grpc

type ConnWithNodeMeta struct {
	*grpc.ClientConn

	Node *node.Node
}

type NodeSelectionFeedback struct {
	// ID is the node identifier.
	ID signature.PublicKey

	// Bad being non-nil signals that the currently selected node is bad and contains the reason
	// that lead to the decision.
	Bad error
}

type NodeSelectionPolicy interface {
	// UpdateNodes updates the set of available nodes.
	UpdateNodes([]signature.PublicKey)

	// UpdatePolicy submits feedback to the policy which can cause the policy to update its current
	// node selection.
	UpdatePolicy(feedback NodeSelectionFeedback)

	// Pick picks a node from the set of available nodes accoording to the policy.
	Pick() signature.PublicKey
}

type NodesClient interface {
	// GetConnections returns the set of connections to nodes.
	GetConnections() []*grpc.ClientConn

	// GetConnectionsWithMeta returns the set of connections to nodes including node metadata
	// for each connection.
	GetConnectionsWithMeta() []*ConnWithNodeMeta

	// GetConnectionsMap returns the set of connections to nodes including node metadata
	// for each connection.
	GetConnectionsMap() map[signature.PublicKey]*ConnWithNodeMeta

	// GetConnection returns a connection based on the configured node selection policy.
	//
	// If no connections are available this method will return nil.
	GetConnection() *grpc.ClientConn

	// UpdateNodeSelectionPolicy submits feedback to the policy which can cause the policy to update
	// its current node selection.
	UpdateNodeSelectionPolicy(feedback NodeSelectionFeedback)

	// EnsureVersion waits for the client to be fully synced to the given watcher version.
	//
	// When client is using a non-versioned watcher, this method should return ErrNotVersionedWatcher error.
	EnsureVersion(ctx context.Context, version int64) error

	// Initialized returns a channel that will be closed once the first connection is available.
	Initialized() <-chan struct{}
}

type Option func(nc *nodesClient)