type Authority struct {
	// XDSServers contains the list of server configurations for this authority.
	//
	// See Config.Servers for more details.
	XDSServers []ServerConfig
}

type Config struct {
	// Servers specifies a list of xDS management servers to connect to. The
	// order of the servers in this list reflects the order of preference of
	// the data returned by those servers. The xDS client uses the first
	// available server from the list.
	//
	// See gRFC A71 for more details on fallback behavior when the primary
	// xDS server is unavailable.
	//
	// gRFC A71: https://github.com/grpc/proposal/blob/master/A71-xds-fallback.md
	Servers []ServerConfig

	// Authorities defines the configuration for each xDS authority.  Federated resources
	// will be fetched from the servers specified by the corresponding Authority.
	Authorities map[string]Authority

	// Node is the identity of the xDS client connecting to the xDS
	// management server.
	Node clients.Node

	// TransportBuilder is used to create connections to xDS management servers.
	TransportBuilder clients.TransportBuilder

	// ResourceTypes is a map from resource type URLs to resource type
	// implementations. Each resource type URL uniquely identifies a specific
	// kind of xDS resource, and the corresponding resource type implementation
	// provides logic for parsing, validating, and processing resources of that
	// type.
	//
	// For example: "type.googleapis.com/envoy.config.listener.v3.Listener"
	ResourceTypes map[string]ResourceType
}

type DecodeOptions struct {
	// Config contains the complete configuration passed to the xDS client.
	// This contains useful data for resource validation.
	Config *Config

	// ServerConfig contains the configuration of the xDS server that provided
	// the current resource being decoded.
	ServerConfig *ServerConfig
}

type DecodeResult struct {
	// Name is the name of the decoded resource.
	Name string

	// Resource contains the configuration associated with the decoded
	// resource.
	Resource ResourceData
}

type Decoder interface {
	// Decode deserializes and validates an xDS resource as received from the
	// xDS management server.
	//
	// If deserialization fails or resource validation fails, it returns a
	// non-nil error. Otherwise, returns a fully populated DecodeResult.
	Decode(resource []byte, options DecodeOptions) (*DecodeResult, error)
}

type ResourceData interface {
	// Equal returns true if the passed in resource data is equal to that of
	// the receiver.
	Equal(other ResourceData) bool

	// Bytes returns the underlying raw bytes of the resource proto.
	Bytes() []byte
}

type ResourceType struct {
	// TypeURL is the xDS type URL of this resource type for the v3 xDS
	// protocol. This URL is used as the key to look up the corresponding
	// ResourceType implementation in the ResourceTypes map provided in the
	// Config.
	TypeURL string

	// TypeName is a shorter representation of the TypeURL to identify the
	// resource type. It is used for logging/debugging purposes.
	TypeName string

	// AllResourcesRequiredInSotW indicates whether this resource type requires
	// that all resources be present in every SotW response from the server. If
	// true, a response that does not include a previously seen resource will
	// be interpreted as a deletion of that resource.
	AllResourcesRequiredInSotW bool

	// Decoder is used to deserialize and validate an xDS resource received
	// from the xDS management server.
	Decoder Decoder
}

type ResourceWatcher interface {
	// ResourceChanged indicates a new version of the resource is available.
	ResourceChanged(resourceData ResourceData, done func())

	// ResourceError indicates an error occurred while trying to fetch or
	// decode the associated resource. The previous version of the resource
	// should be considered invalid.
	ResourceError(err error, done func())

	// AmbientError indicates an error occurred after a resource has been
	// received that should not modify the use of that resource but may provide
	// useful information about the state of the XDSClient for debugging
	// purposes. The previous version of the resource should still be
	// considered valid.
	AmbientError(err error, done func())
}

type ServerConfig struct {
	ServerIdentifier clients.ServerIdentifier

	// IgnoreResourceDeletion is a server feature which if set to true,
	// indicates that resource deletion errors from xDS management servers can
	// be ignored and cached resource data can be used.
	//
	// This will be removed in the future once we implement gRFC A88
	// and two new fields FailOnDataErrors and
	// ResourceTimerIsTransientError will be introduced.
	IgnoreResourceDeletion bool
}

type XDSClient struct {
}