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.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace KeyBoard
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        // Windows API 导入
        [DllImport("user32.dll")]
        static extern IntPtr GetForegroundWindow();

        [DllImport("user32.dll")]
        static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

        [DllImport("user32.dll")]
        static extern IntPtr GetFocus();

        [DllImport("user32.dll")]
        static extern bool AttachThreadInput(uint idAttach, uint idAttachTo, bool fAttach);

        [DllImport("user32.dll")]
        static extern bool PostMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

        [DllImport("user32.dll")]
        static extern bool PostThreadMessage(uint idThread, uint Msg, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll")]
        static extern uint GetCurrentThreadId();

        // 消息常量
        const uint WM_CHAR = 0x0102;
        const uint WM_KEYDOWN = 0x0100;
        const uint WM_KEYUP = 0x0101;
        const uint WM_LBUTTONDOWN = 0x0201;
        const uint WM_LBUTTONUP = 0x0202;

        // 当前活动窗口句柄
        private IntPtr targetWindow = IntPtr.Zero;
        private uint targetThreadId = 0;
        private uint currentThreadId = 0;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            // 创建按钮样式
            if (!this.Resources.Contains("KeyboardButtonStyle"))
            {
                var style = new System.Windows.Style(typeof(System.Windows.Controls.Button));
                style.Setters.Add(new System.Windows.Setter(System.Windows.Controls.Button.WidthProperty, 60.0));
                style.Setters.Add(new System.Windows.Setter(System.Windows.Controls.Button.HeightProperty, 50.0));
                style.Setters.Add(new System.Windows.Setter(System.Windows.Controls.Button.MarginProperty, new Thickness(2)));
                this.Resources.Add("KeyboardButtonStyle", style);
            }

            // 获取当前线程ID
            currentThreadId = GetCurrentThreadId();
        }

        // 在窗口失去焦点时保存目标窗口信息
        private void Window_Deactivated(object sender, EventArgs e)
        {
            // 获取当前活动窗口
            targetWindow = GetForegroundWindow();
            if (targetWindow != IntPtr.Zero)
            {
                GetWindowThreadProcessId(targetWindow, out targetThreadId);
            }
        }

        // 使用PreviewMouseDown事件而不是Click事件
        private void Button_PreviewMouseDown(object sender, MouseButtonEventArgs e)
        {
            e.Handled = true; // 阻止事件继续传播

            var button = sender as System.Windows.Controls.Button;
            if (button?.Tag != null)
            {
                char keyChar = button.Tag.ToString()[0];
                SendCharacter(keyChar);
            }

            // 防止按钮获得焦点
            this.Focus();
        }

        private void Space_PreviewMouseDown(object sender, MouseButtonEventArgs e)
        {
            e.Handled = true;
            SendCharacter(' ');
            this.Focus();
        }

        private void Backspace_PreviewMouseDown(object sender, MouseButtonEventArgs e)
        {
            e.Handled = true;
            SendBackspace();
            this.Focus();
        }

        // 发送字符到目标窗口
        private void SendCharacter(char ch)
        {
            if (targetWindow != IntPtr.Zero && targetThreadId != 0)
            {
                // 附加到目标线程的输入队列
                AttachThreadInput(currentThreadId, targetThreadId, true);

                // 发送字符消息
                PostMessage(targetWindow, WM_CHAR, new IntPtr(ch), IntPtr.Zero);

                // 分离线程输入
                AttachThreadInput(currentThreadId, targetThreadId, false);
            }
            else
            {
                // 如果没有保存目标窗口，则发送到当前活动窗口
                IntPtr currentForegroundWindow = GetForegroundWindow();
                if (currentForegroundWindow != IntPtr.Zero)
                {
                    PostMessage(currentForegroundWindow, WM_CHAR, new IntPtr(ch), IntPtr.Zero);
                }
            }
        }

        // 发送退格键
        private void SendBackspace()
        {
            IntPtr windowToSend = targetWindow != IntPtr.Zero ? targetWindow : GetForegroundWindow();
            if (windowToSend != IntPtr.Zero)
            {
                uint threadId = targetThreadId != 0 ? targetThreadId : GetWindowThreadProcessId(windowToSend, out _);

                if (threadId != 0)
                {
                    AttachThreadInput(currentThreadId, threadId, true);
                    PostMessage(windowToSend, WM_KEYDOWN, new IntPtr(0x08), IntPtr.Zero); // VK_BACK
                    PostMessage(windowToSend, WM_KEYUP, new IntPtr(0x08), IntPtr.Zero);
                    AttachThreadInput(currentThreadId, threadId, false);
                }
            }
        }

        // 关闭按钮
        private void CloseButton_Click(object sender, RoutedEventArgs e)
        {
            this.Close();
        }
    }
}