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

namespace UnityEditor.Experimental.Rendering.HDPipeline
{
    [CustomEditor(typeof(SubsurfaceScatteringSettings))]
    public sealed partial class SubsurfaceScatteringSettingsEditor : HDBaseEditor<SubsurfaceScatteringSettings>
    {
        sealed class Profile
        {
            internal SerializedProperty self;
            internal SubsurfaceScatteringProfile objReference;

            internal SerializedProperty name;

            internal SerializedProperty scatteringDistance;
            internal SerializedProperty transmissionTint;
            internal SerializedProperty texturingMode;
            internal SerializedProperty transmissionMode;
            internal SerializedProperty thicknessRemap;
            internal SerializedProperty worldScale;
            internal SerializedProperty fresnel0;

            // Old SSS Model >>>
            internal SerializedProperty scatterDistance1;
            internal SerializedProperty scatterDistance2;
            internal SerializedProperty lerpWeight;
            // <<< Old SSS Model

            // Render preview
            internal RenderTexture profileRT;
            internal RenderTexture transmittanceRT;

            internal Profile()
            {
                profileRT       = new RenderTexture(256, 256, 0, RenderTextureFormat.DefaultHDR);
                transmittanceRT = new RenderTexture( 16, 256, 0, RenderTextureFormat.DefaultHDR);
            }

            internal void Release()
            {
                CoreUtils.Destroy(profileRT);
                CoreUtils.Destroy(transmittanceRT);
            }
        }

        SerializedProperty m_UseDisneySSS;
        List<Profile> m_Profiles;

        Material m_ProfileMaterial;
        Material m_TransmittanceMaterial;

        protected override void OnEnable()
        {
            base.OnEnable();

            // These shaders don't need to be reference by RenderPipelineResource as they are not use at runtime
            m_ProfileMaterial       = CoreUtils.CreateEngineMaterial("Hidden/HDRenderPipeline/DrawSssProfile");
            m_TransmittanceMaterial = CoreUtils.CreateEngineMaterial("Hidden/HDRenderPipeline/DrawTransmittanceGraph");

            int count = SssConstants.SSS_N_PROFILES - 1;
            m_Profiles = new List<Profile>();

            m_UseDisneySSS = properties.Find(x => x.useDisneySSS);
            var serializedProfiles = properties.Find(x => x.profiles);

            for (int i = 0; i < count; i++)
            {
                var serializedProfile = serializedProfiles.GetArrayElementAtIndex(i);
                var rp = new RelativePropertyFetcher<SubsurfaceScatteringProfile>(serializedProfile);

                var profile = new Profile
                {
                    self = serializedProfile,
                    objReference = m_Target.profiles[i],

                    name = rp.Find(x => x.name),

                    scatteringDistance = rp.Find(x => x.scatteringDistance),
                    transmissionTint = rp.Find(x => x.transmissionTint),
                    texturingMode = rp.Find(x => x.texturingMode),
                    transmissionMode = rp.Find(x => x.transmissionMode),
                    thicknessRemap = rp.Find(x => x.thicknessRemap),
                    worldScale = rp.Find(x => x.worldScale),
                    fresnel0 = rp.Find(x => x.fresnel0),

                    scatterDistance1 = rp.Find(x => x.scatterDistance1),
                    scatterDistance2 = rp.Find(x => x.scatterDistance2),
                    lerpWeight = rp.Find(x => x.lerpWeight)
                };

                m_Profiles.Add(profile);
            }
        }

        void OnDisable()
        {
            CoreUtils.Destroy(m_ProfileMaterial);
            CoreUtils.Destroy(m_TransmittanceMaterial);

            foreach (var profile in m_Profiles)
                profile.Release();

            m_Profiles = null;
        }

        public override void OnInspectorGUI()
        {
            CheckStyles();

            // Display a warning if this settings asset is not currently in use
            if (m_HDPipeline == null || m_HDPipeline.sssSettings != m_Target)
                EditorGUILayout.HelpBox("These profiles aren't currently in use, assign this asset to the HD render pipeline asset to use them.", MessageType.Warning);

            serializedObject.Update();

            EditorGUILayout.PropertyField(m_UseDisneySSS, s_Styles.useDisneySSS);

            EditorGUILayout.Space();

            if (m_Profiles == null || m_Profiles.Count == 0)
                return;

            bool useDisneySSS = m_UseDisneySSS.boolValue;

            for (int i = 0; i < m_Profiles.Count; i++)
            {
                var profile = m_Profiles[i];

                CoreEditorUtils.DrawSplitter();

                bool state = profile.self.isExpanded;
                state = CoreEditorUtils.DrawHeaderFoldout(profile.name.stringValue, state);

                if (state)
                {
                    EditorGUI.indentLevel++;
                    EditorGUILayout.PropertyField(profile.name);

                    using (var scope = new EditorGUI.ChangeCheckScope())
                    {
                        if (useDisneySSS)
                        {
                            EditorGUILayout.PropertyField(profile.scatteringDistance, s_Styles.profileScatteringDistance);

                            using (new EditorGUI.DisabledScope(true))
                                EditorGUILayout.FloatField(s_Styles.profileMaxRadius, profile.objReference.maxRadius);
                        }
                        else
                        {
                            EditorGUILayout.PropertyField(profile.scatterDistance1, s_Styles.profileScatterDistance1);
                            EditorGUILayout.PropertyField(profile.scatterDistance2, s_Styles.profileScatterDistance2);
                            EditorGUILayout.PropertyField(profile.lerpWeight, s_Styles.profileLerpWeight);
                        }

                        profile.texturingMode.intValue = EditorGUILayout.Popup(s_Styles.texturingMode, profile.texturingMode.intValue, s_Styles.texturingModeOptions);
                        profile.transmissionMode.intValue = EditorGUILayout.Popup(s_Styles.profileTransmissionMode, profile.transmissionMode.intValue, s_Styles.transmissionModeOptions);

                        EditorGUILayout.PropertyField(profile.transmissionTint, s_Styles.profileTransmissionTint);
                        EditorGUILayout.PropertyField(profile.thicknessRemap, s_Styles.profileMinMaxThickness);
                        var thicknessRemap = profile.thicknessRemap.vector2Value;
                        EditorGUILayout.MinMaxSlider(s_Styles.profileThicknessRemap, ref thicknessRemap.x, ref thicknessRemap.y, 0f, 50f);
                        profile.thicknessRemap.vector2Value = thicknessRemap;
                        EditorGUILayout.PropertyField(profile.worldScale, s_Styles.profileWorldScale);
                        EditorGUILayout.Slider(profile.fresnel0, 0.0f, 0.1f, s_Styles.profileFresnel0);

                        EditorGUILayout.Space();
                        EditorGUILayout.LabelField(s_Styles.profilePreview0, s_Styles.centeredMiniBoldLabel);
                        EditorGUILayout.LabelField(s_Styles.profilePreview1, EditorStyles.centeredGreyMiniLabel);
                        EditorGUILayout.LabelField(s_Styles.profilePreview2, EditorStyles.centeredGreyMiniLabel);
                        EditorGUILayout.LabelField(s_Styles.profilePreview3, EditorStyles.centeredGreyMiniLabel);
                        EditorGUILayout.Space();

                        serializedObject.ApplyModifiedProperties();

                        if (scope.changed)
                        {
                            // Validate and update the cache for this profile only
                            profile.objReference.Validate();
                            m_Target.UpdateCache(i);
                        }
                    }

                    RenderPreview(profile, useDisneySSS);

                    EditorGUILayout.Space();
                    EditorGUI.indentLevel--;
                }

                profile.self.isExpanded = state;
            }

            CoreEditorUtils.DrawSplitter();

            serializedObject.ApplyModifiedProperties();
        }

        void RenderPreview(Profile profile, bool useDisneySSS)
        {
            var obj = profile.objReference;
            float r = obj.maxRadius;
            var S = obj.shapeParam;
            var T = (Vector4)profile.transmissionTint.colorValue;
            var R = profile.thicknessRemap.vector2Value;
            bool transmissionEnabled = profile.transmissionMode.intValue != (int)SubsurfaceScatteringProfile.TransmissionMode.None;

            m_ProfileMaterial.SetFloat(HDShaderIDs._MaxRadius, r);
            m_ProfileMaterial.SetVector(HDShaderIDs._ShapeParam, S);

            // Old SSS Model >>>
            CoreUtils.SelectKeyword(m_ProfileMaterial, "SSS_MODEL_DISNEY", "SSS_MODEL_BASIC", useDisneySSS);

            // Apply the three-sigma rule, and rescale.
            float s = (1f / 3f) * SssConstants.SSS_BASIC_DISTANCE_SCALE;
            var scatterDist1 = profile.scatterDistance1.colorValue;
            var scatterDist2 = profile.scatterDistance2.colorValue;
            float rMax = Mathf.Max(scatterDist1.r, scatterDist1.g, scatterDist1.b,
                                    scatterDist2.r, scatterDist2.g, scatterDist2.b);
            var stdDev1 = s * (Vector4)scatterDist1;
            var stdDev2 = s * (Vector4)scatterDist2;
            m_ProfileMaterial.SetVector(HDShaderIDs._StdDev1, stdDev1);
            m_ProfileMaterial.SetVector(HDShaderIDs._StdDev2, stdDev2);
            m_ProfileMaterial.SetFloat(HDShaderIDs._LerpWeight, profile.lerpWeight.floatValue);
            m_ProfileMaterial.SetFloat(HDShaderIDs._MaxRadius, rMax);
            // <<< Old SSS Model

            // Draw the profile.
            EditorGUI.DrawPreviewTexture(GUILayoutUtility.GetRect(256f, 256f), profile.profileRT, m_ProfileMaterial, ScaleMode.ScaleToFit, 1f);

            EditorGUILayout.Space();
            EditorGUILayout.LabelField(s_Styles.transmittancePreview0, s_Styles.centeredMiniBoldLabel);
            EditorGUILayout.LabelField(s_Styles.transmittancePreview1, EditorStyles.centeredGreyMiniLabel);
            EditorGUILayout.LabelField(s_Styles.transmittancePreview2, EditorStyles.centeredGreyMiniLabel);
            EditorGUILayout.Space();

            // Old SSS Model >>>
            // Multiply by 0.1 to convert from millimeters to centimeters. Apply the distance scale.
            float a = 0.1f * SssConstants.SSS_BASIC_DISTANCE_SCALE;
            var halfRcpVarianceAndWeight1 = new Vector4(a * a * 0.5f / (stdDev1.x * stdDev1.x), a * a * 0.5f / (stdDev1.y * stdDev1.y), a * a * 0.5f / (stdDev1.z * stdDev1.z), 4f * (1f - profile.lerpWeight.floatValue));
            var halfRcpVarianceAndWeight2 = new Vector4(a * a * 0.5f / (stdDev2.x * stdDev2.x), a * a * 0.5f / (stdDev2.y * stdDev2.y), a * a * 0.5f / (stdDev2.z * stdDev2.z), 4f * profile.lerpWeight.floatValue);
            m_TransmittanceMaterial.SetVector(HDShaderIDs._HalfRcpVarianceAndWeight1, halfRcpVarianceAndWeight1);
            m_TransmittanceMaterial.SetVector(HDShaderIDs._HalfRcpVarianceAndWeight2, halfRcpVarianceAndWeight2);
            // <<< Old SSS Model

            m_TransmittanceMaterial.SetVector(HDShaderIDs._ShapeParam, S);
            m_TransmittanceMaterial.SetVector(HDShaderIDs._TransmissionTint, transmissionEnabled ? T : Vector4.zero);
            m_TransmittanceMaterial.SetVector(HDShaderIDs._ThicknessRemap, R);

            // Draw the transmittance graph.
            EditorGUI.DrawPreviewTexture(GUILayoutUtility.GetRect(16f, 16f), profile.transmittanceRT, m_TransmittanceMaterial, ScaleMode.ScaleToFit, 16f);
        }
    }
}