using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Interop;

namespace GeekDesk.Util
{
    public class BlurGlassUtil
    {
        internal enum AccentState
        {
            ACCENT_DISABLED = 1,
            ACCENT_ENABLE_GRADIENT = 0,
            ACCENT_ENABLE_TRANSPARENTGRADIENT = 2,
            ACCENT_ENABLE_BLURBEHIND = 3,
            ACCENT_INVALID_STATE = 4
        }

        [StructLayout(LayoutKind.Sequential)]
        internal struct AccentPolicy
        {
            public AccentState AccentState;
            public int AccentFlags;
            public int GradientColor;
            public int AnimationId;
        }

        [StructLayout(LayoutKind.Sequential)]
        internal struct WindowCompositionAttributeData
        {
            public WindowCompositionAttribute Attribute;
            public IntPtr Data;
            public int SizeOfData;
        }

        internal enum WindowCompositionAttribute
        {
            // ...
            WCA_ACCENT_POLICY = 19
            // ...
        }

        [DllImport("user32.dll")]
        internal static extern int SetWindowCompositionAttribute(IntPtr hwnd, ref WindowCompositionAttributeData data);


        public static void EnableBlur(Window window)
        {
            WindowInteropHelper windowHelper = new WindowInteropHelper(window);

            AccentPolicy accent = new AccentPolicy
            {
                AccentState = AccentState.ACCENT_ENABLE_BLURBEHIND
            };

            int accentStructSize = Marshal.SizeOf(accent);

            IntPtr accentPtr = Marshal.AllocHGlobal(accentStructSize);
            Marshal.StructureToPtr(accent, accentPtr, false);

            WindowCompositionAttributeData data = new WindowCompositionAttributeData
            {
                Attribute = WindowCompositionAttribute.WCA_ACCENT_POLICY,
                SizeOfData = accentStructSize,
                Data = accentPtr
            };

            SetWindowCompositionAttribute(windowHelper.Handle, ref data);

            Marshal.FreeHGlobal(accentPtr);
        }
    }
}