/*
Rating system designed to be used in VoIP Carriers World
Copyright (C) 2013 ITsysCOM

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>
*/

package utils

import (
	"crypto/rand"
	"crypto/sha1"
	"encoding/hex"
	"fmt"
	"strconv"
	"time"
)

// Returns first non empty string out of vals. Useful to extract defaults
func FirstNonEmpty(vals ...string) string {
	for _, val := range vals {
		if len(val) != 0 {
			return val
		}
	}
	return ""
}

func FSCgrId(uuid string) string {
	hasher := sha1.New()
	hasher.Write([]byte(uuid))
	return fmt.Sprintf("%x", hasher.Sum(nil))
}

func NewTPid() string {
	hasher := sha1.New()
	uuid := GenUUID()
	hasher.Write([]byte(uuid))
	return fmt.Sprintf("%x", hasher.Sum(nil))
}

// helper function for uuid generation
func GenUUID() string {
	uuid := make([]byte, 16)
	n, err := rand.Read(uuid)
	if n != len(uuid) || err != nil {
		return strconv.FormatInt(time.Now().UnixNano(), 10)
	}
	// TODO: verify the two lines implement RFC 4122 correctly
	uuid[8] = 0x80 // variant bits see page 5
	uuid[4] = 0x40 // version 4 Pseudo Random, see page 7

	return hex.EncodeToString(uuid)
}