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

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

	if not origin.compressed 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 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 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("info", "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.");

		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);

		return

	end

	return inflate_stream

end

-- setup compression for a stream

local function setup_compression(session, deflate_stream)

	local old_send = (session.sends2s or session.send);

	local new_send = function(t)

			--TODO: Better code injection in the sending process

			session.log(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");

				});

				return;

			end

			session.conn:write(compressed);

		end;

	if session.sends2s then session.sends2s = new_send

	elseif session.send then session.send = new_send end

end

-- setup decompression for a stream

local function setup_decompression(session, inflate_stream)

	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");

				});

				return;

			end

			old_data(conn, decompressed);

		end;

end

module:add_handler({"s2sout_unauthed", "s2sout"}, "compressed", xmlns_compression_protocol, 

		function(session ,stanza)

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

			-- create deflate and inflate streams

			local deflate_stream = get_deflate_stream(session);

			if not deflate_stream then return end

			local inflate_stream = get_inflate_stream(session);

			if not inflate_stream then return end

			-- setup compression for session.w

			setup_compression(session, deflate_stream);

			-- setup decompression for session.data

			setup_decompression(session, inflate_stream);

			local session_reset_stream = session.reset_stream;

			session.reset_stream = function(session)

					session_reset_stream(session);

					setup_decompression(session, inflate_stream);

					return true;

				end;

			session:reset_stream();

			local default_stream_attr = {xmlns = "jabber:server", ["xmlns:stream"] = "http://etherx.jabber.org/streams",

										["xmlns:db"] = 'jabber:server:dialback', version = "1.0", to = session.to_host, from = session.from_host};

			session.sends2s("<?xml version='1.0'?>");

			session.sends2s(st.stanza("stream:stream", default_stream_attr):top_tag());

			session.compressed = true;

		end

);

module:add_handler({"c2s_unauthed", "c2s", "s2sin_unauthed", "s2sin"}, "compress", xmlns_compression_protocol,

		function(session, stanza)

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

				return;

			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

				-- create deflate and inflate streams

				local deflate_stream = get_deflate_stream(session);

				if not deflate_stream then return end

				local inflate_stream = get_inflate_stream(session);

				if not inflate_stream then return 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);

				local session_reset_stream = session.reset_stream;

				session.reset_stream = function(session)

						session_reset_stream(session);

						setup_decompression(session, inflate_stream);

						return true;

					end;

				session.compressed = true;

			elseif method then

				session.log("info", "%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

			end

		end

);