package proxy

import (
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"sync/atomic"
)

type Proxy struct {
	targets []*url.URL
	counter uint64
}

func NewProxy(targets []string) *Proxy {
	parsed := []*url.URL{}
	for _, t := range targets {
		u, err := url.Parse(t)
		if err != nil {
			log.Fatalf("")
		}
		parsed = append(parsed, u)
	}
	return &Proxy{targets: parsed}
}

func (p *Proxy) getNextTarget() *url.URL {
	i := atomic.AddUint64(&p.counter, 1)
	return p.targets[(int(i)-1)%len(p.targets)]
}

func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	target := p.getNextTarget()
	proxy := httputil.NewSingleHostReverseProxy(target)
	r.Host = target.Host
	log.Printf("Weiterleitung der Anfrage %s %s --> %s", r.Method, r.URL.Path, target)
	proxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
		log.Printf("!! Proxy error for %s: %v", r.URL.Path, err)
		http.Error(w, "Reverse Proxy Error", http.StatusBadGateway)
	}

	proxy.ServeHTTP(w, r)
}