using System;
using System.Runtime.InteropServices;

public class VJoyFeederApi : IDisposable
{
	private static class NativeMethods
	{
		[DllImport("kernel32.dll", CharSet = CharSet.Unicode, EntryPoint = "LoadLibraryW")]
		internal static extern IntPtr LoadLibrary([In] string fileName);

		[DllImport("kernel32.dll", CharSet = CharSet.Ansi)]
		internal static extern IntPtr GetProcAddress(IntPtr hModule, [In] string procName);

		[DllImport("kernel32.dll")]
		[return: MarshalAs(UnmanagedType.Bool)]
		internal static extern bool FreeLibrary(IntPtr hModule);
	}

	private IntPtr hDll;

	private T LoadProc<T>(string procName)
	{
		IntPtr procAddress = NativeMethods.GetProcAddress(hDll, procName);
		if (procAddress == IntPtr.Zero)
		{
			throw new Exception("failed to find " + procName + "()");
		}
		return (T)(Object)Marshal.GetDelegateForFunctionPointer(procAddress, typeof(T));
	}

	public enum VjdStat
	{
		VJD_STAT_OWN,
		VJD_STAT_FREE,
		VJD_STAT_BUSY,
		VJD_STAT_MISS,
		VJD_STAT_UNKN
	}

	public enum Axis
	{
		HID_USAGE_X = 0x30,
		HID_USAGE_Y = 0x31,
		HID_USAGE_Z = 0x32,
		HID_USAGE_RX = 0x33,
		HID_USAGE_RY = 0x34,
		HID_USAGE_RZ = 0x35,
		HID_USAGE_SL0 = 0x36,
		HID_USAGE_SL1 = 0x37,
		HID_USAGE_WHL = 0x38
	}

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private delegate bool VJoyEnabledDelegateType();
	private VJoyEnabledDelegateType VJoyEnabledDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private delegate bool DriverMatchDelegateType(ref ushort dllVer, ref ushort drvVer);
	private DriverMatchDelegateType DriverMatchDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	private delegate VjdStat GetVJDStatusDelegateType(uint rID);
	private GetVJDStatusDelegateType GetVJDStatusDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private delegate bool AcquireVJDDelegateType(uint rID);
	private AcquireVJDDelegateType AcquireVJDDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	private delegate void RelinquishVJDDelegateType(uint rID);
	private RelinquishVJDDelegateType RelinquishVJDDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	private delegate int GetVJDButtonNumberDelegateType(uint rID);
	private GetVJDButtonNumberDelegateType GetVJDButtonNumberDelegate;

	// SDK のドキュメントでは BOOL を返すと主張しているが、実際は以下の値を返すようである (2.1.9)
	// デバイスが存在しない (VJD_STAT_MISS) :  -2
	// デバイスが存在し、軸が存在しない     : -10
	// デバイスが存在し、軸が存在する       :   1
	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	private delegate int GetVJDAxisExistDelegateType(uint rID, Axis axis);
	private GetVJDAxisExistDelegateType GetVJDAxisExistDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private delegate bool SetAxisDelegateType(int value, uint rID, Axis axis);
	private SetAxisDelegateType SetAxisDelegate;

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private delegate bool SetBtnDelegateType([MarshalAs(UnmanagedType.Bool)] bool value, uint rID, byte nBtn);
	private SetBtnDelegateType SetBtnDelegate;

	public VJoyFeederApi()
	{
		bool is64bit = System.IntPtr.Size == 8;
		object dllLocation = Microsoft.Win32.Registry.GetValue(
			"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\{8E31F76F-74C3-47F1-9550-E041EEDC5FBB}_is1",
			is64bit ? "DllX64Location" : "DllX86Location",
			null
		);
		if (!(dllLocation is string))
		{
			throw new Exception("failed to read DLL location");
		}
		hDll = NativeMethods.LoadLibrary(System.IO.Path.Combine((string)dllLocation, "vJoyInterface.dll"));
		if (hDll == IntPtr.Zero)
		{
			throw new Exception("failed to load DLL");
		}
		VJoyEnabledDelegate = LoadProc<VJoyEnabledDelegateType>("vJoyEnabled");
		DriverMatchDelegate = LoadProc<DriverMatchDelegateType>("DriverMatch");
		GetVJDStatusDelegate = LoadProc<GetVJDStatusDelegateType>("GetVJDStatus");
		AcquireVJDDelegate = LoadProc<AcquireVJDDelegateType>("AcquireVJD");
		RelinquishVJDDelegate = LoadProc<RelinquishVJDDelegateType>("RelinquishVJD");
		GetVJDButtonNumberDelegate = LoadProc<GetVJDButtonNumberDelegateType>("GetVJDButtonNumber");
		GetVJDAxisExistDelegate = LoadProc<GetVJDAxisExistDelegateType>("GetVJDAxisExist");
		SetAxisDelegate = LoadProc<SetAxisDelegateType>("SetAxis");
		SetBtnDelegate = LoadProc<SetBtnDelegateType>("SetBtn");
	}

	public void Dispose()
	{
		NativeMethods.FreeLibrary(hDll);
	}

	public bool VJoyEnabled()
	{
		return VJoyEnabledDelegate();
	}

	public bool DriverMatch(ref ushort dllVer, ref ushort drvVer)
	{
		return DriverMatchDelegate(ref dllVer, ref drvVer);
	}

	public VjdStat GetVJDStatus(uint rID)
	{
		return GetVJDStatusDelegate(rID);
	}

	public bool AcquireVJD(uint rID)
	{
		return AcquireVJDDelegate(rID);
	}

	public void RelinquishVJD(uint rID)
	{
		RelinquishVJDDelegate(rID);
	}

	public int GetVJDButtonNumber(uint rID)
	{
		return GetVJDButtonNumberDelegate(rID);
	}

	public bool GetVJDAxisExist(uint rID, Axis axis)
	{
		return GetVJDAxisExistDelegate(rID, axis) > 0;
	}

	public bool SetAxis(int value, uint rID, Axis axis)
	{
		return SetAxisDelegate(value, rID, axis);
	}

	public bool SetBtn(bool value, uint rID, byte nBtn)
	{
		return SetBtnDelegate(value, rID, nBtn);
	}
}