/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 */
import {
  $getRoot,
  $isDecoratorNode,
  $isElementNode,
  $isParagraphNode,
  $isTextNode,
} from 'lexical';

import {$isRootTextContentEmpty} from './isRootTextContentEmpty';

/**
 * Determines if the input should show the placeholder. If anything is in
 * in the root the placeholder should not be shown.
 * @param isComposing - Is the editor in composition mode due to an active Input Method Editor?
 * @returns true if the input should show the placeholder, false otherwise.
 */
export function $canShowPlaceholder(isComposing: boolean): boolean {
  if (!$isRootTextContentEmpty(isComposing, false)) {
    return false;
  }

  const root = $getRoot();
  const children = root.getChildren();
  const childrenLength = children.length;

  if (childrenLength > 1) {
    return false;
  }

  for (let i = 0; i < childrenLength; i++) {
    const topBlock = children[i];

    if ($isDecoratorNode(topBlock)) {
      return false;
    }

    if ($isElementNode(topBlock)) {
      if (!$isParagraphNode(topBlock)) {
        return false;
      }

      if (topBlock.__indent !== 0) {
        return false;
      }

      const topBlockChildren = topBlock.getChildren();
      const topBlockChildrenLength = topBlockChildren.length;

      for (let s = 0; s < topBlockChildrenLength; s++) {
        const child = topBlockChildren[i];

        if (!$isTextNode(child)) {
          return false;
        }
      }
    }
  }

  return true;
}

/**
 * Returns a function that executes {@link $canShowPlaceholder}
 * @param isEditorComposing - Is the editor in composition mode due to an active Input Method Editor?
 * @returns A function that executes $canShowPlaceholder with arguments.
 */
export function $canShowPlaceholderCurry(
  isEditorComposing: boolean,
): () => boolean {
  return () => $canShowPlaceholder(isEditorComposing);
}