// Copyright 2014 Claudemiro Alves Feitosa Neto. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package utils

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"math"
	"math/rand"
	"regexp"
	"strings"
)

var validChannelName *regexp.Regexp

func init() {
	validChannelName = regexp.MustCompile("^[A-Za-z0-9_\\-=@,.;]+$")
}

// HashMAC Calculates the MAC signing with the given key and returns the hexadecimal encoded Result
func HashMAC(message, key []byte) string {
	mac := hmac.New(sha256.New, key)
	mac.Write(message)
	expected := mac.Sum(nil)

	return hex.EncodeToString(expected)
}

// GenerateSessionID Generate a new random Hash
func GenerateSessionID() string {
	return fmt.Sprintf("%d.%d", rand.Intn(math.MaxInt64), rand.Intn(math.MaxInt64))
}

// IsChannelNameValid Verify if the channel name is valid
func IsChannelNameValid(channelName string) bool {
	return validChannelName.Match([]byte(channelName))
}

func IsPrivateChannel(channelName string) bool {
	return strings.HasPrefix(channelName, "private-")
}

func IsPresenceChannel(channelName string) bool {
	return strings.HasPrefix(channelName, "presence-")
}