package main

import (
	"bytes"
	"io"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"os"
	"os/exec"
	"strings"
)

type Proxy struct {
	proxyTarget *url.URL
}

func NewProxy(target string) *Proxy {
	proxy := &Proxy{}
	urlTarget, err := url.Parse(target)
	if err != nil {
		log.Fatal("Target not a valid URL!", target)
	}
	proxy.proxyTarget = urlTarget

	return proxy
}

// serves as a reverse proxy to http://www.subsonic.org/pages/api.jsp
func (pr Proxy) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	log.Println("req ", req.RequestURI, req.Method)

	proxy := httputil.NewSingleHostReverseProxy(pr.proxyTarget)

	// format: 2023/02/03 14:17:16 req  /rest/stream.view?u=jefklak&t=8c90da505334799b3184e9fb0539814d&s=LEcB8n9&v=1.13.0&c=substreamer&f=json&id=59d5e314f94f72d30df1a20c537e158c&maxBitRate=320&format=mp3&estimateContentLength=false GET
	// returns a binary ID3 file ready to be streamed to the FM receiver system.
	// Warning, this does NOT work with Navidrome's native system that also has a /rest/stream endpoint (without the .view)

	// TODO wat met "pauzeren"?
	// zie https://blog.yossarian.net/2022/11/07/Modernizing-my-1980s-sound-system#fnref:model
	if strings.Contains(req.RequestURI, "/rest/stream.view") {
		proxy.ModifyResponse = func(resp *http.Response) error {
			body, err := io.ReadAll(resp.Body)
			if err != nil {
				return err
			}
			err = resp.Body.Close()
			if err != nil {
				return err
			}

			go func() {
				mp3 := strings.ReplaceAll(req.RequestURI, "/", "_") + ".mp3"
				os.WriteFile(mp3, body, 0666)
				// on Mac: "sudo ln -s /usr/bin/open /usr/local/bin/play"
				go exec.Command("play", mp3).Run()
			}()

			// pass on the original body into a new body 'cause the original one has been read out already.
			resp.Body = io.NopCloser(bytes.NewReader(body))
			return nil
		}
	}

	// allow for SSL redirection if needed
	req.URL.Host = pr.proxyTarget.Host
	req.URL.Scheme = pr.proxyTarget.Scheme
	req.Header.Set("X-Forwarded-Host", req.Header.Get("Host"))
	req.Host = pr.proxyTarget.Host

	proxy.ServeHTTP(w, req)
}

func main() {
	proxy := NewProxy("http://cd.xavier/")
	http.ListenAndServe(":8080", proxy)
}