package http

import (
	"net/http"
	"strconv"
	"strings"

	"github.com/v2fly/v2ray-core/v5/common/net"
)

// ParseXForwardedFor parses X-Forwarded-For header in http headers, and return the IP list in it.
func ParseXForwardedFor(header http.Header) []net.Address {
	xff := header.Get("X-Forwarded-For")
	if xff == "" {
		return nil
	}
	list := strings.Split(xff, ",")
	addrs := make([]net.Address, 0, len(list))
	for _, proxy := range list {
		addrs = append(addrs, net.ParseAddress(proxy))
	}
	return addrs
}

// RemoveHopByHopHeaders remove hop by hop headers in http header list.
func RemoveHopByHopHeaders(header http.Header) {
	// Strip hop-by-hop header based on RFC:
	// http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.5.1
	// https://www.mnot.net/blog/2011/07/11/what_proxies_must_do

	header.Del("Proxy-Connection")
	header.Del("Proxy-Authenticate")
	header.Del("Proxy-Authorization")
	header.Del("TE")
	header.Del("Trailers")
	header.Del("Transfer-Encoding")
	header.Del("Upgrade")
	header.Del("Keep-Alive")

	connections := header.Get("Connection")
	header.Del("Connection")
	if connections == "" {
		return
	}
	for _, h := range strings.Split(connections, ",") {
		header.Del(strings.TrimSpace(h))
	}
}

// ParseHost splits host and port from a raw string. Default port is used when raw string doesn't contain port.
func ParseHost(rawHost string, defaultPort net.Port) (net.Destination, error) {
	port := defaultPort
	host, rawPort, err := net.SplitHostPort(rawHost)
	if err != nil {
		if addrError, ok := err.(*net.AddrError); ok && strings.Contains(addrError.Err, "missing port") {
			host = rawHost
		} else {
			return net.Destination{}, err
		}
	} else if len(rawPort) > 0 {
		intPort, err := strconv.ParseUint(rawPort, 0, 16)
		if err != nil {
			return net.Destination{}, err
		}
		port = net.Port(intPort)
	}

	return net.TCPDestination(net.ParseAddress(host), port), nil
}