1 local st = require "util.stanza";

     2 local cache = require "util.cache";

     3 local add_filter = require "util.filters".add_filter;

     4 

     5 local cache_size = module:get_option_number("presence_dedup_cache_size", 100);

     6 

     7 -- stanza equality tests

     8 local function attr_eq(a, b)

     9 	if a == b then return true; end -- unlikely but not impossible

    10 	for k,v in pairs(a) do if b[k] ~= v then return false; end end

    11 	for k,v in pairs(b) do if a[k] ~= v then return false; end end

    12 	return true;

    13 end

    14 

    15 local function st_eq(a, b)

    16 	if a == b then return true; end

    17 	if type(b) ~= "table" then return false; end

    18 	if getmetatable(b) ~= st.stanza_mt then return false; end

    19 	if a.name ~= b.name then return false; end

    20 	if #a ~= #b then return false; end

    21 	if not attr_eq(a.attr, b.attr) then return false; end

    22 	for i = 1, #a do if not st_eq(a[i], b[i]) then return false; end end

    23 	return true;

    24 end

    25 

    26 local function dedup_presence(stanza, session)

    27 	if session.presence_cache and session.presence

    28 	and getmetatable(stanza) == st.stanza_mt and stanza.name == "presence"

    29 	and stanza.attr.xmlns == nil and stanza.attr.from then

    30 		local cached = session.presence_cache:get(stanza.attr.from);

    31 		if st_eq(stanza, cached) then

    32 			return nil;

    33 		else

    34 			session.presence_cache:set(stanza.attr.from, st.clone(stanza));

    35 		end

    36 	end

    37 	return stanza;

    38 end

    39 

    40 module:hook("presence/initial",	function (event)

    41 	local session, stanza = event.origin, event.stanza;

    42 	session.presence_cache = cache.new(cache_size);

    43 	add_filter(session, "stanzas/out", dedup_presence, 90);

    44 end);