-- 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.

--

local server = require "net.server";

local new_resolver = require "net.dns".resolver;

local log = require "util.logger".init("adns");

local coroutine, tostring, pcall = coroutine, tostring, pcall;

local setmetatable = setmetatable;

local function dummy_send(sock, data, i, j) return (j-i)+1; end

local _ENV = nil;

-- luacheck: std none

local async_resolver_methods = {};

local async_resolver_mt = { __index = async_resolver_methods };

local query_methods = {};

local query_mt = { __index = query_methods };

local function new_async_socket(sock, resolver)

	local peername = "<unknown>";

	local listener = {};

	local handler = {};

	local err;

	function listener.onincoming(conn, data)

		if data then

			resolver:feed(handler, data);

		end

	end

	function listener.ondisconnect(conn, err)

		if err then

			log("warn", "DNS socket for %s disconnected: %s", peername, err);

			local servers = resolver.server;

			if resolver.socketset[conn] == resolver.best_server and resolver.best_server == #servers then

				log("error", "Exhausted all %d configured DNS servers, next lookup will try %s again", #servers, servers[1]);

			end

			resolver:servfail(conn); -- Let the magic commence

		end

	end

	handler, err = server.wrapclient(sock, "dns", 53, listener);

	if not handler then

		return nil, err;

	end

	if handler.set then

		-- server_epoll: only watch for incoming data

		-- avoids sending empty packet on first 'onwritable' event

		handler:set(true, false);

	end

	handler.settimeout = function () end

	handler.setsockname = function (_, ...) return sock:setsockname(...); end

	handler.setpeername = function (_, ...) peername = (...); local ret, err = sock:setpeername(...); _:set_send(dummy_send); return ret, err; end

	handler.connect = function (_, ...) return sock:connect(...) end

	--handler.send = function (_, data) _:write(data);  return _.sendbuffer and _.sendbuffer(); end

	handler.send = function (_, data)

		log("debug", "Sending DNS query to %s", peername);

		return sock:send(data);

	end

	return handler;

end

function async_resolver_methods:lookup(handler, qname, qtype, qclass)

	local resolver = self._resolver;

	return coroutine.wrap(function (peek)

				if peek then

					log("debug", "Records for %s already cached, using those...", qname);

					handler(peek);

					return;

				end

				log("debug", "Records for %s not in cache, sending query (%s)...", qname, tostring(coroutine.running()));

				local ok, err = resolver:query(qname, qtype, qclass);

				if ok then

					coroutine.yield(setmetatable({ resolver, qclass or "IN", qtype or "A", qname, coroutine.running()}, query_mt)); -- Wait for reply

					log("debug", "Reply for %s (%s)", qname, tostring(coroutine.running()));

				end

				if ok then

					ok, err = pcall(handler, resolver:peek(qname, qtype, qclass));

				else

					log("error", "Error sending DNS query: %s", err);

					ok, err = pcall(handler, nil, err);

				end

				if not ok then

					log("error", "Error in DNS response handler: %s", tostring(err));

				end

			end)(resolver:peek(qname, qtype, qclass));

end

function query_methods:cancel(call_handler, reason)

	log("warn", "Cancelling DNS lookup for %s", tostring(self[4]));

	self[1].cancel(self[2], self[3], self[4], self[5], call_handler);

end

local function new_async_resolver()

	local resolver = new_resolver();

	resolver:socket_wrapper_set(new_async_socket);

	return setmetatable({ _resolver = resolver}, async_resolver_mt);

end

return {

	lookup = function (...)

		return new_async_resolver():lookup(...);

	end;

	resolver = new_async_resolver;

	new_async_socket = new_async_socket;

};