using System;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;

namespace GlobalKeyboardHook
{
    class Program
    {
        // Define the hook type
        const int WH_KEYBOARD_LL = 13;
        const int WM_KEYDOWN = 0x0100;
        const int WM_KEYUP = 0x0101;

        // Define the key codes
        const int VK_RETURN = 0x0D;  // Enter key

        // Declare the hook handle and the hook procedure
        private static IntPtr hookId = IntPtr.Zero;
        private static StringBuilder scannedData = new StringBuilder();

        // Define the delegate for the hook procedure
        private static LowLevelKeyboardProc _proc = HookCallback;

        // P/Invoke to set the hook
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern IntPtr SetWindowsHookEx(int hookType, LowLevelKeyboardProc callback, IntPtr hInstance, uint threadId);

        [DllImport("user32.dll")]
        public static extern bool UnhookWindowsHookEx(IntPtr hookId);

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern IntPtr CallNextHookEx(IntPtr hookId, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll")]
        public static extern IntPtr GetModuleHandle(string lpModuleName);

        // The delegate type for the hook procedure
        public delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

        static void Main(string[] args)
        {
            // Hook the keyboard input globally
            hookId = SetHook(_proc);

            // Wait for the user to terminate the application
            Console.WriteLine("请扫描条形码...");
            Console.WriteLine("按 ESC 键退出程序。");

            // Loop indefinitely until the user presses the ESC key
            while (true)
            {
                if (Console.KeyAvailable && Console.ReadKey(true).Key == ConsoleKey.Escape)
                {
                    break; // Exit the loop and terminate the application
                }
                Thread.Sleep(10); // Sleep to avoid high CPU usage
            }

            // Unhook the keyboard input when done
            UnhookWindowsHookEx(hookId);
        }

        // Set the hook for keyboard input
        private static IntPtr SetHook(LowLevelKeyboardProc proc)
        {
            using (var curProcess = System.Diagnostics.Process.GetCurrentProcess())
            using (var curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0);
            }
        }

        // The callback function that will be called when a key is pressed or released
        private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0 && (int)wParam == WM_KEYDOWN)
            {
                // Get the key code
                int vkCode = Marshal.ReadInt32(lParam);

                // If the key is Enter (Carriage Return), treat it as the end of the barcode
                if (vkCode == VK_RETURN)
                {
                    // Print the scanned data
                    string data = scannedData.ToString();
                    Console.WriteLine($"\n条码扫描完成，扫描到的数据是: {data}");

                    // Clear the scanned data for the next scan
                    scannedData.Clear();
                }
                else
                {
                    // Append the character corresponding to the key code
                    char keyChar = (char)vkCode;
                    scannedData.Append(keyChar);

                    // Print the character in real-time (optional)
                    Console.Write(keyChar);
                }
            }

            // Call the next hook in the chain
            return CallNextHookEx(hookId, nCode, wParam, lParam);
        }
    }
}