local is_contact_subscribed = require"core.rostermanager".is_contact_subscribed;

local jid_split = require"util.jid".split;

local jid_bare = require"util.jid".bare;

local st = require"util.stanza";

local datetime = require"util.datetime";

local cache = require "util.cache";

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

local bare_cache = {}; -- [username NUL bare_jid] = { [full_jid] = timestamp, ... }

local function on_evict(cache_key)

	local bare_cache_key = cache_key:match("^%Z+%z[^/]+");

	local full_jid = cache_key:match("%z(.*)$");

	local jids = bare_cache[bare_cache_key];

	if jids then

		jids[full_jid] = nil;

	end

end

-- used indirectly for the on_evict callback

local presence_cache = cache.new(cache_size, on_evict);

local function cache_hook(event)

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

	local typ = stanza.attr.type;

	module:log("debug", "Cache hook, got %s from a %s", stanza:top_tag(), origin.type);

	if origin.type == "s2sin" and ( typ == nil or typ == "unavailable" ) then

		local contact_full = stanza.attr.from;

		local contact_bare = jid_bare(contact_full);

		local username, host = jid_split(stanza.attr.to);

		if not is_contact_subscribed(username, host, contact_bare) then

			module:log("debug", "Presence from jid not in roster");

			return;

		end

		local cache_key = username .. "\0" .. contact_full;

		local bare_cache_key = username .. "\0" .. contact_bare;

		local jids = bare_cache[bare_cache_key];

		if typ == "unavailable" then -- remove from cache

			presence_cache:set(cache_key, nil);

			on_evict(cache_key);

			return;

		end

		local stamp = datetime.datetime();

		if jids then

			jids[contact_full] = stamp;

		else

			jids = { [contact_full] = stamp };

			bare_cache[bare_cache_key] = jids;

		end

		presence_cache:set(cache_key, true);

	end

end

module:hook("presence/bare", cache_hook, 10);

-- module:hook("presence/full", cache_hook, 10);

local function answer_probe_from_cache(event)

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

	if stanza.attr.type ~= "probe" then return; end

	local username = origin.username;

	local contact_bare = stanza.attr.to;

	local bare_cache_key = username .. "\0" .. contact_bare;

	local cached = bare_cache[bare_cache_key];

	if not cached then return end

	for jid, stamp in pairs(cached) do

		local presence = st.presence({ to = origin.full_jid, from = jid })

			:tag("delay", { xmlns = "urn:xmpp:delay", from = module.host, stamp = stamp }):up();

		origin.send(presence);

	end

end

module:hook("pre-presence/bare", answer_probe_from_cache, 10);