func parseRetryAfterHeader()

in internal/requestconfig/requestconfig.go [265:318]
42 lines of code
7 McCabe index (conditional complexity)

func parseRetryAfterHeader(resp *http.Response) (time.Duration, bool) {
	if resp == nil {
		return 0, false
	}

	type retryData struct {
		header string
		units  time.Duration

		// custom is used when the regular algorithm failed and is optional.
		// the returned duration is used verbatim (units is not applied).
		custom func(string) (time.Duration, bool)
	}

	nop := func(string) (time.Duration, bool) { return 0, false }

	// the headers are listed in order of preference
	retries := []retryData{
		{
			header: "Retry-After-Ms",
			units:  time.Millisecond,
			custom: nop,
		},
		{
			header: "Retry-After",
			units:  time.Second,

			// retry-after values are expressed in either number of
			// seconds or an HTTP-date indicating when to try again
			custom: func(ra string) (time.Duration, bool) {
				t, err := time.Parse(time.RFC1123, ra)
				if err != nil {
					return 0, false
				}
				return time.Until(t), true
			},
		},
	}

	for _, retry := range retries {
		v := resp.Header.Get(retry.header)
		if v == "" {
			continue
		}
		if retryAfter, err := strconv.ParseFloat(v, 64); err == nil {
			return time.Duration(retryAfter * float64(retry.units)), true
		}
		if d, ok := retry.custom(v); ok {
			return d, true
		}
	}

	return 0, false
}