using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using FidelityFX;
using UnityEngine;
using UnityEngine.Rendering;

/// <summary>
/// This class is responsible for hooking into various Unity events and translating them to the FSR2 subsystem.
/// This includes creation and destruction of the FSR2 context, as well as dispatching commands at the right time.
/// This class also exposes various FSR2 parameters to the Unity inspector.
/// </summary>
public class Fsr2Controller : MonoBehaviour
{
    [SerializeField]
    private bool performSharpenPass = true;

    [SerializeField, Range(0, 1)]
    private float sharpness = 0.8f;
    
    [HideInInspector]
    public Camera gameCamera;

    [HideInInspector]
    public Camera outputCamera;

    [HideInInspector]
    public float renderScale;

    private Fsr2Context _context;
    private readonly Fsr2.DispatchDescription _dispatchDescription = new Fsr2.DispatchDescription();

    private RenderTexture _upscaleRT;
    private RenderTexture _outputRT;
    private Texture2D _exposure;
    
    private Material _testMaterial;
    private Material TestMaterial
    {
        get
        {
            if (_testMaterial == null)
            {
                var testShader = Fsr2.GlobalCallbacks.LoadShader("Shaders/FSRTest");
                _testMaterial = new Material(testShader);
            }

            return _testMaterial;
        }
    }

    private void OnEnable()
    {
        RenderPipelineManager.endContextRendering += OnEndContextRendering;

        _context = Fsr2.CreateContext();

        _upscaleRT = new RenderTexture(Screen.width, Screen.height, 24, RenderTextureFormat.ARGBHalf);
        _upscaleRT.Create();

        _outputRT = new RenderTexture(Screen.width, Screen.height, 24, RenderTextureFormat.ARGBHalf);
        _outputRT.enableRandomWrite = true;
        _outputRT.Create();

        _exposure = new Texture2D(1, 1);
        _exposure.name = "FSR2 Exposure";
        _exposure.SetPixel(0, 0, Color.white);
        _exposure.Apply();
    }

    private void OnDisable()
    {
        if (_exposure != null)
        {
            Destroy(_exposure);
            _exposure = null;
        }

        if (_outputRT != null)
        {
            _outputRT.Release();
            _outputRT = null;
        }

        if (_upscaleRT != null)
        {
            _upscaleRT.Release();
            _upscaleRT = null;
        }

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

        RenderPipelineManager.endContextRendering -= OnEndContextRendering;
    }

    // For scriptable rendering pipeline
    private void OnEndContextRendering(ScriptableRenderContext context, List<Camera> cameras)
    {
        Debug.Log($"OnEndContentRendering, cameras = {string.Join(", ", cameras.Select(c => c.name))}");
    }

    // For legacy built-in render pipeline
    private void OnRenderImage(RenderTexture src, RenderTexture dest)
    {
        // Do a dumb upscale first
        Graphics.Blit(gameCamera.targetTexture, _upscaleRT, TestMaterial);

        _dispatchDescription.Input = _upscaleRT;
        _dispatchDescription.Output = _outputRT;
        _dispatchDescription.Exposure = _exposure;
        _dispatchDescription.PreExposure = 1.0f;
        _dispatchDescription.EnableSharpening = performSharpenPass;
        _dispatchDescription.Sharpness = sharpness;
        _dispatchDescription.MotionVectorScale.x = gameCamera.pixelWidth;
        _dispatchDescription.MotionVectorScale.y = gameCamera.pixelHeight;
        _dispatchDescription.FrameTimeDelta = Time.unscaledDeltaTime;
        _dispatchDescription.CameraNear = gameCamera.nearClipPlane;
        _dispatchDescription.CameraFar = gameCamera.farClipPlane;
        _dispatchDescription.CameraFovAngleVertical = gameCamera.fieldOfView * Mathf.Deg2Rad;

        _context.Dispatch(_dispatchDescription);
        
        // Output sharpened image to screen
        Graphics.Blit(_outputRT, dest);
    }
}