-- zrtp_sas_proxy.lua
--
-- Copyright (c) 2011-2013 Travis Cross
--
-- Permission is hereby granted, free of charge, to any person obtaining a copy
-- of this software and associated documentation files (the "Software"), to deal
-- in the Software without restriction, including without limitation the rights
-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-- copies of the Software, and to permit persons to whom the Software is
-- furnished to do so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in
-- all copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-- THE SOFTWARE.
--
--
-- When we're acting as a ZRTP man-in-the-middle, proxy the SAS (Short
-- Authentication String) from one leg of the call to the other.
--
-- This script should be called asynchonously with luarun.  e.g.:
--
-- <action application="export" data="nolocal:api_on_answer=luarun zrtp_sas_proxy.lua ${uuid}"/>
--
aleg=argv[1]
api=freeswitch.API()

function log(level,msg) return freeswitch.consoleLog(level,"zrtp_sas: "..msg.."\n") end
function sleep(sec) return freeswitch.msleep(sec*1000) end
function ready() return api:execute("uuid_exists",aleg)=="true" end
function getvar(uuid,var)
  local x=api:execute("uuid_getvar",uuid.." "..var)
  if x=="_undef_" then return nil end
  return x
end
function getvarp(uuid,var) return getvar(uuid,var)=="true" end
function display(uuid,msg)
  local cidn=getvar(uuid,"caller_id_name")
  return api:execute("uuid_display",uuid.." "..msg.." "..cidn)
end

function mk_sas(sas1,sas2)
  if sas1 and sas2 then return sas1.." "..sas2
  else return sas1 or sas2 or "" end
end

function get_sas(uuid)
  return mk_sas(getvar(uuid,"zrtp_sas1_string_audio"),
                getvar(uuid,"zrtp_sas2_string"))
end

function log_sas(leg,uuid)
  return log("notice",leg..": "..uuid.." sas: "..get_sas(uuid))
end

function display_sas(to,from)
  return display(to," ("..get_sas(from)..")")
  -- return api:execute("say","en name_spelled pronounced" .. "..get_sas(from)..")
end

function get_bleg(aleg)
  local retries=15 bleg=nil
  while ready() do
    if retries<1 then return nil end
    local bleg=getvar(aleg,"signal_bond")
    if bleg then return bleg end
    log("debug","waiting for bleg uuid...")
    sleep(1)
    retries=retries-1
  end
end

function handle_sas(aleg,bleg)
  local retries=45 zrtp_time=0 af=false bf=false
  while ready() do
    if retries<1 then return nil end
    if not af and getvarp(aleg,"zrtp_secure_media_confirmed_audio") then
      af=true
      log("debug","aleg secure..."..aleg)
      log_sas("aleg",aleg)
      display_sas(bleg,aleg)
      -- time to assume other leg will remain unencrypted
      zrtp_time=retries-2
    end
    if not bf and getvarp(bleg,"zrtp_secure_media_confirmed_audio") then
      bf=true
      log("debug","bleg secure..."..bleg)
      log_sas("bleg",bleg)
      display_sas(aleg,bleg)
      zrtp_time=retries-2
    end
    if (af and bf) then break end
    if (af or bf) then log("debug","one legged zrtp..."..aleg) end
    if af then log("debug","waiting on bleg zrtp...")
    elseif bf then log("debug","waiting on aleg zrtp...")
    else log("debug","waiting for zrtp...") end
    if retries == zrtp_time then
      log("debug","sending sas: "..get_sas(aleg))
      -- works: api:executeString("uuid_displace "..aleg.." start /usr/local/freeswitch/sounds/music/8000/danza-espanola-op-37-h-142-xii-arabesca.wav 300 mux")
      -- works: api:executeString("uuid_broadcast "..aleg.." say::'en NUMBER pronounced FEMININE 12345' both")
      command = " say::\'en NAME_PHONETIC pronounced FEMININE "..get_sas(aleg).."\'"
      -- log("debug",command)
      api:executeString("uuid_broadcast "..aleg..command.." both")
      -- all done, terminate
      return nil
    end
    sleep(1)
    retries=retries-1
  end
end

if not (getvarp(aleg,"zrtp_passthru") or getvarp(aleg,"proxy_media")) then
  log("debug","zrtp_sas_proxy.lua enter")
  handle_sas(aleg,get_bleg(aleg))
  log("debug","zrtp_sas_proxy.lua exit")
end