*: split docker.go for future pkg creation

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

docker_image_src.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/projectatomic/skopeo/reference"
+	"github.com/projectatomic/skopeo/types"
+)
+
+type errFetchManifest struct {
+	statusCode int
+	body       []byte
+}
+
+func (e errFetchManifest) Error() string {
+	return fmt.Sprintf("error fetching manifest: status code: %d, body: %s", e.statusCode, string(e.body))
+}
+
+type dockerImageSource struct {
+	ref reference.Named
+	tag string
+	c   *dockerClient
+}
+
+// newDockerImageSource is the same as NewDockerImageSource, only it returns the more specific *dockerImageSource type.
+func newDockerImageSource(img, certPath string, tlsVerify bool) (*dockerImageSource, error) {
+	ref, tag, err := parseDockerImageName(img)
+	if err != nil {
+		return nil, err
+	}
+	c, err := newDockerClient(ref.Hostname(), certPath, tlsVerify)
+	if err != nil {
+		return nil, err
+	}
+	return &dockerImageSource{
+		ref: ref,
+		tag: tag,
+		c:   c,
+	}, nil
+}
+
+// NewDockerImageSource creates a new ImageSource for the specified image and connection specification.
+func NewDockerImageSource(img, certPath string, tlsVerify bool) (types.ImageSource, error) {
+	return newDockerImageSource(img, certPath, tlsVerify)
+}
+
+func (s *dockerImageSource) GetManifest() (manifest []byte, unverifiedCanonicalDigest string, err error) {
+	url := fmt.Sprintf(manifestURL, s.ref.RemoteName(), s.tag)
+	// TODO(runcom) set manifest version header! schema1 for now - then schema2 etc etc and v1
+	// TODO(runcom) NO, switch on the resulter manifest like Docker is doing
+	res, err := s.c.makeRequest("GET", url, nil, nil)
+	if err != nil {
+		return nil, "", err
+	}
+	defer res.Body.Close()
+	manblob, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return nil, "", err
+	}
+	if res.StatusCode != http.StatusOK {
+		return nil, "", errFetchManifest{res.StatusCode, manblob}
+	}
+	return manblob, res.Header.Get("Docker-Content-Digest"), nil
+}
+
+func (s *dockerImageSource) GetLayer(digest string) (io.ReadCloser, error) {
+	url := fmt.Sprintf(blobsURL, s.ref.RemoteName(), digest)
+	logrus.Infof("Downloading %s", url)
+	res, err := s.c.makeRequest("GET", url, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+	if res.StatusCode != http.StatusOK {
+		// print url also
+		return nil, fmt.Errorf("Invalid status code returned when fetching blob %d", res.StatusCode)
+	}
+	return res.Body, nil
+}
+
+func (s *dockerImageSource) GetSignatures() ([][]byte, error) {
+	return [][]byte{}, nil
+}