%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (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.mozilla.org/MPL/
%%
%% 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.
%%
%% The Original Code is RabbitMQ.
%%
%% The Initial Developer of the Original Code is GoPivotal, Inc.
%% Copyright (c) 2007-2014 GoPivotal, Inc.  All rights reserved.
%%

-module(rabbit_trace).

-export([init/1, enabled/1, tap_in/2, tap_out/2, start/1, stop/1]).

-include("rabbit.hrl").
-include("rabbit_framing.hrl").

-define(TRACE_VHOSTS, trace_vhosts).
-define(XNAME, <<"amq.rabbitmq.trace">>).

%%----------------------------------------------------------------------------

-ifdef(use_specs).

-type(state() :: rabbit_types:exchange() | 'none').

-spec(init/1 :: (rabbit_types:vhost()) -> state()).
-spec(enabled/1 :: (rabbit_types:vhost()) -> boolean()).
-spec(tap_in/2 :: (rabbit_types:basic_message(), state()) -> 'ok').
-spec(tap_out/2 :: (rabbit_amqqueue:qmsg(), state()) -> 'ok').

-spec(start/1 :: (rabbit_types:vhost()) -> 'ok').
-spec(stop/1 :: (rabbit_types:vhost()) -> 'ok').

-endif.

%%----------------------------------------------------------------------------

init(VHost) ->
    case enabled(VHost) of
        false -> none;
        true  -> {ok, X} = rabbit_exchange:lookup(
                             rabbit_misc:r(VHost, exchange, ?XNAME)),
                 X
    end.

enabled(VHost) ->
    {ok, VHosts} = application:get_env(rabbit, ?TRACE_VHOSTS),
    lists:member(VHost, VHosts).

tap_in(_Msg, none) -> ok;
tap_in(Msg = #basic_message{exchange_name = #resource{name = XName}}, TraceX) ->
    trace(TraceX, Msg, <<"publish">>, XName, []).

tap_out(_Msg, none) -> ok;
tap_out({#resource{name = QName}, _QPid, _QMsgId, Redelivered, Msg}, TraceX) ->
    RedeliveredNum = case Redelivered of true -> 1; false -> 0 end,
    trace(TraceX, Msg, <<"deliver">>, QName,
          [{<<"redelivered">>, signedint, RedeliveredNum}]).

%%----------------------------------------------------------------------------

start(VHost) ->
    rabbit_log:info("Enabling tracing for vhost '~s'~n", [VHost]),
    update_config(fun (VHosts) -> [VHost | VHosts -- [VHost]] end).

stop(VHost) ->
    rabbit_log:info("Disabling tracing for vhost '~s'~n", [VHost]),
    update_config(fun (VHosts) -> VHosts -- [VHost] end).

update_config(Fun) ->
    {ok, VHosts0} = application:get_env(rabbit, ?TRACE_VHOSTS),
    VHosts = Fun(VHosts0),
    application:set_env(rabbit, ?TRACE_VHOSTS, VHosts),
    rabbit_channel:refresh_config_local(),
    ok.

%%----------------------------------------------------------------------------

trace(#exchange{name = Name}, #basic_message{exchange_name = Name},
      _RKPrefix, _RKSuffix, _Extra) ->
    ok;
trace(X, Msg = #basic_message{content = #content{payload_fragments_rev = PFR}},
      RKPrefix, RKSuffix, Extra) ->
    {ok, _} = rabbit_basic:publish(
                X, <<RKPrefix/binary, ".", RKSuffix/binary>>,
                #'P_basic'{headers = msg_to_table(Msg) ++ Extra}, PFR),
    ok.

msg_to_table(#basic_message{exchange_name = #resource{name = XName},
                            routing_keys  = RoutingKeys,
                            content       = Content}) ->
    #content{properties = Props} =
        rabbit_binary_parser:ensure_content_decoded(Content),
    {PropsTable, _Ix} =
        lists:foldl(fun (K, {L, Ix}) ->
                            V = element(Ix, Props),
                            NewL = case V of
                                       undefined -> L;
                                       _         -> [{a2b(K), type(V), V} | L]
                                   end,
                            {NewL, Ix + 1}
                    end, {[], 2}, record_info(fields, 'P_basic')),
    [{<<"exchange_name">>, longstr, XName},
     {<<"routing_keys">>,  array,   [{longstr, K} || K <- RoutingKeys]},
     {<<"properties">>,    table,   PropsTable},
     {<<"node">>,          longstr, a2b(node())}].

a2b(A) -> list_to_binary(atom_to_list(A)).

type(V) when is_list(V)    -> table;
type(V) when is_integer(V) -> signedint;
type(_V)                   -> longstr.