var (
	// ErrBlobExists returned when blob already exists
	ErrBlobExists = errors.New("blob exists")

	// ErrBlobDigestUnsupported when blob digest is an unsupported version.
	ErrBlobDigestUnsupported = errors.New("unsupported blob digest")

	// ErrBlobUnknown when blob is not found.
	ErrBlobUnknown = errors.New("unknown blob")

	// ErrBlobUploadUnknown returned when upload is not found.
	ErrBlobUploadUnknown = errors.New("blob upload unknown")

	// ErrBlobInvalidLength returned when the blob has an expected length on
	// commit, meaning mismatched with the descriptor or an invalid value.
	ErrBlobInvalidLength = errors.New("blob invalid length")
)

var ErrManifestNotModified = errors.New("manifest not modified")

var ErrUnsupported = errors.New("operation unsupported")

var GlobalScope = Scope(fullScope{})

type BlobCreateOption interface {
	Apply(interface{}) error
}

type BlobDeleter interface {
	Delete(ctx context.Context, dgst digest.Digest) error
}

type BlobDescriptorService interface {
	BlobStatter

	// SetDescriptor assigns the descriptor to the digest. The provided digest and
	// the digest in the descriptor must map to identical content but they may
	// differ on their algorithm. The descriptor must have the canonical
	// digest of the content and the digest algorithm must match the
	// annotators canonical algorithm.
	//
	// Such a facility can be used to map blobs between digest domains, with
	// the restriction that the algorithm of the descriptor must match the
	// canonical algorithm (ie sha256) of the annotator.
	SetDescriptor(ctx context.Context, dgst digest.Digest, desc Descriptor) error

	// Clear enables descriptors to be unlinked
	Clear(ctx context.Context, dgst digest.Digest) error
}

type BlobIngester interface {
	// Put inserts the content p into the blob service, returning a descriptor
	// or an error.
	Put(ctx context.Context, mediaType string, p []byte) (Descriptor, error)

	// Create allocates a new blob writer to add a blob to this service. The
	// returned handle can be written to and later resumed using an opaque
	// identifier. With this approach, one can Close and Resume a BlobWriter
	// multiple times until the BlobWriter is committed or cancelled.
	Create(ctx context.Context, options ...BlobCreateOption) (BlobWriter, error)

	// Resume attempts to resume a write to a blob, identified by an id.
	Resume(ctx context.Context, id string) (BlobWriter, error)
}

type BlobProvider interface {
	// Get returns the entire blob identified by digest along with the descriptor.
	Get(ctx context.Context, dgst digest.Digest) ([]byte, error)

	// Open provides a ReadSeekCloser to the blob identified by the provided
	// descriptor. If the blob is not known to the service, an error will be
	// returned.
	Open(ctx context.Context, dgst digest.Digest) (ReadSeekCloser, error)
}

type BlobServer interface {
	// ServeBlob attempts to serve the blob, identifed by dgst, via http. The
	// service may decide to redirect the client elsewhere or serve the data
	// directly.
	//
	// This handler only issues successful responses, such as 2xx or 3xx,
	// meaning it serves data or issues a redirect. If the blob is not
	// available, an error will be returned and the caller may still issue a
	// response.
	//
	// The implementation may serve the same blob from a different digest
	// domain. The appropriate headers will be set for the blob, unless they
	// have already been set by the caller.
	ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error
}

type BlobService interface {
	BlobStatter
	BlobProvider
	BlobIngester
}

type BlobStatter interface {
	// Stat provides metadata about a blob identified by the digest. If the
	// blob is unknown to the describer, ErrBlobUnknown will be returned.
	Stat(ctx context.Context, dgst digest.Digest) (Descriptor, error)
}

type BlobStore interface {
	BlobService
	BlobServer
	BlobDeleter
}

type BlobWriter interface {
	io.WriteSeeker
	io.ReaderFrom
	io.Closer

	// ID returns the identifier for this writer. The ID can be used with the
	// Blob service to later resume the write.
	ID() string

	// StartedAt returns the time this blob write was started.
	StartedAt() time.Time

	// Commit completes the blob writer process. The content is verified
	// against the provided provisional descriptor, which may result in an
	// error. Depending on the implementation, written data may be validated
	// against the provisional descriptor fields. If MediaType is not present,
	// the implementation may reject the commit or assign "application/octet-
	// stream" to the blob. The returned descriptor may have a different
	// digest depending on the blob store, referred to as the canonical
	// descriptor.
	Commit(ctx context.Context, provisional Descriptor) (canonical Descriptor, err error)

	// Cancel ends the blob write without storing any data and frees any
	// associated resources. Any data written thus far will be lost. Cancel
	// implementations should allow multiple calls even after a commit that
	// result in a no-op. This allows use of Cancel in a defer statement,
	// increasing the assurance that it is correctly called.
	Cancel(ctx context.Context) error

	// Get a reader to the blob being written by this BlobWriter
	Reader() (io.ReadCloser, error)
}

type Describable interface {
	Descriptor() Descriptor
}

type Descriptor struct {
	// MediaType describe the type of the content. All text based formats are
	// encoded as utf-8.
	MediaType string `json:"mediaType,omitempty"`

	// Size in bytes of content.
	Size int64 `json:"size,omitempty"`

	// Digest uniquely identifies the content. A byte stream can be verified
	// against against this digest.
	Digest digest.Digest `json:"digest,omitempty"`
}

type ErrBlobInvalidDigest struct {
	Digest digest.Digest
	Reason error
}

type ErrBlobMounted struct {
	From       reference.Canonical
	Descriptor Descriptor
}

type ErrManifestBlobUnknown struct {
	Digest digest.Digest
}

type ErrManifestNameInvalid struct {
	Name   string
	Reason error
}

type ErrManifestUnknown struct {
	Name string
	Tag  string
}

type ErrManifestUnknownRevision struct {
	Name     string
	Revision digest.Digest
}

type ErrManifestUnverified struct{}

type ErrManifestVerification []error

type ErrRepositoryNameInvalid struct {
	Name   string
	Reason error
}

type ErrRepositoryUnknown struct {
	Name string
}

type ErrTagUnknown struct {
	Tag string
}

type Manifest interface {
	// References returns a list of objects which make up this manifest.
	// The references are strictly ordered from base to head. A reference
	// is anything which can be represented by a distribution.Descriptor
	References() []Descriptor

	// Payload provides the serialized format of the manifest, in addition to
	// the mediatype.
	Payload() (mediatype string, payload []byte, err error)
}

type ManifestBuilder interface {
	// Build creates the manifest from his builder.
	Build(ctx context.Context) (Manifest, error)

	// References returns a list of objects which have been added to this
	// builder. The dependencies are returned in the order they were added,
	// which should be from base to head.
	References() []Descriptor

	// AppendReference includes the given object in the manifest after any
	// existing dependencies. If the add fails, such as when adding an
	// unsupported dependency, an error may be returned.
	AppendReference(dependency Describable) error
}

type ManifestService interface {
	// Exists returns true if the manifest exists.
	Exists(ctx context.Context, dgst digest.Digest) (bool, error)

	// Get retrieves the manifest specified by the given digest
	Get(ctx context.Context, dgst digest.Digest, options ...ManifestServiceOption) (Manifest, error)

	// Put creates or updates the given manifest returning the manifest digest
	Put(ctx context.Context, manifest Manifest, options ...ManifestServiceOption) (digest.Digest, error)

	// Delete removes the manifest specified by the given digest. Deleting
	// a manifest that doesn't exist will return ErrManifestNotFound
	Delete(ctx context.Context, dgst digest.Digest) error
}

type ManifestServiceOption interface {
	Apply(ManifestService) error
}

type Namespace interface {
	// Scope describes the names that can be used with this Namespace. The
	// global namespace will have a scope that matches all names. The scope
	// effectively provides an identity for the namespace.
	Scope() Scope

	// Repository should return a reference to the named repository. The
	// registry may or may not have the repository but should always return a
	// reference.
	Repository(ctx context.Context, name reference.Named) (Repository, error)

	// Repositories fills 'repos' with a lexigraphically sorted catalog of repositories
	// up to the size of 'repos' and returns the value 'n' for the number of entries
	// which were filled.  'last' contains an offset in the catalog, and 'err' will be
	// set to io.EOF if there are no more entries to obtain.
	Repositories(ctx context.Context, repos []string, last string) (n int, err error)
}

type ReadSeekCloser interface {
	io.ReadSeeker
	io.Closer
}

type Repository interface {
	// Name returns the name of the repository.
	Name() reference.Named

	// Manifests returns a reference to this repository's manifest service.
	// with the supplied options applied.
	Manifests(ctx context.Context, options ...ManifestServiceOption) (ManifestService, error)

	// Blobs returns a reference to this repository's blob service.
	Blobs(ctx context.Context) BlobStore

	// Tags returns a reference to this repositories tag service
	Tags(ctx context.Context) TagService
}

type Scope interface {
	// Contains returns true if the name belongs to the namespace.
	Contains(name string) bool
}

type TagService interface {
	// Get retrieves the descriptor identified by the tag. Some
	// implementations may differentiate between "trusted" tags and
	// "untrusted" tags. If a tag is "untrusted", the mapping will be returned
	// as an ErrTagUntrusted error, with the target descriptor.
	Get(ctx context.Context, tag string) (Descriptor, error)

	// Tag associates the tag with the provided descriptor, updating the
	// current association, if needed.
	Tag(ctx context.Context, tag string, desc Descriptor) error

	// Untag removes the given tag association
	Untag(ctx context.Context, tag string) error

	// All returns the set of tags managed by this tag service
	All(ctx context.Context) ([]string, error)

	// Lookup returns the set of tags referencing the given digest.
	Lookup(ctx context.Context, digest Descriptor) ([]string, error)
}

type UnmarshalFunc func([]byte) (Manifest, Descriptor, error)