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// shunt - domain matcher
//
// Compiles the policies' domain patterns into an exact and a wildcard map
// and answers which policies claim a queried name.
//
// SPDX-License-Identifier: GPL-3.0-or-later
// Copyright (c) 2026 Dirk Brenken <dev@brenken.org>
export const LIM = {
name: 253,
label: 63
};
function ok_label(s) {
if (!length(s) || length(s) > LIM.label)
return false;
for (let i = 0; i < length(s); i++) {
let c = ord(s, i);
if ((c >= 0x61 && c <= 0x7a) || (c >= 0x30 && c <= 0x39) ||
c == 0x2d || c == 0x5f)
continue;
return false;
}
return true;
}
export function normalize(s) {
s = lc(trim(s ?? ''));
while (length(s) && substr(s, -1) == '.')
s = substr(s, 0, length(s) - 1);
return s;
};
function validate(name) {
if (!length(name))
return 'empty';
if (length(name) > LIM.name)
return 'too long';
for (let l in split(name, '.'))
if (!ok_label(l))
return `bad label '${l}'`;
return null;
}
export function compile(policies) {
let exact = {}, wild = {}, issues = [];
function reject(policy, pattern, reason) {
push(issues, { policy, pattern, reason });
}
for (let pi = 0; pi < length(policies ?? []); pi++) {
let p = policies[pi];
let pname = p?.name ?? `#${pi}`;
for (let raw in (p?.domains ?? [])) {
let pat = normalize(raw);
let is_wild = false;
if (substr(pat, 0, 2) == '*.') {
is_wild = true;
pat = substr(pat, 2);
}
if (index(pat, '*') >= 0) {
reject(pname, raw, 'wildcard only allowed as leading *. label');
continue;
}
let bad = validate(pat);
if (bad) {
reject(pname, raw, bad);
continue;
}
let map = is_wild ? wild : exact;
if (!map[pat])
map[pat] = [];
let dup = false;
for (let owner in map[pat])
if (owner == pname)
dup = true;
if (!dup)
push(map[pat], pname);
}
}
// A list even for one element - a caller that has to distinguish shapes
// gets it wrong exactly once, in the rare case, in production.
function test(qname) {
let q = normalize(qname);
if (!length(q) || length(q) > LIM.name)
return null;
if (exists(exact, q))
return exact[q];
let off = index(q, '.');
while (off >= 0) {
let sfx = substr(q, off + 1);
if (exists(wild, sfx))
return wild[sfx];
let nxt = index(sfx, '.');
off = (nxt < 0) ? -1 : off + 1 + nxt;
}
return null;
}
return {
test,
issues,
size: { exact: length(keys(exact)), wild: length(keys(wild)) }
};
};
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