using System;
using UnityEngine;
using UnityEngine.Rendering;

namespace UnityEditor.Experimental.ScriptableRenderLoop
{
    internal class UnlitGUI : ShaderGUI
    {
        public enum SurfaceType
        {
            Opaque,
            Transparent
        }
        public enum BlendMode
        {
            Lerp,
            Add,
            SoftAdd,
            Multiply,
            Premultiply
        }

        public enum DoubleSidedMode
        {
            None,
            DoubleSided
        }

        private static class Styles
        {
            public static string OptionText = "Options";
            public static string SurfaceTypeText = "Surface Type";
            public static string BlendModeText = "Blend Mode";

            public static GUIContent alphaCutoffEnableText = new GUIContent("Alpha Cutoff Enable", "Threshold for alpha cutoff");
            public static GUIContent alphaCutoffText = new GUIContent("Alpha Cutoff", "Threshold for alpha cutoff");
            public static GUIContent doubleSidedModeText = new GUIContent("Double Sided", "This will render the two face of the objects (disable backface culling)");

            public static readonly string[] surfaceTypeNames = Enum.GetNames(typeof(SurfaceType));
            public static readonly string[] blendModeNames = Enum.GetNames(typeof(BlendMode));

            public static string InputsOptionsText = "Inputs options";

            public static string InputsText = "Inputs";

            public static string InputsMapText = "";

            public static GUIContent colorText = new GUIContent("Color + Opacity", "Albedo (RGB) and Opacity (A)");

            public static GUIContent emissiveText = new GUIContent("Emissive Color", "Emissive");
            public static GUIContent emissiveIntensityText = new GUIContent("Emissive Intensity", "Emissive");
        }

        MaterialProperty surfaceType = null;
        MaterialProperty blendMode = null;
        MaterialProperty alphaCutoff = null;
        MaterialProperty alphaCutoffEnable = null;
        MaterialProperty doubleSidedMode = null;

        MaterialProperty color = null;
        MaterialProperty colorMap = null;

        MaterialProperty emissiveColor = null;
        MaterialProperty emissiveColorMap = null;
        MaterialProperty emissiveIntensity = null;

        protected MaterialEditor m_MaterialEditor;

        protected const string kSurfaceType = "_SurfaceType";
        protected const string kBlendMode = "_BlendMode";
        protected const string kAlphaCutoff = "_AlphaCutoff";
        protected const string kAlphaCutoffEnabled = "_AlphaCutoffEnable";
        protected const string kDoubleSidedMode = "_DoubleSidedMode";
 
        protected const string kEmissiveColorMap = "_EmissiveColorMap";
 
        public void FindOptionProperties(MaterialProperty[] props)
        {
            surfaceType = FindProperty(kSurfaceType, props);
            blendMode = FindProperty(kBlendMode, props);
            alphaCutoff = FindProperty(kAlphaCutoff, props);
            alphaCutoffEnable = FindProperty(kAlphaCutoffEnabled, props);
            doubleSidedMode = FindProperty(kDoubleSidedMode, props);
        }

        public void FindInputProperties(MaterialProperty[] props)
        {
            color = FindProperty("_Color", props);
            colorMap = FindProperty("_ColorMap", props);
            emissiveColor = FindProperty("_EmissiveColor", props);
            emissiveColorMap = FindProperty(kEmissiveColorMap, props);
            emissiveIntensity = FindProperty("_EmissiveIntensity", props);
        }

        public override void OnGUI(MaterialEditor materialEditor, MaterialProperty[] props)
        {
            FindOptionProperties(props); // MaterialProperties can be animated so we do not cache them but fetch them every event to ensure animated values are updated correctly
            FindInputProperties(props);

            m_MaterialEditor = materialEditor;
            Material material = materialEditor.target as Material;
            ShaderPropertiesGUI(material);
        }

        protected void ShaderOptionsGUI()
        {
            EditorGUI.indentLevel++;
            GUILayout.Label(Styles.OptionText, EditorStyles.boldLabel);
            SurfaceTypePopup();
            if ((SurfaceType)surfaceType.floatValue == SurfaceType.Transparent)
            {
                BlendModePopup();
            }
            m_MaterialEditor.ShaderProperty(alphaCutoffEnable, Styles.alphaCutoffEnableText.text);
            if (alphaCutoffEnable.floatValue == 1.0)
            {
                m_MaterialEditor.ShaderProperty(alphaCutoff, Styles.alphaCutoffText.text);
            }
            m_MaterialEditor.ShaderProperty(doubleSidedMode, Styles.doubleSidedModeText.text);

            EditorGUI.indentLevel--;
        }

        protected void ShaderInputOptionsGUI()
        {
            EditorGUI.indentLevel++;
            EditorGUI.indentLevel--;
        }

        protected void ShaderInputGUI()
        {
            EditorGUI.indentLevel++;

            GUILayout.Label(Styles.InputsText, EditorStyles.boldLabel);

            m_MaterialEditor.TexturePropertySingleLine(Styles.colorText, colorMap, color);

            m_MaterialEditor.TexturePropertySingleLine(Styles.emissiveText, emissiveColorMap, emissiveColor);
            m_MaterialEditor.ShaderProperty(emissiveIntensity, Styles.emissiveIntensityText);
            m_MaterialEditor.LightmapEmissionProperty(MaterialEditor.kMiniTextureFieldLabelIndentLevel + 1);

            EditorGUI.indentLevel--;
        }

        public void ShaderPropertiesGUI(Material material)
        {
            // Use default labelWidth
            EditorGUIUtility.labelWidth = 0f;

            // Detect any changes to the material
            EditorGUI.BeginChangeCheck();
            {
                ShaderOptionsGUI();
                EditorGUILayout.Space();

                ShaderInputOptionsGUI();

                EditorGUILayout.Space();
                ShaderInputGUI();
            }

            if (EditorGUI.EndChangeCheck())
            {
                foreach (var obj in m_MaterialEditor.targets)
                    SetupMaterial((Material)obj);
            }
        }

        // TODO: try to setup minimun value to fall back to standard shaders and reverse
        public override void AssignNewShaderToMaterial(Material material, Shader oldShader, Shader newShader)
        {
            base.AssignNewShaderToMaterial(material, oldShader, newShader);
        }

        void SurfaceTypePopup()
        {
            EditorGUI.showMixedValue = surfaceType.hasMixedValue;
            var mode = (SurfaceType)surfaceType.floatValue;

            EditorGUI.BeginChangeCheck();
            mode = (SurfaceType)EditorGUILayout.Popup(Styles.SurfaceTypeText, (int)mode, Styles.surfaceTypeNames);
            if (EditorGUI.EndChangeCheck())
            {
                m_MaterialEditor.RegisterPropertyChangeUndo("Surface Type");
                surfaceType.floatValue = (float)mode;
            }

            EditorGUI.showMixedValue = false;
        }

        void BlendModePopup()
        {
            EditorGUI.showMixedValue = blendMode.hasMixedValue;
            var mode = (BlendMode)blendMode.floatValue;

            EditorGUI.BeginChangeCheck();
            mode = (BlendMode)EditorGUILayout.Popup(Styles.BlendModeText, (int)mode, Styles.blendModeNames);
            if (EditorGUI.EndChangeCheck())
            {
                m_MaterialEditor.RegisterPropertyChangeUndo("Blend Mode");
                blendMode.floatValue = (float)mode;
            }

            EditorGUI.showMixedValue = false;
        }

        protected virtual void SetupKeywordsForInputMaps(Material material)
        {
            SetKeyword(material, "_EMISSIVE_COLOR_MAP", material.GetTexture(kEmissiveColorMap));
        }

        protected void SetupMaterial(Material material)
        {
            // Note: keywords must be based on Material value not on MaterialProperty due to multi-edit & material animation
            // (MaterialProperty value might come from renderer material property block)

            bool alphaTestEnable = material.GetFloat(kAlphaCutoffEnabled) == 1.0;
            SurfaceType surfaceType = (SurfaceType)material.GetFloat(kSurfaceType);
            BlendMode blendMode = (BlendMode)material.GetFloat(kBlendMode);
            DoubleSidedMode doubleSidedMode = (DoubleSidedMode)material.GetFloat(kDoubleSidedMode);

            if (surfaceType == SurfaceType.Opaque)
            {
                material.SetOverrideTag("RenderType", alphaTestEnable ? "TransparentCutout" : "");
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                material.SetInt("_ZWrite", 1);
                material.renderQueue = alphaTestEnable ? (int)UnityEngine.Rendering.RenderQueue.AlphaTest : -1;
            }
            else
            {
                material.SetOverrideTag("RenderType", "Transparent");
                material.SetInt("_ZWrite", 0);
                material.renderQueue = (int)UnityEngine.Rendering.RenderQueue.Transparent;

                switch (blendMode)
                {
                    case BlendMode.Lerp:
                        material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
                        material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                        break;

                    case BlendMode.Add:
                        material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                        material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.One);
                        break;

                    case BlendMode.SoftAdd:
                        material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusDstColor);
                        material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.One);
                        break;

                    case BlendMode.Multiply:
                        material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.DstColor);
                        material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                        break;

                    case BlendMode.Premultiply:
                        material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                        material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                        break;
                }
            }

            if (doubleSidedMode == DoubleSidedMode.None)
            {
                material.SetInt("_CullMode", (int)UnityEngine.Rendering.CullMode.Back);
            }
            else
            {
                material.SetInt("_CullMode", (int)UnityEngine.Rendering.CullMode.Off);
            }

            SetKeyword(material, "_ALPHATEST_ON", alphaTestEnable);

            SetupKeywordsForInputMaps(material);

            // Setup lightmap emissive flags

            MaterialGlobalIlluminationFlags flags = material.globalIlluminationFlags;
            if ((flags & (MaterialGlobalIlluminationFlags.BakedEmissive | MaterialGlobalIlluminationFlags.RealtimeEmissive)) != 0)
            {
                if (LitGUI.ShouldEmissionBeEnabled(material))
                    flags &= ~MaterialGlobalIlluminationFlags.EmissiveIsBlack;
                else
                    flags |= MaterialGlobalIlluminationFlags.EmissiveIsBlack;

                material.globalIlluminationFlags = flags;
            }
        }

        bool HasValidEmissiveKeyword(Material material)
        {
            /*
            // Material animation might be out of sync with the material keyword.
            // So if the emission support is disabled on the material, but the property blocks have a value that requires it, then we need to show a warning.
            // (note: (Renderer MaterialPropertyBlock applies its values to emissionColorForRendering))
            bool hasEmissionKeyword = material.IsKeywordEnabled ("_EMISSION");
            if (!hasEmissionKeyword && ShouldEmissionBeEnabled (material, emissionColorForRendering.colorValue))
                return false;
            else
                return true;
            */

            return true;
        }

        protected void SetKeyword(Material m, string keyword, bool state)
        {
            if (state)
                m.EnableKeyword(keyword);
            else
                m.DisableKeyword(keyword);
        }
    }
} // namespace UnityEditor