package main

import (
	"encoding/csv"
	"context"
	"errors"
	"flag"
	"fmt"
	"log"
	"net"
	"net/http"
	"net/url"
	"os"
	"time"
	"crypto/tls"
	"strings"

	xproxy "golang.org/x/net/proxy"

	se "github.com/Snawoot/opera-proxy/seclient"
)

var (
	version = "undefined"
)

func perror(msg string) {
	fmt.Fprintln(os.Stderr, "")
	fmt.Fprintln(os.Stderr, msg)
}

func arg_fail(msg string) {
	perror(msg)
	perror("Usage:")
	flag.PrintDefaults()
	os.Exit(2)
}

type CLIArgs struct {
	country      string
	listCountries bool
	listProxies bool
	bindAddress string
	verbosity    int
	timeout      time.Duration
	resolver     string
	showVersion  bool
	proxy        string
	apiLogin     string
	apiPassword  string
}

func parse_args() CLIArgs {
	var args CLIArgs
	flag.StringVar(&args.country, "country", "EU", "desired proxy location")
	flag.BoolVar(&args.listCountries, "list-countries", false, "list available countries and exit")
	flag.BoolVar(&args.listProxies, "list-proxies", false, "output proxy list and exit")
	flag.StringVar(&args.bindAddress, "bind-address", "127.0.0.1:18080", "HTTP proxy listen address")
	flag.IntVar(&args.verbosity, "verbosity", 20, "logging verbosity "+
		"(10 - debug, 20 - info, 30 - warning, 40 - error, 50 - critical)")
	flag.DurationVar(&args.timeout, "timeout", 10*time.Second, "timeout for network operations")
	flag.StringVar(&args.resolver, "resolver", "https://cloudflare-dns.com/dns-query",
		"DNS/DoH/DoT resolver to workaround Hola blocked hosts. "+
			"See https://github.com/ameshkov/dnslookup/ for upstream DNS URL format.")
	flag.BoolVar(&args.showVersion, "version", false, "show program version and exit")
	flag.StringVar(&args.proxy, "proxy", "", "sets base proxy to use for all dial-outs. "+
		"Format: <http|https|socks5|socks5h>://[login:password@]host[:port] "+
		"Examples: http://user:password@192.168.1.1:3128, socks5://10.0.0.1:1080")
	flag.StringVar(&args.apiLogin, "api-login", "se0316", "SurfEasy API login")
	flag.StringVar(&args.apiPassword, "api-password", "SILrMEPBmJuhomxWkfm3JalqHX2Eheg1YhlEZiMh8II", "SurfEasy API password")
	flag.Parse()
	if args.country == "" {
		arg_fail("Country can't be empty string.")
	}
	if args.listCountries && args.listProxies {
		arg_fail("list-countries and list-proxies flags are mutually exclusive")
	}
	return args
}

func proxyFromURLWrapper(u *url.URL, next xproxy.Dialer) (xproxy.Dialer, error) {
	cdialer, ok := next.(ContextDialer)
	if !ok {
		return nil, errors.New("only context dialers are accepted")
	}

	return ProxyDialerFromURL(u, cdialer)
}

func run() int {
	args := parse_args()
	if args.showVersion {
		fmt.Println(version)
		return 0
	}

	logWriter := NewLogWriter(os.Stderr)
	defer logWriter.Close()

	mainLogger := NewCondLogger(log.New(logWriter, "MAIN    : ",
		log.LstdFlags|log.Lshortfile),
		args.verbosity)
	proxyLogger := NewCondLogger(log.New(logWriter, "PROXY   : ",
		log.LstdFlags|log.Lshortfile),
		args.verbosity)

	mainLogger.Info("opera-proxy client version %s is starting...", version)

	var dialer ContextDialer = &net.Dialer{
		Timeout:   30 * time.Second,
		KeepAlive: 30 * time.Second,
	}
	if args.proxy != "" {
		xproxy.RegisterDialerType("http", proxyFromURLWrapper)
		xproxy.RegisterDialerType("https", proxyFromURLWrapper)
		proxyURL, err := url.Parse(args.proxy)
		if err != nil {
			mainLogger.Critical("Unable to parse base proxy URL: %v", err)
			return 6
		}
		pxDialer, err := xproxy.FromURL(proxyURL, dialer)
		if err != nil {
			mainLogger.Critical("Unable to instantiate base proxy dialer: %v", err)
			return 7
		}
		dialer = pxDialer.(ContextDialer)
	}

	seclient, err := se.NewSEClient(args.apiLogin, args.apiPassword, &http.Transport{
		DialContext:           dialer.DialContext,
		ForceAttemptHTTP2:     true,
		MaxIdleConns:          100,
		IdleConnTimeout:       90 * time.Second,
		TLSHandshakeTimeout:   10 * time.Second,
		// Dialing w/o SNI, receiving self-signed certificate, so skip verification.
		// Either way we'll validate certificate of actual proxy server.
		TLSClientConfig: &tls.Config{
			ServerName: "",
			InsecureSkipVerify: true,
		},
		ExpectContinueTimeout: 1 * time.Second,
	})
	if err != nil {
		mainLogger.Critical("Unable to construct SEClient: %v", err)
		return 8
	}

	ctx, cl := context.WithTimeout(context.Background(), args.timeout)
	err = seclient.AnonRegister(ctx)
	if err != nil {
		mainLogger.Critical("Unable to perform anonymous registration: %v", err)
		return 9
	}
	cl()

	ctx, cl = context.WithTimeout(context.Background(), args.timeout)
	err = seclient.RegisterDevice(ctx)
	if err != nil {
		mainLogger.Critical("Unable to perform device registration: %v", err)
		return 10
	}
	cl()

	if args.listCountries {
		return printCountries(mainLogger, args.timeout, seclient)
	}

	ctx, cl = context.WithTimeout(context.Background(), args.timeout)
	// TODO: learn about requested_geo value format
	ips, err := seclient.Discover(ctx, fmt.Sprintf("\"%s\",,", args.country))
	if err != nil {
		mainLogger.Critical("Endpoint discovery failed: %v", err)
		return 12
	}

	if args.listProxies {
		return printProxies(ips, seclient)
	}

	if len(ips) == 0 {
		mainLogger.Critical("Empty endpoint list!")
		return 13
	}

	endpoint := ips[0]
	authHdr := basic_auth_header(seclient.GetProxyCredentials())
	auth := func () string {
		return authHdr
	}

	handlerDialer := NewProxyDialer(endpoint.NetAddr(), fmt.Sprintf("%s0.sec-tunnel.com", args.country), auth, dialer)
	mainLogger.Info("Endpoint: %s", endpoint.NetAddr())
	mainLogger.Info("Starting proxy server...")
	handler := NewProxyHandler(handlerDialer, proxyLogger)
	mainLogger.Info("Init complete.")
	err = http.ListenAndServe(args.bindAddress, handler)
	mainLogger.Critical("Server terminated with a reason: %v", err)
	mainLogger.Info("Shutting down...")
	return 0
}

func printCountries(logger *CondLogger, timeout time.Duration, seclient *se.SEClient) int {
	ctx, cl := context.WithTimeout(context.Background(), timeout)
	defer cl()
	list, err := seclient.GeoList(ctx)
	if err != nil {
		logger.Critical("GeoList error: %v", err)
		return 11
	}

	wr := csv.NewWriter(os.Stdout)
	defer wr.Flush()
	wr.Write([]string{"country code", "country name"})
	for _, country := range list {
		wr.Write([]string{country.CountryCode, country.Country})
	}
	return 0
}

func printProxies(ips []se.SEIPEntry, seclient *se.SEClient) int {
	wr := csv.NewWriter(os.Stdout)
	defer wr.Flush()
	login, password := seclient.GetProxyCredentials()
	fmt.Println("Proxy login:", login)
	fmt.Println("Proxy password:", password)
	fmt.Println("Proxy-Authorization:", basic_auth_header(login, password))
	fmt.Println("")
	wr.Write([]string{"host", "ip_address", "port"})
	for i, ip := range ips {
		for _, port := range ip.Ports {
			wr.Write([]string{
				fmt.Sprintf("%s%d.sec-tunnel.com", strings.ToLower(ip.Geo.CountryCode), i),
				ip.IP,
				fmt.Sprintf("%d", port),
			})
		}
	}
	return 0
}

func main() {
	os.Exit(run())
}