--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_client_proxy/mod_client_proxy.lua	Sun Jun 03 13:55:10 2018 +0200
@@ -0,0 +1,208 @@
+if module:get_host_type() ~= "component" then
+	error("proxy_component should be loaded as component", 0);
+end
+
+local comp_host = module:get_host();
+local comp_name = module:get_option_string("name", "Proxy Component");
+
+local jid_split = require "util.jid".split;
+local jid_bare = require "util.jid".bare;
+local jid_prep = require "util.jid".prep;
+local st = require "util.stanza";
+local array = require "util.array";
+
+local target_address = module:get_option_string("target_address");
+
+local hosts = prosody.hosts;
+
+sessions = array{};
+local sessions = sessions;
+
+local function handle_target_presence(origin, stanza)
+	local type = stanza.attr.type;
+	module:log("debug", "received presence from destination: %s", type)
+	local _, _, resource = jid_split(stanza.attr.from);
+	if type == "error" then
+		-- drop all known sessions
+		for k in pairs(sessions) do
+			sessions[k] = nil
+		end
+		module:log(
+			"debug",
+			"received error presence, dropping all target sessions",
+			resource
+		)
+	elseif type == "unavailable" then
+		for k in pairs(sessions) do
+			if sessions[k] == resource then
+				sessions[k] = nil
+				module:log(
+					"debug",
+					"dropped target session: %s",
+					resource
+				)
+				break
+			end
+		end
+	elseif not type then
+		-- available
+		local found = false;
+		for k in pairs(sessions) do
+			if sessions[k] == resource then
+				found = true;
+				break
+			end
+		end
+		if not found then
+			module:log(
+				"debug",
+				"registered new target session: %s",
+				resource
+			)
+			sessions:push(resource)
+		end
+	end
+end
+
+local function handle_from_target(origin, stanza)
+	local type = stanza.attr.type
+	module:log(
+		"debug",
+		"non-presence stanza from target: name = %s, type = %s",
+		stanza.name,
+		type
+	)
+	if stanza.name == "iq" then
+		if type == "error" or type == "result" then
+			-- de-NAT message
+			local _, _, denatted_to_unprepped = jid_split(stanza.attr.to);
+			local denatted_to = jid_prep(denatted_to_unprepped);
+			if not denatted_to then
+				module:log(
+					"debug",
+					"cannot de-NAT stanza, invalid to: %s",
+					denatted_to_unprepped
+				)
+				return
+			end
+			local denatted_from = module:get_host();
+
+			module:log(
+				"debug",
+				"de-NAT-ed stanza: from: %s -> %s, to: %s -> %s",
+				stanza.attr.from,
+				denatted_from,
+				stanza.attr.to,
+				denatted_to
+			)
+
+			stanza.attr.from = denatted_from
+			stanza.attr.to = denatted_to
+
+			module:send(stanza)
+		else
+			-- FIXME: we don’t support NATing outbund requests atm.
+			module:send(st.error_reply(stanza, "cancel", "feature-not-implemented"))
+		end
+	elseif stanza.name == "message" then
+		-- not implemented yet, we need a way to ensure that routing doesn’t
+		-- break
+		module:send(st.error_reply(stanza, "cancel", "feature-not-implemented"))
+	end
+end
+
+local function handle_to_target(origin, stanza)
+	local type = stanza.attr.type;
+	module:log(
+		"debug",
+		"stanza to target: name = %s, type = %s",
+		stanza.name, type
+	)
+	if stanza.name == "presence" then
+		if type ~= "error" then
+			module:send(st.error_reply(stanza, "cancel", "bad-request"))
+			return
+		end
+	elseif stanza.name == "iq" then
+		if type == "get" or type == "set" then
+			if #sessions == 0 then
+				-- no sessions available to send to
+				module:log("debug", "no sessions to send to!")
+				module:send(st.error_reply(stanza, "cancel", "service-unavailable"))
+				return
+			end
+
+			-- find a target session
+			local target_session = sessions:random()
+			local target = target_address .. "/" .. target_session
+
+			-- encode sender JID in resource
+			local natted_from = module:get_host() .. "/" .. stanza.attr.from;
+
+			module:log(
+				"debug",
+				"NAT-ed stanza: from: %s -> %s, to: %s -> %s",
+				stanza.attr.from,
+				natted_from,
+				stanza.attr.to,
+				target
+			)
+
+			stanza.attr.from = natted_from
+			stanza.attr.to = target
+
+			module:send(stanza)
+		else
+			-- FIXME: handle and forward result/error correctly
+		end
+	elseif stanza.name == "message" then
+		-- not implemented yet, we need a way to ensure that routing doesn’t
+		-- break
+		module:send(st.error_reply(stanza, "cancel", "feature-not-implemented"))
+	end
+end
+
+local function stanza_handler(event)
+	local origin, stanza = event.origin, event.stanza
+	module:log("debug", "received stanza from %s session", origin.type)
+
+	local bare_from = jid_bare(stanza.attr.from);
+	local _, _, to = jid_split(stanza.attr.to);
+	if bare_from == target_address then
+		-- from our target, to whom?
+		if not to then
+			-- directly to component
+			if stanza.name == "presence" then
+				handle_target_presence(origin, stanza)
+			else
+				module:send(st.error_reply(stanza, "cancel", "bad-request"))
+				return true
+			end
+		else
+			-- to someone else
+			handle_from_target(origin, stanza)
+		end
+	else
+		handle_to_target(origin, stanza)
+	end
+	return true
+end
+
+module:hook("iq/bare", stanza_handler, -1);
+module:hook("message/bare", stanza_handler, -1);
+module:hook("presence/bare", stanza_handler, -1);
+module:hook("iq/full", stanza_handler, -1);
+module:hook("message/full", stanza_handler, -1);
+module:hook("presence/full", stanza_handler, -1);
+module:hook("iq/host", stanza_handler, -1);
+module:hook("message/host", stanza_handler, -1);
+module:hook("presence/host", stanza_handler, -1);
+
+module:log("debug", "loaded proxy on %s", module:get_host())
+
+subscription_request = st.presence({
+	type = "subscribe",
+	to = target_address,
+	from = module:get_host()}
+)
+module:send(subscription_request)