--[[
Copyright (c) 2015, 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.
]]--

local rspamd_logger = require "rspamd_logger"
local rspamd_util = require "rspamd_util"
local fun = require "fun"

local options = {
  dmarc_allow_symbol = 'DMARC_POLICY_ALLOW',
  spf_allow_symbol = 'R_SPF_ALLOW',
  dkim_allow_symbol = 'R_DKIM_ALLOW',

  rules = {}
}

local E = {}

local function whitelist_cb(symbol, rule, task)

  local domains = {}

  local function find_domain(dom)
    local mult = 1.0

    if rule['map'] then
      local val = rule['map']:get_key(dom)
      if val then
        if #val > 0 then
          mult = tonumber(val)
        end

        table.insert(domains, dom)
        return true,mult
      end
    elseif rule['maps'] then
      for map, mmult in pairs(rule['maps']) do
        local val = map:get_key(dom)
        if val then
          if #val > 0 then
            mult = tonumber(val)
          else
            mult = mmult
          end
          table.insert(domains, dom)
          return true,mult
        end
      end
    else
      mult = rule['domains'][dom]
      if mult then
        table.insert(domains, dom)
        return true, mult
      end
    end

    return false,0.0
  end

  local found = false
  local mult = 1.0
  local spf_violated = false
  local dkim_violated = false
  local dmarc_violated = false

  if rule['valid_spf'] then
    if not task:has_symbol(options['spf_allow_symbol']) then
      -- Not whitelisted
      if not rule['blacklist'] or rule['strict'] then
        return
      end

      spf_violated = true
    end

    -- Now we can check from domain or helo
    local from = task:get_from(1)

    if ((from or E)[1] or E).domain then
      local tld = rspamd_util.get_tld(from[1]['domain'])

      if tld then
        found,mult = find_domain(tld)
      end
    else
      local helo = task:get_helo()

      if helo then
        local tld = rspamd_util.get_tld(helo)

        if tld then
          found, mult = find_domain(tld)
        end
      end
    end
  end

  if rule['valid_dkim'] then
    local sym = task:get_symbol(options['dkim_allow_symbol'])
    if not sym then
      if not rule['blacklist'] or rule['strict'] then
        return
      end

      dkim_violated = true
    end

    local dkim_opts = sym[1]['options']
    if dkim_opts then
      fun.each(function(val)
        if not found then
          local tld = rspamd_util.get_tld(val)

          if tld then
            found, mult = find_domain(tld)
          end
        end
      end, dkim_opts)
    end
  end

  if rule['valid_dmarc'] then
    if not task:has_symbol(options['dmarc_allow_symbol']) then
      if not rule['blacklist'] or rule['strict'] then
        return
      end

      dmarc_violated = true
    end
    local from = task:get_from(2)

    if ((from or E)[1] or E).domain then
      local tld = rspamd_util.get_tld(from[1]['domain'])

      if tld then
        found, mult = find_domain(tld)
      end
    end
  end

  if found then
    if not rule['blacklist'] or rule['strict'] then
      task:insert_result(symbol, mult, domains)
    else
      -- Additional constraints for blacklist
      if rule['valid_spf'] or rule['valid_dkim'] or rule['valid_dmarc'] then
        if dmarc_violated or dkim_violated or spf_violated then

          if rule['strict'] then
            -- Inverse multiplier to convert whitelist to blacklist
            mult = -mult
          end

          task:insert_result(symbol, mult, domains)
        elseif rule['strict'] then
          -- Add whitelist score (negative)
          task:insert_result(symbol, mult, domains)
        end
      else
        -- Unconstrained input
        task:insert_result(symbol, mult, domains)
      end
    end
  end

end

local function gen_whitelist_cb(symbol, rule)
  return function(task)
    whitelist_cb(symbol, rule, task)
  end
end

local configure_whitelist_module = function()
  local opts =  rspamd_config:get_all_opt('whitelist')
  if opts then
    for k,v in pairs(opts) do
      options[k] = v
    end
  else
    rspamd_logger.infox(rspamd_config, 'Module is unconfigured')
    return
  end

  if options['rules'] then
    fun.each(function(symbol, rule)
      if rule['domains'] then
        if type(rule['domains']) == 'string' then
          rule['map'] = rspamd_config:add_kv_map(rule['domains'],
            "Whitelist map for " .. symbol)
        elseif type(rule['domains']) == 'table' then
          -- Transform ['domain1', 'domain2' ...] to indexes:
          -- {'domain1' = 1, 'domain2' = 1 ...]
          rule['maps'] = fun.tomap(fun.map(function(d)
            local name
            local value = 1

            if type(d) == 'table' then
              name = rspamd_config:add_map({
                url = d[1],
                type = 'map',
              })
              value = tonumber(d[2])
            else
              name = rspamd_config:add_map({
                url = d,
                type = 'map',
              })
            end

            if name and value then
              return name,value
            end
          end, rule['domains']))
        else
          rspamd_logger.errx(rspamd_config, 'whitelist %s has bad "domains" value',
            symbol)
          return
        end

        local flags = 'nice,empty'
        if rule['blacklist'] then
          flags = 'empty'
        end

        local id = rspamd_config:register_symbol({
          name = symbol,
          flags = flags,
          callback = gen_whitelist_cb(symbol, rule)
        })

        if rule['valid_spf'] then
          rspamd_config:register_dependency(id, options['spf_allow_symbol'])
        end
        if rule['valid_dkim'] then
          rspamd_config:register_dependency(id, options['dkim_allow_symbol'])
        end
        if rule['valid_dmarc'] then
          rspamd_config:register_dependency(id, options['dmarc_allow_symbol'])
        end

        if rule['score'] then
          if not rule['group'] then
            rule['group'] = 'whitelist'
          end
          rule['name'] = symbol
          rspamd_config:set_metric_symbol(rule)
        end
      end
    end, options['rules'])
  end
end

configure_whitelist_module()
