package selfupdate

import (
	"archive/tar"
	"archive/zip"
	"bytes"
	"compress/gzip"
	"fmt"
	"io"
	"io/ioutil"
	"strings"
)

func uncompress(src io.Reader, url, cmd string) (io.Reader, error) {
	if strings.HasSuffix(url, ".zip") {
		// Zip format requires its file size for uncompressing.
		// So we need to read the HTTP response into a buffer at first.
		buf, err := ioutil.ReadAll(src)
		if err != nil {
			return nil, err
		}

		r := bytes.NewReader(buf)
		z, err := zip.NewReader(r, r.Size())
		if err != nil {
			return nil, err
		}

		for _, file := range z.File {
			if file.Name == cmd {
				return file.Open()
			}
		}

		return nil, fmt.Errorf("File '%s' for the command is not found in %s", cmd, url)
	} else if strings.HasSuffix(url, ".gzip") {
		return gzip.NewReader(src)
	} else if strings.HasSuffix(url, ".tar.gz") {
		gz, err := gzip.NewReader(src)
		if err != nil {
			return nil, err
		}

		t := tar.NewReader(gz)
		for {
			h, err := t.Next()
			if err == io.EOF {
				break
			}
			if err != nil {
				return nil, err
			}
			if h.Name == cmd {
				return t, nil
			}
		}

		return nil, fmt.Errorf("File '%s' for the command is not found in %s", cmd, url)
	}

	return src, nil
}