# frozen_string_literal: true

# Builds random human-friendly usernames (e.g. "QuietFalcon42") for accounts
# created without user input, where no signup data can (or may) be used to
# derive one. The word lists are site settings so communities can tailor them
# to their tone or language.
module RandomUsernameGenerator
  # Returns nil when the site has opted out, or when the configured word lists
  # can't produce a usable name, so callers fall back to their own suggestion.
  def self.generate
    return nil if !SiteSetting.enable_random_usernames

    adjective = pick(SiteSetting.random_username_adjectives_map)
    noun = pick(SiteSetting.random_username_nouns_map)
    return nil if adjective.blank? || noun.blank?

    # A numeric suffix widens the namespace well beyond the word-pair count,
    # so very large sites don't exhaust it.
    candidate = "#{adjective}#{noun}#{rand(10..99)}"
    UserNameSuggester.find_available_username_based_on(
      UserNameSuggester.rightsize_username(candidate),
    )
  end

  # Words are admin-supplied, so skip any that sanitization would rewrite (a
  # non-Latin word once unicode usernames are turned back off, say) rather than
  # letting the replacement character leak into generated names.
  def self.pick(words)
    word = words.shuffle.find { |w| UserNameSuggester.sanitize_username(w) == w }
    # Only the leading letter, so a word like "McFly" keeps its shape.
    word&.sub(/\A./) { |first| first.upcase }
  end
  private_class_method :pick
end