using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using IPClab1.Models;
using Microsoft.UI.Xaml.Media.Imaging;
using Windows.Graphics.Imaging;

namespace IPClab1.Services;

public partial class WindowListService
{
    #region Win32 P/Invoke Declarations

    private const uint WM_GETICON = 0x007F;
    private const IntPtr ICON_SMALL = 0;
    private const IntPtr ICON_BIG = 1;
    private const IntPtr ICON_SMALL2 = 2;

    private const int GCLP_HICON = -14;
    private const int GCLP_HICONSM = -34;

    private delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);

    [LibraryImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);

    [LibraryImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool IsWindowVisible(IntPtr hWnd);

    [LibraryImport("user32.dll", EntryPoint = "GetWindowTextW", SetLastError = true)]
    private static partial int GetWindowText(IntPtr hWnd, [Out] char[] lpString, int nMaxCount);

    [LibraryImport("user32.dll", EntryPoint = "GetWindowTextLengthW", SetLastError = true)]
    private static partial int GetWindowTextLength(IntPtr hWnd);

    [LibraryImport("user32.dll", EntryPoint = "SendMessageW")]
    private static partial IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

    [LibraryImport("user32.dll", EntryPoint = "GetClassLongPtrW")]
    private static partial IntPtr GetClassLongPtr64(IntPtr hWnd, int nIndex);

    [LibraryImport("user32.dll", EntryPoint = "GetClassLongW")]
    private static partial uint GetClassLong32(IntPtr hWnd, int nIndex);

    [LibraryImport("user32.dll", SetLastError = true)]
    private static partial uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

    [LibraryImport("shell32.dll", EntryPoint = "ExtractIconW", StringMarshalling = StringMarshalling.Utf16)]
    private static partial IntPtr ExtractIcon(IntPtr hInst, string lpszExeFileName, int nIconIndex);

    private IntPtr GetClassLongPtr(IntPtr hWnd, int nIndex)
    {
        return IntPtr.Size == 8 ? GetClassLongPtr64(hWnd, nIndex) : new IntPtr(GetClassLong32(hWnd, nIndex));
    }

    #endregion

    /// <summary>
    /// Retrieves a list of structs representing all visible top-level windows with titles and native WinUI 3 icons.
    /// </summary>
    public async Task<List<WindowInfo>> GetVisibleWindowsAsync(bool onlyVisible)
    {
        var windowList = new List<WindowInfo>();
        var handles = new List<IntPtr>();

        // 1. Gather all raw visible window handles that actually contain titles
        EnumWindows((hWnd, lParam) =>
        {
            if ((IsWindowVisible(hWnd) || !onlyVisible) && GetWindowTextLength(hWnd) > 0)
            {
                handles.Add(hWnd);
            }
            return true;
        }, IntPtr.Zero);

        // 2. Iterate and async decode titles, process info, and UI image references
        foreach (var hWnd in handles)
        {
            // Fetch window text title cleanly
            var length = GetWindowTextLength(hWnd);
            var titleBuffer = new char[length + 1];

            var actualLength = GetWindowText(hWnd, titleBuffer, titleBuffer.Length);
            var title = actualLength > 0 ? new string(titleBuffer, 0, actualLength) : string.Empty;

            // Fetch numeric process identifier
            GetWindowThreadProcessId(hWnd, out var processId);

            // Fetch and map the icon image synchronously/asynchronously into WinUI structures
            SoftwareBitmapSource iconSource = await GetWinUi3IconAsync(hWnd);

            windowList.Add(new WindowInfo
            {
                Hwnd = hWnd,
                ProcessId = processId,
                WindowTitle = title,
                IconSource = iconSource
            });
        }

        return windowList;
    }

    private Icon GetIconFromHwnd(IntPtr hWnd)
    {
        var hIcon = SendMessage(hWnd, WM_GETICON, ICON_BIG, IntPtr.Zero);

        if (hIcon == IntPtr.Zero)
            hIcon = SendMessage(hWnd, WM_GETICON, ICON_SMALL2, IntPtr.Zero);

        if (hIcon == IntPtr.Zero)
            hIcon = GetClassLongPtr(hWnd, GCLP_HICON);

        if (hIcon == IntPtr.Zero)
            hIcon = GetClassLongPtr(hWnd, GCLP_HICONSM);

        if (hIcon != IntPtr.Zero)
        {
            try
            {
                using var rawIcon = Icon.FromHandle(hIcon);
                return (Icon)rawIcon.Clone();
            }
            catch { /* Proceed to alternate extraction fallback */ }
        }

        try
        {
            GetWindowThreadProcessId(hWnd, out uint processId);
            if (processId != 0)
            {
                using var proc = Process.GetProcessById((int)processId);
                string exePath = proc.MainModule?.FileName;
                if (!string.IsNullOrEmpty(exePath) && File.Exists(exePath))
                {
                    IntPtr hExtracted = ExtractIcon(IntPtr.Zero, exePath, 0);
                    if (hExtracted != IntPtr.Zero && hExtracted != new IntPtr(1))
                    {
                        using var rawIcon = Icon.FromHandle(hExtracted);
                        return (Icon)rawIcon.Clone();
                    }
                }
            }
        }
        catch { /* Protection fallback */ }

        return null;
    }

    private async Task<SoftwareBitmapSource> GetWinUi3IconAsync(IntPtr hWnd)
    {
        using Icon icon = GetIconFromHwnd(hWnd);
        if (icon == null) return null;

        try
        {
            using Bitmap bitmap = icon.ToBitmap();
            using var stream = new MemoryStream();

            bitmap.Save(stream, System.Drawing.Imaging.ImageFormat.Png);
            stream.Position = 0;

            var decoder = await BitmapDecoder.CreateAsync(stream.AsRandomAccessStream());
            var softwareBitmap = await decoder.GetSoftwareBitmapAsync(
                BitmapPixelFormat.Bgra8,
                BitmapAlphaMode.Premultiplied);

            var source = new SoftwareBitmapSource();
            await source.SetBitmapAsync(softwareBitmap);
            return source;
        }
        catch
        {
            return null;
        }
    }
}