import * as React from "react";
import { useUpdateEffect } from "reakit-utils/useUpdateEffect";
import { warning } from "reakit-warning";
import { getFirstTabbableIn } from "reakit-utils/tabbable";
import { hasFocusWithin } from "reakit-utils/hasFocusWithin";
import { ensureFocus } from "reakit-utils/ensureFocus";
import { DialogOptions } from "../Dialog";

export function useFocusOnShow(
  dialogRef: React.RefObject<HTMLElement>,
  nestedDialogs: Array<React.RefObject<HTMLElement>>,
  options: DialogOptions
) {
  const initialFocusRef = options.unstable_initialFocusRef;
  const shouldFocus = options.visible && options.unstable_autoFocusOnShow;
  const animating = !!(options.animated && options.animating);

  useUpdateEffect(() => {
    const dialog = dialogRef.current;

    warning(
      !!shouldFocus && !dialog,
      "[reakit/Dialog]",
      "Can't set initial focus on dialog because `ref` wasn't passed to the dialog element.",
      "See https://reakit.io/docs/dialog"
    );

    if (!shouldFocus) return;
    if (!dialog) return;
    if (animating) return;

    // If there're nested open dialogs, let them handle focus
    if (nestedDialogs.some((child) => child.current && !child.current.hidden)) {
      return;
    }

    if (initialFocusRef?.current) {
      initialFocusRef.current.focus({ preventScroll: true });
    } else {
      const tabbable = getFirstTabbableIn(dialog, true);
      const isActive = () => hasFocusWithin(dialog);
      if (tabbable) {
        ensureFocus(tabbable, { preventScroll: true, isActive });
      } else {
        ensureFocus(dialog, { preventScroll: true, isActive });
        warning(
          dialog.tabIndex === undefined || dialog.tabIndex < 0,
          "It's recommended to have at least one tabbable element inside dialog. The dialog element has been automatically focused.",
          "If this is the intended behavior, pass `tabIndex={0}` to the dialog element to disable this warning.",
          "See https://reakit.io/docs/dialog/#initial-focus",
          dialog
        );
      }
    }
  }, [dialogRef, shouldFocus, animating, nestedDialogs, initialFocusRef]);
}