sources: Add Fedora support

Resolves #23

Signed-off-by: Thomas Hipp <thomas.hipp@canonical.com>

shared/definition.go

@@ -186,6 +186,7 @@ func (d *Definition) Validate() error {
 		"archlinux-http",
 		"centos-http",
 		"debootstrap",
+		"fedora-http",
 		"ubuntu-http",
 	}
 	if !shared.StringInSlice(strings.TrimSpace(d.Source.Downloader), validDownloaders) {

sources/fedora-http.go

@@ -0,0 +1,156 @@
+package sources
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+
+	lxd "github.com/lxc/lxd/shared"
+
+	"github.com/lxc/distrobuilder/shared"
+)
+
+// FedoraHTTP represents the Fedora HTTP downloader.
+type FedoraHTTP struct {
+	fname string
+}
+
+// NewFedoraHTTP creates a new FedoraHTTP instance.
+func NewFedoraHTTP() *FedoraHTTP {
+	return &FedoraHTTP{}
+}
+
+// Run downloads a container base image and unpacks it and its layers.
+func (s *FedoraHTTP) Run(definition shared.Definition, rootfsDir string) error {
+	baseURL := fmt.Sprintf("%s/packages/Fedora-Container-Base",
+		definition.Source.URL)
+
+	// Get latest build
+	build, err := s.getLatestBuild(baseURL, definition.Image.Release)
+	if err != nil {
+		return err
+	}
+
+	fname := fmt.Sprintf("Fedora-Container-Base-%s-%s.%s.tar.xz",
+		definition.Image.Release, build, definition.Image.ArchitectureMapped)
+
+	// Download image
+	err = shared.Download(fmt.Sprintf("%s/%s/%s/images/%s",
+		baseURL, definition.Image.Release, build, fname), "")
+	if err != nil {
+		return err
+	}
+
+	// Unpack the base image
+	err = lxd.Unpack(filepath.Join(os.TempDir(), fname), rootfsDir, false, false)
+	if err != nil {
+		return err
+	}
+
+	// Unpack the rest of the image (/bin, /sbin, /usr, etc.)
+	return s.unpackLayers(rootfsDir)
+}
+
+func (s *FedoraHTTP) unpackLayers(rootfsDir string) error {
+	// Read manifest file which contains the path to the layers
+	file, err := os.Open(filepath.Join(rootfsDir, "manifest.json"))
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	data, err := ioutil.ReadAll(file)
+	if err != nil {
+		return err
+	}
+
+	// Structure of the manifest excluding RepoTags
+	var manifests []struct {
+		Layers []string
+		Config string
+	}
+
+	err = json.Unmarshal(data, &manifests)
+	if err != nil {
+		return err
+	}
+
+	pathsToRemove := []string{
+		filepath.Join(rootfsDir, "manifest.json"),
+		filepath.Join(rootfsDir, "repositories"),
+	}
+
+	// Unpack tarballs (or layers) which contain the rest of the rootfs, and
+	// remove files not relevant to the image.
+	for _, manifest := range manifests {
+		for _, layer := range manifest.Layers {
+			err := lxd.Unpack(filepath.Join(rootfsDir, layer), rootfsDir,
+				false, false)
+			if err != nil {
+				return err
+			}
+
+			pathsToRemove = append(pathsToRemove,
+				filepath.Join(rootfsDir, filepath.Dir(layer)))
+		}
+
+		pathsToRemove = append(pathsToRemove, filepath.Join(rootfsDir, manifest.Config))
+	}
+
+	// Clean up /tmp since there are unnecessary files there
+	files, err := filepath.Glob(filepath.Join(rootfsDir, "tmp", "*"))
+	if err != nil {
+		return err
+	}
+	pathsToRemove = append(pathsToRemove, files...)
+
+	// Clean up /root since there are unnecessary files there
+	files, err = filepath.Glob(filepath.Join(rootfsDir, "root", "*"))
+	if err != nil {
+		return err
+	}
+	pathsToRemove = append(pathsToRemove, files...)
+
+	for _, f := range pathsToRemove {
+		os.RemoveAll(f)
+	}
+
+	return nil
+}
+
+func (s *FedoraHTTP) getLatestBuild(URL, release string) (string, error) {
+	resp, err := http.Get(fmt.Sprintf("%s/%s", URL, release))
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	content, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	// Builds are formatted in one of two ways:
+	//   - <yyyy><mm><dd>.<build_number>
+	//   - <yyyy><mm><dd>.n.<build_number>
+	re := regexp.MustCompile(`\d{8}\.(n\.)?\d`)
+
+	// Find all builds
+	matches := re.FindAllString(string(content), -1)
+
+	if len(matches) == 0 {
+		return "", errors.New("Unable to find latest build")
+	}
+
+	// Sort builds
+	sort.Strings(matches)
+
+	// Return latest build
+	return matches[len(matches)-1], nil
+}

sources/source.go

@@ -10,16 +10,18 @@ type Downloader interface {
 // Get returns a Downloader.
 func Get(name string) Downloader {
 	switch name {
-	case "ubuntu-http":
-		return NewUbuntuHTTP()
-	case "debootstrap":
-		return NewDebootstrap()
+	case "alpinelinux-http":
+		return NewAlpineLinuxHTTP()
 	case "archlinux-http":
 		return NewArchLinuxHTTP()
 	case "centos-http":
 		return NewCentOSHTTP()
-	case "alpinelinux-http":
-		return NewAlpineLinuxHTTP()
+	case "debootstrap":
+		return NewDebootstrap()
+	case "fedora-http":
+		return NewFedoraHTTP()
+	case "ubuntu-http":
+		return NewUbuntuHTTP()
 	}
 
 	return nil