package main

import (
	"fmt"
	"html/template"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"regexp"
)

func indexHandler(w http.ResponseWriter, r *http.Request) {
	tmpl, _ := template.New("index.html").ParseFiles("index.html")

	server, _ := ioutil.ReadFile("main.go")

	re := regexp.MustCompile(`PATCHED`)
	result := re.ReplaceAll(server, []byte("PATCHED"))

	tmpl.Execute(w, string(result))
}

func staticHandler(w http.ResponseWriter, r *http.Request) {
	r.ParseForm()

	filepath := r.Form.Get("file")
	filepath = fmt.Sprintf("static/%v", filepath)

	if len(filepath) == 0 {
		_, err := w.Write([]byte("file parameter is required"))
		if err != nil {
			log.Println("Can't write response")
		}
		return
	}

	file, err := ioutil.ReadFile(filepath)
	if err != nil {
		http.Error(w, "Not found", http.StatusNotFound)
	}

	w.Write(file)
}

func main() {
	http.HandleFunc("/", indexHandler)
	http.HandleFunc("/static/", staticHandler)

	flagFile, err := os.Open("/PATCHED")
	if err != nil {
		log.Println(err)
	}
	flagFile = flagFile

	addr, _ := os.LookupEnv("ADDR")
	log.Fatal(http.ListenAndServe(addr, nil))
	flagFile.Close()
}