// Copyright (C) 2016-2017 Luke Shumaker <lukeshu@sbcglobal.net>
//
// 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 sd_login

import (
	"strconv"
	"strings"

	"golang.org/x/sys/unix"
)

// A MachineName is a name representing a locally running container or
// virtual machine that is registerd with (systemd-)machined.
type MachineName string

func (m MachineName) isValid() bool {
	if len(m) > host_name_max {
		// Note that Linux HOST_NAME_MAX is 64, but DNS allows
		// 255, so names from DNS might be invalid.
		return false
	}

	n_dots := 0
	dot := true
	for _, c := range m {
		if c == '.' {
			if dot {
				return false
			}
			dot = true
			n_dots++
		} else {
			if !strings.ContainsRune(letters+digits+"-_.", c) {
				return false
			}
			dot = false
		}
	}

	if dot { // trailing dot or empty
		return false
	}

	return true
}

// GetMachines returns a list of currently running containers/virtual
// machines.
func GetMachines() ([]MachineName, error) {
	strs, err := get_files_in_directory("/run/systemd/machines/")
	if err != nil {
		return nil, err
	}
	var machines []MachineName
	for _, str := range strs {
		machine := MachineName(str)
		if strings.HasPrefix(str, "unit:") || machine.isValid() {
			continue
		}
		machines = append(machines, machine)
	}
	return machines, nil
}

// GetClass returns the class of a locally running machine.  The class
// is either "vm" or "container", depending on if the machine is an
// virtual machine or a container.
func (m MachineName) GetClass() (string, error) {
	if !m.isValid() {
		return "", unix.EINVAL
	}

	env, err := parse_env_file("/run/systemd/machines/" + string(m))
	if err != nil {
		return "", err
	}
	class, ok := env["CLASS"]
	if !ok {
		return "", unix.ENXIO // or EIO?
	}
	return class, nil
}

// GetIfIndices returns the numeric indices of the network interfaces
// on the host that are pointing toward this machine.
func (m MachineName) GetIfIndices() ([]int, error) {
	if !m.isValid() {
		return nil, unix.EINVAL
	}

	env, err := parse_env_file("/run/systemd/machines/" + string(m))
	if err != nil {
		return nil, err
	}
	netif, ok := env["NETIF"]
	if !ok {
		return nil, unix.ENXIO // or EIO?
	}

	var ifindices []int
	for _, word := range strings.FieldsFunc(netif, func(c rune) bool { return strings.ContainsRune(whitespace, c) }) {
		ifindex, err := strconv.Atoi(word)
		if err != nil {
			return nil, err
		}
		ifindices = append(ifindices, ifindex)
	}
	return ifindices, nil
}