package distribution
 
 import (
 	"net/url"
 	"strings"
 	"syscall"
 
 	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/client"

 	"github.com/docker/distribution/registry/client/auth"

 	"github.com/docker/docker/distribution/xfer"
 )
 
 // ErrNoSupport is an error type used for errors indicating that an operation
 // is not supported. It encapsulates a more specific error.
 type ErrNoSupport struct{ Err error }
 
 func (e ErrNoSupport) Error() string {
 	if e.Err == nil {
 		return "not supported"
 	}
 	return e.Err.Error()
 }
 
 // fallbackError wraps an error that can possibly allow fallback to a different
 // endpoint.
 type fallbackError struct {
 	// err is the error being wrapped.
 	err error
 	// confirmedV2 is set to true if it was confirmed that the registry
 	// supports the v2 protocol. This is used to limit fallbacks to the v1
 	// protocol.
 	confirmedV2 bool

 	// transportOK is set to true if we managed to speak HTTP with the
 	// registry. This confirms that we're using appropriate TLS settings
 	// (or lack of TLS).
 	transportOK bool

 }
 
 // Error renders the FallbackError as a string.
 func (f fallbackError) Error() string {
 	return f.err.Error()
 }
 
 // shouldV2Fallback returns true if this error is a reason to fall back to v1.
 func shouldV2Fallback(err errcode.Error) bool {
 	switch err.Code {
 	case errcode.ErrorCodeUnauthorized, v2.ErrorCodeManifestUnknown, v2.ErrorCodeNameUnknown:
 		return true
 	}
 	return false
 }
 
 // continueOnError returns true if we should fallback to the next endpoint
 // as a result of this error.
 func continueOnError(err error) bool {
 	switch v := err.(type) {
 	case errcode.Errors:
 		if len(v) == 0 {
 			return true
 		}
 		return continueOnError(v[0])
 	case ErrNoSupport:
 		return continueOnError(v.Err)
 	case errcode.Error:
 		return shouldV2Fallback(v)
 	case *client.UnexpectedHTTPResponseError:
 		return true
 	case ImageConfigPullError:
 		return false
 	case error:
 		return !strings.Contains(err.Error(), strings.ToLower(syscall.ENOSPC.Error()))
 	}
 	// let's be nice and fallback if the error is a completely
 	// unexpected one.
 	// If new errors have to be handled in some way, please
 	// add them to the switch above.
 	return true
 }
 
 // retryOnError wraps the error in xfer.DoNotRetry if we should not retry the
 // operation after this error.
 func retryOnError(err error) error {
 	switch v := err.(type) {
 	case errcode.Errors:

 		if len(v) != 0 {
 			return retryOnError(v[0])
 		}

 	case errcode.Error:
 		switch v.Code {
 		case errcode.ErrorCodeUnauthorized, errcode.ErrorCodeUnsupported, errcode.ErrorCodeDenied:
 			return xfer.DoNotRetry{Err: err}
 		}
 	case *url.Error:

 		switch v.Err {
 		case auth.ErrNoBasicAuthCredentials, auth.ErrNoToken:

 			return xfer.DoNotRetry{Err: v.Err}
 		}

 		return retryOnError(v.Err)
 	case *client.UnexpectedHTTPResponseError:
 		return xfer.DoNotRetry{Err: err}
 	case error:
 		if strings.Contains(err.Error(), strings.ToLower(syscall.ENOSPC.Error())) {
 			return xfer.DoNotRetry{Err: err}
 		}
 	}
 	// let's be nice and fallback if the error is a completely
 	// unexpected one.
 	// If new errors have to be handled in some way, please
 	// add them to the switch above.
 	return err
 }