const (
	BaseLayer refKind = iota
	Layer
	Merge
	Diff
)

var (
	ErrLocked = errors.New("locked")
)

var ErrNoBlobs = errors.Errorf("no blobs for snapshot")

var NoUpdateLastUsed noUpdateLastUsed

type Accessor interface {
	MetadataStore

	GetByBlob(ctx context.Context, desc ocispecs.Descriptor, parent ImmutableRef, opts ...RefOption) (ImmutableRef, error)
	Get(ctx context.Context, id string, pg progress.Controller, opts ...RefOption) (ImmutableRef, error)

	New(ctx context.Context, parent ImmutableRef, s session.Group, opts ...RefOption) (MutableRef, error)
	GetMutable(ctx context.Context, id string, opts ...RefOption) (MutableRef, error) // Rebase?
	IdentityMapping() *idtools.IdentityMapping
	Merge(ctx context.Context, parents []ImmutableRef, pg progress.Controller, opts ...RefOption) (ImmutableRef, error)
	Diff(ctx context.Context, lower, upper ImmutableRef, pg progress.Controller, opts ...RefOption) (ImmutableRef, error)
}

type Controller interface {
	DiskUsage(ctx context.Context, info client.DiskUsageInfo) ([]*client.UsageInfo, error)
	Prune(ctx context.Context, ch chan client.UsageInfo, info ...client.PruneInfo) error
}

type DescHandler struct {
	Provider       func(session.Group) content.Provider
	Progress       progress.Controller
	SnapshotLabels map[string]string
	Annotations    map[string]string
	Ref            string // string representation of desc origin, can be used as a sync key
}

type DescHandlerKey digest.Digest

type DescHandlers map[digest.Digest]*DescHandler

type ExternalRefChecker interface {
	Exists(string, []digest.Digest) bool
}

type ExternalRefCheckerFunc func() (ExternalRefChecker, error)

type ImmutableRef interface {
	Ref
	Clone() ImmutableRef
	// Finalize commits the snapshot to the driver if it's not already.
	// This means the snapshot can no longer be mounted as mutable.
	Finalize(context.Context) error

	Extract(ctx context.Context, s session.Group) error // +progress
	GetRemotes(ctx context.Context, createIfNeeded bool, cfg config.RefConfig, all bool, s session.Group) ([]*solver.Remote, error)
	LayerChain() RefList
	FileList(ctx context.Context, s session.Group) ([]string, error)
}

type Manager interface {
	Accessor
	Controller
	Close() error
}

type ManagerOpt struct {
	Snapshotter     snapshot.Snapshotter
	ContentStore    content.Store
	LeaseManager    leases.Manager
	PruneRefChecker ExternalRefCheckerFunc
	GarbageCollect  func(ctx context.Context) (gc.Stats, error)
	Applier         diff.Applier
	Differ          diff.Comparer
	MetadataStore   *metadata.Store
	MountPoolRoot   string
}

type MetadataStore interface {
	Search(context.Context, string) ([]RefMetadata, error)
}

type Mountable interface {
	Mount(ctx context.Context, readonly bool, s session.Group) (snapshot.Mountable, error)
}

type MutableRef interface {
	Ref
	Commit(context.Context) (ImmutableRef, error)
}

type NeedsRemoteProviderError []digest.Digest //nolint:errname

type Ref interface {
	Mountable
	RefMetadata
	Release(context.Context) error
	IdentityMapping() *idtools.IdentityMapping
	DescHandler(digest.Digest) *DescHandler
}

type RefList []ImmutableRef

type RefMetadata interface {
	ID() string

	GetDescription() string
	SetDescription(string) error

	GetCreatedAt() time.Time
	SetCreatedAt(time.Time) error

	HasCachePolicyDefault() bool
	SetCachePolicyDefault() error
	HasCachePolicyRetain() bool
	SetCachePolicyRetain() error

	GetLayerType() string
	SetLayerType(string) error

	GetRecordType() client.UsageRecordType
	SetRecordType(client.UsageRecordType) error

	GetEqualMutable() (RefMetadata, bool)

	// generic getters/setters for external packages
	GetString(string) string
	SetString(key, val, index string) error

	GetExternal(string) ([]byte, error)
	SetExternal(string, []byte) error

	ClearValueAndIndex(string, string) error
}

type RefOption interface{}

type Unlazier interface {
	Unlazy(ctx context.Context) error
}

type Unlazy session.Group