--[[
Copyright (c) 2019, 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 vadesecure
-- This module contains Vadesecure Filterd interface
--]]

local lua_util = require "lua_util"
local http = require "rspamd_http"
local upstream_list = require "rspamd_upstream_list"
local rspamd_logger = require "rspamd_logger"
local ucl = require "ucl"
local common = require "lua_scanners/common"

local N = 'vadesecure'

local function vade_config(opts)

  local vade_conf = {
    name = N,
    default_port = 23808,
    url = '/api/v1/scan',
    use_https = false,
    timeout = 5.0,
    log_clean = false,
    retransmits = 1,
    cache_expire = 7200, -- expire redis in 2h
    message = '${SCANNER}: spam message found: "${VIRUS}"',
    detection_category = "hash",
    default_score = 1,
    action = false,
    log_spamcause = true,
    symbol_fail = 'VADE_FAIL',
    symbol = 'VADE_CHECK',
    symbols = {
      clean = {
        symbol = 'VADE_CLEAN',
        score = -0.5,
        description = 'VadeSecure decided message to be clean'
      },
      spam = {
        high = {
          symbol = 'VADE_SPAM_HIGH',
          score = 8.0,
          description = 'VadeSecure decided message to be clearly spam'
        },
        medium = {
          symbol = 'VADE_SPAM_MEDIUM',
          score = 5.0,
          description = 'VadeSecure decided message to be highly likely spam'
        },
        low = {
          symbol = 'VADE_SPAM_LOW',
          score = 2.0,
          description = 'VadeSecure decided message to be likely spam'
        },
      },
      malware = {
        symbol = 'VADE_MALWARE',
        score = 8.0,
        description = 'VadeSecure decided message to be malware'
      },
      scam = {
        symbol = 'VADE_SCAM',
        score = 7.0,
        description = 'VadeSecure decided message to be scam'
      },
      phishing = {
        symbol = 'VADE_PHISHING',
        score = 8.0,
        description = 'VadeSecure decided message to be phishing'
      },
      commercial =  {
        symbol = 'VADE_COMMERCIAL',
        score = 0.0,
        description = 'VadeSecure decided message to be commercial message'
      },
      community =  {
        symbol = 'VADE_COMMUNITY',
        score = 0.0,
        description = 'VadeSecure decided message to be community message'
      },
      transactional =  {
        symbol = 'VADE_TRANSACTIONAL',
        score = 0.0,
        description = 'VadeSecure decided message to be transactional message'
      },
      suspect = {
        symbol = 'VADE_SUSPECT',
        score = 3.0,
        description = 'VadeSecure decided message to be suspicious message'
      },
      bounce = {
        symbol = 'VADE_BOUNCE',
        score = 0.0,
        description = 'VadeSecure decided message to be bounce message'
      },
      other = 'VADE_OTHER',
    }
  }

  vade_conf = lua_util.override_defaults(vade_conf, opts)

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

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

  if not vade_conf.servers and vade_conf.socket then
    vade_conf.servers = vade_conf.socket
  end

  if not vade_conf.servers then
    rspamd_logger.errx(rspamd_config, 'no servers defined')

    return nil
  end

  vade_conf.upstreams = upstream_list.create(rspamd_config,
      vade_conf.servers,
      vade_conf.default_port)

  if vade_conf.upstreams then
    lua_util.add_debug_alias('external_services', vade_conf.name)
    return vade_conf
  end

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

local function vade_check(task, content, digest, rule)
  local function vade_check_uncached()
    local function vade_url(addr)
      local url
      if rule.use_https then
        url = string.format('https://%s:%d%s', tostring(addr),
            rule.default_port, rule.url)
      else
        url = string.format('http://%s:%d%s', tostring(addr),
            rule.default_port, rule.url)
      end

      return url
    end

    local upstream = rule.upstreams:get_upstream_round_robin()
    local addr = upstream:get_addr()
    local retransmits = rule.retransmits

    local url = vade_url(addr)
    local hdrs = {}

    local helo = task:get_helo()
    if helo then
      hdrs['X-Helo'] = helo
    end
    local mail_from = task:get_from('smtp') or {}
    if mail_from[1] and #mail_from[1].addr > 1 then
      hdrs['X-Mailfrom'] = mail_from[1].addr
    end

    local rcpt_to = task:get_recipients('smtp')
    if rcpt_to then
      hdrs['X-Rcptto'] = {}
      for _, r in ipairs(rcpt_to) do
        table.insert(hdrs['X-Rcptto'], r.addr)
      end
    end

    local fip = task:get_from_ip()
    if fip and fip:is_valid() then
      hdrs['X-Inet'] = tostring(fip)
    end

    local request_data = {
      task = task,
      url = url,
      body = task:get_content(),
      headers = hdrs,
      timeout = rule.timeout,
    }

    local function vade_callback(http_err, code, body, headers)

      local function vade_requery()
        -- 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

          lua_util.debugm(rule.name, task,
              '%s: Request Error: %s - retries left: %s',
              rule.log_prefix, http_err, retransmits)

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

          lua_util.debugm(rule.name, task, '%s: retry IP: %s:%s',
              rule.log_prefix, addr, addr:get_port())
          request_data.url = url

          http.request(request_data)
        else
          rspamd_logger.errx(task, '%s: failed to scan, maximum retransmits '..
              'exceed', rule.log_prefix)
          task:insert_result(rule['symbol_fail'], 0.0, 'failed to scan and '..
              'retransmits exceed')
        end
      end

      if http_err then
        vade_requery()
      else
        -- Parse the response
        if upstream then upstream:ok() end
        if code ~= 200 then
          rspamd_logger.errx(task, 'invalid HTTP code: %s, body: %s, headers: %s', code, body, headers)
          task:insert_result(rule.symbol_fail, 1.0, 'Bad HTTP code: ' .. code)
          return
        end
        local parser = ucl.parser()
        local ret, err = parser:parse_string(body)
        if not ret then
          rspamd_logger.errx(task, 'vade: bad response body (raw): %s', body)
          task:insert_result(rule.symbol_fail, 1.0, 'Parser error: ' .. err)
          return
        end
        local obj = parser:get_object()
        local verdict = obj.verdict
        if not verdict then
          rspamd_logger.errx(task, 'vade: bad response JSON (no verdict): %s', obj)
          task:insert_result(rule.symbol_fail, 1.0, 'No verdict/unknown verdict')
          return
        end
        local vparts = lua_util.str_split(verdict, ":")
        verdict = table.remove(vparts, 1) or verdict

        local sym = rule.symbols[verdict]
        if not sym then
          sym = rule.symbols.other
        end

        if not sym.symbol then
          -- Subcategory match
          local lvl = 'low'
          if vparts and vparts[1] then
            lvl = vparts[1]
          end

          if sym[lvl] then
            sym = sym[lvl]
          else
            sym = rule.symbols.other
          end
        end

        local opts = {}
        if obj.score then
          table.insert(opts, 'score=' .. obj.score)
        end
        if obj.elapsed then
          table.insert(opts, 'elapsed=' .. obj.elapsed)
        end

        if rule.log_spamcause and obj.spamcause then
          rspamd_logger.infox(task, 'vadesecure verdict="%s", score=%s, spamcause="%s", message-id="%s"',
              verdict, obj.score, obj.spamcause, task:get_message_id())
        else
          lua_util.debugm(rule.name, task, 'vadesecure returned verdict="%s", score=%s, spamcause="%s"',
              verdict, obj.score, obj.spamcause)
        end

        if #vparts > 0 then
          table.insert(opts, 'verdict=' .. verdict .. ';' .. table.concat(vparts, ':'))
        end

        task:insert_result(sym.symbol, 1.0, opts)
      end
    end

    request_data.callback = vade_callback
    http.request(request_data)
  end

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

end

return {
  type = {'vadesecure', 'scanner'},
  description = 'VadeSecure Filterd interface',
  configure = vade_config,
  check = vade_check,
  name = N
}