using UnityEditor;
using UnityEngine;
using UnityEngine.Experimental.Rendering;
using UnityEngine.Rendering;
using UnityEngine.Rendering.HighDefinition;
using UnityEngine.Rendering.RendererUtils;

namespace Misaki.HdrpToon
{
    [HideInInspector]
    internal class UTSHairShadowPass : DrawRenderersCustomPass
    {
        public enum ShadowQuality
        {
            Low,
            High
        }

        private const string Hair_Shadow_RTHandle_Scale_Prop_Name = "_HairShadowRTHandleScale";
        private const string Hair_Shadow_Distance_Prop_Name = "_HairShadowDistance";
        private const string Hair_Shadow_Distance_Scale_Prop_Name = "_HairShadowDistanceScaleFactor";
        private const string Hair_Shadow_Depth_Bias_Prop_Name = "_HairShadowDepthBias";
        private const string Hair_Shadow_FadeIn_Prop_Name = "_HairShadowFadeInDistance";
        private const string Hair_Shadow_Fade_Out_Prop_Name = "_HairShadowFadeOutDistance";

        private const string Output_RT_Name = "_HairShadowTex";

        private RTHandle _outputRTHandle;
        private bool _needReallocate;

        private ShadowQuality _shadowQuality = ShadowQuality.High;
        internal ShadowQuality CurrentShadowQuality
        {
            get => _shadowQuality;
            set
            {
                if (_shadowQuality == value)
                {
                    return;
                }

                _shadowQuality = value;
                _needReallocate = true;
            }
        }

        private bool ShouldReallocateBuffer()
        {
            return _outputRTHandle == null || _outputRTHandle.rt == null || !_outputRTHandle.rt.IsCreated() || _needReallocate;
        }

        private void ReallocateBuffer()
        {
#if UNITY_EDITOR
            if (EditorApplication.isCompiling)
            {
                return;
            }
#endif

            var scale = _shadowQuality switch
            {
                ShadowQuality.Low => new Vector2(0.5f, 0.5f),
                ShadowQuality.High => Vector2.one,
                _ => Vector2.zero
            };

            var format = _shadowQuality switch
            {
                ShadowQuality.Low => GraphicsFormat.D16_UNorm,
                ShadowQuality.High => GraphicsFormat.D32_SFloat,
                _ => GraphicsFormat.D16_UNorm
            };

            _outputRTHandle?.Release();
            _outputRTHandle = RTHandles.Alloc(scale, colorFormat: format, filterMode: FilterMode.Bilinear, wrapMode: TextureWrapMode.Clamp, isShadowMap: true, name: Output_RT_Name);
            Shader.SetGlobalTexture(Output_RT_Name, _outputRTHandle);

            _needReallocate = false;
        }

        protected override void Setup(ScriptableRenderContext renderContext, CommandBuffer cmd)
        {
            ReallocateBuffer();
        }

        protected override void Execute(CustomPassContext ctx)
        {
            if (ShouldReallocateBuffer())
            {
                ReallocateBuffer();
                return;
            }

            CoreUtils.SetRenderTarget(ctx.cmd, _outputRTHandle, ClearFlag.DepthStencil);

            var utsRenderer = ctx.hdCamera.volumeStack.GetComponent<UTSRenderer>();
            var shouldRender = utsRenderer != null && utsRenderer.enableHairShadow.value && utsRenderer.state.value;
            if (!shouldRender)
            {
                CoreUtils.ClearRenderTarget(ctx.cmd, ClearFlag.DepthStencil, Color.black);
                return;
            }

            var mask = RenderStateMask.Nothing;
            var stateBlock = new RenderStateBlock(mask)
            {
                depthState = new DepthState(true, CompareFunction.LessEqual),
            };

            var result = new RendererListDesc(UtsShaderPassName.hairShadowCasterPassId, ctx.cullingResults, ctx.hdCamera.camera)
            {
                renderQueueRange = GetRenderQueueRange(RenderQueueType.All),
                sortingCriteria = SortingCriteria.CommonOpaque,
                excludeObjectMotionVectors = false,
                stateBlock = stateBlock,
            };

            CoreUtils.DrawRendererList(ctx.renderContext, ctx.cmd, ctx.renderContext.CreateRendererList(result));

            Shader.SetGlobalVector(Hair_Shadow_RTHandle_Scale_Prop_Name, _outputRTHandle.rtHandleProperties.rtHandleScale);
            Shader.SetGlobalFloat(Hair_Shadow_Distance_Prop_Name, utsRenderer.shadowDistance.value);
            Shader.SetGlobalFloat(Hair_Shadow_Distance_Scale_Prop_Name, utsRenderer.shadowDistanceScale.value);
            Shader.SetGlobalFloat(Hair_Shadow_Depth_Bias_Prop_Name, utsRenderer.shadowDepthBias.value);
            Shader.SetGlobalFloat(Hair_Shadow_FadeIn_Prop_Name, utsRenderer.shadowFadeIn.value);
            Shader.SetGlobalFloat(Hair_Shadow_Fade_Out_Prop_Name, utsRenderer.shadowFadeOut.value);
        }

        protected override void Cleanup()
        {
            Release();
        }

        public void Release()
        {
#if UNITY_EDITOR
            if (EditorApplication.isCompiling)
            {
                return;
            }
#endif
            _outputRTHandle?.Release();
        }
    }
}