using System.Runtime.InteropServices;
using Zio;
using Zio.FileSystems;

internal static class Program
{
    private static readonly IFileSystem SdFileSystem = new PhysicalFileSystem();
    private static readonly UPath SdRoot = new UPath(Path.Combine(AppContext.BaseDirectory, "sd").Replace('\\', '/').Replace("C:", "/mnt/c"));

    private static UPath GetSlotFilePath(uint slotIdx, string filePath)
    {
        var normalizedPath = (filePath ?? string.Empty).Replace('\\', '/').TrimStart('/');
        return SdRoot / $"slot{slotIdx}" / normalizedPath;
    }

    private static readonly Nova64Core.DisplayFlushDelegate DisplayFlush = (buffer, width, height) => { };
    private static readonly Nova64Core.AudioOutputDelegate AudioOutput = (samples, count) => { };
    private static readonly Nova64Core.SdReadFileDelegate SdReadFile = (slotIdx, filePath, destinationBuffer, destinationLength) =>
    {
        var path = GetSlotFilePath(slotIdx, filePath);
        Console.WriteLine($"[Core] SD read request: slot {slotIdx}, file '{filePath}', resolved path '{path}' destination length {destinationLength}");

        if (destinationBuffer == IntPtr.Zero)
        {
            Console.WriteLine("[Core] SD read request failed: destination buffer is null.");
            return -1;
        }

        if (!SdFileSystem.FileExists(path))
        {
            Console.WriteLine($"[Core] SD read request failed: file not found '{path}'");
            return -1;
        }

        try
        {
            using var stream = SdFileSystem.OpenFile(path, FileMode.Open, FileAccess.Read, FileShare.Read);
            var bytesToRead = (int)Math.Min(destinationLength, stream.Length);
            var buffer = new byte[bytesToRead];
            var bytesRead = stream.Read(buffer, 0, bytesToRead);
            Marshal.Copy(buffer, 0, destinationBuffer, bytesRead);
            return bytesRead;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"[Core] SD read request failed: {ex.Message}");
            return -1;
        }
    };
    private static readonly Nova64Core.SdGetFileSizeDelegate SdGetFileSize = (slotIdx, filePath) =>
    {
        var path = GetSlotFilePath(slotIdx, filePath);
        Console.WriteLine($"[Core] SD get file size request: slot {slotIdx}, file '{filePath}', resolved path '{path}'");

        if (!SdFileSystem.FileExists(path))
        {
            Console.WriteLine($"[Core] SD get file size failed: file not found '{path}'");
            return -1;
        }

        try
        {
            var length = SdFileSystem.GetFileLength(path);
            return length > int.MaxValue ? -1 : (int)length;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"[Core] SD get file size failed: {ex.Message}");
            return -1;
        }
    };
    private static readonly Nova64Core.CartridgeStatusDelegate CartridgeStatus = (slotIdx, isInserted) => { };
    private static readonly Nova64Core.LogMessageDelegate LogMessage = (message) =>
    {
        Console.Write($"[Core] {message}");
        Console.Out.Flush();
    };

    private static GCHandle? _ioHandle;
    private static Thread? _coreThread;
    private static readonly ManualResetEventSlim _coreStartedEvent = new(false);

    private static void CoreThreadProc()
    {
        if (_ioHandle == null)
        {
            Console.WriteLine("[Sim] Core thread failed: IO handle missing.");
            return;
        }

        if (!Nova64Core.nova64_init(_ioHandle.Value.AddrOfPinnedObject()))
        {
            Console.WriteLine("[Sim] nova64_init failed in core thread.");
            _coreStartedEvent.Set();
            return;
        }

        _coreStartedEvent.Set();

        var result = Nova64Core.nova64_main();
        Console.WriteLine($"[Sim] nova64_main returned: {result}");
    }

    private static void Main()
    {
        Console.WriteLine("[Sim] simulator starting...");

        try
        {
            var version = Nova64Core.nova64_get_version();
            Console.WriteLine($"[Sim] Loaded nova64_core native library. Version: 0x{version:X}");

            var ioInterface = new Nova64Core.Nova64IoInterface
            {
                display_flush = Marshal.GetFunctionPointerForDelegate(DisplayFlush),
                audio_output = Marshal.GetFunctionPointerForDelegate(AudioOutput),
                sd_read_file = Marshal.GetFunctionPointerForDelegate(SdReadFile),
                sd_get_file_size = Marshal.GetFunctionPointerForDelegate(SdGetFileSize),
                cartridge_status = Marshal.GetFunctionPointerForDelegate(CartridgeStatus),
                log_message = Marshal.GetFunctionPointerForDelegate(LogMessage)
            };

            _ioHandle = GCHandle.Alloc(ioInterface, GCHandleType.Pinned);
            _coreThread = new Thread(CoreThreadProc)
            {
                IsBackground = true,
                Name = "Nova64CoreThread"
            };
            _coreThread.Start();

            if (_coreStartedEvent.Wait(TimeSpan.FromSeconds(5)))
            {
                Console.WriteLine("[Sim] core thread started.");
            }
            else
            {
                Console.WriteLine("[Sim] Core thread did not signal startup in time.");
            }

            Console.WriteLine("[Sim] Press Enter to stop the simulator.");
            Console.ReadLine();

            if (_coreThread != null && _coreThread.IsAlive)
            {
                Console.WriteLine("[Sim] Requesting core shutdown...");
                if (Nova64Core.nova64_shutdown())
                {
                    int timeoutMs = 1000;
                    while (!Nova64Core.nova64_is_finalized() && timeoutMs > 0)
                    {
                        Thread.Sleep(10);
                        timeoutMs -= 10;
                    }
                    Console.WriteLine($"[Sim] Core shutdown complete after {1000 - timeoutMs}ms.");
                    _coreThread = null;
                }
                else
                {
                    Console.WriteLine("[Sim] Core shutdown request failed.");
                }
            }
        }
        catch (DllNotFoundException ex)
        {
            Console.WriteLine($"[Sim] Native library not found: {ex.Message}");
        }
        catch (EntryPointNotFoundException ex)
        {
            Console.WriteLine($"[Sim] Native entry point missing: {ex.Message}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"[Sim] Failed to initialize native library: {ex.Message}");
        }
        finally
        {
            if (_coreThread != null && _coreThread.IsAlive)
            {
                Console.WriteLine("Core thread still running; leaving native handle pinned until process exit.");
            }
            else if (_ioHandle.HasValue && _ioHandle.Value.IsAllocated)
            {
                _ioHandle.Value.Free();
            }
        }
    }
}