Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Microsoft.Win32;
using Pharmacy_Management_Sysytem.BusinessLogic;
using Pharmacy_Management_Sysytem.Common;
using Pharmacy_Management_Sysytem.Models;
using Pharmacy_Management_Sysytem.Services;

namespace Pharmacy_Management_Sysytem
{
    /// <summary>
    /// Sign-in form for user authentication
    /// </summary>
    public partial class signInForm : Form
    {
        private readonly IUserService _userService;

        /// <summary>
        /// Initializes a new instance of the signInForm class
        /// </summary>
        public signInForm()
        {
            InitializeComponent();
            _userService = Program.Services.UserService;
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Color Black  = Color.Black;
            Pen pen = new Pen(Black);
            pen.Width = 10;
            e.Graphics.DrawLine(pen, 500, 50, 500, 510);
        }

        /// <summary>
        /// Handles the sign-in button click event
        /// </summary>
        /// <param name="sender">The event sender</param>
        /// <param name="e">The event arguments</param>
        private void btnSignIn_Click(object sender, EventArgs e)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(txtBoxUserName.Text) || string.IsNullOrWhiteSpace(txtBoxPassword.Text))
                {
                    MessageBox.Show("Please enter both username and password.", "Validation Error", 
                                  MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    return;
                }

                // Check if this is the first time (no users in database) - use default admin
                var allUsersResult = _userService.GetAllUsers();
                if (allUsersResult.IsSuccess && allUsersResult.Data.Count == 0)
                {
                    // First time setup - use default admin credentials
                    if (txtBoxUserName.Text == Configuration.DefaultAdminUsername && 
                        txtBoxPassword.Text == Configuration.DefaultAdminPassword)
                    {
                        SaveCredentialsToRegistry();
                        var adminForm = new adminstratorForm();
                        adminForm.Show();
                        this.Hide();
                        return;
                    }
                    else
                    {
                        MessageBox.Show("Wrong User Name Or Password.", "Authentication Error", 
                                      MessageBoxButtons.OK, MessageBoxIcon.Error);
                        return;
                    }
                }

                // Authenticate user using the service layer
                var authResult = _userService.AuthenticateUser(txtBoxUserName.Text, txtBoxPassword.Text);
                if (authResult.IsSuccess)
                {
                    var user = authResult.Data;
                    SaveCredentialsToRegistry();

                    if (user.UserRole == UserRole.Administrator)
                    {
                        var adminForm = new adminstratorForm(user.UserName);
                        adminForm.Show();
                        this.Hide();
                    }
                    else if (user.UserRole == UserRole.Pharmacist)
                    {
                        var pharmacistForm = new PharmacistForm();
                        pharmacistForm.Show();
                        this.Hide();
                    }
                    else
                    {
                        MessageBox.Show("Invalid user role.", "Authentication Error", 
                                      MessageBoxButtons.OK, MessageBoxIcon.Error);
                    }
                }
                else
                {
                    MessageBox.Show($"Authentication failed: {authResult.ErrorMessage}\n\nPlease check:\n1. Database connection\n2. Username and password\n3. Database has users table with data", "Authentication Error", 
                                  MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show($"An error occurred during sign-in: {ex.Message}", "Error", 
                              MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        /// <summary>
        /// Saves user credentials to the Windows registry for auto-login
        /// </summary>
        private void SaveCredentialsToRegistry()
        {
            try
            {
                string keyPath = @"HKEY_CURRENT_USER\SOFTWARE\Pharmacy";
                Registry.SetValue(keyPath, "UserName", txtBoxUserName.Text, RegistryValueKind.String);
                Registry.SetValue(keyPath, "Password", txtBoxPassword.Text, RegistryValueKind.String);
            }
            catch (Exception ex)
            {
                // Log the error but don't show to user as this is not critical
                System.Diagnostics.Debug.WriteLine($"Failed to save credentials to registry: {ex.Message}");
            }
        }

        private void signInForm_Load(object sender, EventArgs e)
        {
            string keyPath = @"HKEY_CURRENT_USER\SOFTWARE\Pharmacy";

            string userName = "UserName";
           
            string passWord = "Password";
            

            try
            {
               string userData =  Registry.GetValue(keyPath, userName, null) as string;
                string passWordData = Registry.GetValue(keyPath, passWord, null) as string;

                if (userData != null)
                {
                    txtBoxUserName.Text = userData;
                }
                if (passWordData != null)
                {
                    txtBoxPassword.Text = passWordData;
                }
            }
            catch { 
            
            
            
            }
        }
    }
}