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% SPDX-FileCopyrightText: 2025 Johannes Christ
% SPDX-License-Identifier: AGPL-3.0-or-later
Definitions.
ALPHA = [a-zA-Z]
WHITESPACE = \s
% 4.6.1
QUALIFIER = \+|-|\?|~
% TODO: technically macro spec
DOMAIN_SPEC = [^\s]+
QNUM = ([0-9]|([1-9][0-9])|(1[0-9][0-9])|(2[0-4][0-9])|(25[0-5]))
IP4_NETWORK = {QNUM}\.{QNUM}\.{QNUM}\.{QNUM}
IP4_CIDR_LENGTH = /([0-9]|([1-2][0-9])|(3[0-2]))
% XXX: the following causes "cannot match because a previous clause always matches"
% maybe consider unifying these two cidr lengths
IP6_CIDR_LENGTH = /[0-9]|([1-9][0-9])|(1[0-1][0-9])|(12[0-8])
% parsing is done by erlang, I'm not writing a regex for that
IP6_NETWORK = [a-zA-Z0-9:]+
MECHANISM_WITH_IP4_NET = ip4:{IP4_NETWORK}({IP4_CIDR_LENGTH})?
MECHANISM_WITH_IP6_NET = ip6:{IP6_NETWORK}({IP6_CIDR_LENGTH})?
MECHANISM_NETWORK = {MECHANISM_WITH_IP4_NET}|{MECHANISM_WITH_IP6_NET}
MECHANISM_WITH_OPTIONAL_DOMAIN = ptr(:{DOMAIN_SPEC})?
MECHANISM_WITH_MANDATORY_DOMAIN = (exists|redirect|include):{DOMAIN_SPEC}
MECHANISM_WITH_DOMAIN_AND_CIDR = (a|mx)(:{DOMAIN_SPEC}({DUAL_CIDR_LENGTH})?)?
MECHANISM_DOMAIN = {MECHANISM_WITH_MANDATORY_DOMAIN}|{MECHANISM_WITH_OPTIONAL_DOMAIN}|{MECHANISM_WITH_DOMAIN_AND_CIDR}
MECHANISM = (all|{MECHANISM_NETWORK}|{MECHANISM_DOMAIN})
MECHANISM_TRAILER = :|/
NAME = [a-zA-Z][a-zA-Z0-9_.-]*
KNOWN_MODIFIER = (exp|redirect)={DOMAIN_SPEC}
UNKNOWN_MODIFIER = {NAME}={DOMAIN_SPEC}
MACRO_STRING = {DOMAIN_SPEC}
% TODO: 4.6.1: mechanism and modifier names are case-insensitive - WHAT THE FUCK!
Rules.
({QUALIFIER})?{MECHANISM} : {token, {directive, mechanism(TokenChars)}}.
% {QUALIFIER}?{MECHANISM} : {token, {directive, mechanism(TokenChars)}}.
{KNOWN_MODIFIER} : {token, {modifier, modifier(TokenChars)}}.
% {MECHANISM} : {token, {mechanism, TokenChars}}.
% {NAME} : {token, {name, TokenChars}}.
% = : {token, equal}.
{WHITESPACE}+ : skip_token.
% where "name" is not any known modifier
{UNKNOWN_MODIFIER} : {token, {unknown_modifier, modifier(TokenChars)}}.
Erlang code.
split_by(Value, Char) ->
[Head | Tail] = string:split(Value, Char),
case Tail of
"" -> {Head, ""};
Rest -> {Head, lists:flatten(lists:join(Char, Rest))}
end.
split_name(Value) -> split_by(Value, ":").
split_domain_spec(Value) ->
[Head | Tail] = string:split(Value, ":"),
{Head, lists:join(Tail, ":")}.
parse_ip_maybe_cidr(Value) ->
case string:split(Value, "/") of
[IP, RawMask] ->
{ok, Address} = inet:parse_address(IP),
{Mask, []} = string:to_integer(RawMask),
{Address, Mask};
[IP] ->
{ok, Address} = inet:parse_address(IP),
Address
end.
parse_mechanism("ip4:" ++ Ip4MaybeCidr) -> parse_ip_maybe_cidr(Ip4MaybeCidr);
parse_mechanism("ip6:" ++ Ip6MaybeCidr) -> parse_ip_maybe_cidr(Ip6MaybeCidr);
parse_mechanism(Value) -> split_by(Value, ":").
% 4.6.2
mechanism("+" ++ Value) -> {pass, parse_mechanism(Value)};
mechanism("-" ++ Value) -> {fail, parse_mechanism(Value)};
mechanism("~" ++ Value) -> {softfail, parse_mechanism(Value)};
mechanism("?" ++ Value) -> {neutral, parse_mechanism(Value)};
mechanism(Value) -> {pass, parse_mechanism(Value)}.
modifier(Value) -> split_by(Value, "=").
% vim: ft=erlang:
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