From 5dc508346cd05ea755581ffd9ca8baa6ff8d4d91 Mon Sep 17 00:00:00 2001
From: mq1 <74494945+chan-mai@users.noreply.github.com>
Date: Wed, 15 Apr 2026 09:02:43 +0900
Subject: [PATCH] =?UTF-8?q?fix(backend):=20ULID=E3=82=92=E6=AD=A3=E3=81=97?=
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fix(backend): fix parseUlidFull to correctly handle Crockford Base32 chars W/X/Y/Z
---
 packages/backend/src/misc/id/ulid.ts    | 11 +++++--
 packages/backend/test/unit/misc/ulid.ts | 41 +++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 packages/backend/test/unit/misc/ulid.ts

diff --git a/packages/backend/src/misc/id/ulid.ts b/packages/backend/src/misc/id/ulid.ts
index 8b81702d19..291a33385f 100644
--- a/packages/backend/src/misc/id/ulid.ts
+++ b/packages/backend/src/misc/id/ulid.ts
@@ -5,12 +5,19 @@
 
 // Crockford's Base32
 // https://github.com/ulid/spec#encoding
-import { parseBigInt32 } from '@/misc/bigint.js';
 
 const CHARS = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
 
 export const ulidRegExp = /^[0123456789ABCDEFGHJKMNPQRSTVWXYZ]{26}$/;
 
+function parseBigIntCrockford(str: string): bigint {
+	let result = 0n;
+	for (let i = 0; i < str.length; i++) {
+		result = result * 32n + BigInt(CHARS.indexOf(str[i]));
+	}
+	return result;
+}
+
 function parseBase32(timestamp: string) {
 	let time = 0;
 	for (let i = 0; i < timestamp.length; i++) {
@@ -26,6 +33,6 @@ export function parseUlid(id: string): { date: Date; } {
 export function parseUlidFull(id: string): { date: number; additional: bigint; } {
 	return {
 		date: parseBase32(id.slice(0, 10)),
-		additional: parseBigInt32(id.slice(10, 26)),
+		additional: parseBigIntCrockford(id.slice(10, 26)),
 	};
 }
diff --git a/packages/backend/test/unit/misc/ulid.ts b/packages/backend/test/unit/misc/ulid.ts
new file mode 100644
index 0000000000..b79e3bc2b4
--- /dev/null
+++ b/packages/backend/test/unit/misc/ulid.ts
@@ -0,0 +1,41 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { describe, expect, test } from '@jest/globals';
+import { parseUlidFull } from '@/misc/id/ulid.js';
+
+// Timestamp part "01KPS7S300" encodes 1776816000000ms (2026-04-22T00:00:00.000Z)
+// Verified: 1*32^8 + 19*32^7 + 22*32^6 + 25*32^5 + 7*32^4 + 25*32^3 + 3*32^2 = 1776816000000
+
+describe('misc:ulid', () => {
+	test('parseUlidFull - timestamp is parsed correctly', () => {
+		// id[10..25] = all zeros (valid Crockford Base32)
+		// 2026-04-22T00:00:00.000Z
+		const { date } = parseUlidFull('01KPS7S3000000000000000000');
+		expect(date).toBe(1776816000000);
+	});
+
+	test('parseUlidFull - W/X/Y/Z at id[10] (chunk 1 head) do not throw', () => {
+		// id[10] = W
+		expect(() => parseUlidFull('01KPS7S300W000000000000000')).not.toThrow();
+		// id[10] = X
+		expect(() => parseUlidFull('01KPS7S300X000000000000000')).not.toThrow();
+		// id[10] = Y
+		expect(() => parseUlidFull('01KPS7S300Y000000000000000')).not.toThrow();
+		// id[10] = Z
+		expect(() => parseUlidFull('01KPS7S300Z000000000000000')).not.toThrow();
+	});
+
+	test('parseUlidFull - W/X/Y/Z at id[16] (chunk 2 head) do not throw', () => {
+		// id[16] = W
+		expect(() => parseUlidFull('01KPS7S300ABCDEFW000000000')).not.toThrow();
+		// id[16] = X
+		expect(() => parseUlidFull('01KPS7S300ABCDEFX000000000')).not.toThrow();
+		// id[16] = Y
+		expect(() => parseUlidFull('01KPS7S300ABCDEFY000000000')).not.toThrow();
+		// id[16] = Z
+		expect(() => parseUlidFull('01KPS7S300ABCDEFZ000000000')).not.toThrow();
+	});
+});