package main

import (
	"bytes"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"math/rand"
	"net/http"
	"time"

	"golang.org/x/time/rate"
)

func main() {
	rand.Seed(time.Now().UnixNano())
	var port int
	var conf string
	var proxy bool
	flag.IntVar(&port, "p", 8080, "port to listen on")
	flag.StringVar(&conf, "c", "/dev/null", "line delimited file to read urls from")
	flag.BoolVar(&proxy, "proxy", false, "proxy content rather than redirect, so refresh works")
	flag.Parse()
	b, err := ioutil.ReadFile(conf)
	if err != nil {
		panic(err)
	}
	links := bytes.Split(b, []byte{'\n'})
	log.Print(port)
	limiter := rate.NewLimiter(1, 1)
	if err := http.ListenAndServe(fmt.Sprintf(":%d", port), http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		limiter.Wait(r.Context())
		link := ""
		for len(link) == 0 {
			link = string(links[rand.Intn(len(links))])
		}
		if proxy {
			resp, err := http.Get(link)
			if err != nil {
				http.Error(w, err.Error(), http.StatusBadGateway)
			}
			for k, v := range resp.Header {
				for _, v2 := range v {
					w.Header().Add(k, v2)
				}
			}
			w.WriteHeader(resp.StatusCode)
			io.Copy(w, resp.Body)
		} else {
			http.Redirect(w, r, link, http.StatusTemporaryRedirect)
		}
	})); err != nil {
		panic(err)
	}
}