validate: {
      validDirectoryString () {
        // Required here - because it's not defined on init (Framework limitations)
        const Directory = require('../models').Directory
        const bookmark = this

        if (!this.directory_id && (!this.directory || (this.directory === '/'))) {
          // It belongs to root directory, and is not a problem
          return true
        }

        if (this.directory_id) {
          return Directory.findOne({where: {id: this.directory_id}}).then(dir => {
            if (!dir) throw new Error('Invalid directory ID - directory could not be found.')
            bookmark.directory = dir.directory
          })
        }

        let dirList = directoryMixin.parseDirList(this.directory)

        // Recursive promise magic - each element of the directory structure gets
        // thrown onto the promise chain, until the whole structure is built
        function recursiveDirectoryCreation (dirList, index, parentId) {
          function _recursePromise (newDir) {
            let parent = newDir ? newDir.id : null
            let directoryName = '/' + dirList.slice(0, index + 1).join('/') + '/'
            if (dirList.length === (index + 1)) {
              return Directory.create({directory: directoryName, parent: parent, user_id: bookmark.user_id})
            }
            index += 1

            return Directory.create({
              directory: directoryName,
              parent: parent,
              user_id: bookmark.user_id
            }).then(_recursePromise)
          }

          return _recursePromise(null)
        }

        return Directory.find({where: {
          user_id: bookmark.user_id,
          directory: bookmark.directory
        }}).then((matchedDir) => {
          if (!matchedDir) {
            return recursiveDirectoryCreation(dirList, 0, null).then((dir) => {
              bookmark.directory_id = dir.id
            })
          }
          bookmark.directory_id = matchedDir.id
        })
      }
    },