// Copyright (C) 2016 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 (
	"strings"
)

func valid_session_name(id string) bool {
	if id == "" {
		return false
	}

	return strings.TrimLeft(id, letters+digits) == ""
}

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

func valid_machine_name(s string) bool {
	if len(s) > 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 s {
		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
}

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
	unit_name_any      = unit_name_plain | unit_name_instance | unit_name_template
)

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
}