var (
	// ErrNoToken is returned if a request is successful but the body does not
	// contain an authorization token.
	ErrNoToken = errors.New("authorization server did not include a token in the response")

	// ErrInvalidAuthorization is used when credentials are passed to a server but
	// those credentials are rejected.
	ErrInvalidAuthorization = errors.New("authorization failed")
)

type Authorizer interface {
	// Authorize sets the appropriate `Authorization` header on the given
	// request.
	//
	// If no authorization is found for the request, the request remains
	// unmodified. It may also add an `Authorization` header as
	//  "bearer <some bearer token>"
	//  "basic <base64 encoded credentials>"
	Authorize(context.Context, *http.Request) error

	// AddResponses adds a 401 response for the authorizer to consider when
	// authorizing requests. The last response should be unauthorized and
	// the previous requests are used to consider redirects and retries
	// that may have led to the 401.
	//
	// If response is not handled, returns `ErrNotImplemented`
	AddResponses(context.Context, []*http.Response) error
}

type ResolverOptions struct {
	// Authorizer is used to authorize registry requests
	Authorizer Authorizer

	// Credentials provides username and secret given a host.
	// If username is empty but a secret is given, that secret
	// is interpretted as a long lived token.
	// Deprecated: use Authorizer
	Credentials func(string) (string, string, error)

	// Host provides the hostname given a namespace.
	Host func(string) (string, error)

	// PlainHTTP specifies to use plain http and not https
	PlainHTTP bool

	// Client is the http client to used when making registry requests
	Client *http.Client

	// Tracker is used to track uploads to the registry. This is used
	// since the registry does not have upload tracking and the existing
	// mechanism for getting blob upload status is expensive.
	Tracker StatusTracker
}

type Status struct {
	content.Status

	// UploadUUID is used by the Docker registry to reference blob uploads
	UploadUUID string
}

type StatusTracker interface {
	GetStatus(string) (Status, error)
	SetStatus(string, Status)
}