Function useful to compress a variadic of files in a zip file byte slice

compress.go

package compress

import (
	"archive/zip"
	"bytes"
	"fmt"
)

type SingleCompressError struct {
	Index    int
	Filename string
	err      error
}

type CompressError struct {
	Err  string
	Errs []SingleCompressError
}

func (c CompressError) Error() string {

	if c.Errs != nil && len(c.Errs) > 0 {
		return fmt.Sprintf("error compressing %d files", len(c.Errs))
	} else {
		return c.Err
	}

}

func addGenericError(compressError *CompressError, err error) *CompressError {

	if compressError == nil {
		compressError = &CompressError{}
	}

	compressError.Err = err.Error()
	return compressError

}

func addError(compressError *CompressError, index int, filename string, err error) *CompressError {

	if compressError == nil {
		compressError = &CompressError{
			Err:  "",
			Errs: []SingleCompressError{},
		}
	}

	compressError.Errs = append(compressError.Errs, SingleCompressError{
		Index:    index,
		Filename: filename,
		err:      err,
	})

	return compressError

}

func Compress(files ...struct {
	Filename string
	Content  []byte
}) ([]byte, *CompressError) {
	
	buf := new(bytes.Buffer)
	var compressError *CompressError = nil

	// Create a new zip archive.
	zipWriter := zip.NewWriter(buf)
	for index, file := range files {

		zipFile, err := zipWriter.Create(file.Filename)
		if err != nil {
			compressError = addError(compressError, index, file.Filename, err)
		}

		_, err = zipFile.Write(file.Content)
		if err != nil {
			compressError = addError(compressError, index, file.Filename, err)
		}

	}

	err := zipWriter.Close()
	if err != nil {
		compressError = addGenericError(compressError, err)
	}

	return buf.Bytes(), nil

}