--[[
Copyright (c) 2018, Vsevolod Stakhov <vsevolod@highsecure.ru>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
]]--

--[[[
-- @module savapi
-- This module contains avira savapi antivirus access functions
--]]

local lua_util = require "lua_util"
local tcp = require "rspamd_tcp"
local upstream_list = require "rspamd_upstream_list"
local rspamd_logger = require "rspamd_logger"
local common = require "lua_scanners/common"

local N = "sophos"

local default_message = '${SCANNER}: virus found: "${VIRUS}"'

local function sophos_config(opts)
  local sophos_conf = {
    name = N,
    scan_mime_parts = true,
    scan_text_mime = false,
    scan_image_mime = false,
    default_port = 4010,
    timeout = 15.0,
    log_clean = false,
    retransmits = 2,
    cache_expire = 3600, -- expire redis in one hour
    message = default_message,
    detection_category = "virus",
  }

  sophos_conf = lua_util.override_defaults(sophos_conf, opts)

  if not sophos_conf.prefix then
    sophos_conf.prefix = 'rs_' .. sophos_conf.name .. '_'
  end

  if not sophos_conf.log_prefix then
    if sophos_conf.name:lower() == sophos_conf.type:lower() then
      sophos_conf.log_prefix = sophos_conf.name
    else
      sophos_conf.log_prefix = sophos_conf.name .. ' (' .. sophos_conf.type .. ')'
    end
  end

  if not sophos_conf['servers'] then
    rspamd_logger.errx(rspamd_config, 'no servers defined')

    return nil
  end

  sophos_conf['upstreams'] = upstream_list.create(rspamd_config,
      sophos_conf['servers'],
      sophos_conf.default_port)

  if sophos_conf['upstreams'] then
    lua_util.add_debug_alias('antivirus', sophos_conf.name)
    return sophos_conf
  end

  rspamd_logger.errx(rspamd_config, 'cannot parse servers %s',
      sophos_conf['servers'])
  return nil
end

local function sophos_check(task, content, digest, rule)
  local function sophos_check_uncached ()
    local upstream = rule.upstreams:get_upstream_round_robin()
    local addr = upstream:get_addr()
    local retransmits = rule.retransmits
    local protocol = 'SSSP/1.0\n'
    local streamsize = string.format('SCANDATA %d\n', #content)
    local bye = 'BYE\n'

    local function sophos_callback(err, data, conn)

      if err then
        -- set current upstream to fail because an error occurred
        upstream:fail()

        -- retry with another upstream until retransmits exceeds
        if retransmits > 0 then

          retransmits = retransmits - 1

          -- Select a different upstream!
          upstream = rule.upstreams:get_upstream_round_robin()
          addr = upstream:get_addr()

          lua_util.debugm(rule.name, task, '%s: error: %s; retry IP: %s; retries left: %s',
              rule.log_prefix, err, addr, retransmits)

          tcp.request({
            task = task,
            host = addr:to_string(),
            port = addr:get_port(),
            timeout = rule['timeout'],
            callback = sophos_callback,
            data = { protocol, streamsize, content, bye }
          })
        else
          rspamd_logger.errx(task, '%s [%s]: failed to scan, maximum retransmits exceed', rule['symbol'], rule['type'])
          common.yield_result(task, rule, 'failed to scan and retransmits exceed', 0.0, 'fail')
        end
      else
        upstream:ok()
        data = tostring(data)
        lua_util.debugm(rule.name, task,
            '%s [%s]: got reply: %s', rule['symbol'], rule['type'], data)
        local vname = string.match(data, 'VIRUS (%S+) ')
        local cached
        if vname then
          common.yield_result(task, rule, vname)
          common.save_cache(task, digest, rule, vname)
        else
          if string.find(data, 'DONE OK') then
            if rule['log_clean'] then
              rspamd_logger.infox(task, '%s: message or mime_part is clean', rule.log_prefix)
            else
              lua_util.debugm(rule.name, task,
                  '%s: message or mime_part is clean', rule.log_prefix)
            end
            cached = 'OK'
            -- not finished - continue
          elseif string.find(data, 'ACC') or string.find(data, 'OK SSSP') then
            conn:add_read(sophos_callback)
          elseif string.find(data, 'FAIL 0212') then
            rspamd_logger.warnx(task, 'Message is encrypted (FAIL 0212): %s', data)
            common.yield_result(task, rule, 'SAVDI: Message is encrypted (FAIL 0212)', 0.0, 'encrypted')
            cached = 'ENCRYPTED'
          elseif string.find(data, 'REJ 4') then
            rspamd_logger.warnx(task, 'Message is oversized (REJ 4): %s', data)
            common.yield_result(task, rule, 'SAVDI: Message oversized (REJ 4)', 0.0, 'fail')
            -- excplicitly set REJ1 message when SAVDIreports a protocol error
          elseif string.find(data, 'REJ 1') then
            rspamd_logger.errx(task, 'SAVDI (Protocol error (REJ 1)): %s', data)
            common.yield_result(task, rule, 'SAVDI: Protocol error (REJ 1)', 0.0, 'fail')
          else
            rspamd_logger.errx(task, 'unhandled response: %s', data)
            common.yield_result(task, rule, 'unhandled response: ' .. data, 0.0, 'fail')
          end
          if cached then
            common.save_cache(task, digest, rule, cached)
          end
        end
      end
    end

    tcp.request({
      task = task,
      host = addr:to_string(),
      port = addr:get_port(),
      timeout = rule['timeout'],
      callback = sophos_callback,
      data = { protocol, streamsize, content, bye }
    })
  end

  if common.condition_check_and_continue(task, content, rule, digest, sophos_check_uncached) then
    return
  else
    sophos_check_uncached()
  end

end

return {
  type = 'antivirus',
  description = 'sophos antivirus',
  configure = sophos_config,
  check = sophos_check,
  name = N
}