using OptimeGBA;
using System;
using System.IO;
using System.Threading;
using UnityEngine;
using UnityEngine.UI;

public class Emulator : MonoBehaviour
{
    public static Emulator instance;
    const int FrameCycles = 70224 * 4;
    const int ScanlineCycles = 1232;
    const float FrameRate = 59.7275f;
    static bool SyncToAudio = true;

    //public Renderer screenRenderer;
    public VideoProvider videoProvider;
    public AudioProvider audioProvider;
    public static System.Diagnostics.Stopwatch sw = System.Diagnostics.Stopwatch.StartNew();

    public bool ShowBackBuf = false;
    public bool RunEmulator;
    public bool EnableAudio;
    public bool BootBIOS = false;
    public bool RomLoaded { get; private set; } = false;

    public Gba gba;
    Thread EmulationThread;
    AutoResetEvent ThreadSync = new AutoResetEvent(false);

    private int _samplesAvailable;
    //private PipeStream _pipeStream;
    private byte[] _buffer;
    public float audioGain = 1.0f;

    // key delegate
    public delegate bool IsKeyPressed(GBAKeyCode keyCode);
    public IsKeyPressed KeyPressed;


    public Button btnStart;
    private void Awake()
    {
        instance = this;
        //BetterStreamingAssets.Initialize();
        // must set it to 60 or it won't sync with audio or run too fast.
        Application.targetFrameRate = (int)FrameRate;
        //audioSource = GetComponent<AudioSource>();
        //AudioClip clip = AudioClip.Create("blank", GbaAudio.SampleRate * 2, 2, GbaAudio.SampleRate, true);
        //audioSource.clip = clip;
        //audioSource.playOnAwake = true;
        //audioSource.enabled = false;
        //screenRenderer.material.mainTexture = new Texture2D(240, 160, TextureFormat.RGBA32, false, false);

        // Get Unity Buffer size
        AudioSettings.GetDSPBufferSize(out int bufferLength, out _);
        _samplesAvailable = bufferLength;
        // Must be set to 32768
        var audioConfig = AudioSettings.GetConfiguration();
        audioConfig.sampleRate = GbaAudio.SampleRate;
        AudioSettings.Reset(audioConfig);
        // Prepare our buffer
        //_pipeStream = new PipeStream();
        //_pipeStream.MaxBufferLength = _samplesAvailable * 2 * sizeof(float);
        _buffer = new byte[_samplesAvailable * 2 * sizeof(float)];
    }
    void Start()
    {
        byte[] bios = Resources.Load<TextAsset>("gba_bios.bin").bytes;
        //byte[] bios = BetterStreamingAssets.ReadAllBytes("gba_bios.bin");
        Debug.Log(bios.Length);
        gba = new Gba(new ProviderGba(bios, new byte[0], "", audioProvider.AudioReady) { BootBios = BootBIOS });
        EmulationThread = new Thread(EmulationThreadHandler);
        EmulationThread.Name = "Emulation Core";
        EmulationThread.Start();

        btnStart.onClick.AddListener(
            () =>
            {
                byte[] romdata = Resources.Load<TextAsset>("mario_world.gba").bytes;
                LoadRom(romdata, "mario_world.gba");
            }
            );
    }

    // Update is called once per frame
    void Update()
    {
        if (RomLoaded)
        {
            videoProvider.OnRenderFrame();
        }
        OnUpdateFrame();
    }

    public void LoadRom(byte[] rom, string name)
    {
        string savPath = Application.persistentDataPath + "/" + name.Substring(0, name.Length - 3) + "sav";
        byte[] sav = new byte[0];
        if (File.Exists(savPath))
        {
            Debug.Log($"{savPath} exists, loading");
            try
            {
                sav = File.ReadAllBytes(savPath);
            }
            catch
            {
                Debug.Log("Failed to load .sav file!");
            }
        }
        else
        {
            Debug.Log(".sav not available");
        }

        LoadRomAndSave(rom, sav, savPath);
        Debug.Log("Load Rom Success");
        audioProvider.Initialize();
        RomLoaded = true;
        RunEmulator = true;
    }

    public void LoadRomAndSave(byte[] rom, byte[] sav, string savPath)
    {
        var bios = gba.Provider.Bios;
        gba = new Gba(new ProviderGba(bios, rom, savPath, audioProvider.AudioReady) { BootBios = BootBIOS });
        gba.Mem.SaveProvider.LoadSave(sav);
    }

    public void ResetGba()
    {
        byte[] save = gba.Mem.SaveProvider.GetSave();
        ProviderGba p = gba.Provider;
        gba = new Gba(p);
        gba.Mem.SaveProvider.LoadSave(save);
    }

    public void EmulationThreadHandler()
    {
        while (true)
        {
            ThreadSync.WaitOne();

            int cyclesLeft = 70224 * 4;
            while (cyclesLeft > 0 && !gba.Cpu.Errored)
            {
                cyclesLeft -= (int)gba.Step();
            }

            while (!SyncToAudio && !gba.Cpu.Errored && RunEmulator)
            {
                gba.Step();
            }
        }
    }

    public int GetOutputSampleRate()
    {
        return AudioSettings.outputSampleRate;
    }

    public int GetSamplesAvailable()
    {
        return _samplesAvailable;
    }

    //private void OnAudioFilterRead(float[] data, int channels)
    //{
    //    if (!EnableAudio) return;

    //    int r = _pipeStream.Read(_buffer, 0, data.Length * sizeof(float));
    //    float[] pcm = CoreUtil.ByteToFloatArray(_buffer);
    //    Array.Copy(pcm, data, data.Length);
    //}

    

    public void RunCycles(int cycles)
    {
        while (cycles > 0 && !gba.Cpu.Errored && RunEmulator)
        {
            cycles -= (int)gba.Step();
        }
    }

    int CyclesLeft;
    public void RunFrame()
    {
        CyclesLeft += FrameCycles;
        while (CyclesLeft > 0 && !gba.Cpu.Errored)
        {
            CyclesLeft -= (int)gba.Step();
        }
    }

    public void RunScanline()
    {
        CyclesLeft += ScanlineCycles;
        while (CyclesLeft > 0 && !gba.Cpu.Errored)
        {
            CyclesLeft -= (int)gba.Step();
        }
    }


    public void OnUpdateFrame()
    {
        gba.Keypad.B = KeyPressed(GBAKeyCode.B);
        gba.Keypad.A = KeyPressed(GBAKeyCode.A);
        gba.Keypad.Left = KeyPressed(GBAKeyCode.Left);
        gba.Keypad.Up = KeyPressed(GBAKeyCode.Up);
        gba.Keypad.Right = KeyPressed(GBAKeyCode.Right);
        gba.Keypad.Down = KeyPressed(GBAKeyCode.Down);
        gba.Keypad.Start = KeyPressed(GBAKeyCode.Start);
        gba.Keypad.Select = KeyPressed(GBAKeyCode.Select);
        gba.Keypad.L = KeyPressed(GBAKeyCode.L);
        gba.Keypad.R = KeyPressed(GBAKeyCode.R);

        SyncToAudio = !(Input.GetKey(KeyCode.Tab) || Input.GetKey(KeyCode.Space));

        if (RunEmulator)
        {
            ThreadSync.Set();
        }

        if (gba.Mem.SaveProvider.Dirty)
        {
            DumpSav();
        }
    }
    
    public void DumpSav()
    {
        try
        {
            //File.WriteAllBytesAsync(gba.Provider.SavPath, gba.Mem.SaveProvider.GetSave());
            File.WriteAllBytes(gba.Provider.SavPath, gba.Mem.SaveProvider.GetSave());
        }
        catch
        {
            Debug.Log("Failed to write .sav file!");
        }
    }
    
}