From abec0f1f388e6f45af4b7052b09777e44e1f24ba Mon Sep 17 00:00:00 2001
From: Marco Link <marco.link@contentful.com>
Date: Tue, 26 Sep 2023 15:48:14 +0200
Subject: [PATCH] chore: more throtteling tests

---
 src/rate-limit-throttle.ts            | 16 +++++++++++++---
 src/rate-limit.ts                     |  2 +-
 test/unit/rate-limit-throttle.spec.ts | 17 +++++++++++++++++
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/rate-limit-throttle.ts b/src/rate-limit-throttle.ts
index d7e14f1..11f76c5 100644
--- a/src/rate-limit-throttle.ts
+++ b/src/rate-limit-throttle.ts
@@ -8,7 +8,16 @@ type ThrottleType = 'auto' | string
 
 const PERCENTAGE_REGEX = /(?<value>\d+)(%)/
 
-function calculateLimit(type: ThrottleType, max = 7) {
+const HEADERS = {
+  // @desc The maximum amount of requests which can be made in a second.
+  RATE_LIMIT: 'x-contentful-ratelimit-second-limit',
+  // @desc The number of seconds until the next request can be made.
+  RATE_LIMIT_RESET: 'x-contentful-ratelimit-second-reset',
+  // @desc The remaining amount of requests which can be made until the next secondly reset.
+  RATE_LIMIT_REMAINING: 'x-contentful-ratelimit-second-remaining',
+} as const
+
+export function calculateLimit(type: ThrottleType, max = 7) {
   let limit = max
 
   if (PERCENTAGE_REGEX.test(type)) {
@@ -47,14 +56,15 @@ export default (axiosInstance: AxiosInstance, type: ThrottleType | number = 'aut
 
   const responseInterceptorId = axiosInstance.interceptors.response.use(
     (response) => {
+      // If we haven't yet calculated the limit based on the headers, do so now
       if (
         !isCalculated &&
         isString(type) &&
         (type === 'auto' || PERCENTAGE_REGEX.test(type)) &&
         response.headers &&
-        response.headers['x-contentful-ratelimit-second-limit']
+        response.headers[HEADERS.RATE_LIMIT]
       ) {
-        const rawLimit = parseInt(response.headers['x-contentful-ratelimit-second-limit'])
+        const rawLimit = parseInt(response.headers[HEADERS.RATE_LIMIT])
         const nextLimit = calculateLimit(type, rawLimit)
 
         if (nextLimit !== limit) {
diff --git a/src/rate-limit.ts b/src/rate-limit.ts
index 907020a..37b08cf 100644
--- a/src/rate-limit.ts
+++ b/src/rate-limit.ts
@@ -58,7 +58,7 @@ export default function rateLimit(instance: AxiosInstance, maxRetry = 5): void {
       } else if (response.status === 429) {
         // 429 errors are exceeded rate limit exceptions
         retryErrorType = 'Rate limit'
-        // all headers are lowercased by axios https://github.com/mzabriskie/axios/issues/413
+        // all headers are lower-cased by axios https://github.com/mzabriskie/axios/issues/413
         if (response.headers && error.response.headers['x-contentful-ratelimit-reset']) {
           wait = response.headers['x-contentful-ratelimit-reset']
         }
diff --git a/test/unit/rate-limit-throttle.spec.ts b/test/unit/rate-limit-throttle.spec.ts
index 5f8be74..64fce53 100644
--- a/test/unit/rate-limit-throttle.spec.ts
+++ b/test/unit/rate-limit-throttle.spec.ts
@@ -4,6 +4,7 @@ import axios from 'axios'
 import MockAdapter from 'axios-mock-adapter'
 import { AxiosInstance } from '../../src'
 import createHttpClient from '../../src/create-http-client'
+import { calculateLimit } from '../../src/rate-limit-throttle'
 
 const logHandlerStub = vi.fn()
 
@@ -141,3 +142,19 @@ describe('throttle to rate limit axios interceptor', () => {
     },
   )
 })
+
+describe('a calculate limit function', () => {
+  describe('with type "auto"', () => {
+    it('always returns the given max limit', () => {
+      expect(calculateLimit('auto', 10)).toEqual(10)
+      expect(calculateLimit('auto', 1)).toEqual(1)
+    })
+  })
+  describe('with %', () => {
+    it('always returns % of max limit', () => {
+      expect(calculateLimit('0%', 10)).toEqual(1)
+      expect(calculateLimit('50%', 10)).toEqual(5)
+      expect(calculateLimit('100%', 10)).toEqual(10)
+    })
+  })
+})