package archive

import (
	"os"
	"fmt"
	"github.com/blakesmith/ar"
	"bytes"
	"io"
	"strings"
	"compress/gzip"
	"archive/tar"
	"log"
)

func InspectPackage(filename string) (string, error) {
	f, err := os.Open(filename)

	if err != nil {
		return "", fmt.Errorf("error opening package file %s: %s", filename, err)
	}

	arReader := ar.NewReader(f)
	defer f.Close()
	var controlBuf bytes.Buffer

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

		if err == io.EOF {
			break
		}

		if err != nil {
			return "", fmt.Errorf("error in inspectPackage loop: %s", err)
		}

		if strings.Trim(header.Name, "/") == "control.tar.gz" {
			io.Copy(&controlBuf, arReader)
			return InspectPackageControl(controlBuf)
		}
	}
	return "", nil
}

func InspectPackageControl(filename bytes.Buffer) (string, error) {
	gzf, err := gzip.NewReader(bytes.NewReader(filename.Bytes()))
	if err != nil {
		return "", fmt.Errorf("error creating gzip reader: %s", err)
	}

	tarReader := tar.NewReader(gzf)
	var controlBuf bytes.Buffer
	for {
		header, err := tarReader.Next()

		if err == io.EOF {
			break
		}

		if err != nil {
			return "", fmt.Errorf("failed to inspect package: %s", err)
		}

		name := header.Name

		switch header.Typeflag {
		case tar.TypeDir:
			continue
		case tar.TypeReg:
			if name == "./control" {
				io.Copy(&controlBuf, tarReader)
				return controlBuf.String(), nil
			}
		default:
			log.Printf(
				"Unable to figure out type : %c in file %s\n",
				header.Typeflag, name,
			)
		}
	}
	return "", nil
}