using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using Microsoft.Win32;

namespace ThemeToggler
{
    static class Program
    {
        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        private static extern IntPtr SendMessageTimeout(
            IntPtr hWnd, uint Msg, UIntPtr wParam, string lParam, uint fuFlags, uint uTimeout, out UIntPtr lpdwResult);

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern bool DestroyIcon(IntPtr handle);

        [DllImport("user32.dll", SetLastError = true)]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

        [DllImport("user32.dll", SetLastError = true)]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

        private const int WM_SETTINGCHANGE = 0x001A;
        private const uint HWND_BROADCAST = 0xFFFF;
        private const uint SMTO_ABORTIFHUNG = 0x0002;

        private const int HOTKEY_ID = 9000;
        private const uint MOD_ALT = 0x0001;
        private const uint MOD_CONTROL = 0x0002;
        private const uint MOD_WIN = 0x0008;

        public static NotifyIcon? TrayIcon { get; private set; }
        private static ToolStripMenuItem? _startupMenuItem;
        private static IntPtr _currentIconHandle = IntPtr.Zero;

        [STAThread]
        static void Main()
        {
            ApplicationConfiguration.Initialize();

            // Prevents multiple instances
            using (var mutex = new System.Threading.Mutex(true, "ThemeTogglerMutex", out bool createdNew))
            {
                if (!createdNew)
                {
                    MessageBox.Show("ThemeToggler כבר פועל ברקע.", "Theme Toggler", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }

                // Set up tray icon
                TrayIcon = new NotifyIcon();
                TrayIcon.Text = "Theme Toggler";
                TrayIcon.Click += TrayIcon_Click;
                
                // Context Menu
                var contextMenu = new ContextMenuStrip();
                
                var toggleItem = new ToolStripMenuItem("החלף מצב תצוגה", null, (s, e) => ToggleTheme());
                toggleItem.Font = new Font(toggleItem.Font, FontStyle.Bold);
                contextMenu.Items.Add(toggleItem);
                
                contextMenu.Items.Add(new ToolStripSeparator());

                _startupMenuItem = new ToolStripMenuItem("הפעל בעליית המחשב", null, Startup_Click);
                _startupMenuItem.Checked = IsRunAtStartupEnabled();
                contextMenu.Items.Add(_startupMenuItem);

                contextMenu.Items.Add(new ToolStripSeparator());
                
                contextMenu.Items.Add("יציאה", null, (s, e) => Application.Exit());

                TrayIcon.ContextMenuStrip = contextMenu;

                UpdateIcon();
                TrayIcon.Visible = true;

                // Watch registry for external theme changes
                SystemEvents.UserPreferenceChanged += SystemEvents_UserPreferenceChanged;

                // Register Thread-Level Hotkey (hWnd = IntPtr.Zero)
                // This registers the hotkey directly to the message loop thread, avoiding window handle issues.
                bool registered = RegisterHotKey(IntPtr.Zero, HOTKEY_ID, MOD_WIN | MOD_ALT, 0x54); // Win + Alt + T
                if (!registered)
                {
                    // Fallback: Ctrl + Alt + T
                    registered = RegisterHotKey(IntPtr.Zero, HOTKEY_ID, MOD_CONTROL | MOD_ALT, 0x54);
                    if (registered)
                    {
                        // Let the user know via balloon tip
                        TrayIcon.ShowBalloonTip(3000, "Theme Toggler", "קיצור המקשים Win+Alt+T תפוס. הוגדר קיצור דרך חלופי: Ctrl+Alt+T", ToolTipIcon.Info);
                    }
                    else
                    {
                        int errorCode = Marshal.GetLastWin32Error();
                        MessageBox.Show($"שגיאה ברישום קיצור המקשים.\nקוד שגיאה: {errorCode}\nודא שאין תוכנה אחרת המשתמשת בקיצורים אלו במקביל.", "Theme Toggler", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    }
                }

                // Add message filter to intercept hotkey messages
                var filter = new HotkeyMessageFilter();
                Application.AddMessageFilter(filter);

                // Run the thread message loop
                Application.Run();

                // Cleanup
                Application.RemoveMessageFilter(filter);
                UnregisterHotKey(IntPtr.Zero, HOTKEY_ID);
                SystemEvents.UserPreferenceChanged -= SystemEvents_UserPreferenceChanged;
                
                if (_currentIconHandle != IntPtr.Zero)
                {
                    DestroyIcon(_currentIconHandle);
                }

                TrayIcon.Visible = false;
                TrayIcon.Dispose();
            }
        }

        private static void SystemEvents_UserPreferenceChanged(object sender, UserPreferenceChangedEventArgs e)
        {
            if (e.Category == UserPreferenceCategory.General || e.Category == UserPreferenceCategory.Color)
            {
                UpdateIcon();
            }
        }

        private static void TrayIcon_Click(object? sender, EventArgs e)
        {
            var mouseEventArgs = e as MouseEventArgs;
            if (mouseEventArgs != null && mouseEventArgs.Button == MouseButtons.Left)
            {
                ToggleTheme();
            }
        }

        public static void ToggleTheme()
        {
            try
            {
                bool currentIsLight = IsLightTheme();
                SetTheme(!currentIsLight);
                UpdateIcon();
            }
            catch (Exception ex)
            {
                MessageBox.Show($"שגיאה בשינוי ערכת הנושא: {ex.Message}", "Theme Toggler - שגיאה", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private static void UpdateIcon()
        {
            if (TrayIcon == null) return;

            bool isLight = IsLightTheme();
            Bitmap bmp = new Bitmap(32, 32);

            if (isLight)
            {
                // Draw Sun
                using (var g = Graphics.FromImage(bmp))
                {
                    g.SmoothingMode = SmoothingMode.AntiAlias;
                    g.Clear(Color.Transparent);

                    // Sun body
                    using (var brush = new SolidBrush(Color.FromArgb(255, 180, 0))) // Golden orange
                    {
                        g.FillEllipse(brush, 10, 10, 12, 12);
                    }

                    // Sun rays
                    using (var pen = new Pen(Color.FromArgb(255, 180, 0), 2.5f))
                    {
                        pen.StartCap = LineCap.Round;
                        pen.EndCap = LineCap.Round;
                        for (int i = 0; i < 8; i++)
                        {
                            double angle = i * Math.PI / 4.0;
                            float x1 = 16f + (float)(8.0 * Math.Cos(angle));
                            float y1 = 16f + (float)(8.0 * Math.Sin(angle));
                            float x2 = 16f + (float)(13.0 * Math.Cos(angle));
                            float y2 = 16f + (float)(13.0 * Math.Sin(angle));
                            g.DrawLine(pen, x1, y1, x2, y2);
                        }
                    }
                }
                TrayIcon.Text = "מצב תצוגה: בהיר\nלחץ להחלפה לכהה";
            }
            else
            {
                // Draw Moon
                using (var g = Graphics.FromImage(bmp))
                {
                    g.SmoothingMode = SmoothingMode.AntiAlias;
                    g.Clear(Color.Transparent);

                    // Moon base (silver-white circle)
                    using (var brush = new SolidBrush(Color.FromArgb(200, 220, 255)))
                    {
                        g.FillEllipse(brush, 6, 6, 20, 20);
                    }

                    // Subtract offset circle
                    g.CompositingMode = CompositingMode.SourceCopy;
                    using (var brush = new SolidBrush(Color.Transparent))
                    {
                        g.FillEllipse(brush, 12, 4, 20, 20);
                    }
                }
                TrayIcon.Text = "מצב תצוגה: כהה\nלחץ להחלפה לבהיר";
            }

            IntPtr hIcon = bmp.GetHicon();
            Icon icon = Icon.FromHandle(hIcon);
            
            // Set icon
            var oldIcon = TrayIcon.Icon;
            IntPtr oldHandle = _currentIconHandle;

            TrayIcon.Icon = icon;
            _currentIconHandle = hIcon;

            // Dispose old icon and bitmap resources to avoid GDI leaks
            if (oldIcon != null)
            {
                oldIcon.Dispose();
            }
            if (oldHandle != IntPtr.Zero)
            {
                DestroyIcon(oldHandle);
            }
            bmp.Dispose();
        }

        private static bool IsLightTheme()
        {
            using var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize");
            if (key != null)
            {
                object? val = key.GetValue("AppsUseLightTheme");
                if (val is int i)
                {
                    return i != 0;
                }
            }
            return true;
        }

        private static void SetTheme(bool lightMode)
        {
            int val = lightMode ? 1 : 0;
            using (var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize", true))
            {
                if (key != null)
                {
                    key.SetValue("AppsUseLightTheme", val, RegistryValueKind.DWord);
                    key.SetValue("SystemUsesLightTheme", val, RegistryValueKind.DWord);
                }
            }

            // Notify system
            SendMessageTimeout((IntPtr)HWND_BROADCAST, WM_SETTINGCHANGE, UIntPtr.Zero, "ImmersiveColorSet", SMTO_ABORTIFHUNG, 1000, out _);
        }

        private static bool IsRunAtStartupEnabled()
        {
            using var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Run", false);
            if (key != null)
            {
                return key.GetValue("ThemeToggler") != null;
            }
            return false;
        }

        private static void SetRunAtStartup(bool enable)
        {
            using var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Run", true);
            if (key != null)
            {
                if (enable)
                {
                    key.SetValue("ThemeToggler", $"\"{Application.ExecutablePath}\"");
                }
                else
                {
                    key.DeleteValue("ThemeToggler", false);
                }
            }
        }

        private static void Startup_Click(object? sender, EventArgs e)
        {
            if (_startupMenuItem == null) return;
            
            try
            {
                bool newState = !_startupMenuItem.Checked;
                SetRunAtStartup(newState);
                _startupMenuItem.Checked = newState;
            }
            catch (Exception ex)
            {
                MessageBox.Show($"שגיאה בהגדרת הפעלה אוטומטית: {ex.Message}", "Theme Toggler - שגיאה", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
    }

    // Message filter to intercept WM_HOTKEY messages at thread level
    public class HotkeyMessageFilter : IMessageFilter
    {
        private const int WM_HOTKEY = 0x0312;
        private const int HOTKEY_ID = 9000;

        public bool PreFilterMessage(ref Message m)
        {
            if (m.Msg == WM_HOTKEY && m.WParam.ToInt32() == HOTKEY_ID)
            {
                Program.ToggleTheme();
                return true; // Mark as handled
            }
            return false;
        }
    }
}