use fraction seconds for rate limit headers

packages/backend/src/misc/rate-limit-utils.ts

@@ -126,14 +126,20 @@ export function hasMinLimit(limit: LegacyRateLimit): limit is LegacyRateLimit &
 
 export function sendRateLimitHeaders(reply: FastifyReply, info: LimitInfo): void {
 	// Number of seconds until the limit has fully reset.
-	reply.header('X-RateLimit-Clear', info.fullResetSec.toString());
+	const clear = (info.fullResetMs / 1000).toFixed(3);
+	reply.header('X-RateLimit-Clear', clear);
+
 	// Number of calls that can be made before being limited.
-	reply.header('X-RateLimit-Remaining', info.remaining.toString());
+	const remaining = info.remaining.toString();
+	reply.header('X-RateLimit-Remaining', remaining);
 
 	if (info.blocked) {
 		// Number of seconds to wait before trying again. Left for backwards compatibility.
-		reply.header('Retry-After', info.resetSec.toString());
+		const retry = info.resetSec.toString();
+		reply.header('Retry-After', retry);
+
 		// Number of milliseconds to wait before trying again.
-		reply.header('X-RateLimit-Reset', info.resetMs.toString());
+		const reset = (info.resetMs / 1000).toFixed(3);
+		reply.header('X-RateLimit-Reset', reset);
 	}
 }

packages/backend/test/unit/misc/rate-limit-utils-tests.ts

@@ -0,0 +1,62 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { jest } from '@jest/globals';
+import { Mock } from 'jest-mock';
+import type { FastifyReply } from 'fastify';
+import { LimitInfo, sendRateLimitHeaders } from '@/misc/rate-limit-utils.js';
+
+/* eslint-disable @typescript-eslint/no-non-null-assertion */
+
+describe(sendRateLimitHeaders, () => {
+	let mockHeader: Mock<((name: string, value: unknown) => void)> = null!;
+	let mockReply: FastifyReply = null!;
+	let fakeInfo: LimitInfo = null!;
+
+	beforeEach(() => {
+		mockHeader = jest.fn<((name: string, value: unknown) => void)>();
+		mockReply = {
+			header: mockHeader,
+		} as unknown as FastifyReply;
+		fakeInfo = {
+			blocked: false,
+			remaining: 1,
+			resetSec: 1,
+			resetMs: 567,
+			fullResetSec: 10,
+			fullResetMs: 9876,
+		};
+	});
+
+	it('should send X-RateLimit-Clear', () => {
+		sendRateLimitHeaders(mockReply, fakeInfo);
+
+		expect(mockHeader).toHaveBeenCalledWith('X-RateLimit-Clear', '9.876');
+	});
+
+	it('should send X-RateLimit-Remaining', () => {
+		sendRateLimitHeaders(mockReply, fakeInfo);
+
+		expect(mockHeader).toHaveBeenCalledWith('X-RateLimit-Remaining', '1');
+	});
+
+	describe('when limit is blocked', () => {
+		it('should send X-RateLimit-Reset', () => {
+			fakeInfo.blocked = true;
+
+			sendRateLimitHeaders(mockReply, fakeInfo);
+
+			expect(mockHeader).toHaveBeenCalledWith('X-RateLimit-Reset', '0.567');
+		});
+
+		it('should send Retry-After', () => {
+			fakeInfo.blocked = true;
+
+			sendRateLimitHeaders(mockReply, fakeInfo);
+
+			expect(mockHeader).toHaveBeenCalledWith('Retry-After', '1');
+		});
+	});
+});