using System;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace Ultron.Ngrok
{
    static class Program
    {
        #region WindowsAPI

        /// <summary>
        /// 显示窗口
        /// </summary>
        /// <param name="hWnd"></param>
        /// <param name="cmdShow"></param>
        /// <returns></returns>
        [DllImport("User32.dll")]
        private static extern bool ShowWindowAsync(System.IntPtr hWnd, int cmdShow);

        /// <summary>
        /// 根据窗体句柄获得窗体标题
        /// </summary>
        /// <param name="hWnd"></param>
        /// <param name="lpText"></param>
        /// <param name="nCount"></param>
        /// <returns></returns>
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern int GetWindowText(IntPtr hWnd, StringBuilder lpText, int nCount);

        /// <summary>
        /// 根据窗体句柄获得其进程ID
        /// </summary>
        /// <param name="hwnd"></param>
        /// <param name="ID"></param>
        /// <returns></returns>
        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        private static extern int GetWindowThreadProcessId(IntPtr hwnd, out int ID);

        /// <summary>
        /// 枚举窗体
        /// </summary>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <returns></returns>
        [DllImport("user32")]
        private static extern int EnumWindows(CallBack x, int y);

        #endregion

        #region 属性字段委托

        /// <summary>
        /// 窗体标题
        /// </summary>
        public static string FormName = "uNgrok";

        /// <summary>
        /// 显示窗口参数
        /// </summary>
        private const int SW_RESTORE = 9;

        /// <summary>
        /// 已存在的进程实例
        /// </summary>
        private static Process instance = null;

        private delegate bool CallBack(IntPtr hwnd, int lParam);

        #endregion

        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            //获取运行的进程
            instance = RunningInstance();
            if (instance == null)
            {
                //没有进程在运行
                Application.Run(new FormMain());
            }
            else
            {
                //是否托盘化, 托盘状态窗口句柄为0
                if (instance.MainWindowHandle.ToInt32() != 0) 
                {
                    //调用api函数，正常显示窗口
                    ShowWindowAsync(instance.MainWindowHandle, SW_RESTORE); 
                }
                else
                {
                    CallBack callback = new CallBack(Report);
                    EnumWindows(callback, 0);
                }

                Environment.Exit(Environment.ExitCode);
            }
        }

        #region 方法

        /// <summary>
        /// 获取运行中的进程
        /// </summary>
        /// <returns></returns>
        private static Process RunningInstance()
        {
            Process current = Process.GetCurrentProcess();
            Process[] processes = Process.GetProcessesByName(current.ProcessName);
            //遍历与当前进程名称相同的进程列表
            foreach (Process process in processes)
            {
                //如果实例已经存在则忽略当前进程
                if (process.Id != current.Id)
                {
                    //保证要打开的进程同已经存在的进程来自同一文件路径
                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == current.MainModule.FileName)
                    {
                        //返回已经存在的进程
                        return process;
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// 枚举窗口回调
        /// </summary>
        /// <param name="hwnd"></param>
        /// <param name="lParam"></param>
        /// <returns></returns>
        private static bool Report(IntPtr hwnd, int lParam)
        {
            //获得窗体标题
            StringBuilder sb = new StringBuilder(100);
            GetWindowText(hwnd, sb, sb.Capacity);

            //获取进程ID   
            GetWindowThreadProcessId(hwnd, out int calcID);

            //标题栏、进程id符合
            if ((sb.ToString() == FormName) && (instance != null) && (calcID == instance.Id))
            {
                //调用api函数，正常显示窗口
                ShowWindowAsync(hwnd, SW_RESTORE);
                return false;
            }

            return true;
        }

        #endregion
    }
}