package main

import (
	"context"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"time"

	"github.com/pkg/errors"
)

func printFiles(dir string) error {
	return filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
		fmt.Println(path)
		return nil
	})
}

func renameImageFile(dir, newName string) error {
	entries, err := ioutil.ReadDir(dir)
	if err != nil {
		return err
	}

	if len(entries) != 1 || entries[0].IsDir() {
		return errors.Errorf("Invalid container image")
	}

	src := filepath.Join(dir, entries[0].Name())
	target := filepath.Join(dir, newName)

	if err := os.Rename(src, target); err != nil {
		return err
	}
	return nil
}

func main() {
	port := flag.Int("p", 8100, "server port")
	directory := flag.String("image-dir", ".", "directory to serve")
	readyFile := flag.String("ready-file", "/shared/ready", "file to create when ready for connections")
	doneFile := flag.String("done-file", "/shared/done", "file created when the client is done")
	imageName := flag.String("image-name", "disk.img", "name of the image to serve up")
	flag.Parse()

	if err := printFiles(*directory); err != nil {
		log.Fatalf("Failed walking the directory %s: %v", *directory, err)
	}
	if err := renameImageFile(*directory, *imageName); err != nil {
		log.Fatalf("Failed renaming image file %s, directory %s: %v", *imageName, *directory, err)
	}
	server := &http.Server{
		Handler: http.FileServer(http.Dir(*directory)),
	}
	addr := fmt.Sprintf("localhost:%d", *port)
	listener, err := net.Listen("tcp", addr)
	if err != nil {
		log.Fatalf("Failed listening on %s err: %v", addr, err)
	}

	f, err := os.OpenFile(*readyFile, os.O_CREATE|os.O_EXCL, 0666)
	if err != nil {
		log.Fatalf("Failed creating \"ready\" file: %v", err)
	}
	defer os.Remove(*readyFile)
	f.Close()

	go func() {
		log.Printf("Serving %s on HTTP port: %d\n", *directory, *port)
		if err := server.Serve(listener); err != nil && err != http.ErrServerClosed {
			log.Fatalf("Serve failed: %v", err)
		}
	}()

	for {
		if _, err := os.Stat(*doneFile); err == nil {
			break
		}
		time.Sleep(time.Second)
	}

	os.Remove(*doneFile)
	if err := server.Shutdown(context.TODO()); err != nil {
		log.Printf("Shutdown failed: %v\n", err)
	}
	log.Println("Importer has completed")
}