repositories

type CharmID struct {

	// URL of the given charm, includes the reference name and a revision.
	// Old style charm URLs are also supported i.e. charmstore.
	URL *charm.URL

	// Origin holds the origin of a charm. This includes the source of the
	// charm, along with the revision and channel to identify where the charm
	// originated from.
	Origin state.CharmOrigin
}

type EntityRepository interface {
	// GetResource returns the resource data for the identified resource.
	GetResource(name string) (resource.Resource, error)

	// SetResource stores the resource in the local cache.
	SetResource(res charmresource.Resource, reader io.Reader, _ state.IncrementCharmModifiedVersionType) (resource.Resource, error)

	// OpenResource returns metadata about the resource, and a reader
	// for the resource.
	OpenResource(name string) (resource.Resource, io.ReadCloser, error)

	// FetchLock provides a lock to serialize resource fetching.
	FetchLock(name string) sync.Locker
}

type GetResourceArgs struct {
	// Client is the charm store client to use.
	Client ResourceGetter

	// EntityRepository is the charm store cache to use. It is optional.
	Repository EntityRepository

	// CharmID indicates the charm for which to get the resource.
	CharmID CharmID

	// Name is the name of the resource.
	Name string
}

type ResourceGetter interface {
	// GetResource returns a reader for the resource's data. That data
	// is streamed from the charm store. The charm's revision, if any,
	// is ignored. If the identified resource is not in the charm store
	// then errors.NotFound is returned.
	//
	// But if you write any code that assumes a NotFound error returned
	// from this method means that the resource was not found, you fail
	// basic logic.
	GetResource(ResourceRequest) (charmstore.ResourceData, error)
}

type ResourceRequest struct {
	// Channel is the channel from which to request the resource info.
	CharmID CharmID

	// Name is the name of the resource we're asking about.
	Name string

	// Revision is the specific revision of the resource we're asking about.
	Revision int
}