-- Prosody IM

-- Copyright (C) 2009 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 xmlns_compression_feature = "http://jabber.org/features/compress"

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

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

local compression_level = module:get_option("compression_level");

-- if not defined assume admin wants best compression

if compression_level == nil then compression_level = 9 end;

compression_level = tonumber(compression_level);

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:add_event_hook("stream-features",

		function (session, features)

			if not session.compressed then

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

				features:add_child(compression_stream_feature);

			end

		end

);

-- TODO Support compression on S2S level too.

		function(session, stanza)

			-- fail if we are already compressed

			if session.compressed then

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

				session.send(error_st);

				session.log("warn", "Tried to establish another compression layer.");

			end

			-- checking if the compression method is supported

			local method = stanza:child_with_name("method")[1];

			if method == "zlib" then

				session.log("info", method.." compression selected.");

				session:reset_stream();

				-- create deflate and inflate streams

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

					module:log("error", deflate_stream);

					return

				end

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

					module:log("error", inflate_stream);

					return

				end

				-- setup compression for session.w

				local old_send = session.send;

				session.send = function(t)

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

						if status == false then

							session:close({

								condition = "undefined-condition";

								text = compressed;

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

							});

							module:log("warn", compressed);

							return;

						end

						old_send(compressed);

					end;

				-- setup decompression for session.data

				local function setup_decompression(session)

					local old_data = session.data

					session.data = function(conn, data)

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

							if status == false then

								session:close({

									condition = "undefined-condition";

									text = decompressed;

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

								});

								module:log("warn", decompressed);

								return;

							end

							old_data(conn, decompressed);

						end;

				end

				setup_decompression(session);

				local session_reset_stream = session.reset_stream;

				session.reset_stream = function(session)

						session_reset_stream(session);

						setup_decompression(session);

						return true;

					end;

				session.compressed = true;

			else

				session.log("info", method.." compression selected. But we don't support it.");

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

			end

		end

);