package main

import (
	"archive/tar"
	"fmt"
	"io"
	"log"
	"os"

	tartar "github.com/vbatts/tar-split/archive/tar"
)

const length int64 = 8589934592

// README: first a random test file needs to be created with this command:
// $ head -c 8589934592 </dev/urandom >file
//
// randomness is important. With a file the same size but containing only zeros,
// the issue is not triggered.
//
func main() {
	limit := length // KO
	// limit := length - 1 // OK

	pr, pw := io.Pipe()

	go func() {
		// var b bytes.Buffer
		tw := tar.NewWriter(pw)

		if err := tw.WriteHeader(&tar.Header{
			Format: tar.FormatPAX,
			Name:   "test",
			Size:   limit,
		}); err != nil {
			log.Fatal(err)
		}

		src, err := os.Open("file")
		if err != nil {
			log.Fatal(err)
		}

		if _, err := io.Copy(tw, io.LimitReader(src, limit)); err != nil {
			log.Fatal(err)
		}

		if err := tw.Close(); err != nil {
			log.Fatal(err)
		}
	}()

	ttr, err := newInputTarStream(pr)
	if err != nil {
		log.Fatal(err)
	}

	tr := tar.NewReader(ttr)
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			break // End of archive
		}
		if err != nil {
			log.Fatalln("Next", err)
		}
		fmt.Println("Size of", hdr.Name, hdr.Size)
	}
}

func newInputTarStream(r io.Reader) (io.Reader, error) {
	pR, pW := io.Pipe()
	outputRdr := io.TeeReader(r, pW)

	go func() {
		tr := tartar.NewReader(outputRdr)
		for {
			hdr, err := tr.Next()
			if err != nil {
				if err != io.EOF {
					pW.CloseWithError(err)
					return
				}
				break
			}

			if hdr == nil {
				break
			}
		}
		pW.Close()
	}()

	return pR, nil
}