// Copyright (c) 2020 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0
//

package cgroups

import (
	"fmt"
	"path/filepath"
	"regexp"
)

// prepend a kata specific string to oci cgroup path to
// form a different cgroup path, thus cAdvisor couldn't
// find kata containers cgroup path on host to prevent it
// from grabbing the stats data.
const CgroupKataPrefix = "kata"

// DefaultCgroupPath runtime-determined location in the cgroups hierarchy.
const DefaultCgroupPath = "/vc"

func RenameCgroupPath(path string) (string, error) {
	if path == "" {
		return "", fmt.Errorf("Cgroup path is empty")
	}

	cgroupPathDir := filepath.Dir(path)
	cgroupPathName := fmt.Sprintf("%s_%s", CgroupKataPrefix, filepath.Base(path))
	return filepath.Join(cgroupPathDir, cgroupPathName), nil

}

// validCgroupPath returns a valid cgroup path.
// see https://github.com/opencontainers/runtime-spec/blob/master/config-linux.md#cgroups-path
func ValidCgroupPath(path string, systemdCgroup bool) (string, error) {
	if IsSystemdCgroup(path) {
		return path, nil
	}

	if systemdCgroup {
		return "", fmt.Errorf("malformed systemd path '%v': expected to be of form 'slice:prefix:name'", path)
	}

	// In the case of an absolute path (starting with /), the runtime MUST
	// take the path to be relative to the cgroups mount point.
	if filepath.IsAbs(path) {
		return RenameCgroupPath(filepath.Clean(path))
	}

	// In the case of a relative path (not starting with /), the runtime MAY
	// interpret the path relative to a runtime-determined location in the cgroups hierarchy.
	// clean up path and return a new path relative to DefaultCgroupPath
	return RenameCgroupPath(filepath.Join(DefaultCgroupPath, filepath.Clean("/"+path)))
}

func IsSystemdCgroup(cgroupPath string) bool {
	// systemd cgroup path: slice:prefix:name
	re := regexp.MustCompile(`([[:alnum:]]|\.)+:([[:alnum:]]|\.)+:([[:alnum:]]|\.)+`)
	found := re.FindStringIndex(cgroupPath)

	// if found string is equal to cgroupPath then
	// it's a correct systemd cgroup path.
	return found != nil && cgroupPath[found[0]:found[1]] == cgroupPath
}