--[[
Copyright (c) 2022, Vsevolod Stakhov <vsevolod@rspamd.com>
Copyright (c) 2016, Andrew Lewis <nerf@judo.za.org>

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.
]]--

-- A plugin that triggers, if a spam trapped email address was detected

local rspamd_logger = require "rspamd_logger"
local redis_params
local use_redis = false;
local M = 'spamtrap'
local lua_util = require "lua_util"
local fun = require "fun"

local settings = {
  symbol = 'SPAMTRAP',
  score = 0.0,
  learn_fuzzy = false,
  learn_spam = false,
  fuzzy_flag = 1,
  fuzzy_weight = 10.0,
  key_prefix = 'sptr_',
  allow_multiple_rcpts = false,
}

local check_authed = true
local check_local = true

local function spamtrap_cb(task)
  local rcpts = task:get_recipients('smtp')
  local authed_user = task:get_user()
  local ip_addr = task:get_ip()
  local called_for_domain = false

  if ((not check_authed and authed_user) or
      (not check_local and ip_addr and ip_addr:is_local())) then
    rspamd_logger.infox(task, "skip spamtrap checks for local networks or authenticated user");
    return
  end

  local function do_action(rcpt)
    if settings['learn_fuzzy'] then
      rspamd_plugins.fuzzy_check.learn(task,
          settings['fuzzy_flag'],
          settings['fuzzy_weight'])
    end
    local act_flags = ''
    if settings['learn_spam'] then
      task:set_flag("learn_spam")
      -- Allow processing as we still need to learn and do other stuff
      act_flags = 'process_all'
    end
    task:insert_result(settings['symbol'], 1, rcpt)

    if settings.action then
      rspamd_logger.infox(task, 'spamtrap found: <%s>', rcpt)
      local smtp_message
      if settings.smtp_message then
        smtp_message = lua_util.template(settings.smtp_message, { rcpt = rcpt })
      else
        smtp_message = 'unknown error'
        if settings.action == 'no action' then
          smtp_message = 'message accepted'
        elseif settings.action == 'reject' then
          smtp_message = 'message rejected'
        end
      end
      task:set_pre_result { action = settings.action,
                            message = smtp_message,
                            module = 'spamtrap',
                            flags = act_flags }
    end

    return true
  end

  local function gen_redis_spamtrap_cb(target)
    return function(err, data)
      if err ~= nil then
        rspamd_logger.errx(task, 'redis_spamtrap_cb received error: %1', err)
        return
      end

      if data and type(data) ~= 'userdata' then
        do_action(target)
      else
        if not called_for_domain then
          -- Recurse for @catchall domain
          target = rcpts[1]['domain']:lower()
          local key = settings['key_prefix'] .. '@' .. target
          local ret = rspamd_redis_make_request(task,
              redis_params, -- connect params
              key, -- hash key
              false, -- is write
              gen_redis_spamtrap_cb(target), -- callback
              'GET', -- command
              { key } -- arguments
          )
          if not ret then
            rspamd_logger.errx(task, "redis request wasn't scheduled")
          end
          called_for_domain = true
        else
          lua_util.debugm(M, task, 'skip spamtrap for %s', target)
        end
      end
    end
  end

  -- Do not risk a FP by checking for more than one recipient
  if rcpts and (#rcpts == 1 or (#rcpts > 0 and settings.allow_multiple_rcpts)) then
    local targets = fun.map(function(r)
      return r['addr']:lower()
    end, rcpts)
    if use_redis then
      fun.each(function(target)
        local key = settings['key_prefix'] .. target
        local ret = rspamd_redis_make_request(task,
            redis_params, -- connect params
            key, -- hash key
            false, -- is write
            gen_redis_spamtrap_cb(target), -- callback
            'GET', -- command
            { key } -- arguments
        )
        if not ret then
          rspamd_logger.errx(task, "redis request wasn't scheduled")
        end
      end, targets)

    elseif settings['map'] then
      local function check_map_functor(target)
        if settings['map']:get_key(target) then
          return do_action(target)
        end
      end
      if not fun.any(check_map_functor, targets) then
        lua_util.debugm(M, task, 'skip spamtrap')
      end
    end
  end
end

-- Module setup

local opts = rspamd_config:get_all_opt('spamtrap')
if not (opts and type(opts) == 'table') then
  rspamd_logger.infox(rspamd_config, 'module is unconfigured')
  return
end

local auth_and_local_conf = lua_util.config_check_local_or_authed(rspamd_config, 'spamtrap',
    false, false)
check_local = auth_and_local_conf[1]
check_authed = auth_and_local_conf[2]

if opts then
  for k, v in pairs(opts) do
    settings[k] = v
  end
  if settings['map'] then
    settings['map'] = rspamd_config:add_map {
      url = settings['map'],
      description = string.format("Spamtrap map for %s", settings['symbol']),
      type = "regexp"
    }
  else
    redis_params = rspamd_parse_redis_server('spamtrap')
    if not redis_params then
      rspamd_logger.errx(
          rspamd_config, 'no redis servers are specified, disabling module')
      return
    end
    use_redis = true;
  end

  local id = rspamd_config:register_symbol({
    name = "SPAMTRAP_CHECK",
    type = "callback,postfilter",
    callback = spamtrap_cb
  })
  rspamd_config:register_symbol({
    name = settings['symbol'],
    parent = id,
    type = 'virtual',
    score = settings.score
  })
end