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

using Microsoft.Win32;

/// <summary>
/// Helper class to flash client in tool bar when
/// message has been recieved
/// source: http://stackoverflow.com/a/8929473
/// </summary>
public class FlashWindowHelper
{
    private IntPtr mainWindowHWnd;
    private Application theApp;

    public FlashWindowHelper(Application app)
    {
        this.theApp = app;
    }

    public void FlashApplicationWindow()
    {
        InitializeHandle();
        Flash(this.mainWindowHWnd, 5);
    }

    public void StopFlashing()
    {
        InitializeHandle();

        if (Win2000OrLater)
        {
            FLASHWINFO fi = CreateFlashInfoStruct(this.mainWindowHWnd, FLASHW_STOP, uint.MaxValue, 0);
            FlashWindowEx(ref fi);
        }
    }

    private void InitializeHandle()
    {
        if (this.mainWindowHWnd == IntPtr.Zero)
        {
            // Delayed creation of Main Window IntPtr as Application.Current passed in to ctor does not have the MainWindow set at that time
            var mainWindow = this.theApp.MainWindow;
            this.mainWindowHWnd = new System.Windows.Interop.WindowInteropHelper(mainWindow).Handle;
        }
    }

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool FlashWindowEx(ref FLASHWINFO pwfi);

    [StructLayout(LayoutKind.Sequential)]
    private struct FLASHWINFO
    {
        /// <summary>
        /// The size of the structure in bytes.
        /// </summary>
        public uint cbSize;
        /// <summary>
        /// A Handle to the Window to be Flashed. The window can be either opened or minimized.
        /// </summary>
        public IntPtr hwnd;
        /// <summary>
        /// The Flash Status.
        /// </summary>
        public uint dwFlags;
        /// <summary>
        /// The number of times to Flash the window.
        /// </summary>
        public uint uCount;
        /// <summary>
        /// The rate at which the Window is to be flashed, in milliseconds. If Zero, the function uses the default cursor blink rate.
        /// </summary>
        public uint dwTimeout;
    }

    /// <summary>
    /// Stop flashing. The system restores the window to its original stae.
    /// </summary>
    public const uint FLASHW_STOP = 0;

    /// <summary>
    /// Flash the window caption.
    /// </summary>
    public const uint FLASHW_CAPTION = 1;

    /// <summary>
    /// Flash the taskbar button.
    /// </summary>
    public const uint FLASHW_TRAY = 2;

    /// <summary>
    /// Flash both the window caption and taskbar button.
    /// This is equivalent to setting the FLASHW_CAPTION | FLASHW_TRAY flags.
    /// </summary>
    public const uint FLASHW_ALL = 3;

    /// <summary>
    /// Flash continuously, until the FLASHW_STOP flag is set.
    /// </summary>
    public const uint FLASHW_TIMER = 4;

    /// <summary>
    /// Flash continuously until the window comes to the foreground.
    /// </summary>
    public const uint FLASHW_TIMERNOFG = 12;

    /// <summary>
    /// Flash the spacified Window (Form) until it recieves focus.
    /// </summary>
    /// <param name="hwnd"></param>
    /// <returns></returns>
    public static bool Flash(IntPtr hwnd)
    {
        // Make sure we're running under Windows 2000 or later
        if (Win2000OrLater)
        {
            FLASHWINFO fi = CreateFlashInfoStruct(hwnd, FLASHW_ALL | FLASHW_TIMERNOFG, uint.MaxValue, 0);

            return FlashWindowEx(ref fi);
        }
        return false;
    }

    private static FLASHWINFO CreateFlashInfoStruct(IntPtr handle, uint flags, uint count, uint timeout)
    {
        FLASHWINFO fi = new FLASHWINFO();
        fi.cbSize = Convert.ToUInt32(Marshal.SizeOf(fi));
        fi.hwnd = handle;
        fi.dwFlags = flags;
        fi.uCount = count;
        fi.dwTimeout = timeout;
        return fi;
    }

    /// <summary>
    /// Flash the specified Window (form) for the specified number of times
    /// </summary>
    /// <param name="hwnd">The handle of the Window to Flash.</param>
    /// <param name="count">The number of times to Flash.</param>
    /// <returns></returns>
    public static bool Flash(IntPtr hwnd, uint count)
    {
        if (Win2000OrLater)
        {
            FLASHWINFO fi = CreateFlashInfoStruct(hwnd, FLASHW_ALL | FLASHW_TIMERNOFG, count, 0);

            return FlashWindowEx(ref fi);
        }

        return false;
    }

    /// <summary>
    /// A boolean value indicating whether the application is running on Windows 2000 or later.
    /// </summary>
    private static bool Win2000OrLater
    {
        get { return Environment.OSVersion.Version.Major >= 5; }
    }
}
