package main

import (
	"bytes"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"runtime"
	"sync"
	"time"
)

var (
	client     = flag.Bool("client", false, "client")
	addr       = flag.String("addr", "localhost:8544", "addr")
	url        = flag.String("url", "https://hostname", "url")
	concurrent = flag.Bool("concurrent", true, "concurrent")
)

func main() {
	flag.Parse()
	if !*client {
		fmt.Println("listening on", *addr)
		http.HandleFunc("/", func(writer http.ResponseWriter, request *http.Request) {
			io.Copy(ioutil.Discard, request.Body)
			request.Body.Close()
			writer.WriteHeader(http.StatusOK)
		})
		http.ListenAndServe(*addr, nil)
		return
	}
	fmt.Println("client to", *url)
	wg := new(sync.WaitGroup)
	var cDialer = &net.Dialer{
		Timeout: 10 * time.Second,
	}
	var cNetTransport = &http.Transport{
		DialContext:         cDialer.DialContext,
		TLSHandshakeTimeout: 10 * time.Second,
		MaxIdleConns:        20,
		MaxIdleConnsPerHost: 10,
		IdleConnTimeout:     60 * time.Second,
	}
	var cNetClient = &http.Client{
		Timeout:   time.Second * 30,
		Transport: cNetTransport,
	}
	for i := 0; i < runtime.GOMAXPROCS(-1); i++ {
		wg.Add(1)
		go func(id int) {
			// Constructing a client per goroutine.
			var dialer = &net.Dialer{
				Timeout: 10 * time.Second,
			}
			var netTransport = &http.Transport{
				DialContext:         dialer.DialContext,
				TLSHandshakeTimeout: 10 * time.Second,
				MaxIdleConns:        20,
				MaxIdleConnsPerHost: 10,
				IdleConnTimeout:     60 * time.Second,
			}
			var netClient = &http.Client{
				Timeout:   time.Second * 30,
				Transport: netTransport,
			}
			if *concurrent {
				// Using concurrent client instead.
				netClient = cNetClient
			}
			for {
				buf := make([]byte, 10000)
				req, err := http.NewRequest(http.MethodPost, *url+fmt.Sprintf("/%d", id), bytes.NewReader(buf))
				if err != nil {
					log.Fatal(err)
				}
				res, err := netClient.Do(req)
				if err != nil {
					fmt.Println("err", err)
					continue
				}
				// Ensuring connection reuse.
				io.Copy(ioutil.Discard, res.Body)
				res.Body.Close()

				if res.StatusCode != http.StatusOK {
					fmt.Println(res.Status)
				}
			}
		}(i)
	}
	wg.Wait()
}