package service

import (
	"net/http"
	"strings"
)

// copied from https://github.com/go-chi/chi/blob/c97bc988430d623a14f50b7019fb40529036a35a/middleware/realip.go#L42

var trueClientIP = http.CanonicalHeaderKey("True-Client-IP")
var xForwardedFor = http.CanonicalHeaderKey("X-Forwarded-For")
var xRealIP = http.CanonicalHeaderKey("X-Real-IP")

func extractIP(r *http.Request) string {
	var ip string

	if tcip := r.Header.Get(trueClientIP); tcip != "" {
		ip = tcip
	} else if xrip := r.Header.Get(xRealIP); xrip != "" {
		ip = xrip
	} else if xff := r.Header.Get(xForwardedFor); xff != "" {
		i := strings.Index(xff, ",")
		if i == -1 {
			i = len(xff)
		}
		ip = xff[:i]
	}

	return ip
}