// Window layout, folded in from focus_dosbox.ps1:
//   1. the RENDERER (GL bridge) -> always-on-top, so the out-the-window view is
//      never covered by a head window.
//   2. DOSBox-X -> parked at (x,y) with FOREGROUND focus, so its emulation
//      thread keeps foreground priority -- else the RIO ACK deadline is missed
//      and the board storms (the RIO focus-sensitivity issue).
// A topmost renderer stays visually above the focused-but-non-topmost DOSBox,
// yet DOSBox stays the active window.

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

namespace VwePod
{
    internal static class Focus
    {
        public static string Apply(int x, int y)
        {
            var s = new StringBuilder();

            // 1) renderer -> topmost
            IntPtr r = FindRenderer();
            if (r != IntPtr.Zero)
            {
                SetWindowPos(r, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
                s.Append("renderer topmost; ");
            }
            else s.Append("renderer NOT found; ");

            // 2) DOSBox -> parked + foreground
            IntPtr d = FindWindow("DOSBox-X");
            if (d == IntPtr.Zero) return s.Append("DOSBox NOT found").ToString();

            SetWindowPos(d, IntPtr.Zero, x, y, 0, 0, SWP_NOSIZE | SWP_NOZORDER);
            ShowWindow(d, SW_RESTORE);

            uint fgThread = GetWindowThreadProcessId(GetForegroundWindow(), out _);
            uint me = GetCurrentThreadId();
            AttachThreadInput(me, fgThread, true);
            BringWindowToTop(d);
            SetForegroundWindow(d);
            AttachThreadInput(me, fgThread, false);

            s.Append("DOSBox at ").Append(x).Append(',').Append(y)
             .Append(" focused=").Append(GetForegroundWindow() == d);
            return s.ToString();
        }

        private static IntPtr FindRenderer()
        {
            IntPtr h = FindWindow("dpl3-revive renderer");
            return h != IntPtr.Zero ? h : FindWindow("VelociRender");
        }

        private static IntPtr FindWindow(string needle)
        {
            IntPtr found = IntPtr.Zero;
            EnumWindows((h, l) =>
            {
                if (!IsWindowVisible(h)) return true;
                var b = new byte[512];
                int n = GetWindowTextA(h, b, b.Length);
                if (n > 0 && Encoding.ASCII.GetString(b, 0, n).Contains(needle)) { found = h; return false; }
                return true;
            }, IntPtr.Zero);
            return found;
        }

        // ---- native ----
        private static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);
        private const uint SWP_NOSIZE = 0x0001, SWP_NOMOVE = 0x0002, SWP_NOZORDER = 0x0004;
        private const int SW_RESTORE = 9;

        private delegate bool EnumProc(IntPtr h, IntPtr l);

        [DllImport("user32.dll")] private static extern bool EnumWindows(EnumProc cb, IntPtr l);
        [DllImport("user32.dll")] private static extern int GetWindowTextA(IntPtr h, byte[] b, int max);
        [DllImport("user32.dll")] private static extern bool IsWindowVisible(IntPtr h);
        [DllImport("user32.dll")] private static extern bool SetWindowPos(IntPtr h, IntPtr after, int x, int y, int w, int hh, uint flags);
        [DllImport("user32.dll")] private static extern bool SetForegroundWindow(IntPtr h);
        [DllImport("user32.dll")] private static extern bool BringWindowToTop(IntPtr h);
        [DllImport("user32.dll")] private static extern bool ShowWindow(IntPtr h, int cmd);
        [DllImport("user32.dll")] private static extern IntPtr GetForegroundWindow();
        [DllImport("user32.dll")] private static extern uint GetWindowThreadProcessId(IntPtr h, out uint pid);
        [DllImport("user32.dll")] private static extern bool AttachThreadInput(uint a, uint b, bool attach);
        [DllImport("kernel32.dll")] private static extern uint GetCurrentThreadId();
    }
}