selector

type Balancer interface {
	Pick(ctx context.Context, nodes []WeightedNode) (selected WeightedNode, done DoneFunc, err error)
}

type BalancerBuilder interface {
	Build() Balancer
}

type Builder interface {
	Build() Selector
}

type Default struct {
	NodeBuilder WeightedNodeBuilder
	Balancer    Balancer
	Filters     []Filter
	// contains filtered or unexported fields
}

type DefaultBuilder struct {
	Node     WeightedNodeBuilder
	Balancer BalancerBuilder
	Filters  []Filter
}

type DefaultNode struct {
	// contains filtered or unexported fields
}

type DoneFunc func(ctx context.Context, di DoneInfo)

type DoneInfo struct {
	// Response Error
	Err error
	// Response Metadata
	ReplyMeta ReplyMeta

	// BytesSent indicates if any bytes have been sent to the server.
	BytesSent bool
	// BytesReceived indicates if any byte has been received from the server.
	BytesReceived bool
}

type Filter func(context.Context, []Node) []Node

type Node interface {
	// Address is the unique address under the same service
	Address() string

	// ServiceName is service name
	ServiceName() string

	// InitialWeight is the initial value of scheduling weight
	// if not set return nil
	InitialWeight() *int64

	// Version is service node version
	Version() string

	// Metadata is the kv pair metadata associated with the service instance.
	// version,namespace,region,protocol etc..
	Metadata() map[string]string
}

type Rebalancer interface {
	// Apply is apply all nodes when any changes happen
	Apply(nodes []Node)
}

type ReplyMeta interface {
	Get(key string) string
}

type SelectOption func(*SelectOptions)

type SelectOptions struct {
	Filters []Filter
}

type Selector interface {
	Rebalancer

	// Select nodes
	// if err == nil, selected and done must not be empty.
	Select(ctx context.Context, opts ...SelectOption) (selected Node, done DoneFunc, err error)
}

type WeightedNode interface {
	Node

	// Raw returns the original node
	Raw() Node

	// Weight is the runtime calculated weight
	Weight() float64

	// Pick the node
	Pick() DoneFunc

	// PickElapsed is time elapsed since the latest pick
	PickElapsed() time.Duration
}

type WeightedNodeBuilder interface {
	Build(Node) WeightedNode
}