package selfupdate

import (
	"archive/tar"
	"archive/zip"
	"bytes"
	"compress/gzip"
	"fmt"
	"io"
	"io/ioutil"
	"path/filepath"
	"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, fmt.Errorf("Failed to create buffer for zip file: %s", err)
		}

		r := bytes.NewReader(buf)
		z, err := zip.NewReader(r, r.Size())
		if err != nil {
			return nil, fmt.Errorf("Failed to uncompress zip file: %s", err)
		}

		for _, file := range z.File {
			_, name := filepath.Split(file.Name)
			if !file.FileInfo().IsDir() && 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, ".tar.gz") {
		gz, err := gzip.NewReader(src)
		if err != nil {
			return nil, fmt.Errorf("Failed to uncompress .tar.gz file: %s", err)
		}

		t := tar.NewReader(gz)
		for {
			h, err := t.Next()
			if err == io.EOF {
				break
			}
			if err != nil {
				return nil, fmt.Errorf("Failed to unarchive .tar file: %s", err)
			}
			_, name := filepath.Split(h.Name)
			if name == cmd {
				return t, nil
			}
		}

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

		name := r.Header.Name
		if name != cmd {
			return nil, fmt.Errorf("File name '%s' does not match to command '%s' found in %s", name, cmd, url)
		}

		return r, nil
	}

	return src, nil
}