using System;
using System.Text;

namespace Birdmap.Common
{
    public static class PasswordHelper
    {
        public static void CreatePasswordHash(string password, out byte[] passwordHash, out byte[] passwordSalt)
        {
            if (string.IsNullOrWhiteSpace(password)) throw new ArgumentException("Value cannot be null or empty.", "password");

            using var hmac = new System.Security.Cryptography.HMACSHA512();

            passwordSalt = hmac.Key;
            passwordHash = hmac.ComputeHash(Encoding.UTF8.GetBytes(password));
        }

        public static bool VerifyPasswordHash(string password, byte[] storedHash, byte[] storedSalt)
        {
            if (string.IsNullOrWhiteSpace(password)) throw new ArgumentException("Value cannot be null or empty.", nameof(password));
            if (storedHash.Length != 64) throw new ArgumentException("Invalid length of password hash (64 bytes expected).", nameof(storedHash));
            if (storedSalt.Length != 128) throw new ArgumentException("Invalid length of password salt (128 bytes expected).", nameof(storedSalt));

            using var hmac = new System.Security.Cryptography.HMACSHA512(storedSalt);

            var computedHash = hmac.ComputeHash(Encoding.UTF8.GetBytes(password));
            for (int i = 0; i < computedHash.Length; i++)
            {
                if (computedHash[i] != storedHash[i]) return false;
            }

            return true;
        }
    }
}