local adns = require "net.adns";

local inet_pton = require "util.net".pton;

local inet_ntop = require "util.net".ntop;

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

local unpack = table.unpack or unpack; -- luacheck: ignore 113

local methods = {};

local resolver_mt = { __index = methods };

-- FIXME RFC 6724

-- Find the next target to connect to, and

-- pass it to cb()

function methods:next(cb)

	if self.targets then

		if #self.targets == 0 then

			cb(nil);

			return;

		end

		local next_target = table.remove(self.targets, 1);

		cb(unpack(next_target, 1, 4));

		return;

	end

	if not self.hostname then

		self.last_error = "hostname failed IDNA";

		cb(nil);

		return;

	end

	local secure = true;

	local tlsa = {};

	local targets = {};

	local n = 3;

	local function ready()

		n = n - 1;

		if n > 0 then return; end

		self.targets = targets;

		if self.extra and self.extra.use_dane then

			if secure and tlsa[1] then

				self.extra.tlsa = tlsa;

				self.extra.dane_hostname = self.hostname;

			else

				self.extra.tlsa = nil;

				self.extra.dane_hostname = nil;

			end

		end

		self:next(cb);

	end

	-- Resolve DNS to target list

	local dns_resolver = adns.resolver();

	if not self.extra or self.extra.use_ipv4 ~= false then

		dns_resolver:lookup(function (answer, err)

			if answer then

				secure = secure and answer.secure;

				for _, record in ipairs(answer) do

					table.insert(targets, { self.conn_type.."4", record.a, self.port, self.extra });

				end

				if answer.bogus then

					self.last_error = "Validation error in A lookup";

				elseif answer.status then

					self.last_error = answer.status .. " in A lookup";

				end

			else

				self.last_error = err;

			end

			ready();

		end, self.hostname, "A", "IN");

	else

		ready();

	end

	if not self.extra or self.extra.use_ipv6 ~= false then

		dns_resolver:lookup(function (answer, err)

			if answer then

				secure = secure and answer.secure;

				for _, record in ipairs(answer) do

					table.insert(targets, { self.conn_type.."6", record.aaaa, self.port, self.extra });

				end

				if answer.bogus then

					self.last_error = "Validation error in AAAA lookup";

				elseif answer.status then

					self.last_error = answer.status .. " in AAAA lookup";

				end

			else

				self.last_error = err;

			end

			ready();

		end, self.hostname, "AAAA", "IN");

	else

		ready();

	end

	if self.extra and self.extra.use_dane == true then

		dns_resolver:lookup(function (answer, err)

			if answer then

				secure = secure and answer.secure;

				for _, record in ipairs(answer) do

					table.insert(tlsa, record.tlsa);

				end

				if answer.bogus then

					self.last_error = "Validation error in TLSA lookup";

				elseif answer.status then

					self.last_error = answer.status .. " in TLSA lookup";

				end

			else

				self.last_error = err;

			end

			ready();

		end, ("_%d._tcp.%s"):format(self.port, self.hostname), "TLSA", "IN");

	else

		ready();

	end

end

local function new(hostname, port, conn_type, extra)

	local ascii_host = idna_to_ascii(hostname);

	local targets = nil;

	conn_type = conn_type or "tcp";

	local is_ip = inet_pton(hostname);

	if not is_ip and hostname:sub(1,1) == '[' then

		is_ip = inet_pton(hostname:sub(2,-2));

	end

	if is_ip then

		hostname = inet_ntop(is_ip);

		if #is_ip == 16 then

			targets = { { conn_type.."6", hostname, port, extra } };

		elseif #is_ip == 4 then

			targets = { { conn_type.."4", hostname, port, extra } };

		end

	end

	return setmetatable({

		hostname = ascii_host;

		port = port;

		conn_type = conn_type;

		extra = extra;

		targets = targets;

	}, resolver_mt);

end

return {

	new = new;

};