using System;
using System.Collections.Generic;
using System.Linq;
#if UNITY_EDITOR
using UnityEditor;
#endif
using UnityEngine.Graphing;

namespace UnityEngine.MaterialGraph
{
    [Title("Input/Motion Vector Texture")]
    public class MotionVectorTextureNode : PropertyNode, IGeneratesBodyCode, IMayRequireMeshUV
    {
        protected const string kUVSlotName = "UV";
        protected const string kOutputSlotName = "Output";

        public const int UvSlotId = 0;
        public const int OutputSlotId = 1;

        public override bool hasPreview { get { return true; } }

        public Texture2D defaultTexture { get; set; }

        public MotionVectorTextureNode()
        {
            name = "MotionVectorTexture";
            UpdateNodeAfterDeserialization();
        }

        public sealed override void UpdateNodeAfterDeserialization()
        {
            AddSlot(new MaterialSlot(OutputSlotId, kOutputSlotName, kOutputSlotName, SlotType.Output, SlotValueType.Vector4, Vector4.zero));
            AddSlot(new MaterialSlot(UvSlotId, kUVSlotName, kUVSlotName, SlotType.Input, SlotValueType.Vector2, Vector4.zero, false));
            RemoveSlotsNameNotMatching(validSlots);
        }

        protected int[] validSlots
        {
            get { return new[] { OutputSlotId, UvSlotId }; }
        }

        public virtual void GenerateNodeCode(ShaderGenerator visitor, GenerationMode generationMode)
        {
            var uvSlot = FindInputSlot<MaterialSlot>(UvSlotId);
            if (uvSlot == null)
                return;

            var uvName = string.Format("{0}.xy", UVChannel.uv0.GetUVName());
            var edges = owner.GetEdges(uvSlot.slotReference).ToList();

            if (edges.Count > 0)
            {
                var edge = edges[0];
                var fromNode = owner.GetNodeFromGuid<AbstractMaterialNode>(edge.outputSlot.nodeGuid);
                uvName = ShaderGenerator.AdaptNodeOutput(fromNode, edge.outputSlot.slotId, ConcreteSlotValueType.Vector2, true);
            }

            string body = "tex2D (_CameraMotionVectorTexture, " + uvName + ")";
            visitor.AddShaderChunk(precision + "4 " + GetVariableNameForNode() + " = " + body + ";", true);
        }

        public override void CollectPreviewMaterialProperties(List<PreviewProperty> properties)
        {
            properties.Add(GetPreviewProperty());
        }

        public override void GeneratePropertyUsages(ShaderGenerator visitor, GenerationMode generationMode)
        {
            visitor.AddShaderChunk("sampler2D _CameraMotionVectorTexture;", true);
        }

        public override PreviewProperty GetPreviewProperty()
        {
            return new PreviewProperty
            {
                m_Name = propertyName,
                m_PropType = PropertyType.Texture2D,
                m_Texture = defaultTexture
            };
        }

        public override string GetVariableNameForSlot(int slotId)
        {
            return GetVariableNameForNode();
        }

        public override PropertyType propertyType { get { return PropertyType.Texture2D; } }

        public bool RequiresMeshUV(UVChannel channel)
        {
            if (channel != UVChannel.uv0)
            {
                return false;
            }

            var uvSlot = FindInputSlot<MaterialSlot>(UvSlotId);
            if (uvSlot == null)
                return true;

            var edges = owner.GetEdges(uvSlot.slotReference).ToList();
            return edges.Count == 0;
        }
    }
}