-- Prosody IM

-- Copyright (C) 2008-2010 Matthew Wild

-- Copyright (C) 2008-2010 Waqas Hussain

-- 

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

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

--

--- Module containing all the logic for connecting to a remote server

local t_insert = table.insert;

local t_sort = table.sort;

local ipairs = ipairs;

local wrapclient = require "net.server".wrapclient;

local initialize_filters = require "util.filters".initialize;

local idna_to_ascii = require "util.encodings".idna.to_ascii;

local add_task = require "util.timer".add_task;

local st = require "util.stanza";

local new_ip = require "util.ip".new_ip;

local rfc3484_dest = require "util.rfc3484".destination;

local socket = require "socket";

local s2s_new_outgoing = require "core.s2smanager".new_outgoing;

local s2s_destroy_session = require "core.s2smanager".destroy_session;

local s2sout = {};

local s2s_listener;

function s2sout.set_listener(listener)

	s2s_listener = listener;

end

local function compare_srv_priorities(a,b)

	return a.priority < b.priority or (a.priority == b.priority and a.weight > b.weight);

end

local function session_open_stream(session, from, to)

	session.sends2s(st.stanza("stream:stream", {

		xmlns='jabber:server', ["xmlns:db"]='jabber:server:dialback',

		["xmlns:stream"]='http://etherx.jabber.org/streams',

		from=from, to=to, version='1.0', ["xml:lang"]='en'}):top_tag());

end

function s2sout.initiate_connection(host_session)

	initialize_filters(host_session);

	host_session.open_stream = session_open_stream;

	-- Kick the connection attempting machine into life

	if not s2sout.attempt_connection(host_session) then

		-- Intentionally not returning here, the

		-- session is needed, connected or not

		s2s_destroy_session(host_session);

	end

	if not host_session.sends2s then

		-- A sends2s which buffers data (until the stream is opened)

		-- note that data in this buffer will be sent before the stream is authed

		-- and will not be ack'd in any way, successful or otherwise

		local buffer;

		function host_session.sends2s(data)

			if not buffer then

				buffer = {};

				host_session.send_buffer = buffer;

			end

			log("debug", "Buffering data on unconnected s2sout to %s", to_host);

			buffer[#buffer+1] = data;

			log("debug", "Buffered item %d: %s", #buffer, tostring(data));

		end

	end

end

function s2sout.attempt_connection(host_session, err)

	local from_host, to_host = host_session.from_host, host_session.to_host;

	local connect_host, connect_port = to_host and idna_to_ascii(to_host), 5269;

	if not connect_host then

		return false;

	end

	if not err then -- This is our first attempt

		log("debug", "First attempt to connect to %s, starting with SRV lookup...", to_host);

		host_session.connecting = true;

		local handle;

		handle = adns.lookup(function (answer)

			handle = nil;

			host_session.connecting = nil;

			if answer then

				log("debug", to_host.." has SRV records, handling...");

				local srv_hosts = {};

				host_session.srv_hosts = srv_hosts;

				for _, record in ipairs(answer) do

					t_insert(srv_hosts, record.srv);

				end

				if #srv_hosts == 1 and srv_hosts[1].target == "." then

					log("debug", to_host.." does not provide a XMPP service");

					s2s_destroy_session(host_session, err); -- Nothing to see here

					return;

				end

				t_sort(srv_hosts, compare_srv_priorities);

				local srv_choice = srv_hosts[1];

				host_session.srv_choice = 1;

				if srv_choice then

					connect_host, connect_port = srv_choice.target or to_host, srv_choice.port or connect_port;

					log("debug", "Best record found, will connect to %s:%d", connect_host, connect_port);

				end

			else

				log("debug", to_host.." has no SRV records, falling back to A");

			end

			-- Try with SRV, or just the plain hostname if no SRV

			local ok, err = s2sout.try_connect(host_session, connect_host, connect_port);

			if not ok then

				if not s2sout.attempt_connection(host_session, err) then

					-- No more attempts will be made

					s2s_destroy_session(host_session, err);

				end

			end

		end, "_xmpp-server._tcp."..connect_host..".", "SRV");

		return true; -- Attempt in progress

	elseif host_session.ip_hosts then

		return s2sout.try_connect(host_session, connect_host, connect_port, err);

	elseif host_session.srv_hosts and #host_session.srv_hosts > host_session.srv_choice then -- Not our first attempt, and we also have SRV

		host_session.srv_choice = host_session.srv_choice + 1;

		local srv_choice = host_session.srv_hosts[host_session.srv_choice];

		connect_host, connect_port = srv_choice.target or to_host, srv_choice.port or connect_port;

		host_session.log("info", "Connection failed (%s). Attempt #%d: This time to %s:%d", tostring(err), host_session.srv_choice, connect_host, connect_port);

	else

		host_session.log("info", "Out of connection options, can't connect to %s", tostring(host_session.to_host));

		-- We're out of options

		return false;

	end

	if not (connect_host and connect_port) then

		-- Likely we couldn't resolve DNS

		log("warn", "Hmm, we're without a host (%s) and port (%s) to connect to for %s, giving up :(", tostring(connect_host), tostring(connect_port), tostring(to_host));

		return false;

	end

	return s2sout.try_connect(host_session, connect_host, connect_port);

end

function s2sout.try_next_ip(host_session)

	host_session.connecting = nil;

	host_session.ip_choice = host_session.ip_choice + 1;

	local ip = host_session.ip_hosts[host_session.ip_choice];

	local ok, err= s2sout.make_connect(host_session, ip.ip, ip.port);

	if not ok then

		if not s2sout.attempt_connection(host_session, err or "closed") then

			err = err and (": "..err) or "";

			s2s_destroy_session(host_session, "Connection failed"..err);

		end

	end

end

function s2sout.try_connect(host_session, connect_host, connect_port, err)

	local sources;

	host_session.connecting = true;

	if not err then

		local IPs = {};

		host_session.ip_hosts = IPs;

		local handle4, handle6;

		local has_other = false;

		if not sources then

			sources = {};

			for i, source in ipairs(cfg_sources) do

				if source == "*" then

					sources[i] = new_ip("0.0.0.0", "IPv4");

				else

					sources[i] = new_ip(source, (source:find(":") and "IPv6") or "IPv4");

				end

			end

		end

		handle4 = adns.lookup(function (reply, err)

			handle4 = nil;

			-- COMPAT: This is a compromise for all you CNAME-(ab)users :)

			if not (reply and reply[#reply] and reply[#reply].a) then

				local count = max_dns_depth;

				reply = dns.peek(connect_host, "CNAME", "IN");

				while count > 0 and reply and reply[#reply] and not reply[#reply].a and reply[#reply].cname do

					log("debug", "Looking up %s (DNS depth is %d)", tostring(reply[#reply].cname), count);

					reply = dns.peek(reply[#reply].cname, "A", "IN") or dns.peek(reply[#reply].cname, "CNAME", "IN");

					count = count - 1;

				end

			end

			-- end of CNAME resolving

			if reply and reply[#reply] and reply[#reply].a then

				for _, ip in ipairs(reply) do

					log("debug", "DNS reply for %s gives us %s", connect_host, ip.a);

					IPs[#IPs+1] = new_ip(ip.a, "IPv4");

				end

			end

			if has_other then

				if #IPs > 0 then

					rfc3484_dest(host_session.ip_hosts, sources);

					for i = 1, #IPs do

						IPs[i] = {ip = IPs[i], port = connect_port};

					end

					host_session.ip_choice = 0;

					s2sout.try_next_ip(host_session);

				else

					log("debug", "DNS lookup failed to get a response for %s", connect_host);

					host_session.ip_hosts = nil;

					if not s2sout.attempt_connection(host_session, "name resolution failed") then -- Retry if we can

						log("debug", "No other records to try for %s - destroying", host_session.to_host);

						err = err and (": "..err) or "";

						s2s_destroy_session(host_session, "DNS resolution failed"..err); -- End of the line, we can't

					end

				end

			else

				has_other = true;

			end

		end, connect_host, "A", "IN");

		handle6 = adns.lookup(function (reply, err)

			handle6 = nil;

			if reply and reply[#reply] and reply[#reply].aaaa then

				for _, ip in ipairs(reply) do

					log("debug", "DNS reply for %s gives us %s", connect_host, ip.aaaa);

					IPs[#IPs+1] = new_ip(ip.aaaa, "IPv6");

				end

			end

			if has_other then

				if #IPs > 0 then

					rfc3484_dest(host_session.ip_hosts, sources);

					for i = 1, #IPs do

						IPs[i] = {ip = IPs[i], port = connect_port};

					end

					host_session.ip_choice = 0;

					s2sout.try_next_ip(host_session);

				else

					log("debug", "DNS lookup failed to get a response for %s", connect_host);

					host_session.ip_hosts = nil;

					if not s2sout.attempt_connection(host_session, "name resolution failed") then -- Retry if we can

						log("debug", "No other records to try for %s - destroying", host_session.to_host);

						err = err and (": "..err) or "";

						s2s_destroy_session(host_session, "DNS resolution failed"..err); -- End of the line, we can't

					end

				end

			else

				has_other = true;

			end

		end, connect_host, "AAAA", "IN");

		return true;

	elseif host_session.ip_hosts and #host_session.ip_hosts > host_session.ip_choice then -- Not our first attempt, and we also have IPs left to try

		s2sout.try_next_ip(host_session);

	else

		host_session.ip_hosts = nil;

		if not s2sout.attempt_connection(host_session, "out of IP addresses") then -- Retry if we can

			log("debug", "No other records to try for %s - destroying", host_session.to_host);

			err = err and (": "..err) or "";

			s2s_destroy_session(host_session, "Connecting failed"..err); -- End of the line, we can't

			return false;

		end

	end

	return true;

end

function s2sout.make_connect(host_session, connect_host, connect_port)

	(host_session.log or log)("info", "Beginning new connection attempt to %s ([%s]:%d)", host_session.to_host, connect_host.addr, connect_port);

	-- Ok, we're going to try to connect

	local from_host, to_host = host_session.from_host, host_session.to_host;

	local conn, handler;

	if connect_host.proto == "IPv4" then

		conn, handler = socket.tcp();

	else

		conn, handler = socket.tcp6();

	end

	if not conn then

		log("warn", "Failed to create outgoing connection, system error: %s", handler);

		return false, handler;

	end

	conn:settimeout(0);

	local success, err = conn:connect(connect_host.addr, connect_port);

	if not success and err ~= "timeout" then

		log("warn", "s2s connect() to %s (%s:%d) failed: %s", host_session.to_host, connect_host.addr, connect_port, err);

		return false, err;

	end

	conn = wrapclient(conn, connect_host.addr, connect_port, s2s_listener, "*a");

	host_session.conn = conn;

	local filter = initialize_filters(host_session);

	local w, log = conn.write, host_session.log;

	host_session.sends2s = function (t)

		log("debug", "sending: %s", (t.top_tag and t:top_tag()) or t:match("^[^>]*>?"));

		if t.name then

			t = filter("stanzas/out", t);

		end

		if t then

			t = filter("bytes/out", tostring(t));

			if t then

				return w(conn, tostring(t));

			end

		end

	end

	-- Register this outgoing connection so that xmppserver_listener knows about it

	-- otherwise it will assume it is a new incoming connection

	s2s_listener.register_outgoing(conn, host_session);

	host_session:open_stream(from_host, to_host);

	log("debug", "Connection attempt in progress...");

	return true;

end

return s2sout;