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

namespace GraphicsCat.LitPlus.Experimental
{
    // Fade in/out, supports composite objects
    public class LitPlusAlphaFadeController : MonoBehaviour
    {
        internal class PropertyID
        {
            readonly public static int ZWrite = Shader.PropertyToID("_ZWrite");
            readonly public static int SrcBlend = Shader.PropertyToID("_SrcBlend");
            readonly public static int DstBlend = Shader.PropertyToID("_DstBlend");
            readonly public static int Color = Shader.PropertyToID("_BaseColor");
            readonly public static int BlendMode = Shader.PropertyToID("_SURFACE_TYPE");
        }

        internal class MaterialInfo
        {
            float m_OriginalZWrite;
            float m_OriginalSrcFac;
            float m_OriginalDstFac;
            Color m_OriginalColor;
            int m_OriginalRenderQueue;
            float m_OriginalBlendMode;

            public float originalAlpha 
            { 
                get { return m_OriginalColor.a; } 
            }

            public void Backup(Material material)
            {
                m_OriginalBlendMode = material.GetFloat(PropertyID.BlendMode);
                m_OriginalZWrite = material.GetFloat(PropertyID.ZWrite);
                m_OriginalSrcFac = material.GetFloat(PropertyID.SrcBlend);
                m_OriginalDstFac = material.GetFloat(PropertyID.DstBlend);
                m_OriginalColor = material.GetColor(PropertyID.Color);
                m_OriginalRenderQueue = material.renderQueue;
            }

            public void Restore(Material material)
            {
                material.SetFloat(PropertyID.BlendMode, m_OriginalBlendMode);
                switch (m_OriginalBlendMode)
                {
                    case 0: material.EnableKeyword("_SURFACE_TYPE_OPAQUE"); break;
                    case 1: material.EnableKeyword("_SURFACE_TYPE_CUTOUT"); break;
                }

                material.renderQueue = m_OriginalRenderQueue;

                material.SetFloat(PropertyID.ZWrite, m_OriginalZWrite);
                material.SetFloat(PropertyID.SrcBlend, m_OriginalSrcFac);
                material.SetFloat(PropertyID.DstBlend, m_OriginalDstFac);
                material.SetColor(PropertyID.Color, m_OriginalColor);
            }

            public void OnBeginFade(Material material, float alpha)
            {
                // Still need to write depth, otherwise there may be confusion (e.g., hair and head)
                material.SetFloat(PropertyID.ZWrite, 1);
                material.SetFloat(PropertyID.SrcBlend, (int)BlendMode.SrcAlpha);
                material.SetFloat(PropertyID.DstBlend, (int)BlendMode.OneMinusSrcAlpha);
                var color = material.GetColor(PropertyID.Color);
                color.a = alpha;
                material.SetColor(PropertyID.Color, color);
                material.renderQueue = (int)RenderQueue.Transparent;
                material.EnableKeyword("_SURFACE_TYPE_TRANSPARENT");
            }
        }

        [Range(0.0f, 10.0f)]
        public float fadeTime = 1.0f;

        Dictionary<Material, MaterialInfo> m_MaterialInfos = new Dictionary<Material, MaterialInfo>();

        bool m_IsFading = false;
        float m_FadeTimer = 0;
        bool m_FadeInOrOut = false;

        public void FadeIn()
        {
            Fade(true);
        }

        public void FadeOut()
        {
            Fade(false);
        }

        void Start()
        {
            CollectMaterials(); // Get all materials
        }

        void Update()
        {
            if (m_IsFading) // Alpha fade
            {
                m_FadeTimer += Time.deltaTime;

                var lerpFac = Mathf.Min(m_FadeTimer / fadeTime, 1);
                foreach (var kv in m_MaterialInfos)
                {
                    var material = kv.Key;
                    var materialInfo = kv.Value;

                    var color = material.GetColor(PropertyID.Color);
                    float alphaBegin = m_FadeInOrOut ? 0 : materialInfo.originalAlpha;
                    float alphaEnd = m_FadeInOrOut ? materialInfo.originalAlpha : 0;
                    color.a = Mathf.Lerp(alphaBegin, alphaEnd, lerpFac);

                    material.SetColor(PropertyID.Color, color);
                }

                if (m_FadeTimer >= fadeTime)
                {
                    m_IsFading = false;
                    OnEndFade();
                }
            }
        }

        void Fade(bool inOrOut)
        {
            m_IsFading = true;
            m_FadeTimer = 0;
            m_FadeInOrOut = inOrOut;
            OnBgeinFade(inOrOut ? 0 : 1);
        }

        void OnBgeinFade(float alpha)
        {
            foreach (var kv in m_MaterialInfos)
            {
                var material = kv.Key;
                var materialInfo = kv.Value;
                materialInfo.OnBeginFade(material, alpha);
            }
        }

        void OnEndFade()
        {
            foreach (var kv in m_MaterialInfos)
            {
                var material = kv.Key;
                var materialInfo = kv.Value;
                materialInfo.Restore(material);
            }
        }

        void CollectMaterials()
        {
            var renderres = gameObject.GetComponentsInChildren<Renderer>(false);
            foreach (var renderer in renderres)
            {
                // Cannot use ShareMaterials, otherwise it will affect other objects
                var materials = renderer.materials;
                if (materials == null)
                    continue;

                foreach (var material in materials)
                {
                    if (m_MaterialInfos.ContainsKey(material) == false)
                    {
                        if (material.shader.name.ToLower().IndexOf("graphicscat/litplus") != -1)
                        {
                            var info = new MaterialInfo();
                            info.Backup(material); // Collect original material data
                            m_MaterialInfos.Add(material, info);
                        }
                    }
                }
            }
        }
    }
}