-- SPDX-License-Identifier: GPL-3.0-or-later
-- Module interface

local ffi = require('ffi')
local basexx = require('basexx')
local C = ffi.C

-- Export module interface
local M = {}
M.layer = {}
local base32 = {}
local str = {}
local AF_INET = 2
local AF_INET6 = 10
local INET_ADDRSTRLEN = 16
local INET6_ADDRSTRLEN = 46

ffi.cdef[[
/*
 * Data structures
 */
typedef int socklen_t;
 struct sockaddr_storage{
		 unsigned short int ss_family;
		 unsigned long int __ss_align;
		 char __ss_padding[128 - (2 *sizeof(unsigned long int))];
 };
 struct in_addr{
		 unsigned char  s_addr[4];
 };
 struct in6_addr{
		 unsigned char s6_addr[16];
 };
 struct sockaddr_in{
		 short sin_family;
		 unsigned short sin_port;
		 struct in_addr sin_addr;
		 char sin_zero[8];
 } __attribute__ ((__packed__));
 struct sockaddr_in6{
		 unsigned short sin6_family;
		 unsigned short sin6_port;
		 unsigned int sin6_flowinfo;
		 struct in6_addr sin6_addr;
		 unsigned int sin6_scope_id;
 };
 typedef unsigned short  sa_family_t;
 struct sockaddr_un {
		 sa_family_t sun_family;
		 char        sun_path[108];
 };
 const char *inet_ntop(
        int af,
        const void *cp,
        char *buf,
        socklen_t len);
]]

function base32.pad(b32)
        local m = #b32 % 8
        if m ~= 0 then
                b32 = b32 .. string.rep("=", 8 - m)
        end
        return b32
end

function str.starts(String,Start)
   return string.sub(String,1,string.len(Start))==Start
end

-- Handle DoT signalling NS domains.
function M.layer.consume(state, _, pkt)
	-- Only successful answers
	if state == kres.FAIL then return state end
	-- log_debug(ffi.C.LOG_GRP_DOTAUTH, "%s", pkt:tostring())
	local authority = pkt:section(kres.section.AUTHORITY)
	local additional = pkt:section(kres.section.ADDITIONAL)
	for _, rr in ipairs(authority) do
		--log_debug(ffi.C.LOG_GRP_DOTAUTH, "%d %s", rr.type, kres.dname2str(rr.rdata))
		if rr.type == kres.type.NS then
			local name = kres.dname2str(rr.rdata):upper()
			-- log_debug(ffi.C.LOG_GRP_DOTAUTH, "NS %d", name:len())
			if name:len() > 56 and str.starts(name, "DOT-") then
				local k = basexx.to_base64(
					basexx.from_base32(
						base32.pad(string.sub(name, 5, string.find(name, '[.]') - 1))
					)
				)
				for _, rr_add in ipairs(additional) do
					if rr_add.type == kres.type.A or rr_add.type == kres.type.AAAA then
						local name_add = kres.dname2str(rr_add.owner):upper()
						if name == name_add then
              local addrbuf
							if rr_add.type == kres.type.A then
								local ns_addr = ffi.new("struct sockaddr_in")
								ns_addr.sin_family = AF_INET

								ns_addr.sin_addr.s_addr = rr_add.rdata
								addrbuf = ffi.new("char[?]", INET_ADDRSTRLEN)
								C.inet_ntop(AF_INET, ns_addr.sin_addr, addrbuf, INET_ADDRSTRLEN)
							else
								local ns_addr = ffi.new("struct sockaddr_in6")
								ns_addr.sin6_family = AF_INET6

								ns_addr.sin6_addr.s6_addr = rr_add.rdata
								addrbuf = ffi.new("char[?]", INET6_ADDRSTRLEN)
								C.inet_ntop(AF_INET6, ns_addr.sin6_addr, addrbuf, INET6_ADDRSTRLEN)
							end
              net.tls_client(ffi.string(addrbuf).."@853", {k})
							log_info(ffi.C.LOG_GRP_DOTAUTH, "Adding %s IP %s %s", name_add, ffi.string(addrbuf).."@853", k)
						end
					end
				end
			end
		end
	end

	return state

end

return M