// Copyright 2016 DeepFabric, Inc.
//
// Licensed 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package util

import (
	"golang.org/x/net/context"
	"golang.org/x/sync/semaphore"
)

// Limiter limiter implemention by token
type Limiter struct {
	limter *semaphore.Weighted
}

// NewLimiter return a limiter with max
func NewLimiter(max uint64) *Limiter {
	return &Limiter{
		limter: semaphore.NewWeighted(int64(max)),
	}
}

// Wait wait until get the token
func (l *Limiter) Wait(ctx context.Context) error {
	return l.limter.Acquire(ctx, 1)
}

// Release release token
func (l *Limiter) Release() {
	l.limter.Release(1)
}