using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using UnityEngine;

public class UniQuake: MonoBehaviour
{
#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 const int MemSize = 0x8000000;  // 128 MB of heap space

    private IntPtr libraryHandle;

    private QuakeParms quakeParms;
    private SystemModule systemModule;
    private RenderModule renderModule;

    private bool initialized = false;
    private double startTime;

    public MissionPack BaseGame { get; set; }
    public string ModDirectory { get; set; }
    
    /// <summary>
    /// Time since startup for this particular instance of Quake
    /// </summary>
    public double CurrentTime => Time.timeAsDouble - startTime;

    private Action<string> logHandler; 

    void Start()
    {
        logHandler = PrintLog;  // Send each log statement to Unity immediately during startup
        
        systemModule = new SystemModule(this);
        renderModule = new RenderModule(this);

        LoadLibrary();

        List<string> arguments = new List<string>
        {
            "",
            "-window",
            "-width", "1440",
            "-height", "1080",
        };

        switch (BaseGame)
        {
            case MissionPack.Hipnotic:
                arguments.Add("-hipnotic");
                break;
            case MissionPack.Rogue:
                arguments.Add("-rogue");
                break;
        }

        if (!string.IsNullOrEmpty(ModDirectory))
        {
            arguments.AddRange(new[] { "-game", ModDirectory });
        }

        if (Debug.isDebugBuild)
        {
            arguments.AddRange(new[] { "+developer", "1" });
        }

        quakeParms = new QuakeParms
        {
            baseDir = Application.persistentDataPath,
            userDir = null, // TODO set this if user prefs need to be stored somewhere specific, otherwise this will be the same as baseDir
            numCpus = SystemInfo.processorCount,
            errState = 0,
        };
        quakeParms.SetArguments(arguments.ToArray());
        quakeParms.AllocateMemory(MemSize);

        startTime = Time.timeAsDouble;

        try
        {
            UniQuake_SetFmodSystem(AudioManager.Instance.FmodSystem.handle);
            UniQuake_Init(quakeParms.ToNativePtr(), systemModule.CallbacksPtr, renderModule.CallbacksPtr);
            initialized = true;
        }
        catch (QuakeException ex)
        {
            if (ex.ExitCode == 0)
                Debug.Log(ex.Message);
            else
                Debug.LogException(ex);

            Shutdown();
        }
        catch (Exception ex)
        {
            Debug.LogException(ex);
            Shutdown();
        }
    }

    void Update()
    {
        if (!initialized)
            return;

        logHandler = CollectLog;    // Collect and dump logs to Unity once per frame

        try
        {
            UniQuake_Update(Time.deltaTime);
        }
        catch (QuakeException ex)
        {
            if (ex.ExitCode == 0)
                Debug.Log(ex.Message);
            else
                Debug.LogException(ex);

            Shutdown();
        }
        catch (Exception ex)
        {
            Debug.LogException(ex);
            Shutdown();
        }
        
        FlushLog();
    }

    private void Shutdown()
    {
        initialized = false;
        UniQuake_Shutdown();
        Destroy(this);
    }

    private void OnDestroy()
    {
        renderModule.Destroy();
        systemModule.Destroy();

        if (quakeParms != null)
        {
            quakeParms.Destroy();
            quakeParms = null;
        }

        FreeLibrary();
    }

    public void AddLog(string log)
    {
        logHandler?.Invoke(log);
    }
    
    private void PrintLog(string log)
    {
        Debug.Log(log);
    }

    private StringBuilder logBuffer = new StringBuilder();
    
    private void CollectLog(string log)
    {
        logBuffer.Append(log);
    }

    private void FlushLog()
    {
        if (logBuffer.Length > 0)
        {
            Debug.Log(logBuffer.ToString());
            logBuffer.Clear();
        }
    }

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void UniQuake_InitFunc(IntPtr parms, IntPtr sysCalls, IntPtr glCalls);
    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);
    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;
        }
    }
}

public enum MissionPack
{
    Quake,      // Vanilla Quake
    Hipnotic,   // Scourge of Armagon
    Rogue,      // Dissolution of Eternity 
}

public class QuakeException: Exception
{
    public int ExitCode { get; }

    public QuakeException(string message, int exitCode = 0)
        : base(message)
    {
        ExitCode = exitCode;
    }
}