ERP_Auth_Service/Utility/ThirdPartyService.cs

using AuthHex.Models.IOs;
using AuthHex.DTOs;
using System.Text.Json;
using System.Net.Mail;
using System.Net;
using System.Security.Cryptography;
using System.Text;

namespace AuthHex.Utility
{
    public class ThirdPartyService
    {
        private readonly IConfiguration _config;
        private readonly HttpClient _httpClient;

        public ThirdPartyService(IConfiguration config, HttpClient httpClient)
        {
            _config = config;
            _httpClient = httpClient;
        }

        public async Task<ApiResponse> EmailConfiguration(string email, string otpCode, string? subject = null, string? body = null)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(email))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Email is required"
                    };
                }

                if (string.IsNullOrWhiteSpace(otpCode))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "OTP code is required"
                    };
                }

                var testEmail = email;

                var result = await SendEmailAsync(testEmail, otpCode, subject, body);

                return new ApiResponse
                {
                    StatusCode = result.Success ? 200 : 500,
                    Data = new
                    {
                        testEmail,
                        success = result.Success
                    },
                    Message = result.Message
                };
            }
            catch (Exception ex)
            {
                return new ApiResponse
                {
                    StatusCode = 500,
                    Message = ex.Message
                };
            }
        }

        public async Task<OtpResponse> SendSmsAsync(string mobileNumber, string otpCode, string? message = null)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(mobileNumber))
                {
                    return new OtpResponse
                    {
                        StatusCode = 400,
                        Message = "Mobile number is required"
                    };
                }

                if (string.IsNullOrWhiteSpace(otpCode))
                {
                    return new OtpResponse
                    {
                        StatusCode = 400,
                        Message = "OTP code is required"
                    };
                }

                string contactNumber = mobileNumber;
                string apiUrl = _config["Sms:ApiUrl"] ?? "https://backup.introps.com/Sms_common/send_sms";
                string apiKey = Environment.GetEnvironmentVariable("SMS_API_KEY") ?? _config["Sms:ApiKey"] ?? "8989898989";

                var msgText = string.IsNullOrWhiteSpace(message) ? $"Your otp code is: {otpCode}" : message;

                var smsRequest = new SmsRequest
                {
                    api_key = apiKey,
                    phone_number = contactNumber,
                    msg_text = msgText
                };

                var formContent = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair<string, string>("api_key", smsRequest.api_key),
                    new KeyValuePair<string, string>("phone_number", smsRequest.phone_number),
                    new KeyValuePair<string, string>("msg_text", smsRequest.msg_text)
                });

                var response = await _httpClient.PostAsync(apiUrl, formContent);
                var responseContent = await response.Content.ReadAsStringAsync();

                if (response.IsSuccessStatusCode && responseContent.Contains("agent:d"))
                {
                    string jsonString = responseContent.Split(new[] { "agent:d" }, StringSplitOptions.None)[1];

                    var responseJson = JsonSerializer.Deserialize<Dictionary<string, object>>(jsonString);

                    if (responseJson is not null &&
                        responseJson.TryGetValue("stt", out var statusValue) &&
                        statusValue?.ToString() == "ok")
                    {
                        Console.WriteLine($"SMS OTP {otpCode} sent to {contactNumber}");
                        return new OtpResponse
                        {
                            StatusCode = 200,
                            Message = "OTP sent successfully."
                        };
                    }
                }

                Console.WriteLine($"Failed to send SMS OTP to {contactNumber}. Response: {responseContent}");
                return new OtpResponse
                {
                    StatusCode = 500,
                    Message = "Failed to send OTP.",
                    ApiResponse = responseContent
                };
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Exception sending OTP: {ex.Message}");

                return new OtpResponse
                {
                    StatusCode = 500,
                    Message = "Exception occurred while sending OTP.",
                    Error = ex.Message
                };
            }
        }

        private async Task<(bool Success, string Message)> SendEmailAsync(string email, string code, string? subject = null, string? body = null)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(email))
                {
                    return (false, "Email address is required");
                }

                string smtpHost = _config["SmtpSettings:SmtpServer"] ?? "smtp.hostinger.com";
                int smtpPort = int.Parse(_config["SmtpSettings:SmtpPort"] ?? "587");
                string? senderEmail = _config["SmtpSettings:SenderEmail"] ?? Environment.GetEnvironmentVariable("SMTP_USER");
                string? senderPassword = _config["SmtpSettings:SmtpPassword"] ?? Environment.GetEnvironmentVariable("SMTP_PASSWORD");
                string senderName = _config["SmtpSettings:SenderName"] ?? "Hexa Fitness";

                if (string.IsNullOrWhiteSpace(senderEmail) || string.IsNullOrWhiteSpace(senderPassword))
                {
                    return (false, "Email configuration is missing");
                }

                using (var smtpClient = new SmtpClient(smtpHost, smtpPort))
                {
                    smtpClient.Credentials = new NetworkCredential(senderEmail, senderPassword);
                    smtpClient.EnableSsl = true;
                    smtpClient.Timeout = 10000;

                    var emailSubject = string.IsNullOrWhiteSpace(subject) ? "Your OTP Code" : subject;

                    var emailBody = string.IsNullOrWhiteSpace(body) ? $@"
                        <html>
                            <body style='font-family: Arial, sans-serif;'>
                                <h2>OTP Verification</h2>
                                <p>Your OTP code is:</p>
                                <h1 style='color: #007bff; letter-spacing: 2px;'>{code}</h1>
                                <p>This code will expire in 10 minutes.</p>
                                <p>If you did not request this code, please ignore this email.</p>
                            </body>
                        </html>" : body.Replace("{code}", code);

                    var mailMessage = new MailMessage
                    {
                        From = new MailAddress(senderEmail, senderName),
                        Subject = emailSubject,
                        Body = emailBody,
                        IsBodyHtml = true
                    };

                    mailMessage.To.Add(email);

                    await smtpClient.SendMailAsync(mailMessage);

                    Console.WriteLine($"Email OTP {code} sent to {email}");
                    return (true, "Email sent successfully");
                }
            }
            catch (SmtpException ex)
            {
                Console.WriteLine($"SMTP Error sending email: {ex.Message}");
                return (false, $"Failed to send email: {ex.Message}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Exception sending email: {ex.Message}");
                return (false, $"Exception occurred: {ex.Message}");
            }
        }


        public string GenerateSecretKey(int? length = null)
        {
            var keyLength = length ?? int.Parse(_config["GoogleAuthenticator:SecretKeyLength"] ?? "32");
            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
            var random = new Random();
            var secret = new StringBuilder(keyLength);
            
            for (int i = 0; i < keyLength; i++)
            {
                secret.Append(chars[random.Next(chars.Length)]);
            }
            
            return secret.ToString();
        }

        public string GenerateQrCodeData(string userEmail, string secretKey, string? issuer = null)
        {
            var appIssuer = issuer ?? _config["GoogleAuthenticator:Issuer"] ?? "AuthHex";
            var encodedIssuer = Uri.EscapeDataString(appIssuer);
            var encodedEmail = Uri.EscapeDataString(userEmail);
            
            return $"otpauth://totp/{encodedIssuer}:{encodedEmail}?secret={secretKey}&issuer={encodedIssuer}";
        }

        public string GenerateTotpCode(string secretKey, DateTime? timeStamp = null)
        {
            var time = timeStamp ?? DateTime.UtcNow;
            var unixTime = ((DateTimeOffset)time).ToUnixTimeSeconds();
            var timeWindow = int.Parse(_config["GoogleAuthenticator:TimeWindowSeconds"] ?? "30");
            var timeStep = unixTime / timeWindow;
            
            var secretBytes = Base32Decode(secretKey);
            var timeBytes = BitConverter.GetBytes(timeStep);
            
            if (BitConverter.IsLittleEndian)
            {
                Array.Reverse(timeBytes);
            }
            
            using (var hmac = new HMACSHA1(secretBytes))
            {
                var hash = hmac.ComputeHash(timeBytes);
                var offset = hash[hash.Length - 1] & 0x0F;
                
                var code = ((hash[offset] & 0x7F) << 24) |
                          ((hash[offset + 1] & 0xFF) << 16) |
                          ((hash[offset + 2] & 0xFF) << 8) |
                          (hash[offset + 3] & 0xFF);
                
                return (code % 1000000).ToString("D6");
            }
        }

        public bool ValidateTotpCode(string secretKey, string userCode, int? windowSize = null)
        {
            if (string.IsNullOrWhiteSpace(secretKey) || string.IsNullOrWhiteSpace(userCode))
            {
                return false;
            }

            var validationWindow = windowSize ?? int.Parse(_config["GoogleAuthenticator:ValidationWindowSize"] ?? "1");
            var timeWindow = int.Parse(_config["GoogleAuthenticator:TimeWindowSeconds"] ?? "30");
            var currentTime = DateTime.UtcNow;
            
            for (int i = -validationWindow; i <= validationWindow; i++)
            {
                var timeToCheck = currentTime.AddSeconds(i * timeWindow);
                var generatedCode = GenerateTotpCode(secretKey, timeToCheck);
                
                if (generatedCode == userCode)
                {
                    return true;
                }
            }
            
            return false;
        }

        public async Task<ApiResponse> InitiateTwoFASetup(string userEmail, string? userName = null)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(userEmail))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Email is required"
                    };
                }

                var secretKey = GenerateSecretKey();
                var issuer = _config["GoogleAuthenticator:Issuer"] ?? "AuthHex";
                var qrCodeData = GenerateQrCodeData(userEmail, secretKey, issuer);
                var displayName = string.IsNullOrWhiteSpace(userName) ? userEmail : userName;

                return new ApiResponse
                {
                    StatusCode = 200,
                    Data = new
                    {
                        secretKey,
                        qrCodeData,
                        manualEntryKey = FormatSecretForManualEntry(secretKey),
                        userEmail,
                        displayName,
                        issuer,
                        setupInstructions = new
                        {
                            step1 = "Install Google Authenticator app on your mobile device",
                            step2 = "Scan the QR code or enter the manual key",
                            step3 = "Enter the 6-digit code from your app to verify setup"
                        }
                    },
                    Message = "2FA setup initiated. Please verify with your authenticator app to complete setup."
                };
            }
            catch (Exception ex)
            {
                return new ApiResponse
                {
                    StatusCode = 500,
                    Message = ex.Message
                };
            }
        }

        public async Task<ApiResponse> CompleteTwoFASetup(string secretKey, string verificationCode, string? userEmail = null)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(secretKey))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Secret key is required"
                    };
                }

                if (string.IsNullOrWhiteSpace(verificationCode))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Verification code is required"
                    };
                }

                // Validate the code to ensure user has successfully set up their authenticator
                var isValid = ValidateTotpCode(secretKey, verificationCode);

                if (!isValid)
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Invalid verification code. Please check your authenticator app and try again."
                    };
                }

                return new ApiResponse
                {
                    StatusCode = 200,
                    Data = new
                    {
                        secretKey,
                        isVerified = true,
                        verifiedAt = DateTime.UtcNow,
                        userEmail,
                        backupCodes = GenerateBackupCodes() // Generate backup codes for recovery
                    },
                    Message = "2FA setup completed successfully. Please save your backup codes in a secure location."
                };
            }
            catch (Exception ex)
            {
                return new ApiResponse
                {
                    StatusCode = 500,
                    Message = ex.Message
                };
            }
        }

        public async Task<ApiResponse> VerifyTwoFACode(string secretKey, string code)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(secretKey))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Secret key is required"
                    };
                }

                if (string.IsNullOrWhiteSpace(code))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Verification code is required"
                    };
                }

                var isValid = ValidateTotpCode(secretKey, code);

                return new ApiResponse
                {
                    StatusCode = isValid ? 200 : 400,
                    Data = new
                    {
                        isValid,
                        timestamp = DateTime.UtcNow,
                        remainingTime = GetRemainingTimeInCurrentWindow()
                    },
                    Message = isValid ? "Code verified successfully" : "Invalid or expired code"
                };
            }
            catch (Exception ex)
            {
                return new ApiResponse
                {
                    StatusCode = 500,
                    Message = ex.Message
                };
            }
        }

        public async Task<ApiResponse> DisableTwoFA(string secretKey, string verificationCode)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(secretKey))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Secret key is required"
                    };
                }

                if (string.IsNullOrWhiteSpace(verificationCode))
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Verification code is required to disable 2FA"
                    };
                }

                // Require valid code to disable 2FA for security
                var isValid = ValidateTotpCode(secretKey, verificationCode);

                if (!isValid)
                {
                    return new ApiResponse
                    {
                        StatusCode = 400,
                        Message = "Invalid verification code. Cannot disable 2FA without valid code."
                    };
                }

                return new ApiResponse
                {
                    StatusCode = 200,
                    Data = new
                    {
                        disabled = true,
                        disabledAt = DateTime.UtcNow
                    },
                    Message = "2FA has been disabled successfully"
                };
            }
            catch (Exception ex)
            {
                return new ApiResponse
                {
                    StatusCode = 500,
                    Message = ex.Message
                };
            }
        }

        private string[] GenerateBackupCodes(int count = 10)
        {
            var codes = new string[count];
            var random = new Random();
            
            for (int i = 0; i < count; i++)
            {
                codes[i] = random.Next(100000, 999999).ToString();
            }
            
            return codes;
        }

        private int GetRemainingTimeInCurrentWindow()
        {
            var timeWindow = int.Parse(_config["GoogleAuthenticator:TimeWindowSeconds"] ?? "30");
            var currentTime = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
            var remainingSeconds = timeWindow - (currentTime % timeWindow);
            return (int)remainingSeconds;
        }

        
        private byte[] Base32Decode(string input)
        {
            if (string.IsNullOrEmpty(input))
                throw new ArgumentException("Input cannot be null or empty");

            input = input.TrimEnd('=').ToUpper();
            var output = new List<byte>();
            var bits = 0;
            var bitsCount = 0;

            foreach (char c in input)
            {
                var value = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567".IndexOf(c);
                if (value < 0)
                    throw new ArgumentException($"Invalid character in Base32 string: {c}");

                bits = (bits << 5) | value;
                bitsCount += 5;

                if (bitsCount >= 8)
                {
                    output.Add((byte)(bits >> (bitsCount - 8)));
                    bitsCount -= 8;
                }
            }

            return output.ToArray();
        }

        private string FormatSecretForManualEntry(string secret)
        {
            return string.Join(" ", Enumerable.Range(0, secret.Length / 4)
                .Select(i => secret.Substring(i * 4, 4)));
        }

    }

}