package daemon
 
 import (
 	"io"

 	"runtime"

 	"strings"
 

 	dist "github.com/docker/distribution"

 	"github.com/docker/distribution/reference"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/distribution"

 	progressutils "github.com/docker/docker/distribution/utils"

 	"github.com/docker/docker/errdefs"

 	"github.com/docker/docker/pkg/progress"
 	"github.com/docker/docker/registry"

 	"github.com/opencontainers/go-digest"

 	"golang.org/x/net/context"
 )
 
 // PullImage initiates a pull operation. image is the repository name to pull, and
 // tag may be either empty, or indicate a specific tag to pull.

 func (daemon *Daemon) PullImage(ctx context.Context, image, tag, os string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

 	// Special case: "pull -a" may send an image name with a
 	// trailing :. This is ugly, but let's not break API
 	// compatibility.
 	image = strings.TrimSuffix(image, ":")
 

 	ref, err := reference.ParseNormalizedNamed(image)

 	if err != nil {

 		return errdefs.InvalidParameter(err)

 	}
 
 	if tag != "" {
 		// The "tag" could actually be a digest.
 		var dgst digest.Digest

 		dgst, err = digest.Parse(tag)

 		if err == nil {

 			ref, err = reference.WithDigest(reference.TrimNamed(ref), dgst)

 		} else {
 			ref, err = reference.WithTag(ref, tag)
 		}
 		if err != nil {

 			return errdefs.InvalidParameter(err)

 		}
 	}
 

 	return daemon.pullImageWithReference(ctx, ref, os, metaHeaders, authConfig, outStream)

 }
 

 func (daemon *Daemon) pullImageWithReference(ctx context.Context, ref reference.Named, os string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

 	// Include a buffer so that slow client connections don't affect
 	// transfer performance.
 	progressChan := make(chan progress.Progress, 100)
 
 	writesDone := make(chan struct{})
 
 	ctx, cancelFunc := context.WithCancel(ctx)
 
 	go func() {

 		progressutils.WriteDistributionProgress(cancelFunc, outStream, progressChan)

 		close(writesDone)
 	}()
 

 	// Default to the host OS platform in case it hasn't been populated with an explicit value.

 	if os == "" {
 		os = runtime.GOOS

 	}

 	imagePullConfig := &distribution.ImagePullConfig{

 		Config: distribution.Config{
 			MetaHeaders:      metaHeaders,
 			AuthConfig:       authConfig,
 			ProgressOutput:   progress.ChanOutput(progressChan),
 			RegistryService:  daemon.RegistryService,
 			ImageEventLogger: daemon.LogImageEvent,

 			MetadataStore:    daemon.distributionMetadataStore,
 			ImageStore:       distribution.NewImageConfigStoreFromStore(daemon.imageStore),

 			ReferenceStore:   daemon.referenceStore,

 		},
 		DownloadManager: daemon.downloadManager,
 		Schema2Types:    distribution.ImageTypes,

 		OS:              os,

 	}
 
 	err := distribution.Pull(ctx, ref, imagePullConfig)
 	close(progressChan)
 	<-writesDone
 	return err
 }

 // GetRepository returns a repository from the registry.

 func (daemon *Daemon) GetRepository(ctx context.Context, ref reference.Named, authConfig *types.AuthConfig) (dist.Repository, bool, error) {

 	// get repository info
 	repoInfo, err := daemon.RegistryService.ResolveRepository(ref)
 	if err != nil {

 		return nil, false, err

 	}
 	// makes sure name is not empty or `scratch`

 	if err := distribution.ValidateRepoName(repoInfo.Name); err != nil {

 		return nil, false, errdefs.InvalidParameter(err)

 	}
 
 	// get endpoints

 	endpoints, err := daemon.RegistryService.LookupPullEndpoints(reference.Domain(repoInfo.Name))

 	if err != nil {

 		return nil, false, err

 	}
 
 	// retrieve repository

 	var (
 		confirmedV2 bool
 		repository  dist.Repository
 		lastError   error
 	)
 
 	for _, endpoint := range endpoints {
 		if endpoint.Version == registry.APIVersion1 {
 			continue
 		}

 		repository, confirmedV2, lastError = distribution.NewV2Repository(ctx, repoInfo, endpoint, nil, authConfig, "pull")
 		if lastError == nil && confirmedV2 {
 			break

 		}
 	}

 	return repository, confirmedV2, lastError

 }