using System;
using System.IO;
using System.Runtime.InteropServices;
using UnityEngine;

public partial class UniQuake
{
#if UNITY_EDITOR
    private const string DllPath = "Plugins/windows/x86_64/uniquake.dll";
#elif UNITY_STANDALONE_WIN
    #if UNITY_64
    private const string DllPath = "Plugins/x86_64/uniquake.dll";
    #else
    private const string DllPath = "Plugins/x86/uniquake.dll";
    #endif
#endif
    
    private IntPtr libraryHandle;
    
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void UniQuake_InitFunc(IntPtr parms, IntPtr sysCalls, IntPtr glCalls, IntPtr gameCalls);
    private UniQuake_InitFunc UniQuake_Init;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void UniQuake_UpdateFunc(float deltaTime);
    private UniQuake_UpdateFunc UniQuake_Update;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void UniQuake_ShutdownFunc();
    private UniQuake_ShutdownFunc UniQuake_Shutdown;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void UniQuake_SetFmodSystemFunc(IntPtr fmodSystem, int playerNumber = 0);
    private UniQuake_SetFmodSystemFunc UniQuake_SetFmodSystem;

    private void LoadLibrary()
    {
        string dllFile = Path.Combine(Application.dataPath, DllPath);

        // Experimental code to allow running multiple instances of Quake next to each other
        // string dllName = Path.GetFileNameWithoutExtension(dllFile);
        // string dllExt = Path.GetExtension(dllFile);
        // string dllCopy = Path.Combine(Application.persistentDataPath, $"{dllName}{GetInstanceID()}{dllExt}");
        // File.Copy(dllFile, dllCopy, true);
        // dllFile = dllCopy;
        
        libraryHandle = SystemLibrary.LoadLibrary(dllFile);
        if (libraryHandle == IntPtr.Zero)
        {
            throw new DllNotFoundException($"Failed to load UniQuake library from path: {dllFile}, last error = {Marshal.GetLastWin32Error()}");
        }

        UniQuake_Init = LoadLibraryFunction<UniQuake_InitFunc>("UniQuake_Init");
        UniQuake_Update = LoadLibraryFunction<UniQuake_UpdateFunc>("UniQuake_Update");
        UniQuake_Shutdown = LoadLibraryFunction<UniQuake_ShutdownFunc>("UniQuake_Shutdown");
        UniQuake_SetFmodSystem = LoadLibraryFunction<UniQuake_SetFmodSystemFunc>("UniQuake_SetFmodSystem");
    }

    private TDelegate LoadLibraryFunction<TDelegate>(string functionName)
    {
        IntPtr procAddress = SystemLibrary.GetProcAddress(libraryHandle, functionName);
        if (procAddress == IntPtr.Zero)
        {
            throw new DllNotFoundException($"Could not find library function: {functionName}");
        }

        return Marshal.GetDelegateForFunctionPointer<TDelegate>(procAddress);
    }

    private void FreeLibrary()
    {
        if (libraryHandle != IntPtr.Zero)
        {
            SystemLibrary.FreeLibrary(libraryHandle);
            libraryHandle = IntPtr.Zero;
        }
    }
}