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

namespace Journal.WebGateway.Security;

public static class GatewayPasswordHasher
{
    private const string AlgorithmName = "PBKDF2-SHA256";
    private const int SaltSize = 16;
    private const int KeySize = 32;
    private const int IterationCount = 600_000;

    public static string HashPassword(string password)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(password);

        var salt = RandomNumberGenerator.GetBytes(SaltSize);
        var key = Rfc2898DeriveBytes.Pbkdf2(
            Encoding.UTF8.GetBytes(password),
            salt,
            IterationCount,
            HashAlgorithmName.SHA256,
            KeySize);

        return string.Join(
            '$',
            AlgorithmName,
            IterationCount.ToString(System.Globalization.CultureInfo.InvariantCulture),
            Convert.ToBase64String(salt),
            Convert.ToBase64String(key));
    }

    public static bool VerifyPassword(string password, string passwordHash)
    {
        if (string.IsNullOrWhiteSpace(password) || string.IsNullOrWhiteSpace(passwordHash))
            return false;

        var parts = passwordHash.Split('$', StringSplitOptions.None);
        if (parts.Length != 4)
            return false;

        if (!string.Equals(parts[0], AlgorithmName, StringComparison.Ordinal))
            return false;

        if (!int.TryParse(parts[1], out var iterations) || iterations <= 0)
            return false;

        byte[] salt;
        byte[] expectedKey;
        try
        {
            salt = Convert.FromBase64String(parts[2]);
            expectedKey = Convert.FromBase64String(parts[3]);
        }
        catch (FormatException)
        {
            return false;
        }

        var actualKey = Rfc2898DeriveBytes.Pbkdf2(
            Encoding.UTF8.GetBytes(password),
            salt,
            iterations,
            HashAlgorithmName.SHA256,
            expectedKey.Length);

        return CryptographicOperations.FixedTimeEquals(actualKey, expectedKey);
    }
}