using System.Collections;
using UnityEngine;
using UnityEngine.Experimental.Rendering;
using UnityEngine.Rendering;

namespace FidelityFX
{
    /// <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 component also exposes various FSR2 parameters to the Unity inspector.
    /// </summary>
    [RequireComponent(typeof(Camera))]
    public class Fsr2Controller : MonoBehaviour
    {
        [SerializeField] private Fsr2.QualityMode qualityMode;
        
        [SerializeField] private bool performSharpenPass = true;

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

        [SerializeField] private bool enableFP16 = false;

        private Fsr2Context _context;
        private Vector2Int _renderSize;
        private Vector2Int _displaySize;
        private bool _reset;
        
        private Camera _renderCamera;
        private RenderTexture _originalRenderTarget;
        private DepthTextureMode _originalDepthTextureMode;
        private Rect _originalRect;

        private readonly Fsr2.DispatchDescription _dispatchDescription = new Fsr2.DispatchDescription();
        private readonly Fsr2.GenerateReactiveDescription _genReactiveDescription = new Fsr2.GenerateReactiveDescription();

        private Fsr2.QualityMode _prevQualityMode;
        private Vector2Int _prevDisplaySize;

        private CommandBuffer _dispatchCommandBuffer;
        private CommandBuffer _opaqueOnlyCommandBuffer;
        private CommandBuffer _inputsCommandBuffer;
        
        private void OnEnable()
        {
            Fsr2.InitializationFlags flags = Fsr2.InitializationFlags.EnableMotionVectorsJitterCancellation;
            if (enableFP16)
                flags |= Fsr2.InitializationFlags.EnableFP16Usage;
            
            _displaySize = new Vector2Int(Screen.width, Screen.height);
            Fsr2.GetRenderResolutionFromQualityMode(out var renderWidth, out var renderHeight, _displaySize.x, _displaySize.y, qualityMode);
            _renderSize = new Vector2Int(renderWidth, renderHeight);
            _context = Fsr2.CreateContext(_displaySize, _renderSize, flags);

            // Set up the original camera to output all of the required FSR2 input resources at the desired resolution
            _renderCamera = GetComponent<Camera>();
            _originalDepthTextureMode = _renderCamera.depthTextureMode;
            _renderCamera.depthTextureMode = _originalDepthTextureMode | DepthTextureMode.Depth | DepthTextureMode.MotionVectors;
            
            _dispatchCommandBuffer = new CommandBuffer { name = "FSR2 Dispatch" };

            // Create command buffers to bind the camera's output at the right moments in the render loop
            _opaqueOnlyCommandBuffer = new CommandBuffer { name = "FSR2 Opaque Input" };
            // TODO: may need to copy the opaque-only render buffer to a temp RT here, in which case we'll need an additional CommandBuffer to release the temp RT again
            _opaqueOnlyCommandBuffer.SetGlobalTexture(Fsr2Pipeline.SrvOpaqueOnly, BuiltinRenderTextureType.CameraTarget, RenderTextureSubElement.Color);
            _renderCamera.AddCommandBuffer(CameraEvent.BeforeImageEffectsOpaque, _opaqueOnlyCommandBuffer);

            _inputsCommandBuffer = new CommandBuffer { name = "FSR2 Inputs" };
            _inputsCommandBuffer.SetGlobalTexture(Fsr2Pipeline.SrvInputColor, BuiltinRenderTextureType.CameraTarget, RenderTextureSubElement.Color);
            _inputsCommandBuffer.SetGlobalTexture(Fsr2Pipeline.SrvInputDepth, BuiltinRenderTextureType.CameraTarget, RenderTextureSubElement.Depth);
            _inputsCommandBuffer.SetGlobalTexture(Fsr2Pipeline.SrvInputMotionVectors, BuiltinRenderTextureType.MotionVectors);
            _renderCamera.AddCommandBuffer(CameraEvent.BeforeImageEffects, _inputsCommandBuffer);

            // Apply a mipmap bias so that textures retain their original sharpness
            float biasOffset = Fsr2.GetMipmapBiasOffset(_renderSize.x, _displaySize.x);
            Fsr2.GlobalCallbacks.ApplyMipmapBias(biasOffset);

            _prevDisplaySize = _displaySize;
            _prevQualityMode = qualityMode;
        }

        private void OnDisable()
        {
            float biasOffset = Fsr2.GetMipmapBiasOffset(_renderSize.x, _prevDisplaySize.x);
            Fsr2.GlobalCallbacks.ApplyMipmapBias(-biasOffset);

            if (_opaqueOnlyCommandBuffer != null)
            {
                _renderCamera.RemoveCommandBuffer(CameraEvent.BeforeImageEffectsOpaque, _opaqueOnlyCommandBuffer);
                _opaqueOnlyCommandBuffer.Release();
                _opaqueOnlyCommandBuffer = null;
            }

            if (_inputsCommandBuffer != null)
            {
                _renderCamera.RemoveCommandBuffer(CameraEvent.BeforeImageEffects, _inputsCommandBuffer);
                _inputsCommandBuffer.Release();
                _inputsCommandBuffer = null;
            }

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

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

        private void Update()
        {
            if (Screen.width != _prevDisplaySize.x || Screen.height != _prevDisplaySize.y || qualityMode != _prevQualityMode)
            {
                // Force all resources to be destroyed and recreated with the new settings
                OnDisable();
                OnEnable();
            }
        }

        public void Reset()
        {
            _reset = true;
        }

        private void OnPreRender()
        {
            // Render to a smaller portion of the screen by manipulating the camera's viewport rect
            _originalRect = _renderCamera.rect;
            _renderCamera.aspect = (Screen.width * _originalRect.width) / (Screen.height * _originalRect.height);
            _renderCamera.rect = new Rect(0, 0, _originalRect.width * _renderSize.x / _displaySize.x, _originalRect.height * _renderSize.y / _displaySize.y);

            _genReactiveDescription.RenderSize = _renderSize;
            _genReactiveDescription.Scale = 1.0f;
            _genReactiveDescription.CutoffThreshold = 0.2f;
            _genReactiveDescription.BinaryValue = 0.9f;
            _genReactiveDescription.Flags = 0;  // ApplyTonemap, ApplyInverseTonemap, ApplyThreshold, UseComponentsMax
            
            _dispatchDescription.Color = null;
            _dispatchDescription.Depth = null;
            _dispatchDescription.MotionVectors = null;
            _dispatchDescription.Output = null;
            _dispatchDescription.Exposure = null;
            _dispatchDescription.Reactive = null;
            _dispatchDescription.PreExposure = 0;
            _dispatchDescription.EnableSharpening = performSharpenPass;
            _dispatchDescription.Sharpness = sharpness;
            _dispatchDescription.MotionVectorScale.x = -_renderCamera.pixelWidth;
            _dispatchDescription.MotionVectorScale.y = -_renderCamera.pixelHeight;
            _dispatchDescription.RenderSize = _renderSize;
            _dispatchDescription.FrameTimeDelta = Time.unscaledDeltaTime;
            _dispatchDescription.CameraNear = _renderCamera.nearClipPlane;
            _dispatchDescription.CameraFar = _renderCamera.farClipPlane;
            _dispatchDescription.CameraFovAngleVertical = _renderCamera.fieldOfView * Mathf.Deg2Rad;
            _dispatchDescription.ViewSpaceToMetersFactor = 1.0f; // 1 unit is 1 meter in Unity
            _dispatchDescription.Reset = _reset;
            _reset = false;

            // Perform custom jittering of the camera's projection matrix according to FSR2's instructions
            int jitterPhaseCount = Fsr2.GetJitterPhaseCount(_renderSize.x, _displaySize.x);
            Fsr2.GetJitterOffset(out float jitterX, out float jitterY, Time.frameCount, jitterPhaseCount);

            _dispatchDescription.JitterOffset = new Vector2(jitterX, jitterY);

            jitterX = 2.0f * jitterX / _renderSize.x;
            jitterY = 2.0f * jitterY / _renderSize.y;

            var jitterTranslationMatrix = Matrix4x4.Translate(new Vector3(jitterX, jitterY, 0));
            _renderCamera.projectionMatrix = jitterTranslationMatrix * _renderCamera.nonJitteredProjectionMatrix;
        }
        
        private void OnRenderImage(RenderTexture src, RenderTexture dest)
        {
            // Restore the camera's viewport rect so we can output at full resolution
            _renderCamera.rect = _originalRect;
            _renderCamera.ResetProjectionMatrix();

            _dispatchCommandBuffer.Clear();
            
            // UpscaleReactive: width, height, VK_FORMAT_R8_UNORM
            //Context.GenerateReactiveMask();
            
            _dispatchDescription.InputResourceSize = new Vector2Int(src.width, src.height);

            if (dest != null)
            {
                Debug.Log($"src = {src.width}x{src.height}, dest = {dest.width}x{dest.height}");
                // We have more image effects lined up after this, so FSR2 can output straight to the intermediate render texture
                // TODO: we should probably use a shader to include depth & motion vectors into the output, making sure they match the expected output resolution
                _dispatchCommandBuffer.SetGlobalTexture(Fsr2Pipeline.UavUpscaledOutput, dest);
            }
            else
            {
                // We are rendering to the backbuffer, so we need a temporary render texture for FSR2 to output to
                _dispatchCommandBuffer.GetTemporaryRT(Fsr2Pipeline.UavUpscaledOutput, Screen.width, Screen.height, 0, default, GraphicsFormat.R16G16B16A16_SFloat, 1, true);
            }

            _context.Dispatch(_dispatchDescription, _dispatchCommandBuffer);

            // Output upscaled image to screen
            // TODO: if `dest` is null, we likely don't care about the depth & motion vectors anymore
            if (dest == null)
            {
                _dispatchCommandBuffer.Blit(Fsr2Pipeline.UavUpscaledOutput, dest);
                _dispatchCommandBuffer.ReleaseTemporaryRT(Fsr2Pipeline.UavUpscaledOutput);
            }

            Graphics.ExecuteCommandBuffer(_dispatchCommandBuffer);

            // Shut up the Unity warning about not writing to the destination texture 
            Graphics.SetRenderTarget(dest);
        }
    }
}