path: root/app/lib/command_tag/processor.rb

# frozen_string_literal: true

#                  .~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.                  #
###################              Cthulhu Code!              ###################
#                  `~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`                  #
# - Interprets and executes user input.  THIS CAN BE VERY DANGEROUS!          #
# - Has a high complexity level and needs tests.                              #
# - May destroy objects passed to it.                                         #
# - Incurs a high performance penalty.                                        #
#                                                                             #
###############################################################################

class CommandTag::Processor
  include Redisable
  include ImgProxyHelper
  include CommandTag::Commands

  STATEMENT_RE = /^\s*#!\s*([^\n]+ (?:start|begin|do)$.*?)\n\s*#!\s*(?:end|stop|done)\s*$|^\s*#!\s*(.*?)\s*$/im.freeze
  STATEMENT_STRIP_RE = /^\s*#!\s*(?:[^\n]+ (?:start|begin|do)$.*?)\n\s*#!\s*(?:end|stop|done)\s*$\n?|^\s*#!\s*(?:.*?)\s*$\n?/im.freeze
  TEMPLATE_RE = /%%\s*(.*?)\s*%%/.freeze
  ESCAPE_MAP = {
    '\n' => "\n",
    '\r' => "\r",
    '\t' => "\t",
    '\\\\' => '\\',
  }.freeze

  def initialize(account, status)
    @account      = account
    @status       = status
    @parent       = status.thread
    @conversation = status.conversation
    @run_once     = Set[]
    @vars         = {}
    @text         = prepare_input(status.text)
    @statements   = []

    return unless @account.present? && @account.local? && @status.present?
  end

  def process!
    reset_status_caches

    parse_statements
    @text = @text.gsub(STATEMENT_STRIP_RE, '').split("\n")

    %w(at_start once_at_start).each { |suffix| execute_statements(suffix) }
    @text = parse_templates(@text.join("\n")).rstrip
    %w(before_save once_before_save).each { |suffix| execute_statements(suffix) }

    if @text.blank? || @text.gsub(Account::MENTION_RE, '').strip.blank?
      %w(when_blank once_when_blank).each { |suffix| execute_statements(suffix) }

      unless (@status.published? && !@status.edited.zero?) || @text.present?
        %w(before_destroy once_before_destroy).each { |suffix| execute_statements(suffix) }
        @status.destroy
        %w(after_destroy once_after_destroy).each { |suffix| execute_statements(suffix) }
      end
    elsif @status.destroyed?
      %w(after_destroy once_after_destroy).each { |suffix| execute_statements(suffix) }
    else
      update_semiprivate_attribute
      @status.text = @text
      process_inline_images!
      if @status.save
        %w(after_save once_after_save).each { |suffix| execute_statements(suffix) }
      else
        %w(after_save_fail once_after_save_fail).each { |suffix| execute_statements(suffix) }
      end
    end

    %w(at_end once_at_end).each { |suffix| execute_statements(suffix) }
    reset_status_caches
  end

  private

  def prepare_input(text)
    text.gsub(/\r\n|\n\r|\r/, "\n")
        .gsub(/^\s*((?:(?:#{Account::MENTION_RE}|#{Tag::HASHTAG_RE})\s*)+)#!/, "\\1\n#!")
  end

  def parse_templates(text)
    text.gsub(TEMPLATE_RE) do
      return if Regexp.last_match(1).blank?

      template = Regexp.last_match(1).scan(/'([^']*)'|"([^"]*)"|(\S+)/).flatten.compact
      return if template[0].blank?

      name      = normalize(template[0])
      separator = "\n"

      if template.count > 2
        if %w(by with using sep separator delim delimiter).include?(template[-2].downcase)
          separator = unescape_literals(template[-1])
          template = template[0..-3]
        elsif !template[-1].match?(/\A[-+]?[0-9]+\z/)
          separator = unescape_literals(template[-1])
          template.pop
        end
      end

      index_start = to_integer(template[1])
      index_end   = to_integer(template[2])

      if ['all', '[]'].include?(template[1])
        var(name).join(separator)
      elsif index_end.zero?
        var(name)[index_start].presence || ''
      else
        var(name)[index_start..index_end].presence || ''
      end
    end
  end

  def parse_statements
    @text.scan(STATEMENT_RE).flatten.compact.each do |statement|
      next if statement.blank?

      statement = statement.scan(/'([^']*)'|"([^"]*)"|(\S+)|\s+(?:start|begin|do)\s*$\n+(.*)/im).flatten.compact
      statement[0] = statement[0].strip.tr(':.\- ', '_').gsub(/__+/, '_').downcase
      statement[-1].rstrip! if statement.count > 1

      add_statement_handlers_for(statement) if statement[0].present?
    end
  end

  def potential_handlers_for(name)
    ['_once', ''].each_with_index do |count_affix, index|
      %w(at_start when_blank at_end).each do |when_affix|
        yield ["handle_#{name}#{count_affix}_#{when_affix}", index.zero?]
      end

      %w(destroy save postprocess save_fail).each do |event_affix|
        %w(before after).each do |when_affix|
          yield ["handle_#{name}#{count_affix}_#{when_affix}_#{event_affix}", index.zero?]
        end
      end
    end
  end

  def add_statement_handlers_for(statement_array)
    potential_handlers_for(statement_array[0]) do |handler, once|
      (@statements << [handler, statement_array[1..-1]]) if respond_to?(handler) && !(once && @run_once.include?(handler))
      @run_once << handler if once
    end
  end

  def execute_statements(event)
    @statements.select { |handler, _| handler.end_with?("_#{event}") }.each do |handler, arguments|
      public_send(handler, arguments)
    end
  end

  def reset_status_caches
    [@status, @parent].each do |status|
      next unless @account.id == status&.account_id

      Rails.cache.delete_matched("statuses/#{status.id}-*")
      Rails.cache.delete("statuses/#{status.id}")
      Rails.cache.delete(status)
      redis.zremrangebyscore("spam_check:#{status.account.id}", status.id, status.id)
    end
  end

  def author_of_status?
    @account.id == @status.account_id
  end

  def author_of_parent?
    @account.id == @parent&.account_id
  end

  def destroy_status!
    @status.destroy unless @status.destroyed?
  end

  def status_still_semiprivate?
    @status.domain_permissions.exists? || @account.followers.where(domain: @account.domain_permissions.select(:domain)).exists?
  end

  def update_semiprivate_attribute
    @status.semiprivate = @semiprivate.presence || status_still_semiprivate?
  end

  def normalize(text)
    text.to_s.strip.downcase
  end

  def to_integer(text)
    text&.strip.to_i
  end

  def unescape_literals(text)
    ESCAPE_MAP.each { |escaped, unescaped| text.gsub!(escaped, unescaped) }
    text
  end

  def html_encode(text)
    (@html_entities ||= HTMLEntities.new).encode(text)
  end

  def var(name)
    @vars[name].presence || []
  end

  def read_visibility_from(arg)
    return if arg.strip.blank?

    arg = case arg.strip
          when 'p', 'pu', 'all', 'world'
            'public'
          when 'u', 'ul'
            'unlisted'
          when 'f', 'follower', 'followers', 'packmates', 'follower-only', 'followers-only', 'packmates-only'
            'private'
          when 'd', 'dm', 'pm', 'directmessage'
            'direct'
          when 'default', 'reset'
            @account.user.setting_default_privacy
          else
            arg.strip
          end

    %w(public unlisted private limited direct).include?(arg) ? arg : nil
  end

  def read_falsy_from(arg)
    %w(false no off disable).include?(arg)
  end

  def read_truthy_from(arg)
    %w(true yes on enable).include?(arg)
  end

  def read_boolean_from(arg)
    arg.present? && (read_truthy_from(arg) || !read_falsy_from(arg))
  end

  def normalize_domain(domain)
    return if domain&.strip.blank? || !domain.include?('.')

    domain.split('.').map(&:strip).reject(&:blank?).join('.').downcase
  end

  def federating_with_domain?(domain)
    return false if domain.blank?

    DomainAllow.where(domain: domain).exists? || Account.where(domain: domain, suspended_at: nil).exists?
  end
end