/*
 * 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 limiter

import (
	"fmt"
)

var ErrReachLimitation = fmt.Errorf("reach limitation")

var (
	Verbose = false
)

const (
	HillClimbingLimiter = iota
)

type Limiter interface {
	Inflight() uint64
	Remaining() uint64
	// Acquire inspects the current status of the system:
	// - if reaches the limitation, reject the request immediately.
	// - if not, grant this request and return an Updater defined below.
	Acquire() (Updater, error)
}

type Updater interface {
	// DoUpdate is called once an invocation is finished, it tells Updater that the invocation is finished, and please
	// update the Remaining, Inflight parameters of the Limiter.
	DoUpdate() error
}
