-- Prosody IM

-- Copyright (C) 2009-2012 Tobias Markmann

-- 

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local st = require "util.stanza";

local zlib = require "zlib";

local pcall = pcall;

local tostring = tostring;

local xmlns_compression_feature = "http://jabber.org/features/compress"

local xmlns_compression_protocol = "http://jabber.org/protocol/compress"

local xmlns_stream = "http://etherx.jabber.org/streams";

local compression_stream_feature = st.stanza("compression", {xmlns=xmlns_compression_feature}):tag("method"):text("zlib"):up();

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

local compression_level = module:get_option_number("compression_level", 7);

if not compression_level or compression_level < 1 or compression_level > 9 then

	module:log("warn", "Invalid compression level in config: %s", tostring(compression_level));

	module:log("warn", "Module loading aborted. Compression won't be available.");

	return;

end

module:hook("stream-features", function(event)

	local origin, features = event.origin, event.features;

	if not origin.compressed and (origin.type == "c2s" or origin.type == "s2sin" or origin.type == "s2sout") then

		-- FIXME only advertise compression support when TLS layer has no compression enabled

		features:add_child(compression_stream_feature);

	end

end);

module:hook("s2s-stream-features", function(event)

	local origin, features = event.origin, event.features;

	-- FIXME only advertise compression support when TLS layer has no compression enabled

	if not origin.compressed and (origin.type == "c2s" or origin.type == "s2sin" or origin.type == "s2sout") then

		features:add_child(compression_stream_feature);

	end

end);

-- Hook to activate compression if remote server supports it.

module:hook_stanza(xmlns_stream, "features",

		function (session, stanza)

			if not session.compressed and (session.type == "c2s" or session.type == "s2sin" or session.type == "s2sout") then

				-- does remote server support compression?

				local comp_st = stanza:child_with_name("compression");

				if comp_st then

					-- do we support the mechanism

					for a in comp_st:children() do

						local algorithm = a[1]

						if algorithm == "zlib" then

							session.sends2s(st.stanza("compress", {xmlns=xmlns_compression_protocol}):tag("method"):text("zlib"))

							session.log("debug", "Enabled compression using zlib.")

							return true;

						end

					end

					session.log("debug", "Remote server supports no compression algorithm we support.")

				end

			end

		end

, 250);

-- returns either nil or a fully functional ready to use inflate stream

local function get_deflate_stream(session)

	local status, deflate_stream = pcall(zlib.deflate, compression_level);

	if status == false then

		local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");

		(session.sends2s or session.send)(error_st);

		session.log("error", "Failed to create zlib.deflate filter.");

		module:log("error", "%s", tostring(deflate_stream));

		return

	end

	return deflate_stream

end

-- returns either nil or a fully functional ready to use inflate stream

local function get_inflate_stream(session)

	local status, inflate_stream = pcall(zlib.inflate);

	if status == false then

		local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");

		(session.sends2s or session.send)(error_st);

		session.log("error", "Failed to create zlib.inflate filter.");

		module:log("error", "%s", tostring(inflate_stream));

		return

	end

	return inflate_stream

end

-- setup compression for a stream

local function setup_compression(session, deflate_stream)

	add_filter(session, "bytes/out", function(t)

		local status, compressed, eof = pcall(deflate_stream, tostring(t), 'sync');

		if status == false then

			module:log("warn", "%s", tostring(compressed));

			session:close({

				condition = "undefined-condition";

				text = compressed;

				extra = st.stanza("failure", {xmlns="http://jabber.org/protocol/compress"}):tag("processing-failed");

			});

			return;

		end

		return compressed;

	end);	

end

-- setup decompression for a stream

local function setup_decompression(session, inflate_stream)

	add_filter(session, "bytes/in", function(data)

		local status, decompressed, eof = pcall(inflate_stream, data);

		if status == false then

			module:log("warn", "%s", tostring(decompressed));

			session:close({

				condition = "undefined-condition";

				text = decompressed;

				extra = st.stanza("failure", {xmlns="http://jabber.org/protocol/compress"}):tag("processing-failed");

			});

			return;

		end

		return decompressed;

	end);

end

module:hook("stanza/http://jabber.org/protocol/compress:compressed", function(event)

	local session = event.origin;

	if session.type == "s2sout_unauthed" or session.type == "s2sout" then

		session.log("debug", "Activating compression...")

		-- create deflate and inflate streams

		local deflate_stream = get_deflate_stream(session);

		if not deflate_stream then return true; end

		local inflate_stream = get_inflate_stream(session);

		if not inflate_stream then return true; end

		-- setup compression for session.w

		setup_compression(session, deflate_stream);

		-- setup decompression for session.data

		setup_decompression(session, inflate_stream);

		session:reset_stream();

		session.compressed = true;

		return true;

	end

end);

module:hook("stanza/http://jabber.org/protocol/compress:compress", function(event)

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

	if session.type == "c2s" or session.type == "s2sin" or session.type == "c2s_unauthed" or session.type == "s2sin_unauthed" then

		-- fail if we are already compressed

		if session.compressed then

			local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");

			(session.sends2s or session.send)(error_st);

			session.log("debug", "Client tried to establish another compression layer.");

			return true;

		end

		-- checking if the compression method is supported

		local method = stanza:child_with_name("method");

		method = method and (method[1] or "");

		if method == "zlib" then

			session.log("debug", "zlib compression enabled.");

			-- create deflate and inflate streams

			local deflate_stream = get_deflate_stream(session);

			if not deflate_stream then return true; end

			local inflate_stream = get_inflate_stream(session);

			if not inflate_stream then return true; end

			(session.sends2s or session.send)(st.stanza("compressed", {xmlns=xmlns_compression_protocol}));

			session:reset_stream();

			-- setup compression for session.w

			setup_compression(session, deflate_stream);

			-- setup decompression for session.data

			setup_decompression(session, inflate_stream);

			session.compressed = true;

		elseif method then

			session.log("debug", "%s compression selected, but we don't support it.", tostring(method));

			local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("unsupported-method");

			(session.sends2s or session.send)(error_st);

		else

			(session.sends2s or session.send)(st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed"));

		end

		return true;

	end

end);