      const isHiddenInput = node.tagName === 'INPUT' && node.type === 'hidden';
      if (node.disabled || node.hidden || isHiddenInput)
        return NodeFilter.FILTER_SKIP;
      // `.tabIndex` is not the same as the `tabindex` attribute. It works on the
      // runtime's understanding of tabbability, so this automatically accounts
      // for any kind of element that could be tabbed to.
      return node.tabIndex >= 0
        ? NodeFilter.FILTER_ACCEPT
        : NodeFilter.FILTER_SKIP;
    },
  });
  while (walker.nextNode()) nodes.push(walker.currentNode as HTMLElement);
  // we do not take into account the order of nodes with positive `tabIndex` as it
  // hinders accessibility to have tab order different from visual order.
  return nodes;
}

/**
 * Returns the first visible element in a list.
 * NOTE: Only checks visibility up to the `container`.
 */
function findVisible(elements: HTMLElement[], container: HTMLElement) {
  for (const element of elements) {
    // we stop checking if it's hidden at the `container` level (excluding)
    if (!isHidden(element, { upTo: container })) return element;
  }
  return;
}

function isHidden(node: HTMLElement, { upTo }: { upTo?: HTMLElement }) {
  if (getComputedStyle(node).visibility === 'hidden') return true;
  while (node) {
    // we stop at `upTo` (excluding it)
    if (upTo !== undefined && node === upTo) return false;
    if (getComputedStyle(node).display === 'none') return true;
    node = node.parentElement as HTMLElement;
  }
  return false;
}

function isSelectableInput(
  element: any
): element is FocusableTarget & { select: () => void } {
  return element instanceof HTMLInputElement && 'select' in element;
}

function focus(element?: FocusableTarget | null, { select = false } = {}) {
  // setTimeout because this is triggered often by an action that opens something with an animation
  // so to avoid issues conflicting with the open render / animation wait for next free period
  setTimeout(() => {
    // only focus if that element is focusable
    if (element?.focus) {
      const previouslyFocusedElement = document.activeElement;
      // NOTE: we prevent scrolling on focus, to minimize jarring transitions for users
      element.focus({ preventScroll: true });
      // only select if its not the same element, it supports selection and we need to select
      if (
        element !== previouslyFocusedElement &&
        isSelectableInput(element) &&
        select
      )
        element.select();
    }
  });
}

/* -------------------------------------------------------------------------------------------------
 * FocusScope stack
 * -----------------------------------------------------------------------------------------------*/

type FocusScopeAPI = { paused: boolean; pause(): void; resume(): void };
const focusScopesStack = createFocusScopesStack();

function createFocusScopesStack() {
  /** A stack of focus scopes, with the active one at the top */
  let stack: FocusScopeAPI[] = [];

  return {
    add(focusScope: FocusScopeAPI) {
      // pause the currently active focus scope (at the top of the stack)
      const activeFocusScope = stack[0];
      if (focusScope !== activeFocusScope) {
        activeFocusScope?.pause();
      }
      // remove in case it already exists (because we'll re-add it at the top of the stack)
      stack = arrayRemove(stack, focusScope);
      stack.unshift(focusScope);
    },

    remove(focusScope: FocusScopeAPI) {
      stack = arrayRemove(stack, focusScope);
      stack[0]?.resume();
    },
  };
}

function arrayRemove<T>(array: T[], item: T) {
  const updatedArray = [...array];
  const index = updatedArray.indexOf(item);
  if (index !== -1) {
    updatedArray.splice(index, 1);
  }
  return updatedArray;
}

function removeLinks(items: HTMLElement[]) {
  return items.filter((item) => item.tagName !== 'A');
}

export { FocusScope };

export type { FocusScopeProps };