feat: add IP-based rate limiter (swc/jest replaces ts-jest for TS7 compat)

src/lib/__tests__/rate-limit.test.ts

@@ -0,0 +1,41 @@
+import { isRateLimited } from '../rate-limit'
+
+beforeEach(() => {
+  jest.useFakeTimers()
+  jest.resetModules()
+})
+
+afterEach(() => {
+  jest.useRealTimers()
+})
+
+describe('isRateLimited', () => {
+  it('allows requests under the limit', () => {
+    const ip = '1.2.3.4'
+    for (let i = 0; i < 5; i++) {
+      expect(isRateLimited(ip)).toBe(false)
+    }
+  })
+
+  it('blocks the 6th request within the window', () => {
+    const ip = '10.0.0.1'
+    for (let i = 0; i < 5; i++) isRateLimited(ip)
+    expect(isRateLimited(ip)).toBe(true)
+  })
+
+  it('resets after the window expires', () => {
+    const ip = '10.0.0.2'
+    for (let i = 0; i < 5; i++) isRateLimited(ip)
+    expect(isRateLimited(ip)).toBe(true)
+    jest.advanceTimersByTime(3_600_001)
+    expect(isRateLimited(ip)).toBe(false)
+  })
+
+  it('tracks different IPs independently', () => {
+    const ipA = '192.168.1.1'
+    const ipB = '192.168.1.2'
+    for (let i = 0; i < 5; i++) isRateLimited(ipA)
+    expect(isRateLimited(ipA)).toBe(true)
+    expect(isRateLimited(ipB)).toBe(false)
+  })
+})