Function middleware

packages/rate-limit/src/rate-limit.ts:72–147

(req: RequestWithRateLimit, res: Response, next: NextFunction)

  }

  async function middleware(req: RequestWithRateLimit, res: Response, next: NextFunction) {
    if (shouldSkip(req, res)) return next()

    const key = keyGenerator(req)

    try {
      const { current, resetTime } = await incrementStore(key)
      const maxResult = typeof max === 'function' ? await max(req, res) : max

      req.rateLimit = {
        limit: maxResult,
        current: current,
        remaining: Math.max(maxResult - current, 0),
        resetTime: resetTime
      }

      if (headers && !res.headersSent) {
        res.setHeader('X-RateLimit-Limit', maxResult)
        res.setHeader('X-RateLimit-Remaining', (req as any).rateLimit.remaining)
        if (resetTime instanceof Date) {
          // provide the current date to help avoid issues with incorrect clocks
          res.setHeader('Date', new Date().toUTCString())
          res.setHeader('X-RateLimit-Reset', Math.ceil(resetTime.getTime() / 1000))
        }
      }
      if (draftPolliRatelimitHeaders && !res.headersSent) {
        res.setHeader('RateLimit-Limit', maxResult)
        res.setHeader('RateLimit-Remaining', (req as any).rateLimit.remaining)
        if (resetTime) {
          const deltaSeconds = Math.ceil((resetTime.getTime() - Date.now()) / 1000)
          res.setHeader('RateLimit-Reset', Math.max(0, deltaSeconds))
        }
      }

      if (skipFailedRequests || skipSuccessfulRequests) {
        let decremented = false
        const decrementKey = () => {
          if (!decremented) {
            store.decrement(key)
            decremented = true
          }
        }

        if (skipFailedRequests) {
          res.on('finish', () => {
            if (res.statusCode >= 400) decrementKey()
          })

          res.on('close', () => {
            if (!res.writableEnded) decrementKey()
          })

          res.on('error', () => decrementKey())
        }

        if (skipSuccessfulRequests) {
          res.on('finish', () => {
            if (res.statusCode < 400) store.decrement(key)