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#include <algorithm>
#include <cctype>
#include <iostream>
#include <regex>
#include <string>

#include <openssl/sha.h>

std::string normalizeAndHash(std::string email)
{
    email.erase(0, email.find_first_not_of(" \t\n\r\f\v"));
    email.erase(email.find_last_not_of(" \t\n\r\f\v") + 1);
    std::transform(email.begin(), email.end(), email.begin(),
                   [](unsigned char c) { return std::tolower(c); });

    static const std::regex valid("^[!-?A-~]+@[!-?A-~]+$");
    if (!std::regex_match(email, valid))
        return "";

    const auto at = email.find('@');
    std::string local = email.substr(0, at);
    const std::string domain = email.substr(at + 1);
    if (domain == "gmail.com" || domain == "googlemail.com")
    {
        local = local.substr(0, local.find('+'));
        local.erase(std::remove(local.begin(), local.end(), '.'), local.end());
        if (local.empty())
            return "";
    }

    const std::string normalized = local + "@" + domain;
    unsigned char hash[SHA256_DIGEST_LENGTH];
    SHA256(reinterpret_cast<const unsigned char*>(normalized.data()),
           normalized.size(), hash);

    static constexpr char digits[] = "0123456789abcdef";
    std::string out;
    for (const unsigned char value : hash)
    {
        out += digits[value >> 4];
        out += digits[value & 15];
    }
    return out;
}

int main()
{
    std::cout << normalizeAndHash("  J..A.NE+work.more+extra@GMAIL.COM  ") << "\n";
}

using System;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;

class Program
{
    static readonly Regex Valid = new Regex("^[!-?A-~]+@[!-?A-~]+$");

    static string NormalizeAndHash(string email)
    {
        string trimmed = email.Trim(' ', '\t', '\n', '\r', '\f', '\v').ToLowerInvariant();
        if (!Valid.IsMatch(trimmed))
            return "";

        int at = trimmed.IndexOf('@');
        string local = trimmed.Substring(0, at);
        string domain = trimmed.Substring(at + 1);
        if (domain == "gmail.com" || domain == "googlemail.com")
            local = local.Split('+')[0].Replace(".", "");

        if (local.Length == 0)
            return "";

        using (SHA256 sha256 = SHA256.Create())
        {
            byte[] hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(local + "@" + domain));
            StringBuilder output = new StringBuilder(hash.Length * 2);
            foreach (byte value in hash)
                output.Append(value.ToString("x2"));
            return output.ToString();
        }
    }

    static void Main()
    {
        Console.WriteLine(NormalizeAndHash("  J..A.NE+work.more+extra@GMAIL.COM  "));
    }
}

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HexFormat;
import java.util.regex.Pattern;

public final class EmailHash
{
    private static final Pattern VALID = Pattern.compile( "^[!-?A-~]+@[!-?A-~]+$" );

    static String normalizeAndHash( final String email ) throws NoSuchAlgorithmException
    {
        final String trimmed = email.trim().toLowerCase();
        if ( !VALID.matcher( trimmed ).matches() )
        {
            return "";
        }

        final int at = trimmed.indexOf( '@' );
        final String domain = trimmed.substring( at + 1 );
        String local = trimmed.substring( 0, at );
        if ( domain.equals( "gmail.com" ) || domain.equals( "googlemail.com" ) )
        {
            local = local.split( "\\+", 2 )[0].replace( ".", "" );
            if ( local.isEmpty() )
            {
                return "";
            }
        }

        return HexFormat.of().formatHex( MessageDigest.getInstance( "SHA-256" )
                .digest( ( local + "@" + domain ).getBytes( StandardCharsets.UTF_8 ) ) );
    }

    public static void main( final String[] args ) throws NoSuchAlgorithmException
    {
        System.out.println( normalizeAndHash( "  J..A.NE+work.more+extra@GMAIL.COM  " ) );
    }
}

import { createHash } from "crypto";

function normalizeAndHash(email) {
  const trimmed = email.replace(/^[ \t\n\r\f\v]+|[ \t\n\r\f\v]+$/g, "").toLowerCase();
  if (!/^[!-?A-~]+@[!-?A-~]+$/.test(trimmed)) {
    return "";
  }

  const at = trimmed.indexOf("@");
  let local = trimmed.slice(0, at);
  const domain = trimmed.slice(at + 1);
  if (domain === "gmail.com" || domain === "googlemail.com") {
    local = local.split("+")[0].replaceAll(".", "");
  }

  return local ? createHash("sha256").update(`${local}@${domain}`).digest("hex") : "";
}

console.log(normalizeAndHash("  J..A.NE+work.more+extra@GMAIL.COM  "));

import java.security.MessageDigest

private val VALID = Regex("^[!-?A-~]+@[!-?A-~]+$")

fun normalizeAndHash(email: String): String {
    val trimmed = email.trim(' ', '\t', '\n', '\r', '\u000B', '\u000C').lowercase()
    if (!VALID.matches(trimmed)) return ""

    val (rawLocal, domain) = trimmed.split('@')
    val local = if (domain == "gmail.com" || domain == "googlemail.com") {
        rawLocal.substringBefore('+').replace(".", "").ifEmpty { return "" }
    } else rawLocal

    return MessageDigest.getInstance("SHA-256")
        .digest("$local@$domain".toByteArray())
        .joinToString("") { "%02x".format(it) }
}

fun main() {
    println(normalizeAndHash("  J..A.NE+work.more+extra@GMAIL.COM  "))
}

import hashlib
import re

VALID = re.compile(r"^[!-?A-~]+@[!-?A-~]+$")


def normalize_and_hash(email):
    email = email.strip(" \t\n\r\f\v").lower()
    if not VALID.match(email):
        return ""

    local, _, domain = email.partition("@")
    if domain in ("gmail.com", "googlemail.com"):
        local = local.split("+", 1)[0].replace(".", "")

    return hashlib.sha256(f"{local}@{domain}".encode()).hexdigest() if local else ""


print(normalize_and_hash("  J..A.NE+work.more+extra@GMAIL.COM  "))

import CryptoKit
import Foundation

func normalizeAndHash(_ email: String) -> String {
    let trimmed = email.trimmingCharacters(
        in: CharacterSet(charactersIn: " \t\n\r\u{0b}\u{0c}")).lowercased()
    guard trimmed.range(of: "^[!-?A-~]+@[!-?A-~]+$", options: .regularExpression) != nil
    else { return "" }

    let parts = trimmed.split(separator: "@")
    let domain = String(parts[1])
    var local = String(parts[0])
    if domain == "gmail.com" || domain == "googlemail.com" {
        local = local.prefix { $0 != "+" }.filter { $0 != "." }
    }
    guard !local.isEmpty else { return "" }

    return SHA256.hash(data: Data("\(local)@\(domain)".utf8))
        .map { String(format: "%02x", $0) }.joined()
}

print(normalizeAndHash("  J..A.NE+work.more+extra@GMAIL.COM  "))

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