validatePath.js

function validatePath (path) {
  const components = path.split('/');
  const validatedFolderTree = [];

  const getRootFolders = foldersApi.getTopLevelFolders();

  const finalValidationPromise = components.reduce((promise, folder, index) => {
    const folderName = folder.toLowerCase();
    return promise
      .then(parentChildren => {
        const folderInChildren = parentChildren.find(child => child.name.toLowerCase() === folderName);
        if (!folderInChildren) {
          // Offset index by one since slice's end parameter is exclusive
          // TODO: LOC
          throw new Error(`Path validation failed: The folder ${components.slice(0, index + 1).join('/')} could not be found.`);
        }
        else {
          validatedFolderTree.push(folderInChildren);
          return foldersApi.getChildFolders(folderInChildren.id);
        }
      })
      .then(childFolders => {
        validatedFolderTree[index].children = childFolders;
        return childFolders;
      });
  }, getRootFolders);

  return finalValidationPromise.then(() => validatedFolderTree);
}