/*
Copyright 2019 The Kubernetes Authors.
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,
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 util

import (
	"sync"

	"k8s.io/apimachinery/pkg/util/sets"
)

const (
	// VolumeOperationAlreadyExistsFmt string format to return for concurrent operation
	VolumeOperationAlreadyExistsFmt = "an operation with the given Volume ID %s already exists"

	// SnapshotOperationAlreadyExistsFmt string format to return for concurrent operation
	SnapshotOperationAlreadyExistsFmt = "an operation with the given Snapshot ID %s already exists"
)

// VolumeLocks implements a map with atomic operations. It stores a set of all volume IDs
// with an ongoing operation.
type VolumeLocks struct {
	locks sets.String
	mux   sync.Mutex
}

// NewVolumeLocks returns new VolumeLocks.
func NewVolumeLocks() *VolumeLocks {
	return &VolumeLocks{
		locks: sets.NewString(),
	}
}

// TryAcquire tries to acquire the lock for operating on volumeID and returns true if successful.
// If another operation is already using volumeID, returns false.
func (vl *VolumeLocks) TryAcquire(volumeID string) bool {
	vl.mux.Lock()
	defer vl.mux.Unlock()
	if vl.locks.Has(volumeID) {
		return false
	}
	vl.locks.Insert(volumeID)
	return true
}

// Release deletes the lock on volumeID.
func (vl *VolumeLocks) Release(volumeID string) {
	vl.mux.Lock()
	defer vl.mux.Unlock()
	vl.locks.Delete(volumeID)
}
