Rspamd Lua - match spam with alliteration in from display name, subject and 3 body words

rspamd.lua

-- Match Spam with alliteration in from display name, subject and 3 body words
-- e.g.
-- MIME From: "Schloemer" <axmyyxb@salebig.pro.ac>
-- Subject: Schutjer
-- Body: Seetaram Sesay Sheker
rspamd_config:register_symbol{
  type = 'callback', -- or virtual, callback, prefilter or postfilter
  name = 'SPAM_ALLITERATION',
  score = 0.0, -- Metric score

  callback = function(task)

    local symbol = "SPAM_ALLITERATION"

    local from_dn = (((task:get_from('mime') or E)[1] or E).name or "")
    local from_dn_1 = from_dn:sub(1,1)
    local subject = task:get_subject() or ""
    local subject_1 = subject:sub(1,1)
    local parts = task:get_text_parts() or E

    if from_dn:match("^%a+$") and subject:match("^%a+$")
      and from_dn_1 == subject_1
      then

      local aliteration = true

      for _,p in ipairs(parts) do
        if not p:is_html() then
          local word_c = p:get_words_count(p)

          if word_c == 3 then
            local words = p:get_words('raw')
            for _, w in ipairs(words) do
              if w:sub(1,1) ~= from_dn_1 then
                aliteration = false
              end
            end
          end
        end
      end

      if aliteration then
        task:insert_result(symbol, 1.0, from_dn_1)
        return true
      end
    end

    return false
  end,
}