package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"strings"
	"syscall"
)

const version = "0.1.3"

var config struct {
	Verbose       bool
	Strategy      string
	CheckSite     string
	CheckDuration int
}

func logf(f string, v ...interface{}) {
	if config.Verbose {
		log.Printf(f, v...)
	}
}

func usage() {
	app := os.Args[0]
	fmt.Fprintf(os.Stderr, "%s v%s usage:\n", app, version)
	flag.PrintDefaults()
	fmt.Fprintf(os.Stderr, "\n")

	fmt.Fprintf(os.Stderr, "Available Schemas:\n")
	fmt.Fprintf(os.Stderr, "  mixed: serve as a http/socks5 proxy on the same port. (default)\n")
	fmt.Fprintf(os.Stderr, "  ss: ss proxy\n")
	fmt.Fprintf(os.Stderr, "  socks5: socks5 proxy\n")
	fmt.Fprintf(os.Stderr, "  http: http proxy\n")
	fmt.Fprintf(os.Stderr, "  redir: redirect proxy. (used on linux as a transparent proxy with iptables redirect rules)\n")
	fmt.Fprintf(os.Stderr, "  tcptun: a simple tcp tunnel\n")
	fmt.Fprintf(os.Stderr, "  dnstun: listen on udp port and forward all dns requests to remote dns server via forwarders(tcp)\n")
	fmt.Fprintf(os.Stderr, "\n")

	fmt.Fprintf(os.Stderr, "Available schemas for different modes:\n")
	fmt.Fprintf(os.Stderr, "  listen: mixed ss socks5 http redir tcptun dnstun\n")
	fmt.Fprintf(os.Stderr, "  forward: ss socks5 http\n")
	fmt.Fprintf(os.Stderr, "\n")

	fmt.Fprintf(os.Stderr, "Available methods for ss:\n")
	fmt.Fprintf(os.Stderr, "  "+ListCipher())
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "\n")

	fmt.Fprintf(os.Stderr, "Available forward strategies:\n")
	fmt.Fprintf(os.Stderr, "  rr: Round Robin mode\n")
	fmt.Fprintf(os.Stderr, "  ha: High Availability mode\n")
	fmt.Fprintf(os.Stderr, "\n")

	fmt.Fprintf(os.Stderr, "Examples:\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l :8443 -v\n")
	fmt.Fprintf(os.Stderr, "    -listen on :8443, serve as http/socks5 proxy on the same port.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l ss://AEAD_CHACHA20_POLY1305:pass@:8443\n")
	fmt.Fprintf(os.Stderr, "    -listen on 0.0.0.0:8443 as a shadowsocks server.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l socks5://:1080 -v\n")
	fmt.Fprintf(os.Stderr, "    -listen on :1080 as a socks5 proxy server, in verbose mode.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l http://:8080 -f socks5://127.0.0.1:1080 -v\n")
	fmt.Fprintf(os.Stderr, "    -listen on :8080 as a http proxy server, forward all requests via socks5 server.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l redir://:1081 -f ss://method:pass@1.1.1.1:443\n")
	fmt.Fprintf(os.Stderr, "    -listen on :1081 as a transparent redirect server, forward all requests via remote ss server.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l tcptun://:80=2.2.2.2:80 -f ss://method:pass@1.1.1.1:443\n")
	fmt.Fprintf(os.Stderr, "    -listen on :80 and forward all requests to 2.2.2.2:80 via remote ss server.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l socks5://:1080 -l http://:8080 -f ss://method:pass@1.1.1.1:443\n")
	fmt.Fprintf(os.Stderr, "    -listen on :1080 as socks5 server, :8080 as http proxy server, forward all requests via remote ss server.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l redir://:1081 -l dnstun://:53=8.8.8.8:53 -f ss://method:pass@server1:port1,ss://method:pass@server2:port2\n")
	fmt.Fprintf(os.Stderr, "    -listen on :1081 as transparent redirect server, :53 as dns server, use forward chain: server1 -> server2.\n")
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "  "+app+" -l socks5://:1080 -f ss://method:pass@server1:port1 -f ss://method:pass@server2:port2 -s rr\n")
	fmt.Fprintf(os.Stderr, "    -listen on :1080 as socks5 server, forward requests via server1 and server2 in roundrbin mode.\n")
	fmt.Fprintf(os.Stderr, "\n")
}

type arrFlags []string

// implement flag.Value interface
func (i *arrFlags) String() string {
	return ""
}

// implement flag.Value interface
func (i *arrFlags) Set(value string) error {
	*i = append(*i, value)
	return nil
}

func main() {

	var flags struct {
		Listen  arrFlags
		Forward arrFlags
	}

	flag.BoolVar(&config.Verbose, "v", false, "verbose mode")
	flag.StringVar(&config.Strategy, "s", "rr", "forward strategy, default: rr")
	flag.StringVar(&config.CheckSite, "checksite", "www.apple.com:443", "proxy check address")
	flag.IntVar(&config.CheckDuration, "duration", 30, "proxy check duration(seconds)")

	flag.Var(&flags.Listen, "l", "listen url, format: SCHEMA://[USER|METHOD:PASSWORD@][HOST]:PORT")
	flag.Var(&flags.Forward, "f", "forward url, format: SCHEMA://[USER|METHOD:PASSWORD@][HOST]:PORT[,SCHEMA://[USER|METHOD:PASSWORD@][HOST]:PORT]")

	flag.Usage = usage
	flag.Parse()

	if len(flags.Listen) == 0 {
		flag.Usage()
		fmt.Fprintf(os.Stderr, "ERROR: listen url must be specified.\n")
		return
	}

	var forwarders []Proxy
	for _, chain := range flags.Forward {
		var forward Proxy
		var err error
		for _, url := range strings.Split(chain, ",") {
			forward, err = ProxyFromURL(url, forward)
			if err != nil {
				log.Fatal(err)
			}
		}
		forwarders = append(forwarders, forward)
	}

	for _, listen := range flags.Listen {
		local, err := ProxyFromURL(listen, forwarders...)
		if err != nil {
			log.Fatal(err)
		}

		go local.ListenAndServe()
	}

	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
	<-sigCh
}