From 021d43755fa55a9840514c2ef2d040659683498a Mon Sep 17 00:00:00 2001
From: Feng Lee <feng@emqx.io>
Date: Thu, 30 Aug 2018 18:28:02 +0800
Subject: [PATCH] Add update_expiry/1 function

---
 src/emqx_message.erl | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/emqx_message.erl b/src/emqx_message.erl
index d700c2aee..9ff8e7511 100644
--- a/src/emqx_message.erl
+++ b/src/emqx_message.erl
@@ -22,7 +22,7 @@
 -export([get_flag/2, get_flag/3, set_flag/2, set_flag/3, unset_flag/2]).
 -export([set_headers/2]).
 -export([get_header/2, get_header/3, set_header/3]).
--export([is_expired/1, check_expiry/1, check_expiry/2]).
+-export([is_expired/1, check_expiry/1, check_expiry/2, update_expiry/1]).
 -export([format/1]).
 
 -type(flag() :: atom()).
@@ -96,7 +96,7 @@ set_header(Hdr, Val, Msg = #message{headers = Headers}) ->
 
 -spec(is_expired(emqx_types:message()) -> boolean()).
 is_expired(#message{headers = #{'Message-Expiry-Interval' := Interval}, timestamp = CreatedAt}) ->
-    elapsed(CreatedAt) > Interval;
+    elapsed(CreatedAt) > timer:seconds(Interval);
 is_expired(_Msg) ->
     false.
 
@@ -108,16 +108,23 @@ check_expiry(_Msg) ->
 
 -spec(check_expiry(emqx_types:message(), erlang:timestamp()) -> {ok, pos_integer()} | expired | false).
 check_expiry(#message{headers = #{'Message-Expiry-Interval' := Interval}}, Since) ->
-    case Interval - elapsed(Since) of
-        I when I > 0 -> {ok, I};
+    case Interval - (elapsed(Since) div 1000) of
+        Timeout when Timeout > 0 -> {ok, Timeout};
         _ -> expired
     end;
 check_expiry(_Msg, _Since) ->
     false.
 
+update_expiry(Msg = #message{headers = #{'Message-Expiry-Interval' := Interval}, timestamp = CreatedAt}) ->
+    case elapsed(CreatedAt) of
+        Elapsed when Elapsed > 0 ->
+            set_header('Message-Expiry-Interval', max(1, Interval - (Elapsed div 1000)), Msg);
+        _ -> Msg
+    end.
+
+%% MilliSeconds
 elapsed(Since) ->
-    Secs = timer:now_diff(os:timestamp(), Since) div 1000,
-    if Secs < 0 -> 0; true -> Secs end.
+    max(0, timer:now_diff(os:timestamp(), Since) div 1000).
 
 format(#message{id = Id, qos = QoS, topic = Topic, from = From, flags = Flags, headers = Headers}) ->
     io_lib:format("Message(Id=~s, QoS=~w, Topic=~s, From=~s, Flags=~s, Headers=~s)",