using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;

namespace DetectRemoteApp
{
    public static class RemoteDesktopDetection
    {
        private const int RemoteSessionSystemMetricId = 0x1000;

        [DllImport("user32.dll")]
        private static extern int GetSystemMetrics(int nIndex);

        public static DesktopMode DetectDesktopMode()
        {
            if (IsLocalSession())
                return DesktopMode.Local;
            else if (IsRemoteAppSession())
                return DesktopMode.RemoteApp;
            else
                return DesktopMode.RemoteDesktop;
        }

        private static bool IsLocalSession()
        {
            return GetSystemMetrics(RemoteSessionSystemMetricId) == 0;
        }

        private static bool IsRemoteAppSession()
        {
            // This test isn't perfect, since we don't know for sure if rdpinit.exe will always be running,
            // and there could theoretically be an unrelated process with the same name.
            // Normally we'd be able to test if rdpinit.exe is a parent of our process,
            // but that won't work for ClickOnce apps because they're children of dfsvc.exe.
            int currentSessionId = Process.GetCurrentProcess().SessionId;
            return Process.GetProcesses().Where(p => p.SessionId == currentSessionId)
                .Any(p => p.ProcessName == "rdpinit");
        }
    }
}