// 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"
)

func valid_slice_name(s string) bool {
	return strings.HasSuffix(s, ".slice") && valid_unit_name(s) == unit_name_plain
}

func valid_user_tree(unit string) bool {
	sessStr, sessOk := trimPrefixSuffix(unit, "session-", ".scope")

	ownerStr, ownerOk := trimPrefixSuffix(unit, "user@", ".service")
	_, ownerErr := strconv.Atoi(ownerStr)

	return (sessOk && (SessionName(sessStr).isValid())) || (ownerOk && ownerErr == nil)
}

func valid_filename(s string) bool {
	switch s {
	case "", ".", "..":
		return false
	}
	if strings.ContainsRune(s, '/') {
		return false
	}
	return true
}

const (
	unit_name_invalid  = 0
	unit_name_plain    = 1 << 0 // foo.service
	unit_name_instance = 1 << 1 // foo@bar.service
	unit_name_template = 1 << 2 // foo@.service
)

// valid_unit_name returns returns which type of unit the given unit
// name is valid for.
//
// To simply check whether a unit name is valid, without caring about
// the type, you can simply check that it doesn't return the "invalid"
// type:
//
//     is_valid := valid_unit_name(unitname) != unit_name_invalid
//
// To check whether it matches a specific type (in this example,
// "template"), you can test equality against that type:
//
//     is_valid_template := valid_unit_name(unitname) == unit_name_template
//
// If there are several acceptable types, you can treat multiple types
// as bitmasks, and use the usual bitfield checks:
//
//     is_valid_plain_or_instance := valid_unit_name(unitname)&(unit_name_plain|unit_name_instance) != 0
func valid_unit_name(unit string) int {
	const_unit_name_max := 256
	const_unit_types := []string{
		"service",
		"socket",
		"busname",
		"target",
		"device",
		"mount",
		"automount",
		"swap",
		"timer",
		"path",
		"slice",
		"scope",
	}

	if unit == "" {
		return unit_name_invalid
	}

	// If the unit name is too long
	if len(unit) >= const_unit_name_max {
		return unit_name_invalid
	}

	// If there is no dot in the unit name
	dot := strings.LastIndexByte(unit, '.')
	if dot < 0 || dot == 0 {
		return unit_name_invalid
	}

	// If the .suffix isn't a real unit type
	utype := unit[dot+1:]
	found := false
	for _, _utype := range const_unit_types {
		if utype == _utype {
			found = true
			break
		}
	}
	if !found {
		return unit_name_invalid
	}

	at := strings.IndexByte(unit, '@')

	// If the unit has more than one '@'
	if at >= 0 && strings.IndexByte(unit[at+1:], '@') >= 0 {
		return unit_name_invalid
	}

	// If the '@' is at the start of the unit
	if at == 0 {
		return unit_name_invalid
	}

	if at < 0 {
		return unit_name_plain
	} else {
		if dot > at+1 {
			return unit_name_instance
		}
		if dot == at+1 {
			return unit_name_template
		}
	}

	return unit_name_invalid
}