api/sanitiser/_categories.js

var check = require('check-types');

var ERRORS = {
  empty: 'Categories parameter cannot be left blank. See documentation of service for valid options.',
  invalid: 'Invalid categories parameter value(s). See documentation of service for valid options.'
};

// validate inputs, convert types and apply defaults
function sanitize( raw, clean, validCategories ) {

  // error & warning messages
  var messages = {errors: [], warnings: []};

  // it's not a required parameter, so if it's not provided just move on
  if (!raw.hasOwnProperty('categories')) {
    return messages;
  }

  if (!check.nonEmptyString(raw.categories)) {
    messages.errors.push(ERRORS.empty);
    return messages;
  }

  // if categories string has been set
  // map input categories to valid format
  try {
    clean.categories = raw.categories.split(',')
      .map(function (cat) {
        return cat.toLowerCase().trim(); // lowercase inputs
      })
      .filter(function (cat) {
        if (check.nonEmptyString(cat) && validCategories && validCategories.indexOf(cat) !== -1) {
          return true;
        }
        throw new Error('Empty string value');
      });
  } catch (err) {
    // remove everything from the list if there was any error
    delete clean.categories;
  }

  if (check.undefined(clean.categories) || check.emptyArray(clean.categories)) {
    messages.errors.push(ERRORS.invalid);
  }

  return messages;
}

// export function
module.exports = sanitize;