/*
 * Copyright (c) 2025. Proton AG
 *
 * This file is part of ProtonVPN and modified for Cloak.
 *
 * ProtonVPN 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.
 *
 * ProtonVPN 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 ProtonVPN.  If not, see <https://www.gnu.org/licenses/>.
 */

package server_name_utils

import (
	cryptoRand "crypto/rand"
	"fmt"
	"math/big"
	"math/rand"
)

type ServerNameStrategy int

const (
	ServerNameRandom ServerNameStrategy = iota
	ServerNameTop
	ServerNameHuman = 2
)

var topLevelDomains = []string{"com", "net", "org", "it", "fr", "me", "ru", "cn", "es", "tr", "top", "xyz", "info"}

var domains = []string{
	"accounts.google.com",
	"activity.windows.com",
	"analytics.apis.mcafee.com",
	"android.apis.google.com",
	"android.googleapis.com",
	"api.account.samsung.com",
	"api.accounts.firefox.com",
	"api.accuweather.com",
	"api.amazon.com",
	"api.browser.yandex.net",
	"api.ipify.org",
	"api.onedrive.com",
	"api.reasonsecurity.com",
	"api.samsungcloud.com",
	"api.sec.intl.miui.com",
	"api.vk.com",
	"api.weather.com",
	"app-site-association.cdn-apple.com",
	"apps.mzstatic.com",
	"assets.msn.com",
	"backup.googleapis.com",
	"brave-core-ext.s3.brave.com",
	"caldav.calendar.yahoo.com",
	"cc-api-data.adobe.io",
	"cdn.ampproject.org",
	"cdn.cookielaw.org",
	"client.wns.windows.com",
	"cloudflare.com",
	"cloudflare-dns.com",
	"cloudflare-ech.com",
	"config.extension.grammarly.com",
	"connectivitycheck.android.com",
	"connectivitycheck.gstatic.com",
	"courier.push.apple.com",
	"crl.globalsign.com",
	"dc1-file.ksn.kaspersky-labs.com",
	"dl.google.com",
	"dns.google",
	"dns.quad9.net",
	"doh.cleanbrowsing.org",
	"doh.dns.apple.com",
	"doh.opendns.com",
	"doh.pub",
	"ds.kaspersky.com",
	"ecs.office.com",
	"edge.microsoft.com",
	"events.gfe.nvidia.com",
	"excess.duolingo.com",
	"firefox.settings.services.mozilla.com",
	"fonts.googleapis.com",
	"fonts.gstatic.com",
	"gateway-asset.icloud-content.com",
	"gateway.icloud.com",
	"gdmf.apple.com",
	"github.com",
	"go.microsoft.com",
	"go-updater.brave.com",
	"graph.microsoft.com",
	"gs-loc.apple.com",
	"gtglobal.intl.miui.com",
	"hcaptcha.com",
	"imap.gmail.com",
	"imap-mail.outlook.com",
	"imap.mail.yahoo.com",
	"in.appcenter.ms",
	"ipmcdn.avast.com",
	"itunes.apple.com",
	"loc.map.baidu.com",
	"login.live.com",
	"login.microsoftonline.com",
	"m.media-amazon.com",
	"mobile.events.data.microsoft.com",
	"mozilla.cloudflare-dns.com",
	"mtalk.google.com",
	"nimbus.bitdefender.net",
	"ocsp2.apple.com",
	"outlook.office365.com",
	"play-fe.googleapis.com",
	"play.googleapis.com",
	"play.samsungcloud.com",
	"raw.githubusercontent.com",
	"s3.amazonaws.com",
	"safebrowsing.googleapis.com",
	"s.alicdn.com",
	"self.events.data.microsoft.com",
	"settings-win.data.microsoft.com",
	"setup.icloud.com",
	"sirius.mwbsys.com",
	"spoc.norton.com",
	"ssl.gstatic.com",
	"translate.goo",
	"unpkg.com",
	"update.googleapis.com",
	"weatherapi.intl.xiaomi.com",
	"weatherkit.apple.com",
	"westus-0.in.applicationinsights.azure.com",
	"www.googleapis.com",
	"www.gstatic.com",
	"www.msftconnecttest.com",
	"www.msftncsi.com",
	"www.ntppool.org",
	"www.pool.ntp.org",
	"www.recaptcha.net",
}

// Data pools for linguistic generation
var prefixes = []string{
	"cloud",
	"global", "fast", "secure", "smart", "net", "data", "prime", "alpha", "edge"}
var suffixes = []string{"logic", "stream", "flow", "point", "nexus", "bridge", "lab", "hub", "tech", "base"}
var syllables = []string{"ver", "ant", "ix", "cor", "mon", "tel", "al", "is", "ex", "ta", "vi", "ro"}
var apiRoots = []string{"assets-delivery", "static-cache", "api-gateway", "edge-compute", "cdn-services"}

var domainsSortedByHashes = sortValuesByHash(domains, crc32Hash)

func ServerNameFor(strategy ServerNameStrategy, addr string) string {
	switch strategy {
	case ServerNameTop:
		return serverNameForAddr(addr)
	case ServerNameRandom:
		return randomServerName()
	case ServerNameHuman:
		return randomHumanReadableServerName()
	default:
		return randomServerName()
	}
}

func serverNameForAddr(addr string) string {
	return findClosestValue(addr, domainsSortedByHashes, crc32Hash)
}

func randomServerName() string {
	charNum := int('z') - int('a') + 1
	size := 3 + randInt(10)
	name := make([]byte, size)
	for i := range name {
		name[i] = byte(int('a') + randInt(charNum))
	}
	return string(name) + "." + randItem(topLevelDomains)
}

func randItem(list []string) string {
	return list[randInt(len(list))]
}

func randInt(n int) int {
	size, err := cryptoRand.Int(cryptoRand.Reader, big.NewInt(int64(n)))
	if err == nil {
		return int(size.Int64())
	}
	return rand.Intn(n)
}

func randomHumanReadableServerName() string {
	// Randomly choose a generation style (0: Dictionary, 1: Phonetic, 2: API Mask)
	style := rand.Intn(3)
	var domain string

	switch style {
	case 0: // Dictionary-based (e.g., "secure-bridge.com")
		domain = randItem(prefixes) + "-" + randItem(suffixes) + "." + randItem(topLevelDomains)

	case 1: // Phonetic/Brandable (e.g., "verantix.net")
		// Combine 2 to 3 syllables
		name := ""
		for j := 0; j < (rand.Intn(2) + 2); j++ {
			name += randItem(syllables)
		}
		domain = name + "." + randItem(topLevelDomains)

	case 2: // API/CDN Masking (e.g., "v2-node-42.static-cache.net")
		vNum := rand.Intn(4) + 1
		nodeNum := rand.Intn(90) + 10
		root := randItem(apiRoots)
		tld := ".net"
		if rand.Intn(2) == 0 {
			tld = ".com"
		}
		domain = fmt.Sprintf("v%d-node-%d.%s%s", vNum, nodeNum, root, tld)
	}

	return domain
}