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%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
-module(gen_server).

%%% ---------------------------------------------------
%%%
%%% The idea behind THIS server is that the user module
%%% provides (different) functions to handle different
%%% kind of inputs.
%%% If the Parent process terminates the Module:terminate/2
%%% function is called.
%%%
%%% The user module should export:
%%%
%%% init(Args)
%%% ==> {ok, State}
%%% {ok, State, Timeout}
%%% ignore
%%% {stop, Reason}
%%%
%%% handle_call(Msg, {From, Tag}, State)
%%%
%%% ==> {reply, Reply, State}
%%% {reply, Reply, State, Timeout}
%%% {noreply, State}
%%% {noreply, State, Timeout}
%%% {stop, Reason, Reply, State}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% handle_cast(Msg, State)
%%%
%%% ==> {noreply, State}
%%% {noreply, State, Timeout}
%%% {stop, Reason, State}
%%% Reason = normal | shutdown | Term terminate(State) is called
%%%
%%% handle_info(Info, State) Info is e.g. {'EXIT', P, R}, {nodedown, N}, ...
%%%
%%% ==> {noreply, State}
%%% {noreply, State, Timeout}
%%% {stop, Reason, State}
%%% Reason = normal | shutdown | Term, terminate(State) is called
%%%
%%% terminate(Reason, State) Let the user module clean up
%%% always called when server terminates
%%%
%%% ==> ok
%%%
%%%
%%% The work flow (of the server) can be described as follows:
%%%
%%% User module Generic
%%% ----------- -------
%%% start -----> start
%%% init <----- .
%%%
%%% loop
%%% handle_call <----- .
%%% -----> reply
%%%
%%% handle_cast <----- .
%%%
%%% handle_info <----- .
%%%
%%% terminate <----- .
%%%
%%% -----> reply
%%%
%%%
%%% ---------------------------------------------------

%% API
-export([start/3, start/4,
start_link/3, start_link/4,
call/2, call/3,
cast/2, reply/2,
abcast/2, abcast/3,
multi_call/2, multi_call/3, multi_call/4,
enter_loop/3, enter_loop/4, enter_loop/5, wake_hib/5]).

%% System exports
-export([system_continue/3,
system_terminate/4,
system_code_change/4,
system_get_state/1,
system_replace_state/2,
format_status/2]).

%% Internal exports
-export([init_it/6]).

-import(error_logger, [format/2]).

%%%=========================================================================
%%% API
%%%=========================================================================

-callback init(Args :: term()) ->
    {ok, State :: term()} | {ok, State :: term(), timeout() | hibernate} |
    {stop, Reason :: term()} | ignore.
-callback handle_call(Request :: term(), From :: {pid(), Tag :: term()},
                      State :: term()) ->
    {reply, Reply :: term(), NewState :: term()} |
    {reply, Reply :: term(), NewState :: term(), timeout() | hibernate} |
    {noreply, NewState :: term()} |
    {noreply, NewState :: term(), timeout() | hibernate} |
    {stop, Reason :: term(), Reply :: term(), NewState :: term()} |
    {stop, Reason :: term(), NewState :: term()}.
-callback handle_cast(Request :: term(), State :: term()) ->
    {noreply, NewState :: term()} |
    {noreply, NewState :: term(), timeout() | hibernate} |
    {stop, Reason :: term(), NewState :: term()}.
-callback handle_info(Info :: timeout | term(), State :: term()) ->
    {noreply, NewState :: term()} |
    {noreply, NewState :: term(), timeout() | hibernate} |
    {stop, Reason :: term(), NewState :: term()}.
-callback terminate(Reason :: (normal | shutdown | {shutdown, term()} |
                               term()),
                    State :: term()) ->
    term().
-callback code_change(OldVsn :: (term() | {down, term()}), State :: term(),
                      Extra :: term()) ->
    {ok, NewState :: term()} | {error, Reason :: term()}.

%%% -----------------------------------------------------------------
%%% Starts a generic server.
%%% start(Mod, Args, Options)
%%% start(Name, Mod, Args, Options)
%%% start_link(Mod, Args, Options)
%%% start_link(Name, Mod, Args, Options) where:
%%% Name ::= {local, atom()} | {global, atom()} | {via, atom(), term()}
%%% Mod ::= atom(), callback module implementing the 'real' server
%%% Args ::= term(), init arguments (to Mod:init/1)
%%% Options ::= [{timeout, Timeout} | {debug, [Flag]}]
%%% Flag ::= trace | log | {logfile, File} | statistics | debug
%%% (debug == log && statistics)
%%% Returns: {ok, Pid} |
%%% {error, {already_started, Pid}} |
%%% {error, Reason}
%%% -----------------------------------------------------------------
start(Mod, Args, Options) ->
    gen:start(?MODULE, nolink, Mod, Args, Options).

start(Name, Mod, Args, Options) ->
    gen:start(?MODULE, nolink, Name, Mod, Args, Options).

start_link(Mod, Args, Options) ->
    gen:start(?MODULE, link, Mod, Args, Options).

start_link(Name, Mod, Args, Options) ->
    gen:start(?MODULE, link, Name, Mod, Args, Options).


%% -----------------------------------------------------------------
%% Make a call to a generic server.
%% If the server is located at another node, that node will
%% be monitored.
%% If the client is trapping exits and is linked server termination
%% is handled here (? Shall we do that here (or rely on timeouts) ?).
%% -----------------------------------------------------------------
call(Name, Request) ->
    case catch gen:call(Name, '$gen_call', Request) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, call, [Name, Request]}})
    end.

call(Name, Request, Timeout) ->
    case catch gen:call(Name, '$gen_call', Request, Timeout) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, call, [Name, Request, Timeout]}})
    end.

%% -----------------------------------------------------------------
%% Make a cast to a generic server.
%% -----------------------------------------------------------------
cast({global,Name}, Request) ->
    catch global:send(Name, cast_msg(Request)),
    ok;
cast({via, Mod, Name}, Request) ->
    catch Mod:send(Name, cast_msg(Request)),
    ok;
cast({Name,Node}=Dest, Request) when is_atom(Name), is_atom(Node) ->
    do_cast(Dest, Request);
cast(Dest, Request) when is_atom(Dest) ->
    do_cast(Dest, Request);
cast(Dest, Request) when is_pid(Dest) ->
    do_cast(Dest, Request).

do_cast(Dest, Request) ->
    do_send(Dest, cast_msg(Request)),
    ok.
    
cast_msg(Request) -> {'$gen_cast',Request}.

%% -----------------------------------------------------------------
%% Send a reply to the client.
%% -----------------------------------------------------------------
reply({To, Tag}, Reply) ->
    catch To ! {Tag, Reply}.

%% -----------------------------------------------------------------
%% Asynchronous broadcast, returns nothing, it's just send 'n' pray
%%-----------------------------------------------------------------
abcast(Name, Request) when is_atom(Name) ->
    do_abcast([node() | nodes()], Name, cast_msg(Request)).

abcast(Nodes, Name, Request) when is_list(Nodes), is_atom(Name) ->
    do_abcast(Nodes, Name, cast_msg(Request)).

do_abcast([Node|Nodes], Name, Msg) when is_atom(Node) ->
    do_send({Name,Node},Msg),
    do_abcast(Nodes, Name, Msg);
do_abcast([], _,_) -> abcast.

%%% -----------------------------------------------------------------
%%% Make a call to servers at several nodes.
%%% Returns: {[Replies],[BadNodes]}
%%% A Timeout can be given
%%%
%%% A middleman process is used in case late answers arrives after
%%% the timeout. If they would be allowed to glog the callers message
%%% queue, it would probably become confused. Late answers will
%%% now arrive to the terminated middleman and so be discarded.
%%% -----------------------------------------------------------------
multi_call(Name, Req)
  when is_atom(Name) ->
    do_multi_call([node() | nodes()], Name, Req, infinity).

multi_call(Nodes, Name, Req)
  when is_list(Nodes), is_atom(Name) ->
    do_multi_call(Nodes, Name, Req, infinity).

multi_call(Nodes, Name, Req, infinity) ->
    do_multi_call(Nodes, Name, Req, infinity);
multi_call(Nodes, Name, Req, Timeout)
  when is_list(Nodes), is_atom(Name), is_integer(Timeout), Timeout >= 0 ->
    do_multi_call(Nodes, Name, Req, Timeout).


%%-----------------------------------------------------------------
%% enter_loop(Mod, Options, State, <ServerName>, <TimeOut>) ->_
%%
%% Description: Makes an existing process into a gen_server.
%% The calling process will enter the gen_server receive
%% loop and become a gen_server process.
%% The process *must* have been started using one of the
%% start functions in proc_lib, see proc_lib(3).
%% The user is responsible for any initialization of the
%% process, including registering a name for it.
%%-----------------------------------------------------------------
enter_loop(Mod, Options, State) ->
    enter_loop(Mod, Options, State, self(), infinity).

enter_loop(Mod, Options, State, ServerName = {Scope, _})
  when Scope == local; Scope == global ->
    enter_loop(Mod, Options, State, ServerName, infinity);

enter_loop(Mod, Options, State, ServerName = {via, _, _}) ->
    enter_loop(Mod, Options, State, ServerName, infinity);

enter_loop(Mod, Options, State, Timeout) ->
    enter_loop(Mod, Options, State, self(), Timeout).

enter_loop(Mod, Options, State, ServerName, Timeout) ->
    Name = get_proc_name(ServerName),
    Parent = get_parent(),
    Debug = debug_options(Name, Options),
    loop(Parent, Name, State, Mod, Timeout, Debug).

%%%========================================================================
%%% Gen-callback functions
%%%========================================================================

%%% ---------------------------------------------------
%%% Initiate the new process.
%%% Register the name using the Rfunc function
%%% Calls the Mod:init/Args function.
%%% Finally an acknowledge is sent to Parent and the main
%%% loop is entered.
%%% ---------------------------------------------------
init_it(Starter, self, Name, Mod, Args, Options) ->
    init_it(Starter, self(), Name, Mod, Args, Options);
init_it(Starter, Parent, Name0, Mod, Args, Options) ->
    Name = name(Name0),
    Debug = debug_options(Name, Options),
    case catch Mod:init(Args) of
{ok, State} ->
proc_lib:init_ack(Starter, {ok, self()}),
loop(Parent, Name, State, Mod, infinity, Debug);
{ok, State, Timeout} ->
proc_lib:init_ack(Starter, {ok, self()}),
loop(Parent, Name, State, Mod, Timeout, Debug);
{stop, Reason} ->
%% For consistency, we must make sure that the
%% registered name (if any) is unregistered before
%% the parent process is notified about the failure.
%% (Otherwise, the parent process could get
%% an 'already_started' error if it immediately
%% tried starting the process again.)
unregister_name(Name0),
proc_lib:init_ack(Starter, {error, Reason}),
exit(Reason);
ignore ->
unregister_name(Name0),
proc_lib:init_ack(Starter, ignore),
exit(normal);
{'EXIT', Reason} ->
unregister_name(Name0),
proc_lib:init_ack(Starter, {error, Reason}),
exit(Reason);
Else ->
Error = {bad_return_value, Else},
proc_lib:init_ack(Starter, {error, Error}),
exit(Error)
    end.

name({local,Name}) -> Name;
name({global,Name}) -> Name;
name({via,_, Name}) -> Name;
name(Pid) when is_pid(Pid) -> Pid.

unregister_name({local,Name}) ->
    _ = (catch unregister(Name));
unregister_name({global,Name}) ->
    _ = global:unregister_name(Name);
unregister_name({via, Mod, Name}) ->
    _ = Mod:unregister_name(Name);
unregister_name(Pid) when is_pid(Pid) ->
    Pid.
    
%%%========================================================================
%%% Internal functions
%%%========================================================================
%%% ---------------------------------------------------
%%% The MAIN loop.
%%% ---------------------------------------------------
loop(Parent, Name, State, Mod, hibernate, Debug) ->
    proc_lib:hibernate(?MODULE,wake_hib,[Parent, Name, State, Mod, Debug]);
loop(Parent, Name, State, Mod, Time, Debug) ->
    Msg = receive
Input ->
Input
after Time ->
timeout
end,
    decode_msg(Msg, Parent, Name, State, Mod, Time, Debug, false).

wake_hib(Parent, Name, State, Mod, Debug) ->
    Msg = receive
Input ->
Input
end,
    decode_msg(Msg, Parent, Name, State, Mod, hibernate, Debug, true).

decode_msg(Msg, Parent, Name, State, Mod, Time, Debug, Hib) ->
    case Msg of
{system, From, Req} ->
sys:handle_system_msg(Req, From, Parent, ?MODULE, Debug,
[Name, State, Mod, Time], Hib);
{'EXIT', Parent, Reason} ->
terminate(Reason, Name, Msg, Mod, State, Debug);
_Msg when Debug =:= [] ->
handle_msg(Msg, Parent, Name, State, Mod);
_Msg ->
Debug1 = sys:handle_debug(Debug, fun print_event/3,
Name, {in, Msg}),
handle_msg(Msg, Parent, Name, State, Mod, Debug1)
    end.

%%% ---------------------------------------------------
%%% Send/receive functions
%%% ---------------------------------------------------
do_send(Dest, Msg) ->
    case catch erlang:send(Dest, Msg, [noconnect]) of
noconnect ->
spawn(erlang, send, [Dest,Msg]);
Other ->
Other
    end.

do_multi_call(Nodes, Name, Req, infinity) ->
    Tag = make_ref(),
    Monitors = send_nodes(Nodes, Name, Tag, Req),
    rec_nodes(Tag, Monitors, Name, undefined);
do_multi_call(Nodes, Name, Req, Timeout) ->
    Tag = make_ref(),
    Caller = self(),
    Receiver =
spawn(
fun() ->
%% Middleman process. Should be unsensitive to regular
%% exit signals. The sychronization is needed in case
%% the receiver would exit before the caller started
%% the monitor.
process_flag(trap_exit, true),
Mref = erlang:monitor(process, Caller),
receive
{Caller,Tag} ->
Monitors = send_nodes(Nodes, Name, Tag, Req),
TimerId = erlang:start_timer(Timeout, self(), ok),
Result = rec_nodes(Tag, Monitors, Name, TimerId),
exit({self(),Tag,Result});
{'DOWN',Mref,_,_,_} ->
%% Caller died before sending us the go-ahead.
%% Give up silently.
exit(normal)
end
end),
    Mref = erlang:monitor(process, Receiver),
    Receiver ! {self(),Tag},
    receive
{'DOWN',Mref,_,_,{Receiver,Tag,Result}} ->
Result;
{'DOWN',Mref,_,_,Reason} ->
%% The middleman code failed. Or someone did
%% exit(_, kill) on the middleman process => Reason==killed
exit(Reason)
    end.

send_nodes(Nodes, Name, Tag, Req) ->
    send_nodes(Nodes, Name, Tag, Req, []).

send_nodes([Node|Tail], Name, Tag, Req, Monitors)
  when is_atom(Node) ->
    Monitor = start_monitor(Node, Name),
    %% Handle non-existing names in rec_nodes.
    catch {Name, Node} ! {'$gen_call', {self(), {Tag, Node}}, Req},
    send_nodes(Tail, Name, Tag, Req, [Monitor | Monitors]);
send_nodes([_Node|Tail], Name, Tag, Req, Monitors) ->
    %% Skip non-atom Node
    send_nodes(Tail, Name, Tag, Req, Monitors);
send_nodes([], _Name, _Tag, _Req, Monitors) ->
    Monitors.

%% Against old nodes:
%% If no reply has been delivered within 2 secs. (per node) check that
%% the server really exists and wait for ever for the answer.
%%
%% Against contemporary nodes:
%% Wait for reply, server 'DOWN', or timeout from TimerId.

rec_nodes(Tag, Nodes, Name, TimerId) ->
    rec_nodes(Tag, Nodes, Name, [], [], 2000, TimerId).

rec_nodes(Tag, [{N,R}|Tail], Name, Badnodes, Replies, Time, TimerId ) ->
    receive
{'DOWN', R, _, _, _} ->
rec_nodes(Tag, Tail, Name, [N|Badnodes], Replies, Time, TimerId);
{{Tag, N}, Reply} -> %% Tag is bound !!!
erlang:demonitor(R, [flush]),
rec_nodes(Tag, Tail, Name, Badnodes,
[{N,Reply}|Replies], Time, TimerId);
{timeout, TimerId, _} ->
erlang:demonitor(R, [flush]),
%% Collect all replies that already have arrived
rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies)
    end;
rec_nodes(Tag, [N|Tail], Name, Badnodes, Replies, Time, TimerId) ->
    %% R6 node
    receive
{nodedown, N} ->
monitor_node(N, false),
rec_nodes(Tag, Tail, Name, [N|Badnodes], Replies, 2000, TimerId);
{{Tag, N}, Reply} -> %% Tag is bound !!!
receive {nodedown, N} -> ok after 0 -> ok end,
monitor_node(N, false),
rec_nodes(Tag, Tail, Name, Badnodes,
[{N,Reply}|Replies], 2000, TimerId);
{timeout, TimerId, _} ->
receive {nodedown, N} -> ok after 0 -> ok end,
monitor_node(N, false),
%% Collect all replies that already have arrived
rec_nodes_rest(Tag, Tail, Name, [N | Badnodes], Replies)
    after Time ->
case rpc:call(N, erlang, whereis, [Name]) of
Pid when is_pid(Pid) -> % It exists try again.
rec_nodes(Tag, [N|Tail], Name, Badnodes,
Replies, infinity, TimerId);
_ -> % badnode
receive {nodedown, N} -> ok after 0 -> ok end,
monitor_node(N, false),
rec_nodes(Tag, Tail, Name, [N|Badnodes],
Replies, 2000, TimerId)
end
    end;
rec_nodes(_, [], _, Badnodes, Replies, _, TimerId) ->
    case catch erlang:cancel_timer(TimerId) of
false -> % It has already sent it's message
receive
{timeout, TimerId, _} -> ok
after 0 ->
ok
end;
_ -> % Timer was cancelled, or TimerId was 'undefined'
ok
    end,
    {Replies, Badnodes}.

%% Collect all replies that already have arrived
rec_nodes_rest(Tag, [{N,R}|Tail], Name, Badnodes, Replies) ->
    receive
{'DOWN', R, _, _, _} ->
rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies);
{{Tag, N}, Reply} -> %% Tag is bound !!!
erlang:demonitor(R, [flush]),
rec_nodes_rest(Tag, Tail, Name, Badnodes, [{N,Reply}|Replies])
    after 0 ->
erlang:demonitor(R, [flush]),
rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies)
    end;
rec_nodes_rest(Tag, [N|Tail], Name, Badnodes, Replies) ->
    %% R6 node
    receive
{nodedown, N} ->
monitor_node(N, false),
rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies);
{{Tag, N}, Reply} -> %% Tag is bound !!!
receive {nodedown, N} -> ok after 0 -> ok end,
monitor_node(N, false),
rec_nodes_rest(Tag, Tail, Name, Badnodes, [{N,Reply}|Replies])
    after 0 ->
receive {nodedown, N} -> ok after 0 -> ok end,
monitor_node(N, false),
rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies)
    end;
rec_nodes_rest(_Tag, [], _Name, Badnodes, Replies) ->
    {Replies, Badnodes}.


%%% ---------------------------------------------------
%%% Monitor functions
%%% ---------------------------------------------------

start_monitor(Node, Name) when is_atom(Node), is_atom(Name) ->
    if node() =:= nonode@nohost, Node =/= nonode@nohost ->
Ref = make_ref(),
self() ! {'DOWN', Ref, process, {Name, Node}, noconnection},
{Node, Ref};
       true ->
case catch erlang:monitor(process, {Name, Node}) of
{'EXIT', _} ->
%% Remote node is R6
monitor_node(Node, true),
Node;
Ref when is_reference(Ref) ->
{Node, Ref}
end
    end.

%%% ---------------------------------------------------
%%% Message handling functions
%%% ---------------------------------------------------

dispatch({'$gen_cast', Msg}, Mod, State) ->
    Mod:handle_cast(Msg, State);
dispatch(Info, Mod, State) ->
    Mod:handle_info(Info, State).

handle_msg({'$gen_call', From, Msg}, Parent, Name, State, Mod) ->
    case catch Mod:handle_call(Msg, From, State) of
{reply, Reply, NState} ->
reply(From, Reply),
loop(Parent, Name, NState, Mod, infinity, []);
{reply, Reply, NState, Time1} ->
reply(From, Reply),
loop(Parent, Name, NState, Mod, Time1, []);
{noreply, NState} ->
loop(Parent, Name, NState, Mod, infinity, []);
{noreply, NState, Time1} ->
loop(Parent, Name, NState, Mod, Time1, []);
{stop, Reason, Reply, NState} ->
{'EXIT', R} =
(catch terminate(Reason, Name, Msg, Mod, NState, [])),
reply(From, Reply),
exit(R);
Other -> handle_common_reply(Other, Parent, Name, Msg, Mod, State)
    end;
handle_msg(Msg, Parent, Name, State, Mod) ->
    Reply = (catch dispatch(Msg, Mod, State)),
    handle_common_reply(Reply, Parent, Name, Msg, Mod, State).

handle_msg({'$gen_call', From, Msg}, Parent, Name, State, Mod, Debug) ->
    case catch Mod:handle_call(Msg, From, State) of
{reply, Reply, NState} ->
Debug1 = reply(Name, From, Reply, NState, Debug),
loop(Parent, Name, NState, Mod, infinity, Debug1);
{reply, Reply, NState, Time1} ->
Debug1 = reply(Name, From, Reply, NState, Debug),
loop(Parent, Name, NState, Mod, Time1, Debug1);
{noreply, NState} ->
Debug1 = sys:handle_debug(Debug, fun print_event/3, Name,
{noreply, NState}),
loop(Parent, Name, NState, Mod, infinity, Debug1);
{noreply, NState, Time1} ->
Debug1 = sys:handle_debug(Debug, fun print_event/3, Name,
{noreply, NState}),
loop(Parent, Name, NState, Mod, Time1, Debug1);
{stop, Reason, Reply, NState} ->
{'EXIT', R} =
(catch terminate(Reason, Name, Msg, Mod, NState, Debug)),
_ = reply(Name, From, Reply, NState, Debug),
exit(R);
Other ->
handle_common_reply(Other, Parent, Name, Msg, Mod, State, Debug)
    end;
handle_msg(Msg, Parent, Name, State, Mod, Debug) ->
    Reply = (catch dispatch(Msg, Mod, State)),
    handle_common_reply(Reply, Parent, Name, Msg, Mod, State, Debug).

handle_common_reply(Reply, Parent, Name, Msg, Mod, State) ->
    case Reply of
{noreply, NState} ->
loop(Parent, Name, NState, Mod, infinity, []);
{noreply, NState, Time1} ->
loop(Parent, Name, NState, Mod, Time1, []);
{stop, Reason, NState} ->
terminate(Reason, Name, Msg, Mod, NState, []);
{'EXIT', What} ->
terminate(What, Name, Msg, Mod, State, []);
_ ->
terminate({bad_return_value, Reply}, Name, Msg, Mod, State, [])
    end.

handle_common_reply(Reply, Parent, Name, Msg, Mod, State, Debug) ->
    case Reply of
{noreply, NState} ->
Debug1 = sys:handle_debug(Debug, fun print_event/3, Name,
{noreply, NState}),
loop(Parent, Name, NState, Mod, infinity, Debug1);
{noreply, NState, Time1} ->
Debug1 = sys:handle_debug(Debug, fun print_event/3, Name,
{noreply, NState}),
loop(Parent, Name, NState, Mod, Time1, Debug1);
{stop, Reason, NState} ->
terminate(Reason, Name, Msg, Mod, NState, Debug);
{'EXIT', What} ->
terminate(What, Name, Msg, Mod, State, Debug);
_ ->
terminate({bad_return_value, Reply}, Name, Msg, Mod, State, Debug)
    end.

reply(Name, {To, Tag}, Reply, State, Debug) ->
    reply({To, Tag}, Reply),
    sys:handle_debug(Debug, fun print_event/3, Name,
{out, Reply, To, State} ).


%%-----------------------------------------------------------------
%% Callback functions for system messages handling.
%%-----------------------------------------------------------------
system_continue(Parent, Debug, [Name, State, Mod, Time]) ->
    loop(Parent, Name, State, Mod, Time, Debug).

-spec system_terminate(_, _, _, [_]) -> no_return().

system_terminate(Reason, _Parent, Debug, [Name, State, Mod, _Time]) ->
    terminate(Reason, Name, [], Mod, State, Debug).

system_code_change([Name, State, Mod, Time], _Module, OldVsn, Extra) ->
    case catch Mod:code_change(OldVsn, State, Extra) of
{ok, NewState} -> {ok, [Name, NewState, Mod, Time]};
Else -> Else
    end.

system_get_state([_Name, State, _Mod, _Time]) ->
    {ok, State}.

system_replace_state(StateFun, [Name, State, Mod, Time]) ->
    NState = StateFun(State),
    {ok, NState, [Name, NState, Mod, Time]}.

%%-----------------------------------------------------------------
%% Format debug messages. Print them as the call-back module sees
%% them, not as the real erlang messages. Use trace for that.
%%-----------------------------------------------------------------
print_event(Dev, {in, Msg}, Name) ->
    case Msg of
{'$gen_call', {From, _Tag}, Call} ->
io:format(Dev, "*DBG* ~p got call ~p from ~w~n",
[Name, Call, From]);
{'$gen_cast', Cast} ->
io:format(Dev, "*DBG* ~p got cast ~p~n",
[Name, Cast]);
_ ->
io:format(Dev, "*DBG* ~p got ~p~n", [Name, Msg])
    end;
print_event(Dev, {out, Msg, To, State}, Name) ->
    io:format(Dev, "*DBG* ~p sent ~p to ~w, new state ~w~n",
[Name, Msg, To, State]);
print_event(Dev, {noreply, State}, Name) ->
    io:format(Dev, "*DBG* ~p new state ~w~n", [Name, State]);
print_event(Dev, Event, Name) ->
    io:format(Dev, "*DBG* ~p dbg ~p~n", [Name, Event]).


%%% ---------------------------------------------------
%%% Terminate the server.
%%% ---------------------------------------------------

terminate(Reason, Name, Msg, Mod, State, Debug) ->
    case catch Mod:terminate(Reason, State) of
{'EXIT', R} ->
error_info(R, Name, Msg, State, Debug),
exit(R);
_ ->
case Reason of
normal ->
exit(normal);
shutdown ->
exit(shutdown);
{shutdown,_}=Shutdown ->
exit(Shutdown);
_ ->
FmtState =
case erlang:function_exported(Mod, format_status, 2) of
true ->
Args = [get(), State],
case catch Mod:format_status(terminate, Args) of
{'EXIT', _} -> State;
Else -> Else
end;
_ ->
State
end,
error_info(Reason, Name, Msg, FmtState, Debug),
exit(Reason)
end
    end.

error_info(_Reason, application_controller, _Msg, _State, _Debug) ->
    %% OTP-5811 Don't send an error report if it's the system process
    %% application_controller which is terminating - let init take care
    %% of it instead
    ok;
error_info(Reason, Name, Msg, State, Debug) ->
    Reason1 =
case Reason of
{undef,[{M,F,A,L}|MFAs]} ->
case code:is_loaded(M) of
false ->
{'module could not be loaded',[{M,F,A,L}|MFAs]};
_ ->
case erlang:function_exported(M, F, length(A)) of
true ->
Reason;
false ->
{'function not exported',[{M,F,A,L}|MFAs]}
end
end;
_ ->
Reason
end,
    format("** Generic server ~p terminating \n"
           "** Last message in was ~p~n"
           "** When Server state == ~p~n"
           "** Reason for termination == ~n** ~p~n",
[Name, Msg, State, Reason1]),
    sys:print_log(Debug),
    ok.

%%% ---------------------------------------------------
%%% Misc. functions.
%%% ---------------------------------------------------

opt(Op, [{Op, Value}|_]) ->
    {ok, Value};
opt(Op, [_|Options]) ->
    opt(Op, Options);
opt(_, []) ->
    false.

debug_options(Name, Opts) ->
    case opt(debug, Opts) of
{ok, Options} -> dbg_options(Name, Options);
_ -> dbg_options(Name, [])
    end.

dbg_options(Name, []) ->
    Opts =
case init:get_argument(generic_debug) of
error ->
[];
_ ->
[log, statistics]
end,
    dbg_opts(Name, Opts);
dbg_options(Name, Opts) ->
    dbg_opts(Name, Opts).

dbg_opts(Name, Opts) ->
    case catch sys:debug_options(Opts) of
{'EXIT',_} ->
format("~p: ignoring erroneous debug options - ~p~n",
[Name, Opts]),
[];
Dbg ->
Dbg
    end.

get_proc_name(Pid) when is_pid(Pid) ->
    Pid;
get_proc_name({local, Name}) ->
    case process_info(self(), registered_name) of
{registered_name, Name} ->
Name;
{registered_name, _Name} ->
exit(process_not_registered);
[] ->
exit(process_not_registered)
    end;
get_proc_name({global, Name}) ->
    case global:whereis_name(Name) of
undefined ->
exit(process_not_registered_globally);
Pid when Pid =:= self() ->
Name;
_Pid ->
exit(process_not_registered_globally)
    end;
get_proc_name({via, Mod, Name}) ->
    case Mod:whereis_name(Name) of
undefined ->
exit({process_not_registered_via, Mod});
Pid when Pid =:= self() ->
Name;
_Pid ->
exit({process_not_registered_via, Mod})
    end.

get_parent() ->
    case get('$ancestors') of
[Parent | _] when is_pid(Parent)->
            Parent;
        [Parent | _] when is_atom(Parent)->
            name_to_pid(Parent);
_ ->
exit(process_was_not_started_by_proc_lib)
    end.

name_to_pid(Name) ->
    case whereis(Name) of
undefined ->
case global:whereis_name(Name) of
undefined ->
exit(could_not_find_registered_name);
Pid ->
Pid
end;
Pid ->
Pid
    end.

%%-----------------------------------------------------------------
%% Status information
%%-----------------------------------------------------------------
format_status(Opt, StatusData) ->
    [PDict, SysState, Parent, Debug, [Name, State, Mod, _Time]] = StatusData,
    Header = gen:format_status_header("Status for generic server",
                                      Name),
    Log = sys:get_debug(log, Debug, []),
    DefaultStatus = [{data, [{"State", State}]}],
    Specfic =
case erlang:function_exported(Mod, format_status, 2) of
true ->
case catch Mod:format_status(Opt, [PDict, State]) of
{'EXIT', _} -> DefaultStatus;
                    StatusList when is_list(StatusList) -> StatusList;
Else -> [Else]
end;
_ ->
DefaultStatus
end,
    [{header, Header},
     {data, [{"Status", SysState},
{"Parent", Parent},
{"Logged events", Log}]} |
     Specfic].
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