Add rate limiter middleware with Redis support

Introduced a new rate limiter middleware in TypeScript to control API request volume. The middleware supports both local Redis and Upstash configurations for flexible rate limiting. It ensures that requests exceeding the set limit return a 429 status code.

Took 37 seconds

Author: mikepsinn

middleware/rateLimiter.ts

@@ -0,0 +1,76 @@
+import { Redis } from '@upstash/redis'
+import { createClient, RedisClientType } from 'redis'
+import { NextResponse } from 'next/server'
+import type { NextRequest } from 'next/server'
+
+let redisClient: Redis | RedisClientType | null = null
+
+async function initializeRedisClient() {
+  if (redisClient) return redisClient
+
+  const useLocalRedis = process.env.USE_LOCAL_REDIS === 'true'
+
+  if (useLocalRedis) {
+    const localRedisUrl = process.env.LOCAL_REDIS_URL || 'redis://localhost:6379'
+    redisClient = createClient({ url: localRedisUrl }) as RedisClientType
+    await redisClient.connect()
+  } else {
+    const upstashRedisRestUrl = process.env.UPSTASH_REDIS_REST_URL
+    const upstashRedisRestToken = process.env.UPSTASH_REDIS_REST_TOKEN
+
+    if (upstashRedisRestUrl && upstashRedisRestToken) {
+      redisClient = new Redis({
+        url: upstashRedisRestUrl,
+        token: upstashRedisRestToken
+      })
+    }
+  }
+
+  return redisClient
+}
+
+export async function checkRateLimits(apiKey: string, limits: { perMinute: number }) {
+  const client = await initializeRedisClient()
+  if (!client) throw new Error('Redis client not initialized')
+
+  const now = Date.now()
+  const windowKey = `ratelimit:${apiKey}:${Math.floor(now / 60000)}` // Key for current minute
+
+  let currentCount: number
+  
+  if (client instanceof Redis) {
+    currentCount = await client.incr(windowKey)
+    await client.expire(windowKey, 60)
+  } else {
+    const multi = client.multi()
+    const results = await multi
+      .incr(windowKey)
+      .expire(windowKey, 60)
+      .exec()
+    currentCount = (results?.[0] as number) || 0
+  }
+
+  if (currentCount > limits.perMinute) {
+    throw new Error(`Rate limit exceeded: ${limits.perMinute} requests per minute`)
+  }
+
+  return currentCount
+}
+
+export async function withRateLimit(
+  request: NextRequest,
+  handler: (request: NextRequest) => Promise<NextResponse>,
+  limits: { perMinute: number }
+) {
+  const apiKey = request.headers.get('x-api-key')
+  if (!apiKey) {
+    return NextResponse.json({ error: 'Missing API key' }, { status: 401 })
+  }
+
+  try {
+    await checkRateLimits(apiKey, limits)
+    return await handler(request)
+  } catch (error) {
+    return NextResponse.json({ error: 'Rate limit exceeded' }, { status: 429 })
+  }
+}