discourse/lib/validators/string_setting_validator.rb

class StringSettingValidator
  def initialize(opts = {})
    @opts = opts
    @regex = Regexp.new(opts[:regex]) if opts[:regex]
    @regex_error = opts[:regex_error] || 'site_settings.errors.regex_mismatch'
  end

  def valid_value?(val)
    return true if !val.present?

    if (@opts[:min] && @opts[:min].to_i > (val.length)) || (@opts[:max] && @opts[:max].to_i < (val.length))
      @length_fail = true
      return false
    end

    if @regex && !(val =~ @regex)
      @regex_fail = true
      return false
    end

    true
  end

  def error_message
    if @regex_fail
      I18n.t(@regex_error)
    elsif @length_fail
      if @opts[:min] && @opts[:max]
        I18n.t('site_settings.errors.invalid_string_min_max', min: @opts[:min], max: @opts[:max])
      elsif @opts[:min]
        I18n.t('site_settings.errors.invalid_string_min', min: @opts[:min])
      else
        I18n.t('site_settings.errors.invalid_string_max', max: @opts[:max])
      end
    else
      I18n.t('site_settings.errors.invalid_string')
    end
  end
end