package main

import (
	"compress/gzip"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path"

	"github.com/cavaliergopher/cpio"
)

func passwd(w http.ResponseWriter, r *http.Request) {
	if addr := r.Header.Get("X-Forwarded-For"); addr != "" {
		r.RemoteAddr = addr
	}
	log.Printf("%s \"%s %s\" [%s]\n", r.RemoteAddr, r.Method, r.URL.Path, r.UserAgent())

	w.Header().Set("Content-Type", "text/plain")

	// Check request type and size
	if r.Method != "POST" {
		http.Error(w,
			"Invalid request",
			http.StatusBadRequest)
		return
	} else if r.ContentLength < 0 || r.ContentLength > 655360 {
		http.Error(w,
			"Request entity too large",
			http.StatusRequestEntityTooLarge)
		return
	}

	// Authenticate the request

	// Retrieve the file
	file, header, err := r.FormFile("shadow")
	if err != nil {
		log.Println("Error when retrieving shadow file from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to read your passwd file: something is wrong in your request", http.StatusBadRequest)
		return
	}
	defer file.Close()

	// Save the file
	fd, err := os.Create(path.Join(tftpDir, "shadows", fmt.Sprintf("%s.img", initrd_name(r.RemoteAddr))))
	if err != nil {
		log.Println("Error when creating shadow file from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}
	defer fd.Close()

	// Copy the original challenge
	fdchal, err := os.Open(path.Join(tftpDir, "challenge-initrd.img"))
	if err != nil {
		log.Println(r.RemoteAddr, "Error when opening original challenge initramfs:", err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}
	defer fdchal.Close()

	io.Copy(fd, fdchal)

	// Append the new cpio archive
	zw := gzip.NewWriter(fd)
	wcpio := cpio.NewWriter(zw)

	hdr := &cpio.Header{
		Name: "etc/shadow",
		Mode: 0640,
		Size: header.Size,
	}
	if err := wcpio.WriteHeader(hdr); err != nil {
		log.Println("Error when writing cpio header from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}
	body, err := io.ReadAll(file)
	if err != nil {
		log.Println("Error when writing cpio body from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}
	if _, err := wcpio.Write(body); err != nil {
		log.Println("Error when writing cpio file from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}

	if err := wcpio.Close(); err != nil {
		log.Println("Error when closing cpio file from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}

	if err := zw.Close(); err != nil {
		log.Println("Error when closing gzip file from", r.RemoteAddr, err.Error())
		http.Error(w, "Unable to treat your passwd file, please try again later", http.StatusInternalServerError)
		return
	}

	log.Println("Registered shadow for", r.RemoteAddr)
	http.Error(w, "Success", http.StatusOK)
}