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

ShowDiff plugin for @atlaskit/editor-core

import { AnalyticsStep } from '@atlaskit/adf-schema/steps';
import { areNodesEqualIgnoreAttrs } from '@atlaskit/editor-common/utils/document';
import { ReplaceStep } from '@atlaskit/editor-prosemirror/transform';

/**
 * Attempts to merge two consecutive ReplaceStep operations.
 * This merges steps where:
 * - Both steps replace content at the same starting position
 * - The second step's range encompasses the first step's range
 * - The second step has content to insert
 * Returns null if steps cannot be merged.
 */
function mergeReplaceSteps(step1, step2) {
  if (!(step1 instanceof ReplaceStep) || !(step2 instanceof ReplaceStep)) {
    return null;
  }
  // Confirm the step overlaps exactly with the previous
  const step2Length = step2.to - step2.from;
  if (step1.from === step2.from && step2.to >= step1.to && step2.slice.size >= step2Length && step2Length === step1.slice.size && step2.slice.size >= step1.slice.size && step1.slice.openEnd === step2.slice.openEnd && step1.slice.openStart === step2.slice.openStart) {
    return new ReplaceStep(step1.from, step1.to, step2.slice);
  }
  return null;
}

// Simplifies the steps to improve performance and reduce fragmentation in diffs
export function simplifySteps(steps, originalDoc) {
  const stepsToFilter = removeUnusedSteps(steps, originalDoc);
  return stepsToFilter
  // Remove steps that don't affect document structure or content
  .filter(step => !(step instanceof AnalyticsStep))
  // Merge consecutive steps where possible
  .reduce((acc, step) => {
    var _lastStep$merge, _lastStep$merge2;
    const lastStep = acc[acc.length - 1];
    const merged = (_lastStep$merge = lastStep === null || lastStep === void 0 ? void 0 : (_lastStep$merge2 = lastStep.merge) === null || _lastStep$merge2 === void 0 ? void 0 : _lastStep$merge2.call(lastStep, step)) !== null && _lastStep$merge !== void 0 ? _lastStep$merge : mergeReplaceSteps(lastStep, step);
    if (merged) {
      acc[acc.length - 1] = merged;
    } else {
      acc.push(step);
    }
    return acc;
  }, []);
}

/**
 * Does a first pass to remove steps that don't impact the document
 */
function removeUnusedSteps(steps, originalDoc) {
  const finalSteps = [];
  let firstPassDoc = originalDoc;
  for (const step of steps) {
    const result = step.apply(firstPassDoc);
    if (result.failed === null && result.doc && !areNodesEqualIgnoreAttrs(firstPassDoc, result.doc, ['localId'])) {
      finalSteps.push(step);
      firstPassDoc = result.doc;
    }
  }
  return finalSteps;
}