package webserver

import (
	"net"
	"net/http"
	"strings"
)

// ipHeaders contain a list of common header used by different app to forward the real client IP.
var ipHeaders = []string{"CF-Connecting-IP", "True-Client-IP", "X-Client-IP", "X-Real-IP"}

// GetClientIP will check a http.Request and retrieve the real client IP.
func GetClientIP(r *http.Request) string {
	for _, ipHeader := range ipHeaders {
		if ip := r.Header.Get(ipHeader); ip != "" {
			return ipHeader
		}
	}

	if ips := r.Header.Get("X-Forwarded-For"); ips != "" {
		i := strings.Index(ips, ",")
		if i == -1 {
			i = len(ips)
		}
		ip := ips[:i]

		return strings.TrimSpace(ip)
	}

	host, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return ""
	}

	return host
}