junk/main.go

package main

import (
	"bufio"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"os/signal"
	"strings"
	"syscall"
	"time"
)

const junkaddr = "localhost:18012"
const proxybufsize = 4 << 10

type JunkConf struct {
	Proxy string
	Cmd   *exec.Cmd
}

func main() {
	status := cmain(len(os.Args), os.Args)
	os.Setenv("status", status)
	if status != "" {
		os.Exit(1)
	}
}

func proxy(w http.ResponseWriter, r *http.Request, proxy_path string) {
	var err error
	r.RequestURI = ""
	r.URL, err = url.Parse(proxy_path)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(err.Error()))
		return
	}
	resp, err := http.DefaultClient.Do(r)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return
	}
	for k, v := range resp.Header {
		for _, x := range v {
			w.Header().Add(k, x)
		}
	}
	w.WriteHeader(resp.StatusCode)
	buf := make([]byte, proxybufsize)
	for {
		n, err := resp.Body.Read(buf)
		w.Write(buf[:n])
		if err != nil {
			break
		}
	}
}

func cmain(argc int, argv []string) string {
	fileserver := http.FileServer(http.Dir(""))
	cmdmap := map[string]JunkConf{}
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		p1 := r.URL.Path
		p := strings.Split(p1, "/")[1:]
		seg := p[0]
		if seg == "" {
			fileserver.ServeHTTP(w, r)
			return
		}
		vc, err := r.Cookie("view")
		if err == nil && seg != vc.Value {
			w.Header().Add("Location", "/"+vc.Value+p1)
			w.WriteHeader(http.StatusFound)
			return
		}
		if conf, ok := cmdmap[seg]; ok {
			proxy_path := conf.Proxy + "/" + strings.Join(p[1:], "/")
			proxy(w, r, proxy_path)
			return
		}
		if f, err := os.Open(seg + "/junkrc"); err == nil {
			// info, err := f.Stat()
			s := bufio.NewScanner(f)
			conf := JunkConf{}
			for s.Scan() {
				line := s.Text()
				if len(line) > 2 && line[0:2] == "#;" {
					note := line[2:]
					i := strings.IndexByte(note, '=')
					if i == -1 {
						continue
					}
					key, value := note[:i], note[i+1:]
					switch key {
					case "proxy":
						conf.Proxy = value
					}
				}
			}
			f.Close()
			println("exec:", seg+"/junkrc")
			cmd := exec.Command("./junkrc")
			cmd.Dir = seg
			// cmd.Stdout = os.Stdout
			conf.Cmd = cmd
			err = cmd.Start()
			if err != nil {
				w.WriteHeader(http.StatusServiceUnavailable)
				w.Write([]byte(err.Error()))
				return
			}
			waits := 0
			for {
				_, err := http.Head(conf.Proxy)
				if err != nil {
					if cmd.ProcessState != nil {
						cmd.Wait()
						w.WriteHeader(http.StatusServiceUnavailable)
						w.Write([]byte("process exited early: " + cmd.ProcessState.String()))
						return
					} else {
						waits++
						time.Sleep(500 * time.Millisecond)
						if waits > 10 {
							w.WriteHeader(http.StatusServiceUnavailable)
							w.Write([]byte("starting process: timeout"))
							cmd.Process.Kill()
							cmd.Wait()
							return
						}
						continue
					}
				}
				cmdmap[seg] = conf
				break
			}
			w.Header().Add("Set-Cookie", "view="+seg+"; Path=/; SameSite=Strict; HttpOnly")
			w.Header().Add("Location", p1)
			w.WriteHeader(http.StatusFound)
			// proxy_path := conf.Proxy + "/" + strings.Join(p[1:], "/")
			// proxy(w, r, proxy_path)
			return
		}
		fileserver.ServeHTTP(w, r)
	})
	lock := make(chan os.Signal, 1)
	signal.Notify(lock, os.Interrupt, syscall.SIGTERM)
	go func() {
		println("started:", "http://"+junkaddr+"/")
		http.ListenAndServe(junkaddr, nil)
	}()
	<-lock
	for k, v := range cmdmap {
		println("killing:", k)
		v.Cmd.Process.Kill()
		v.Cmd.Wait()
	}
	return ""
}