JavaScript spike into finding node at a position within another, and then returning a result that supplies information that can be used to construct a selection/range for moving the cursor

find-node-at-position.js

function findNodeAtPosition(node, position) {
  const result = { node: undefined, offset: undefined, found: false, currentPosition: 0 };
  return findNodeAtPositionWithResult(result, node, position);
}

function findNodeAtPositionWithResult(result, node, position, indent = '  ') {
  console.log(indent + 'findNodeAtPositionWithResult: ', result, node, position);

  let currentPosition = result.currentPosition;
  let childNode;
  let offset;

  for (childNode of node.childNodes) {
    console.log(indent + ' childNode: ', childNode);
    offset = 0;

    if (childNode.nodeType === Node.ELEMENT_NODE) {
      result = findNodeAtPositionWithResult({
        node: undefined,
        offset: undefined,
        found: false,
        currentPosition: currentPosition
      }, childNode, position);

      if (result.found) {
        return result;
      } else {
        currentPosition = result.currentPosition + 1; // for a new line
        childNode = result.node;
      }

      console.log(indent + ' after element', result);
    } else if (childNode.nodeType === Node.TEXT_NODE) {
      if (currentPosition + childNode.length >= position) {
        offset = position - currentPosition;
        currentPosition = position;

        console.log(indent + ' text', currentPosition, ' offset ', offset);
        result = { node: childNode, offset: offset, currentPosition: currentPosition, found: true };
        console.log(indent + 'got it: ', result);
        return result;
      } else {
        currentPosition = currentPosition + childNode.length;
      }
    }
  }

  result = { node: childNode, offset: undefined, currentPosition: currentPosition, found: false };
  console.log(indent + ' return',  result);
  return result;
}

find-position-of-cursor-in-node.js

function findPositionOfCursorInNode(node, result = null, sel = null, range = null, indent = ''){
  if (!result) {
    result = { position: 0, found: false };
  }

  if(!sel) {
    sel = window.getSelection();
  }

  if (!range) {
    range = sel.getRangeAt(0);
    console.log('range: ', range);
  }

  for (childNode of node.childNodes) {
    console.log(indent + 'childNode: ', childNode);
    if (childNode === range.startContainer) {
      console.log('found start', childNode)
      return { position: result.position + range.startOffset, found: true };
    } 
    
    if (childNode === range.endContainer) {
      // no-op
    }

    if (childNode.nodeType === Node.ELEMENT_NODE) {
      result = findPositionOfCursorInNode(childNode, result, sel, range, indent + '  ');
      if(result.found) {
        return result;
      } else {
        result = { position: result.position + 1, found: false }; // add 1 for newline
      }

    } else if (childNode.nodeType === Node.TEXT_NODE) {
      console.log(indent + 'result.position + childNode.length: ', result.position + childNode.length, childNode);
      result = { position: result.position + childNode.length, found: false };
    }
  }

  return result;
}