// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License.  You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package loadbalancer

import "fmt"

var (
	ErrNoServerFound = fmt.Errorf("no server found")
	ErrInvalidInput  = fmt.Errorf("invalidate input")
)

// Rule for loadbalancer algorithms
type Rule interface {
	// Choose return the instance by rule
	Choose(interface{}) (interface{}, error)
}

// BaseRule base rule for all implements, holds the lb to
// fetch the latest server lists
type BaseRule struct {
	lb LoadBalancer
}

// SetLoadBalancer set the lb for current rule
func (b *BaseRule) SetLoadBalancer(balancer LoadBalancer) {
	b.lb = balancer
}
