using System.Net;
using System.Text;
using MySql.Data.MySqlClient;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System.Security.Claims;
using System.IdentityModel.Tokens.Jwt;
using Microsoft.IdentityModel.Tokens;
using System.Security.Cryptography;

namespace Server
{
    public class Login : Route
    {
        private static string secretKey = "stronk-key-much-sercret-much-more-stronk-stronk-key-much-sercret-much-more-stronk";

        public static string GenerateToken(string user)
        {
            var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(secretKey));
            var creds = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);

            var token = new JwtSecurityToken(
                issuer: "TimeLogServer",
                audience: "TimeLogWebsite",
                claims: new[]
                {
                new Claim("user", user)
                },
                expires: DateTime.Now.AddHours(2),
                signingCredentials: creds
            );

            return new JwtSecurityTokenHandler().WriteToken(token);
        }

        public static bool VerifyPassword(string enteredPassword, string storedHash)
        {
            byte[] hashBytes = Convert.FromBase64String(storedHash);

            // Extract the salt from the stored hash
            byte[] salt = new byte[16];
            Array.Copy(hashBytes, 0, salt, 0, 16);

            // Hash the entered password with the stored salt
            using (var pbkdf2 = new Rfc2898DeriveBytes(enteredPassword, salt, 10000, HashAlgorithmName.SHA256))
            {
                byte[] newHash = pbkdf2.GetBytes(32);

                // Compare the computed hash with the stored hash
                for (int i = 0; i < 32; i++)
                {
                    if (newHash[i] != hashBytes[i + 16])
                        return false;
                }
                return true;
            }
        }

        public static void HandleRequest(HttpListenerRequest request, HttpListenerResponse response)
        {
            try
            {
                // extract data from body
                string body;
                using (StreamReader bodyReader = new StreamReader(request.InputStream, request.ContentEncoding))
                {
                    body = bodyReader.ReadToEnd();
                }
                JObject jsonObject = JObject.Parse(body);
                string mail = jsonObject["mail"]?.ToString() ?? "";
                string password = jsonObject["password"]?.ToString() ?? "";

                // prepare SQL query
                MySqlCommand cmd = new MySqlCommand();
                cmd.CommandText = @"SELECT u.id, password FROM User u 
                  INNER JOIN Password p ON p.user=u.id 
                  WHERE mail=@mail;";
                cmd.Parameters.AddWithValue("@mail", mail);

                using (MySqlConnection conn = new MySqlConnection(connectionString))
                {
                    cmd.Connection = conn;
                    conn.Open();
                    // execute query and read results
                    MySqlDataReader reader = cmd.ExecuteReader();
                    string? userId = "";
                    string? hashedPass = "";
                    string? jsonResponse;
                    while (reader.Read())
                    {
                        userId = Convert.ToString(reader["id"]);
                        hashedPass = reader.GetString("password");
                    }

                    // check username
                    if (string.IsNullOrEmpty(userId))
                    {
                        throw new Exception("Invalid Username or Password");
                    }
                    //check password
                    if (string.IsNullOrEmpty(password)
                        || string.IsNullOrEmpty(hashedPass)
                        || !VerifyPassword(password, hashedPass))
                    {
                        throw new Exception("Invalid Username or Password");
                    }

                    jsonResponse = JsonConvert.SerializeObject(GenerateToken(userId));

                    // prepare response
                    SendSuccess(response, jsonResponse);
                }
            }
            catch (Exception ex)
            {
                SendError(response, ex);
            }
        }
    }
}