discourse/lib/validators/censored_words_validator.rb

class CensoredWordsValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    if SiteSetting.censored_words.present? && (censored_words = censor_words(value, censored_words_regexp)).present?
      record.errors.add(
        attribute, :contains_censored_words,
        censored_words: join_censored_words(censored_words)
      )
    elsif SiteSetting.censored_pattern.present? && (censored_words = censor_words(value, /#{SiteSetting.censored_pattern}/i)).present?
      record.errors.add(
        attribute, :matches_censored_pattern,
        censored_words: join_censored_words(censored_words)
      )
    end
  end

  private

    def censor_words(value, regexp)
      censored_words = value.scan(regexp)
      censored_words.flatten!
      censored_words.compact!
      censored_words.map!(&:strip)
      censored_words.select!(&:present?)
      censored_words.uniq!
      censored_words
    end

    def join_censored_words(censored_words)
      censored_words.map!(&:downcase)
      censored_words.uniq!
      censored_words.join(", ".freeze)
    end

    def censored_words_regexp
      Regexp.new(
        '\b(' + SiteSetting.censored_words.split('|'.freeze).map! { |w| Regexp.escape(w) }.join('|'.freeze) + ')\b',
        true
      )
    end
end