// Copyright (c) 2023 Nico de Poel
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

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

namespace FidelityFX
{
    /// <summary>
    /// 
    /// </summary>
    [RequireComponent(typeof(Camera))]
    public class Fsr3UpscalerCameraHelper : MonoBehaviour
    {
        [Tooltip("Standard scaling ratio presets.")]
        public Fsr3Upscaler.QualityMode qualityMode = Fsr3Upscaler.QualityMode.Quality;

        private Vector2Int _maxRenderSize;
        private Vector2Int _displaySize;

        private Camera _renderCamera;
        private DepthTextureMode _originalDepthTextureMode;
        private Rect _originalRect;

        private void OnEnable()
        {
            // Set up the original camera to output all of the required FSR3 Upscaler input resources at the desired resolution
            _renderCamera = GetComponent<Camera>();
            _originalDepthTextureMode = _renderCamera.depthTextureMode;
            _renderCamera.depthTextureMode = _originalDepthTextureMode | DepthTextureMode.Depth | DepthTextureMode.MotionVectors;
        }

        private void OnDisable()
        {
            // Restore the camera's original state
            _renderCamera.depthTextureMode = _originalDepthTextureMode;
        }

        private void LateUpdate()
        {
            // Determine the desired rendering and display resolutions
            _displaySize = GetDisplaySize();
            Fsr3Upscaler.GetRenderResolutionFromQualityMode(out var maxRenderWidth, out var maxRenderHeight, _displaySize.x, _displaySize.y, qualityMode);
            _maxRenderSize = new Vector2Int(maxRenderWidth, maxRenderHeight);

            if (_maxRenderSize.x == 0 || _maxRenderSize.y == 0)
            {
                Debug.LogError($"FSR3 Upscaler render size is invalid: {_maxRenderSize.x}x{_maxRenderSize.y}. Please check your screen resolution and camera viewport parameters.");
                enabled = false;
            }
            
            // Remember the original camera viewport before we modify it in OnPreCull
            _originalRect = _renderCamera.rect;
        }

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

            ApplyJitter();
        }
        
        private void ApplyJitter()
        {
            var scaledRenderSize = GetScaledRenderSize();
            
            // Perform custom jittering of the camera's projection matrix according to FSR3's recipe
            int jitterPhaseCount = Fsr3Upscaler.GetJitterPhaseCount(scaledRenderSize.x, _displaySize.x);
            Fsr3Upscaler.GetJitterOffset(out float jitterX, out float jitterY, Time.frameCount, jitterPhaseCount);

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

            var jitterTranslationMatrix = Matrix4x4.Translate(new Vector3(jitterX, jitterY, 0));
            _renderCamera.nonJitteredProjectionMatrix = _renderCamera.projectionMatrix;
            _renderCamera.projectionMatrix = jitterTranslationMatrix * _renderCamera.nonJitteredProjectionMatrix;
            _renderCamera.useJitteredProjectionMatrixForTransparentRendering = true;
        }
        
        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();

            Graphics.Blit(src, dest);
        }

        private Vector2Int GetDisplaySize()
        {
            var targetTexture = _renderCamera.targetTexture;
            if (targetTexture != null)
                return new Vector2Int(targetTexture.width, targetTexture.height);
            
            return new Vector2Int(_renderCamera.pixelWidth, _renderCamera.pixelHeight);
        }

        private bool UsingDynamicResolution()
        {
            var targetTexture = _renderCamera.targetTexture;
            return _renderCamera.allowDynamicResolution || (targetTexture != null && targetTexture.useDynamicScale);
        }

        private Vector2Int GetScaledRenderSize()
        {
            if (UsingDynamicResolution())
                return new Vector2Int(Mathf.CeilToInt(_maxRenderSize.x * ScalableBufferManager.widthScaleFactor), Mathf.CeilToInt(_maxRenderSize.y * ScalableBufferManager.heightScaleFactor));
            
            return _maxRenderSize;
        }
    }
}