package cache

import (
	"archive/tar"
	"compress/gzip"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

// Tar takes a source and variable writers and walks 'source' writing each file
// found to the tar writer; the purpose for accepting multiple writers is to allow
// for multiple outputs (for example a file, or md5 hash)
func Tar(src string, writers ...io.Writer) error {
	if _, err := os.Stat(src); err != nil {
		return fmt.Errorf("unable to tar files - %v", err.Error())
	}

	mw := io.MultiWriter(writers...)

	gzw := gzip.NewWriter(mw)
	defer gzw.Close()

	tw := tar.NewWriter(gzw)
	defer tw.Close()

	// walk path
	return filepath.Walk(src, func(file string, fi os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if !fi.Mode().IsRegular() {
			return nil
		}

		header, err := tar.FileInfoHeader(fi, fi.Name())
		if err != nil {
			return err
		}

		// update the name to correctly reflect the desired destination when untaring
		header.Name = strings.TrimPrefix(strings.Replace(file, src, "", -1), string(filepath.Separator))

		if err := tw.WriteHeader(header); err != nil {
			return err
		}

		f, err := os.Open(file)
		if err != nil {
			return err
		}

		if _, err := io.Copy(tw, f); err != nil {
			f.Close()
			return err
		}

		f.Close()

		return nil
	})
}

// Untar takes a destination path and a reader; a tar reader loops over the tarfile
// creating the file structure at 'dst' along the way, and writing any files
func Untar(dst string, r io.Reader) error {

	gzr, err := gzip.NewReader(r)
	if err != nil {
		return err
	}
	defer gzr.Close()

	tr := tar.NewReader(gzr)

	for {
		header, err := tr.Next()

		if errors.Is(err, io.EOF) || header == nil {
			break
		}
		if err != nil {
			return err
		}

		target := filepath.Join(dst, header.Name)

		switch header.Typeflag {

		// if its a dir and it doesn't exist create it
		case tar.TypeDir:
			if _, err := os.Stat(target); err != nil {
				if err := os.MkdirAll(target, 0755); err != nil {
					return err
				}
			}

		// if it's a file create it
		case tar.TypeReg:
			f, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
			if err != nil {
				return err
			}
			if _, err := io.Copy(f, tr); err != nil {
				return err
			}
			f.Close()
		}
	}
	return nil
}