origin

type MissingETagError struct {
	Bucket string
	Key    string
}

type ObjectInfo struct {
	Size        int64
	ETag        string
	ContentType string
}

type Origin interface {
	// Head returns object metadata. If the blob does not exist, returns
	// ErrNotFound. If the blob is an unsupported type (e.g., azureblob
	// non-BlockBlob), returns UnsupportedBlobTypeError.
	Head(ctx context.Context, bucket, key string) (ObjectInfo, error)

	// GetRange fetches [off, off+n) bytes of the object. The etag is
	// passed as `If-Match: <etag>` so a mid-flight overwrite is detected
	// at the wire (returns OriginETagChangedError).
	GetRange(ctx context.Context, bucket, key, etag string, off, n int64) (io.ReadCloser, error)
}

type OriginETagChangedError struct {
	Bucket string
	Key    string
	Want   string
}

type UnsupportedBlobTypeError struct {
	Bucket   string
	Key      string
	BlobType string
}