曾寫過一篇使用XML實現(xiàn)IVR 。但當(dāng)你要實現(xiàn)更復(fù)雜、更智能的業(yè)務(wù)邏輯時，你免不了跟數(shù)據(jù)庫或其它系統(tǒng)交互。我們曾用Ruby借助event_socket實現(xiàn)過比較復(fù)雜的功能，但當(dāng)業(yè)務(wù)變得更加復(fù)雜時，我們使用Erlang重寫了整個邏輯。

　　什么是 Erlang ?

　　Erlang是一種函數(shù)式編程語言，它天生支持高并發(fā)，高可靠性的編程。

　　為什么使用 Erlang ?

　　Erlang 最初就是設(shè)計用來編寫電信程序的，它具有OTP（開放電信平臺）庫，使用它可以很容易地實現(xiàn)FSM（有限狀態(tài)機）。

　　我們的PBX服務(wù)器運行在辦公室里，但當(dāng)有電話進來時它需要到國外的一臺服務(wù)器上取數(shù)據(jù)，并以此來選擇坐席。呼叫過程中，它也需要更新遠程的數(shù)據(jù)。我們使用HTTP與遠程服務(wù)器交互。如此長距離的通信不僅會有很大的延時，而且經(jīng)常會失敗。FreeSWITCH本身有mod_http及mod_curl模塊，并且其它嵌入式腳本語言也都有HTTP支持，但我們認(rèn)為Erlang會更加健壯。而且，通過使用Erlang的輕量級進程，當(dāng)一有電話進來時，我們可以一邊啟動IVR撥放歡迎詞，一邊spawn一個新進程到遠程HTTP上取數(shù)據(jù)。當(dāng)IVR運行到需要數(shù)據(jù)進行決策時，絕大多數(shù)情況下這些數(shù)據(jù)已經(jīng)有了。即使獲取數(shù)據(jù)失敗，我們也可以以默認(rèn)的方式進行路由。這樣，客戶就不會感覺到任何延遲。

　　實現(xiàn)

　　我們使用mod_erlang_socket的outbound模式。當(dāng)有電話進來時，F(xiàn)reeSWITCH會通過dialplan立即把控制權(quán)交給Erlang。

            <extension name="icall_fsm">
              <condition field="destination_number" expression="^fsm$">
                <action application="erlang" data="icall:fsm acd@192.168.1.27"/>
              </condition>
            </extension>

　　其中，Erlang程序acd運行在節(jié)點192.168.1.27上，F(xiàn)reeSWITCH會使用RPC調(diào)用執(zhí)行icall:fsm()并在Erlang中啟動一個有限狀態(tài)機，它接下來會控制呼叫流程，實現(xiàn)進行狀態(tài)轉(zhuǎn)移，直到呼叫結(jié)束。并且，在呼叫過程中我們還通過db_pbx模塊與數(shù)據(jù)庫及遠程HTTP交互。Erlang實現(xiàn)的FSM代碼真的非常好看。

-module(icall).
-behaviour(gen_fsm).
 
-export([start/0, stop/0, fsm/1, init/1, welcome/2, handle_info/3, handle_event/3, terminate/3]).
-export([welcome_wait_playback/2, main_menu/2, main_menu_wait_dtmf/2, call_hst/2, call_sales/2, call_cc/2, call_extn/2,
 call_cellphone/2, final_loop/2]).
 
-import(freeswitch_msg, [get_var/2, get_var/3, sendmsg/3]).

start() -> gen_fsm:start(icall_fsm, [], []).
stop() ->  gen_fsm:send_all_state_event(self(), stop).
fsm(Ref) ->
 {ok, NewPid} = ?MODULE:start(),
 {Ref, NewPid}.

%% send a stop this will end up in "handle_event"
% stop() -> gen_fsm:send_all_state_event(hello, stopit).
%% -- interface end
% This initialisation routine gets called
init(State) ->
 io:format("icall_fsm init ~p, PID: ~p~n", [State, self()]),
 {ok, welcome, []}.

%% The state machine
welcome([], []) ->
 {next_state, welcome, []};
% welcome(UUID, []) ->
%  {next_state, welcome, [UUID]};
welcome({call, {event, [UUID | Data]}}, []) ->
 CallerID = get_var("Channel-Caller-ID-Number", Data, "00000000"),
 Pid = self(),
 spawn(fun() -> fetch_cc_extn_from_crm(Pid, CallerID) end),
 io:format("New call from [~p]~n", [CallerID]),
 db_pbx:new_call(UUID, Data),
 sendmsg(UUID, playback, "new_sales/1000.wav"),
 {next_state, welcome_wait_playback, UUID}.
 
welcome_wait_playback({call_event, {event, [UUID | Data]} }, UUID) ->
 Name = get_var("Event-Name", Data),
 App = get_var("Application", Data),

 error_logger:info_msg("welcome_wait_playback: Pid ~p: UUID ~p, Event ~p~n",[self(), UUID, Name]),

 case Name of
  "CHANNEL_EXECUTE_COMPLETE" when App =:= "playback" ->
   NextState = route_time_condition(UUID),
   gen_fsm:send_event(self(), UUID),
   {next_state, NextState, UUID};
  _ ->
   {next_state, welcome_wait_playback, UUID}
 end.
 
main_menu(UUID, UUID) ->
 sendmsg(UUID, play_and_get_digits, "1 1 3 5000 # new_sales/1001.wav new_sales/9004.wav menu_number [1-5]"),
 db_pbx:log(UUID, "MainMenu", ""),
 gen_fsm:send_event(self(), {call_event, {event, [UUID]}}),
 {next_state, main_menu_wait_dtmf, UUID}.
main_menu_wait_dtmf({call_event, {event, [UUID | Data]} }, UUID) ->
    Name = get_var("Event-Name", Data),
 App = get_var("Application", Data),

 error_logger:info_msg("Pid ~p: UUID ~p, Event ~p, State: main_menu_wait_dtmf~n",[self(), UUID, Name]),

 case Name of
  "CHANNEL_EXECUTE_COMPLETE" when App =:= "play_and_get_digits" ->
   MenuNumber = get_var("variable_menu_number", Data),
   db_pbx:log(UUID, "MainMenu", MenuNumber),
   case MenuNumber of
    "1" ->
     gen_fsm:send_event(self(), UUID),
     {next_state, call_hst, UUID};
    "5" ->
     %<min> <max> <tries> <timeout> <terminators> <file> <invalid_file> <var_name> <regexp>
     sendmsg(UUID, play_and_get_digits, "3 3 3 5000 # new_sales/2002.wav new_sales/9004.wav extn_number [68]\\d\\d"),
     {next_state, call_extn, no_extn};
    X when X == "2"; X == "3"; X == "4" ->
     gen_fsm:send_event(self(), UUID),
     {next_state, call_sales, UUID};
    _ ->
     sendmsg(UUID, playback, "new_sales/9003.wav"),
     timer:sleep(5000),
     sendmsg(UUID, hangup, ""),
     {next_state, final_loop, UUID}
   end;
  _ ->
   {next_state, main_menu_wait_dtmf, UUID}   
 end.
 
call_hst(UUID, UUID) ->
 transfer(UUID, "fifo_hst"),
 {next_state, final_loop, UUID}.

call_cellphone(UUID, UUID) ->
 transfer(UUID, "fifo_cellphone"),
 {next_state, final_loop, UUID}.

call_sales(UUID, UUID) ->
 case get(cc_extn) of
  undefined ->
   transfer(UUID, "fifo_sales"),
   db_pbx:log(UUID, "SalesFifo", ""),
   {next_state, final_loop, UUID};
  Extn ->
   play_intransfer(UUID),
   sendmsg(UUID, set, "ringback=${us-ring}"),
   sendmsg(UUID, set, "continue_on_fail=true"),
   sendmsg(UUID, set, "hangup_after_bridge=true"),
   sendmsg(UUID, bridge, "user/" ++ Extn),
   db_pbx:log(UUID, "CallCC", Extn),
   {next_state, call_cc, Extn}
 end.

call_cc({call_event, {event, [UUID | Data]} }, Extn) ->
    Name = get_var("Event-Name", Data),
 App = get_var("Application", Data),

    error_logger:info_msg("Pid ~p: UUID ~p, Event ~p, Extn ~p~n",[self(), UUID, Name, Extn]),

 case Name of
  "CHANNEL_EXECUTE_COMPLETE" when App =:= "bridge" ->
   HangupCause = get_var("variable_originate_disposition", Data),
   DialedUser = get_var("variable_dialed_user", Data),
   sendmsg(UUID, play_and_get_digits, "1 1 2 5000 # new_sales/8" ++ Extn ++
    ".wav new_sales/9004.wav cc_menu_number [12]"),
   db_pbx:log(UUID, "CCFailure", HangupCause),
   {next_state, call_cc, Extn};
  "CHANNEL_EXECUTE_COMPLETE" when App =:= "play_and_get_digits" ->
   CCMenuNumber = get_var("variable_cc_menu_number", Data),
   case CCMenuNumber of
    "1" -> sendmsg(UUID, transfer, "Playcell_" ++ Extn);
    "2" -> sendmsg(UUID, transfer, "VM_" ++ Extn);
    _ -> sendmsg(UUID, transfer, "Quit")
   end,
   {next_state, final_loop, UUID};
  _ ->
   {next_state, call_cc, Extn}
 end.
 
call_extn({call_event, {event, [UUID | Data]} }, no_extn) ->
    Name = get_var("Event-Name", Data),
 App = get_var("Application", Data),

 error_logger:info_msg("Pid ~p: UUID ~p, Event ~p, State: call_extn",[self(), UUID, Name]),

 case Name of
  "CHANNEL_EXECUTE_COMPLETE" when App =:= "play_and_get_digits" ->
   Extn = get_var("variable_extn_number", Data),
   db_pbx:log(UUID, "CallExtn", Extn),
   gen_fsm:send_event(self(), UUID),
   {next_state, call_extn, Extn};
  _ ->
   {next_state, call_extn, no_extn}
 end;

call_extn(UUID, Extn) ->
 io:format("Calling extn: ~p~n", [Extn]),
 % sendmsg(UUID, set, "campon=true"),
 sendmsg(UUID, set, "ringback=${us-ring}"),
 sendmsg(UUID, set, "continue_on_fail=true"),
 sendmsg(UUID, set, "hangup_after_bridge=true"),
 DialString = "user/" ++ Extn,
 sendmsg(UUID, bridge, DialString),
 {next_state, call_cc, Extn}.

 
final_loop({call_event, {event, [UUID | Data]} }, UUID) ->
 Name = get_var("Event-Name", Data),

 error_logger:info_msg("final_loop Pid ~p: UUID ~p, Event ~p~n",[self(), UUID, Name]),

 {next_state, final_loop, UUID};
final_loop(UUID, UUID) ->
 {next_state, final_loop, UUID}.

handle_info({cc_extn, error}, State, Data) ->
 {next_state, State, Data};
handle_info({cc_extn, Extn}, State, Data) ->
 put(cc_extn, Extn),
 io:format("Found CC Extn: ~p~n", [Extn]),
 {next_state, State, Data};
handle_info(call_hangup, State, Args) ->
 io:format("Hangup ~p ~p ~n", [State, Args]),
 {stop, normal, State};
handle_info({E, {event, [UUID | Data]}} = Event, State, StateData) ->
 Name = get_var("Event-Name", Data),
 App = list_to_atom(get_var("Application", Data, "undefined")),

 error_logger:info_msg("handle_info: ~p ~p ~p ~p~n~p~n",[self(), UUID, Name, State, StateData]),

 case Name of
  "CHANNEL_HANGUP_COMPLETE"->
   db_pbx:hangup(UUID, Data),
   % {next_state, final_loop, UUID};
   {stop, normal, UUID};
  "CUSTOM" ->
   SubClass = get_var("Event-Subclass", Data),
   Action = get_var("FIFO-Action", Data),

   io:format("Fifo: ~p ~p~n", [SubClass, Action]),

   case SubClass of
    "fifo::info" when Action =:= "bridge-caller" ->
     db_pbx:process(UUID, Data);
    _ -> ok
   end,
   {next_state, State, StateData};
  _ ->
   List = [welcome, welcome_wait_playback, main_menu_wait_dtmf, call_cc, call_extn],
   case lists:any(fun(Elem) -> Elem =:= State end, List) of
    true ->
     gen_fsm:send_event(self(), Event);
    _ -> ok
   end,
   {next_state, State, StateData}
 end;
handle_info(Info, State, Data) ->
 io:format("Got Other Info: ~p ~p ~p ~n", [Info, State, Data]).

handle_event(stop, _StateName, StateData) -> 
  {stop, normal, StateData}.
terminate(normal, _StateName, _StateData) -> 
 io:format("Stop with reason: normal ~p ~p~n", [_StateName, _StateData]),
   ok;
terminate(Reason, _StateName, _StateData) ->
 io:format("Stop with reason: ~p ~p ~p~n", [Reason, _StateName, _StateData]),
   ok.

%% private
 
route_time_condition(UUID) ->
 case db_pbx:get_time_condition("sales_icall") of
  {Action, Args} ->
   case Action of
    % "idp_acd:" ++ ErlAction ->
    %  Fun = list_to_atom(ErlAction),
    %  db_pbx:log(UUID, "TimeCondition", ErlAction ++ " " ++ Args),
    %  ?MODULE:Fun(UUID, Args);
    Action ->
     db_pbx:log(UUID, "TimeCondition", Action ++ " " ++ Args),
     sendmsg(UUID, list_to_atom(Action), Args),
     final_loop
   end;
  _ ->
   {Date, {Hour, Min, _Sec}} = erlang:localtime(),
   Weekday = calendar:day_of_the_week(Date),
   route_work_time(UUID, Weekday, Hour, Min)
 end. 

route_work_time(UUID, Weekday, Hour, Min)
 when Weekday > 5 andalso Hour > 10 andalso (Hour < 20 orelse ( Min < 30 andalso Hour < 21) ) ->
 db_pbx:log(UUID, "Weekend", "10:00 - 20:30"),
 main_menu;
route_work_time(UUID, Weekday, Hour, Min) when Hour > 9 andalso (Hour < 20 orelse (Min < 30 andalso Hour < 21 ))->
 db_pbx:log(UUID, "Workday", "Weekend 9:00 - 20:30"),
 main_menu;
route_work_time(UUID, _Weekday, Hour, Min) when (Hour > 21 orelse (Hour > 20 andalso Min > 30)) andalso Hour < 23 ->
 db_pbx:log(UUID, "Time", "20:30 - 23:00"),
 call_hst;
route_work_time(UUID, _Weekday, _Hour, _Min) ->
 db_pbx:log(UUID, "NonWorktime", "Cellphone"),
 call_cellphone.
 
transfer(UUID, Dest) ->
 transfer(UUID, Dest, "XML", "new_sales").
transfer(UUID, Dest, Dialplan, Context) ->
 sendmsg(UUID, transfer, Dest ++ " " ++ Dialplan ++ " " ++ Context).
 
play_intransfer(UUID) ->
 sendmsg(UUID, playback, "new_sales/1002.wav"),
 timer:sleep(3000).
 
fetch_cc_extn_from_crm(Pid, CallerID) ->
 Extn = case helpers:http_fetch(?CRM_APP, "/voip/cdrs?caller_id=" ++ CallerID) of
  {error, _} -> error;
  Number -> Number
 end,
  
  Pid ! {cc_extn, Extn}.