text: module.exports = function expectCt (options) {
    var headerValue = getHeaderValue(options)
  
    return function expectCt (req, res, next) {
      res.setHeader('Expect-CT', headerValue)
      next()
    }
  }
  
  function getHeaderValue (options) {
    options = options || {}
  
    var directives = []
  
    if (options.enforce) {
      directives.push('enforce')
    }
  
    directives.push('max-age=' + parseMaxAge(options.maxAge))
  
    if (options.reportUri) {
      directives.push('report-uri="' + options.reportUri + '"')
    }
  
    return directives.join('; ')
  }
  
  function parseMaxAge (option) {
    if (option == null) { return 0 }
  
    if ((typeof option !== 'number') || (option < 0)) {
      throw new Error(option + ' is not a valid value for maxAge. Please choose a positive integer.')
    }
  
    return option
  }
  