using System;
using System.Data.SqlClient;
using Microsoft.AspNetCore.Cryptography.KeyDerivation;

namespace SecureCore.Authentication
{
    public class PasswordManager
    {
        private static string ConnectionString = @"Server=DESKTOP-OEDDVKC\SQLEXPRESS;Database=main;Integrated Security=true;";

        public PasswordManager()
        {
        }

        public static (string Hash, string Salt) HashPassword(string password)
        {
            var salt = new byte[Settings.SaltSize];

            ByteGenerator.GetRandomBytes(ref salt);

            return (GetPasswordHash(password, salt), Convert.ToBase64String(salt));
        }

        public static bool PasswordIsValid(string password, string salt, string passwordHash)
        {
            var saltBytes = Convert.FromBase64String(salt);

            return passwordHash == GetPasswordHash(password, saltBytes);
        }

        public static (string PasswordHash, string SaltHash) GetUserPasswordHash(int userId)
        {
            using (var connection = new SqlConnection(ConnectionString))
            {
                using (var command = new SqlCommand("SELECT [Password Hash], [Salt Hash] FROM Login WHERE [User Key] = @UserId", connection))
                {
                    command.Parameters.AddWithValue("UserId", userId);

                    connection.Open();

                    var reader = command.ExecuteReader();

                    if (!reader.HasRows) throw new MissingFieldException("No login records exist for this user.");

                    reader.Read();

                    return (reader["Password Hash"].ToString(), reader["Salt Hash"].ToString());
                }
            }
        }

        private static string GetPasswordHash(string password, byte[] salt)
        {
            return Convert.ToBase64String(KeyDerivation.Pbkdf2(password, salt, Settings.KeyType, Settings.Iterations, Settings.KeySize));
        }
    }
}