--[[
Copyright (c) 2011-2015, 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.
]]--

-- Module for checking mail list headers

local symbol = 'MAILLIST'
-- EZMLM
-- Mailing-List: .*run by ezmlm
-- Precedence: bulk
-- List-Post: <mailto:
-- List-Help: <mailto:
-- List-Unsubscribe: <mailto:[a-zA-Z\.-]+-unsubscribe@
-- List-Subscribe: <mailto:[a-zA-Z\.-]+-subscribe@
local function check_ml_ezmlm(task)
  -- Mailing-List
  local header = task:get_header('mailing-list')
  if not header or not string.find(header, 'ezmlm$') then
    return false
  end
  -- Precedence
  header = task:get_header('precedence')
  if not header or not string.match(header, '^bulk$') then
    return false
  end
  -- Other headers
  header = task:get_header('list-post')
  if not header or not string.find(header, '^<mailto:') then
    return false
  end
  header = task:get_header('list-help')
  if not header or not string.find(header, '^<mailto:') then
    return false
  end
  -- Subscribe and unsubscribe
  header = task:get_header('list-subscribe')
  if not header or not string.find(header, '<mailto:[a-zA-Z.-]+-subscribe@') then
    return false
  end
  header = task:get_header('list-unsubscribe')
  if not header or not string.find(header, '<mailto:[a-zA-Z.-]+-unsubscribe@') then
    return false
  end

  return true
end

-- MailMan (the gnu mailing list manager)
-- Precedence: bulk [or list for v2]
-- List-Help: <mailto:
-- List-Post: <mailto:
-- List-Subscribe: .*<mailto:.*=subscribe>
-- List-Id:
-- List-Unsubscribe: .*<mailto:.*=unsubscribe>
-- List-Archive:
-- X-Mailman-Version: \d
local function check_ml_mailman(task)
  -- Mailing-List
  local header = task:get_header('x-mailman-version')
  if not header or not string.find(header, '^%d') then
    return false
  end
  -- Precedence
  header = task:get_header('precedence')
  if not header or (not string.match(header, '^bulk$') and not string.match(header, '^list$')) then
    return false
  end
  -- For reminders we have other headers than for normal messages
  header = task:get_header('x-list-administrivia')
  local subject = task:get_header('subject')
  if (header and string.find(header, 'yes')) or (subject and string.find(subject, 'mailing list memberships reminder$')) then
    if not task:get_header('errors-to') or not task:get_header('x-beenthere') then
      return false
    end
    header = task:get_header('x-no-archive')
    if not header or not string.find(header, 'yes') then
      return false
    end
    return true
  end

  -- Other headers
  header = task:get_header('list-id')
  if not header then
    return false
  end
  header = task:get_header('list-post')
  if not header or not string.find(header, '^<mailto:') then
    return false
  end
  header = task:get_header('list-help')
  if not header or not string.find(header, '^<mailto:') then
    return false
  end
  -- Subscribe and unsubscribe
  header = task:get_header('list-subscribe')
  if not header or not string.find(header, '<mailto:.*=subscribe>') then
    return false
  end
  header = task:get_header('list-unsubscribe')
  if not header or not string.find(header, '<mailto:.*=unsubscribe>') then
    return false
  end

  return true

end

-- Subscribe.ru
-- Precedence: normal
-- List-Id: <.*.subscribe.ru>
-- List-Help: <http://subscribe.ru/catalog/.*>
-- List-Subscribe: <mailto:.*-sub@subscribe.ru>
-- List-Unsubscribe: <mailto:.*-unsub@subscribe.ru>
-- List-Archive:  <http://subscribe.ru/archive/.*>
-- List-Owner: <mailto:.*-owner@subscribe.ru>
-- List-Post: NO
local function check_ml_subscriberu(task)
  -- List-Id
  local header = task:get_header('list-id')
  if not header or not string.find(header, '^<.*%.subscribe%.ru>$') then
    return false
  end
  -- Precedence
  header = task:get_header('precedence')
  if not header or not string.match(header, '^normal$') then
    return false
  end
  -- Other headers
  header = task:get_header('list-archive')
  if not header or not string.find(header, '^<http://subscribe.ru/archive/.*>$') then
    return false
  end
  header = task:get_header('list-owner')
  if not header or not string.find(header, '^<mailto:.*-owner@subscribe.ru>$') then
    return false
  end
  header = task:get_header('list-help')
  if not header or not string.find(header, '^<http://subscribe.ru/catalog/.*>$') then
    return false
  end
  -- Subscribe and unsubscribe
  header = task:get_header('list-subscribe')
  if not header or not string.find(header, '^<mailto:.*-sub@subscribe.ru>$') then
    return false
  end
  header = task:get_header('list-unsubscribe')
  if not header or not string.find(header, '^<mailto:.*-unsub@subscribe.ru>$') then
    return false
  end

  return true

end

-- RFC 2369 headers
local function check_rfc2369(task)
  local header = task:get_header('List-Unsubscribe')
  if not header or not string.find(header, '<.+>') then
    return false
  end
  header = task:get_header('List-Post')
  if not header or not string.find(header, '<.+>') then
    return false
  end

  return true
end

-- RFC 2919 headers
local function check_rfc2919(task)
  local header = task:get_header('List-Id')
  if not header or not string.find(header, '<.+>') then
    return false
  end

  return check_rfc2369(task)
end

-- Google groups detector
-- header exists X-Google-Loop
-- RFC 2919 headers exist
--
local function check_ml_googlegroup(task)
  local header = task:get_header('X-Google-Loop')

  if not header then
    header = task:get_header('X-Google-Group-Id')

    if not header then
      return false
    end
  end

  return check_rfc2919(task)
end

-- Majordomo detector
-- Check Sender for owner- or -owner
-- Check Precendence for 'Bulk' or 'List'
--
-- And nothing more can be extracted :(
local function check_ml_majordomo(task)
  local header = task:get_header('Sender')
  if not header or (not string.find(header, '^owner-.*$') and not string.find(header, '^.*-owner$')) then
    return false
  end

  header = task:get_header('Precedence')
  if not header or (header ~= 'list' and header ~= 'bulk') then
    return false
  end

  return true
end

-- CGP detector
-- X-Listserver = CommuniGate Pro LIST
-- RFC 2919 headers exist
--
local function check_ml_cgp(task)
  local header = task:get_header('X-Listserver')

  if not header or header ~= 'CommuniGate Pro LIST' then
    return false
  end

  return check_rfc2919(task)
end

local function check_ml_generic(task)
  local header = task:get_header('Precedence')
  if not header or (header ~= 'list' and header ~= 'bulk') then
    return false
  end

  return check_rfc2919(task)
end

local function check_maillist(task)
  if check_ml_ezmlm(task) then
    task:insert_result(symbol, 1, 'ezmlm')
  elseif check_ml_mailman(task) then
    task:insert_result(symbol, 1, 'mailman')
  elseif check_ml_subscriberu(task) then
    task:insert_result(symbol, 1, 'subscribe.ru')
  elseif check_ml_googlegroup(task) then
    task:insert_result(symbol, 1, 'googlegroups')
  elseif check_ml_majordomo(task) then
    task:insert_result(symbol, 1, 'majordomo')
  elseif check_ml_cgp(task) then
    task:insert_result(symbol, 1, 'cgp')
  elseif check_ml_generic(task) then
    task:insert_result(symbol, 0.5, 'generic')
  end
end


-- Configuration
local opts =  rspamd_config:get_all_opt('maillist')
if opts then
  if opts['symbol'] then
    symbol = opts['symbol']
    rspamd_config:register_symbol({
      name = symbol,
      callback = check_maillist
    })
  end
end