using System.Security.Cryptography;

namespace DXPBLL.Auth;

// PBKDF2 (.NET built-in Rfc2898DeriveBytes) — no external dependency needed. Format:
// "{iterations}.{saltBase64}.{hashBase64}", so the iteration count can be raised later without
// invalidating already-hashed passwords (they just keep verifying against their own stored count).
public static class DXPPasswordHasher
{
    private const int SaltSize       = 16;
    private const int HashSize       = 32;
    private const int Iterations     = 210_000; // OWASP-recommended minimum for PBKDF2-SHA256 (2023+)

    public static string Hash(string password)
    {
        var salt = RandomNumberGenerator.GetBytes(SaltSize);
        var hash = Rfc2898DeriveBytes.Pbkdf2(password, salt, Iterations, HashAlgorithmName.SHA256, HashSize);
        return $"{Iterations}.{Convert.ToBase64String(salt)}.{Convert.ToBase64String(hash)}";
    }

    public static bool Verify(string password, string storedHash)
    {
        var parts = storedHash.Split('.', 3);
        if (parts.Length != 3) return false;

        var iterations = int.Parse(parts[0]);
        var salt       = Convert.FromBase64String(parts[1]);
        var expected   = Convert.FromBase64String(parts[2]);

        var actual = Rfc2898DeriveBytes.Pbkdf2(password, salt, iterations, HashAlgorithmName.SHA256, expected.Length);
        return CryptographicOperations.FixedTimeEquals(actual, expected);
    }
}