From 216a0c97b962d101311dc4d44875685f4c7cb008 Mon Sep 17 00:00:00 2001
From: Christophe Romain <christophe.romain@process-one.net>
Date: Wed, 27 Sep 2017 20:39:54 +0200
Subject: PubSub: add RSM support for mnesia backend

---
 src/node_flat.erl | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 67 insertions(+), 3 deletions(-)

(limited to 'src/node_flat.erl')

diff --git a/src/node_flat.erl b/src/node_flat.erl
index 7347747e8..2c11edde7 100644
--- a/src/node_flat.erl
+++ b/src/node_flat.erl
@@ -728,9 +728,53 @@ del_state(#pubsub_state{stateid = {Key, Nidx}, items = Items}) ->
 %% mod_pubsub module.</p>
 %% <p>PubSub plugins can store the items where they wants (for example in a
 %% relational database), or they can even decide not to persist any items.</p>
-get_items(Nidx, _From, _RSM) ->
-    Items = mnesia:index_read(pubsub_item, Nidx, #pubsub_item.nodeidx),
-    {result, {lists:keysort(#pubsub_item.creation, Items), undefined}}.
+get_items(Nidx, _From, undefined) ->
+    RItems = lists:keysort(#pubsub_item.creation,
+			   mnesia:index_read(pubsub_item, Nidx, #pubsub_item.nodeidx)),
+    Count = length(RItems),
+    if Count =< ?MAXITEMS ->
+	 {result, {RItems, undefined}};
+       true ->
+	 ItemsPage = lists:sublist(RItems, ?MAXITEMS),
+	 Rsm = rsm_page(Count, 0, 0, ItemsPage),
+	 {result, {ItemsPage, Rsm}}
+    end;
+
+get_items(Nidx, _From, #rsm_set{max = Max, index = IncIndex,
+				'after' = After, before = Before}) ->
+    RItems = lists:keysort(#pubsub_item.creation,
+			   mnesia:index_read(pubsub_item, Nidx, #pubsub_item.nodeidx)),
+    Count = length(RItems),
+    Limit = case Max of
+		undefined -> ?MAXITEMS;
+		_ -> Max
+	    end,
+    {Offset, ItemsPage} =
+	case {IncIndex, Before, After} of
+	    {I, undefined, undefined} ->
+		SubList = lists:nthtail(I, RItems),
+		{I, lists:sublist(SubList, Limit)};
+	    {_, <<>>, undefined} ->
+		%% 2.5 Requesting the Last Page in a Result Set
+		SubList = lists:reverse(RItems),
+		{0, lists:sublist(SubList, Limit)};
+	    {_, Stamp, undefined} ->
+		BeforeNow = encode_stamp(Stamp),
+		SubList = lists:dropwhile(
+			   fun(#pubsub_item{creation = {Now, _}}) ->
+			      Now >= BeforeNow
+			   end, lists:reverse(RItems)),
+		{0, lists:sublist(SubList, Limit)};
+	    {_, undefined, Stamp} ->
+		AfterNow = encode_stamp(Stamp),
+		SubList = lists:dropwhile(
+			   fun(#pubsub_item{creation = {Now, _}}) ->
+			      Now =< AfterNow
+			   end, RItems),
+		{0, lists:sublist(SubList, Limit)}
+	end,
+    Rsm = rsm_page(Count, IncIndex, Offset, ItemsPage),
+    {result, {ItemsPage, Rsm}}.
 
 get_items(Nidx, JID, AccessModel, PresenceSubscription, RosterGroup, _SubId, RSM) ->
     SubKey = jid:tolower(JID),
@@ -880,6 +924,26 @@ first_in_list(Pred, [H | T]) ->
 	_ -> first_in_list(Pred, T)
     end.
 
+rsm_page(Count, Index, Offset, Items) ->
+    FirstItem = hd(Items),
+    LastItem = lists:last(Items),
+    First = decode_stamp(element(1, FirstItem#pubsub_item.creation)),
+    Last = decode_stamp(element(1, LastItem#pubsub_item.creation)),
+    #rsm_set{count = Count, index = Index,
+	     first = #rsm_first{index = Offset, data = First},
+	     last = Last}.
+
+encode_stamp(Stamp) ->
+    case catch xmpp_util:decode_timestamp(Stamp) of
+	{MS,S,US} -> {MS,S,US};
+	_ -> Stamp
+    end.
+decode_stamp(Stamp) ->
+    case catch xmpp_util:encode_timestamp(Stamp) of
+	TimeStamp when is_binary(TimeStamp) -> TimeStamp;
+	_ -> Stamp
+    end.
+
 transform({pubsub_state, {Id, Nidx}, Is, A, Ss}) ->
     {pubsub_state, {Id, Nidx}, Nidx, Is, A, Ss};
 transform({pubsub_item, {Id, Nidx}, C, M, P}) ->
-- 
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