package retry

import (
	"net/http"
	"strconv"
	"time"
)

// ParseRetryAfter extracts the delay from a Retry-After header (RFC 7231).
// It supports both the delay-seconds format ("120") and the HTTP-date format
// ("Fri, 31 Dec 1999 23:59:59 GMT"). Returns the duration and true if the
// header was present and valid; otherwise returns 0 and false.
func ParseRetryAfter(resp *http.Response) (time.Duration, bool) {
	if resp == nil {
		return 0, false
	}

	val := resp.Header.Get("Retry-After")
	if val == "" {
		return 0, false
	}

	// Try delay-seconds first (most common).
	if seconds, err := strconv.ParseInt(val, 10, 64); err == nil {
		if seconds < 0 {
			return 0, false
		}
		return time.Duration(seconds) * time.Second, true
	}

	// Try HTTP-date format (RFC 7231 section 7.1.1.1).
	t, err := http.ParseTime(val)
	if err != nil {
		return 0, false
	}

	delay := time.Until(t)
	if delay < 0 {
		// The date is in the past; no need to wait.
		return 0, true
	}
	return delay, true
}