package utils
 
 import (
 	"fmt"
 	"io/ioutil"
 	"net/http"

 	"net/url"
 	"os"

 	"os/exec"

 	"path/filepath"

 	"strings"
 

 	"github.com/docker/docker/pkg/symlink"

 	"github.com/docker/docker/pkg/urlutil"
 )
 
 func GitClone(remoteURL string) (string, error) {
 	if !urlutil.IsGitTransport(remoteURL) {
 		remoteURL = "https://" + remoteURL
 	}
 	root, err := ioutil.TempDir("", "docker-build-git")
 	if err != nil {
 		return "", err
 	}
 

 	u, err := url.Parse(remoteURL)
 	if err != nil {
 		return "", err
 	}

 	fragment := u.Fragment
 	clone := cloneArgs(u, root)
 
 	if output, err := git(clone...); err != nil {

 		return "", fmt.Errorf("Error trying to use git: %s (%s)", err, output)
 	}
 

 	return checkoutGit(fragment, root)

 }
 

 func cloneArgs(remoteURL *url.URL, root string) []string {

 	args := []string{"clone", "--recursive"}

 	shallow := len(remoteURL.Fragment) == 0

 	if shallow && strings.HasPrefix(remoteURL.Scheme, "http") {

 		res, err := http.Head(fmt.Sprintf("%s/info/refs?service=git-upload-pack", remoteURL))
 		if err != nil || res.Header.Get("Content-Type") != "application/x-git-upload-pack-advertisement" {
 			shallow = false
 		}
 	}
 
 	if shallow {
 		args = append(args, "--depth", "1")
 	}
 

 	if remoteURL.Fragment != "" {
 		remoteURL.Fragment = ""
 	}
 
 	return append(args, remoteURL.String(), root)
 }
 
 func checkoutGit(fragment, root string) (string, error) {
 	refAndDir := strings.SplitN(fragment, ":", 2)
 
 	if len(refAndDir[0]) != 0 {
 		if output, err := gitWithinDir(root, "checkout", refAndDir[0]); err != nil {
 			return "", fmt.Errorf("Error trying to use git: %s (%s)", err, output)
 		}
 	}
 
 	if len(refAndDir) > 1 && len(refAndDir[1]) != 0 {

 		newCtx, err := symlink.FollowSymlinkInScope(filepath.Join(root, refAndDir[1]), root)
 		if err != nil {
 			return "", fmt.Errorf("Error setting git context, %q not within git root: %s", refAndDir[1], err)
 		}
 

 		fi, err := os.Stat(newCtx)
 		if err != nil {
 			return "", err
 		}
 		if !fi.IsDir() {
 			return "", fmt.Errorf("Error setting git context, not a directory: %s", newCtx)
 		}
 		root = newCtx
 	}
 
 	return root, nil
 }
 
 func gitWithinDir(dir string, args ...string) ([]byte, error) {
 	a := []string{"--work-tree", dir, "--git-dir", filepath.Join(dir, ".git")}
 	return git(append(a, args...)...)
 }
 
 func git(args ...string) ([]byte, error) {
 	return exec.Command("git", args...).CombinedOutput()

 }