Lua rules examples

local ok_langs = {
  ['en'] = true,
  ['ca'] = true,
  ['es'] = true,
  ['fr'] = true,
}

rspamd_config.LANG_FILTER = {
  callback = function(task)
    local any_ok = false
    local parts = task:get_text_parts() or {}
    local ln
    for _,p in ipairs(parts) do
      ln = p:get_language() or ''
      local dash = ln:find('-')
      if dash then
        -- from zh-cn to zh
        ln = ln:sub(1, dash-1)
      end
      if ok_langs[ln] then
        any_ok = true
        break
      end
    end
    if any_ok or not ln or #ln == 0 then
      return false
    end
    return 1.0,ln
  end,
  score = 2.0,
  description = 'no ok languages',
}

local fun = require "fun"
local logger = require "rspamd_logger"

-- Returns newline delimiter for specific task
local function get_newline_delim(task)

  local nlines = task:get_newlines_type()
  local fchars = "\r\n"
  if nlines == 'cr' then
    fchars = "\r"
  elseif nlines == 'lf' then
    fchars = "\n"
  end

  return fchars
end

-- Stores symbols into generic headers
local function symbols_to_header(task)
  local syms = task:get_symbols_all()
  local hdr = {}
  local res = task:get_metric_score()

  hdr[1] = string.format('default: False [%.2f / %.2f]', res[1], res[2])
  local m = fun.map(function(sym)
    return string.format('%s(%.2f)[%s]', sym.name, sym.score, table.concat(sym.options or {}, ','))
  end, syms)

  fun.each(function(e)
    hdr[#hdr + 1] = e
  end, m)

  local crlf = get_newline_delim(task)
  local folded = table.concat(hdr, crlf .. '  ')
  return string.format('%s: %s%s', 'X-Spamd-Result', folded, crlf)
end

-- Performs maildir saving, sharded by day
local function save_task(task, folder, extra_hdrs)
  local util = require "rspamd_util"
  -- To organise moving
  local base_folder = '/var/spool/dovecot/maildir/tmp'
  local dst_folder = '/var/spool/dovecot/maildir'
  
  -- Random filename
  local fname = string.format('%s', util.random_hex(64))
  local src_folder = string.format('%s/', base_folder)
  util.mkdir(src_folder)
  local src_file = string.format('%s/%s', src_folder, fname)
  file = io.open(src_file, 'w')

  if not file then
    logger.errx('cannot save file %s', src_file)
    return false
  end
  
  -- Add some more data when saving
  file:write(tostring(task:get_raw_headers()))
  file:write(symbols_to_header(task))

  for k,v in pairs(extra_hdrs) do
    file:write(k, ': ')
    file:write(util.fold_header(k, v))
    file:write(get_newline_delim(task))
  end

  file:write(get_newline_delim(task))
  file:write(tostring(task:get_rawbody()))
  file:close()
  
  local err,st = util.stat(src_file)
  -- Perform sharding, ensure that dirs are existing
  local dst_folder = string.format('%s/.%s.%s/', dst_folder, os.date('%F'), folder)
  util.mkdir(dst_folder)
  dst_folder = dst_folder .. '/new'
  util.mkdir(dst_folder)
  local dst_file = string.format('%s/%s,S=%s', dst_folder, fname, st.size)
  -- Final rename
  os.rename(src_file, dst_file)

  logger.messagex(task, 'saved in %s', dst_file)

  return true
end

rspamd_config.SAVE_MAILDIR = {
  callback = function(task)

    local foo_var = task:get_mempool():get_variable('FOO')
    local bar_var = task:get_mempool():get_variable('BAR')
    local res = task:get_metric_result()

    if foo_var then
      save_task(task, 'foo', {['X-Rspamd-FOO'] = foo_var})
    elseif bar_var then
      save_task(task, 'bar', {['X-Rspamd-BAR'] = bar_var})
    elseif task:has_symbol('LEAKED_PASSWORD_SCAM') then
      save_task(task, 'bitcoin', {})
    elseif task:has_symbol('DMARC_POLICY_REJECT') or task:has_symbol('R_DKIM_REJECT') then
      save_task(task, 'policy_failure', {})
    elseif res.score <= 0 then
      -- Sampling, 10%
      if math.random() > 0.9 then
        save_task(task, 'ham', {})
      end
    else
      -- Sampling 0.1%
      if math.random() > 0.999 then
        save_task(task, 'gen', {})
      end
    end
  end,
  type = 'idempotent',
  priority = 10,
}