@atlaskit/editor-plugin-show-diff/dist/es2019/pm-plugins/areDocsEqualByBlockStructureAndText.js

ShowDiff plugin for @atlaskit/editor-core

import { Transform } from '@atlaskit/editor-prosemirror/transform';

/**
 * Returns a copy of the document with all marks removed from all text.
 * This normalises mark fragmentation — e.g. annotation marks reordering can split
 * a single text run into many text nodes, making structural comparison unreliable.
 * After stripping, ProseMirror will merge adjacent text nodes so childCounts are stable.
 */
function stripMarks(doc) {
  const tr = new Transform(doc);
  tr.removeMark(0, doc.content.size);
  return tr.doc;
}

/**
 * Returns true if both (mark-stripped) nodes have the same block tree structure (node type and child count at every level)
 */
function isBlockStructureEqual(node1, node2) {
  if (node1.type !== node2.type || node1.childCount !== node2.childCount) {
    return false;
  }
  for (let i = 0; i < node1.childCount; i++) {
    if (!isBlockStructureEqual(node1.child(i), node2.child(i))) {
      return false;
    }
  }
  return true;
}

/**
 * Looser equality for "safe diff" cases: same full text content and same block structure
 * (e.g. text moved across text-node boundaries). Used when strict areNodesEqualIgnoreAttrs fails.
 * This is safe because we ensure decorations get applied to valid positions.
 *
 * Marks are intentionally ignored — two documents that differ only in mark application
 * (e.g. bold/italic boundaries or annotation mark ordering) are considered equal here.
 * Both documents are mark-stripped before comparison so that mark-driven text fragmentation
 * does not produce false inequalities.
 */
export function areDocsEqualByBlockStructureAndText(doc1, doc2) {
  if (doc1.textContent !== doc2.textContent) {
    return false;
  }
  // Strip marks before comparing so that mark-driven text fragmentation
  // (e.g. annotation mark reordering producing different childCounts) does not
  // cause false inequalities.
  const stripped1 = stripMarks(doc1);
  const stripped2 = stripMarks(doc2);
  return doc1.nodeSize === doc2.nodeSize && isBlockStructureEqual(stripped1, stripped2);
}