/*
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"
	"math"
	"strconv"
	"strings"
	"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)
}

// Round return rounded version of x with prec precision.
//
// Special cases are:
//	Round(±0) = ±0
//	Round(±Inf) = ±Inf
//	Round(NaN) = NaN
func Round(x float64, prec int, method string) float64 {
	var rounder float64
	pow := math.Pow(10, float64(prec))
	intermed := x * pow
	_, frac := math.Modf(intermed)

	switch method {
	case ROUNDING_UP:
		rounder = math.Ceil(intermed)
	case ROUNDING_DOWN:
		rounder = math.Floor(intermed)
	case ROUNDING_MIDDLE:
		if frac >= 0.5 {
			rounder = math.Ceil(intermed)
		} else {
			rounder = math.Floor(intermed)
		}
	default:
		rounder = intermed
	}

	return rounder / pow
}

func ParseDate(date string) (expDate time.Time, err error) {
	date = strings.TrimSpace(date)
	switch {
	case date == "*unlimited" || date == "":
		// leave it at zero
	case strings.HasPrefix(date, "+"):
		d, err := time.ParseDuration(date[1:])
		if err != nil {
			return expDate, err
		}
		expDate = time.Now().Add(d)
	case date == "*monthly":
		expDate = time.Now().AddDate(0, 1, 0) // add one month
	case strings.HasSuffix(date, "Z"):
		expDate, err = time.Parse(time.RFC3339, date)
	default:
		unix, err := strconv.ParseInt(date, 10, 64)
		if err != nil {
			return expDate, err
		}
		expDate = time.Unix(unix, 0)
	}
	return expDate, err
}