package main

import (
	"fmt"
	"net"
	"net/http"
	"os"
	"strconv"
	"strings"
)

const usage = "servetls <cert file> <key file>"

func main() {
	if len(os.Args) != 3 {
		fmt.Fprintf(os.Stderr, "%s\n", usage)
		os.Exit(1)
	}
	cert, key := os.Args[1], os.Args[2]

	http.HandleFunc("/", handler)

	tlsPort := 8443
	if os.Getenv("TLS_PORT") != "" {
		p, err := strconv.Atoi(os.Getenv("TLS_PORT"))
		if err != nil {
			fmt.Fprintf(os.Stderr, "could not parse TLS_PORT variable: %s\n", os.Getenv("TLS_PORT"))
			os.Exit(1)
		}
		tlsPort = p
	}

	port := 8000
	if os.Getenv("PORT") != "" {
		p, err := strconv.Atoi(os.Getenv("PORT"))
		if err != nil {
			fmt.Fprintf(os.Stderr, "could not parse PORT variable: %s\n", os.Getenv("PORT"))
			os.Exit(1)
		}
		port = p
	}

	go func() {
		b := &bouncer{tlsPort}

		sm := http.NewServeMux()
		sm.Handle("/", b)

		addr := fmt.Sprintf(":%d", port)
		if err := http.ListenAndServe(addr, sm); err != nil {
			panic(err)
		}
	}()

	fmt.Printf("redirecting on :%d\n", port)
	fmt.Printf("serving on :%d\n", tlsPort)
	addr := fmt.Sprintf(":%d", tlsPort)
	err := http.ListenAndServeTLS(addr, cert, key, nil)
	if err != nil {
		fmt.Fprintf(os.Stderr, "%v\n", err)
		os.Exit(1)
	}
}

func handler(w http.ResponseWriter, req *http.Request) {
	fmt.Fprintf(w, "if you see this without complaints things are likely set up correctly\n")
}

type bouncer struct {
	port int
}

func (b *bouncer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	var host string
	var err error
	if strings.Contains(req.Host, ":") {
		host, _, err = net.SplitHostPort(req.Host)
		if err != nil {
			http.Error(w, "couldn't parse hostname from requeest", http.StatusBadRequest)
			return
		}
	} else {
		host = req.Host
	}
	url := fmt.Sprintf("https://%s:%d/", host, b.port)
	http.Redirect(w, req, url, http.StatusMovedPermanently)
}