/*
   Copyright The containerd 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 label

import (
	"sync"

	"github.com/opencontainers/selinux/go-selinux"
)

// Store is used to store SELinux process labels
type Store struct {
	sync.Mutex
	levels   map[string]int
	Releaser func(string)
	Reserver func(string)
}

// NewStore creates a new SELinux process label store
func NewStore() *Store {
	return &Store{
		levels:   map[string]int{},
		Releaser: selinux.ReleaseLabel,
		Reserver: selinux.ReserveLabel,
	}
}

// Reserve reserves the MLS/MCS level component of the specified label
// and prevents multiple reserves for the same level
func (s *Store) Reserve(label string) error {
	s.Lock()
	defer s.Unlock()

	context, err := selinux.NewContext(label)
	if err != nil {
		return err
	}

	level := context["level"]
	// no reason to count empty
	if level == "" {
		return nil
	}

	if _, ok := s.levels[level]; !ok {
		s.Reserver(label)
	}

	s.levels[level]++
	return nil
}

// Release un-reserves the MLS/MCS level component of the specified label,
// allowing it to be used by another process once labels with the same
// level have been released.
func (s *Store) Release(label string) {
	s.Lock()
	defer s.Unlock()

	context, err := selinux.NewContext(label)
	if err != nil {
		return
	}

	level := context["level"]
	if level == "" {
		return
	}

	count, ok := s.levels[level]
	if !ok {
		return
	}
	switch {
	case count == 1:
		s.Releaser(label)
		delete(s.levels, level)
	case count < 1:
		delete(s.levels, level)
	case count > 1:
		s.levels[level] = count - 1
	}
}