using System;
using System.Collections.Generic;
using System.Linq;
using UnityEditor.Graphing.Util;
using UnityEngine;
using UnityEditor.Graphing;
using Object = UnityEngine.Object;
using UnityEditor.Graphs;

using UnityEditor.Experimental.GraphView;
using UnityEditor.ShaderGraph.Drawing.Colors;
using UnityEditor.ShaderGraph.Internal;
using UnityEngine.UIElements;
using Edge = UnityEditor.Experimental.GraphView.Edge;
using Node = UnityEditor.Experimental.GraphView.Node;

namespace UnityEditor.ShaderGraph.Drawing
{
    sealed class MaterialGraphView : GraphView
    {
        public MaterialGraphView()
        {
            styleSheets.Add(Resources.Load<StyleSheet>("Styles/MaterialGraphView"));
            serializeGraphElements = SerializeGraphElementsImplementation;
            canPasteSerializedData = CanPasteSerializedDataImplementation;
            unserializeAndPaste = UnserializeAndPasteImplementation;
            deleteSelection = DeleteSelectionImplementation;
            RegisterCallback<DragUpdatedEvent>(OnDragUpdatedEvent);
            RegisterCallback<DragPerformEvent>(OnDragPerformEvent);
        }

        protected override bool canCopySelection
        {
            get { return selection.OfType<IShaderNodeView>().Any(x => x.node.canCopyNode) || selection.OfType<Group>().Any() || selection.OfType<BlackboardField>().Any(); }
        }

        public MaterialGraphView(GraphData graph) : this()
        {
            this.graph = graph;
        }

        public GraphData graph { get; private set; }
        public Action onConvertToSubgraphClick { get; set; }

        public override List<Port> GetCompatiblePorts(Port startAnchor, NodeAdapter nodeAdapter)
        {
            var compatibleAnchors = new List<Port>();
            var startSlot = startAnchor.GetSlot();
            if (startSlot == null)
                return compatibleAnchors;

            var startStage = startSlot.stageCapability;
            if (startStage == ShaderStageCapability.All)
                startStage = NodeUtils.GetEffectiveShaderStageCapability(startSlot, true) & NodeUtils.GetEffectiveShaderStageCapability(startSlot, false);

            foreach (var candidateAnchor in ports.ToList())
            {
                var candidateSlot = candidateAnchor.GetSlot();
                if (!startSlot.IsCompatibleWith(candidateSlot))
                    continue;

                if (startStage != ShaderStageCapability.All)
                {
                    var candidateStage = candidateSlot.stageCapability;
                    if (candidateStage == ShaderStageCapability.All)
                        candidateStage = NodeUtils.GetEffectiveShaderStageCapability(candidateSlot, true)
                            & NodeUtils.GetEffectiveShaderStageCapability(candidateSlot, false);
                    if (candidateStage != ShaderStageCapability.All && candidateStage != startStage)
                        continue;
                }

                compatibleAnchors.Add(candidateAnchor);
            }
            return compatibleAnchors;
        }

        public override void BuildContextualMenu(ContextualMenuPopulateEvent evt)
        {
            Vector2 mousePosition = evt.mousePosition;
            base.BuildContextualMenu(evt);
            if(evt.target is GraphView)
            {
                evt.menu.InsertAction(1, "Create Sticky Note", (e) => { AddStickyNote(mousePosition); });
            }

            if (evt.target is GraphView || evt.target is Node)
            {
                InitializeViewSubMenu(evt);

                evt.menu.AppendAction("Convert To Sub-graph", ConvertToSubgraph, ConvertToSubgraphStatus);
                evt.menu.AppendAction("Convert To Inline Node", ConvertToInlineNode, ConvertToInlineNodeStatus);
                evt.menu.AppendAction("Convert To Property", ConvertToProperty, ConvertToPropertyStatus);

                evt.menu.AppendAction("Group Selection", _ => GroupSelection(), (a) =>
                {
                    List<ISelectable> filteredSelection = new List<ISelectable>();

                    foreach (ISelectable selectedObject in selection)
                    {
                        if (selectedObject is Group)
                            return DropdownMenuAction.Status.Disabled;
                        VisualElement ve = selectedObject as VisualElement;
                        if (ve.userData is AbstractMaterialNode)
                        {
                            var selectedNode = selectedObject as Node;
                            if (selectedNode.GetContainingScope() is Group)
                                return DropdownMenuAction.Status.Disabled;

                            filteredSelection.Add(selectedObject);
                        }
                    }

                    if (filteredSelection.Count > 0)
                        return DropdownMenuAction.Status.Normal;
                    else
                        return DropdownMenuAction.Status.Disabled;
                });

                evt.menu.AppendAction("Ungroup Selection", RemoveFromGroupNode, (a) =>
                {
                    List<ISelectable> filteredSelection = new List<ISelectable>();

                    foreach (ISelectable selectedObject in selection)
                    {
                        if (selectedObject is Group)
                            return DropdownMenuAction.Status.Disabled;
                        VisualElement ve = selectedObject as VisualElement;
                        if (ve.userData is AbstractMaterialNode)
                        {
                            var selectedNode = selectedObject as Node;
                            if (selectedNode.GetContainingScope() is Group)
                                filteredSelection.Add(selectedObject);
                        }
                    }

                    if (filteredSelection.Count > 0)
                        return DropdownMenuAction.Status.Normal;
                    else
                        return DropdownMenuAction.Status.Disabled;
                });

                

                var editorView = GetFirstAncestorOfType<GraphEditorView>();
                if (editorView.colorManager.activeSupportsCustom && selection.OfType<MaterialNodeView>().Any())
                {
                    evt.menu.AppendSeparator();
                    evt.menu.AppendAction("Color/Change...", ChangeCustomNodeColor,
                        eventBase => DropdownMenuAction.Status.Normal);

                    evt.menu.AppendAction("Color/Reset", menuAction =>
                    {
                        graph.owner.RegisterCompleteObjectUndo("Reset Node Color");
                        foreach (var selectable in selection)
                        {
                            if (selectable is MaterialNodeView nodeView)
                            {
                                nodeView.node.ResetColor(editorView.colorManager.activeProviderName);
                                editorView.colorManager.UpdateNodeView(nodeView);
                            }
                        }
                    }, eventBase => DropdownMenuAction.Status.Normal);
                }

                if (selection.OfType<IShaderNodeView>().Count() == 1)
                {
                    evt.menu.AppendSeparator();
                    evt.menu.AppendAction("Open Documentation", SeeDocumentation, SeeDocumentationStatus);
                }
                if (selection.OfType<IShaderNodeView>().Count() == 1 && selection.OfType<IShaderNodeView>().First().node is SubGraphNode)
                {
                    evt.menu.AppendSeparator();

                    evt.menu.AppendAction("Open Sub Graph", OpenSubGraph, (a) => DropdownMenuAction.Status.Normal);
                }
            }

            if (evt.target is BlackboardField)
            {
                evt.menu.AppendAction("Delete", (e) => DeleteSelectionImplementation("Delete", AskUser.DontAskUser), (e) => canDeleteSelection ? DropdownMenuAction.Status.Normal : DropdownMenuAction.Status.Disabled);
            }
            if (evt.target is MaterialGraphView)
            {
                foreach (AbstractMaterialNode node in graph.GetNodes<AbstractMaterialNode>())
                {
                    if (node.hasPreview && node.previewExpanded == true)
                        evt.menu.AppendAction("Collapse All Previews", CollapsePreviews, (a) => DropdownMenuAction.Status.Normal);
                    if (node.hasPreview && node.previewExpanded == false)
                        evt.menu.AppendAction("Expand All Previews", ExpandPreviews, (a) => DropdownMenuAction.Status.Normal);
                }
                evt.menu.AppendSeparator();
            }
        }

        private void InitializeViewSubMenu(ContextualMenuPopulateEvent evt)
        {
            // Default the menu buttons to disabled
            DropdownMenuAction.Status expandPreviewAction = DropdownMenuAction.Status.Disabled;
            DropdownMenuAction.Status collapsePreviewAction = DropdownMenuAction.Status.Disabled;
            DropdownMenuAction.Status minimizeAction = DropdownMenuAction.Status.Disabled;
            DropdownMenuAction.Status maximizeAction = DropdownMenuAction.Status.Disabled;

            // Initialize strings
            string expandPreviewText = "View/Expand Previews";
            string collapsePreviewText = "View/Collapse Previews";
            string expandPortText = "View/Expand Ports";
            string collapsePortText = "View/Collapse Ports";
            if (selection.Count == 1)
            {
                collapsePreviewText = "View/Collapse Preview";
                expandPreviewText = "View/Expand Preview";
            }

            // Check if we can expand or collapse the ports/previews
            foreach (MaterialNodeView selectedNode in selection.Where(x => x is MaterialNodeView).Select(x => x as MaterialNodeView))
            {
                if (selectedNode.node.hasPreview)
                {
                    if (selectedNode.node.previewExpanded)
                        collapsePreviewAction = DropdownMenuAction.Status.Normal;
                    else
                        expandPreviewAction = DropdownMenuAction.Status.Normal;
                }

                if (selectedNode.CanToggleExpanded())
                {
                    if (selectedNode.expanded)
                        minimizeAction = DropdownMenuAction.Status.Normal;
                    else
                        maximizeAction = DropdownMenuAction.Status.Normal;
                }
            }

            // Create the menu options
            evt.menu.AppendAction(collapsePortText, _ => SetNodeExpandedOnSelection(false), (a) => minimizeAction);
            evt.menu.AppendAction(expandPortText, _ => SetNodeExpandedOnSelection(true), (a) => maximizeAction);

            evt.menu.AppendSeparator("View/");

            evt.menu.AppendAction(expandPreviewText, _ => SetPreviewExpandedOnSelection(true), (a) => expandPreviewAction);
            evt.menu.AppendAction(collapsePreviewText, _ => SetPreviewExpandedOnSelection(false), (a) => collapsePreviewAction);

            evt.menu.AppendSeparator();
        }

        void ChangeCustomNodeColor(DropdownMenuAction menuAction)
        {
            // Color Picker is internal :(
            var t = typeof(EditorWindow).Assembly.GetTypes().FirstOrDefault(ty => ty.Name == "ColorPicker");
            var m = t?.GetMethod("Show", new[] {typeof(Action<Color>), typeof(Color), typeof(bool), typeof(bool)});
            if (m == null)
            {
                Debug.LogWarning("Could not invoke Color Picker for ShaderGraph.");
                return;
            }

            var editorView = GetFirstAncestorOfType<GraphEditorView>();
            var defaultColor = Color.gray;
            if (selection.FirstOrDefault(sel => sel is MaterialNodeView) is MaterialNodeView selNode1)
            {
                defaultColor = selNode1.GetColor();
                defaultColor.a = 1.0f;
            }

            void ApplyColor(Color pickedColor)
            {
                foreach (var selectable in selection)
                {
                    if(selectable is MaterialNodeView nodeView)
                    {
                        nodeView.node.SetColor(editorView.colorManager.activeProviderName, pickedColor);
                        editorView.colorManager.UpdateNodeView(nodeView);
                    }
                }
            }
            graph.owner.RegisterCompleteObjectUndo("Change Node Color");
            m.Invoke(null, new object[] {(Action<Color>) ApplyColor, defaultColor, true, false});
        }

        protected override bool canDeleteSelection
        {
            get
            {
                return selection.Any(x => !(x is IShaderNodeView nodeView) || nodeView.node.canDeleteNode);
            }
        }

        public void GroupSelection()
        {
            var title = "New Group";
            var groupData = new GroupData(title, new Vector2(10f,10f));

            graph.owner.RegisterCompleteObjectUndo("Create Group Node");
            graph.CreateGroup(groupData);

            foreach (var shaderNodeView in selection.OfType<IShaderNodeView>())
            {
                graph.SetGroup(shaderNodeView.node, groupData);
            }
        }

        public void AddStickyNote(Vector2 position)
        {
            position = contentViewContainer.WorldToLocal(position);
            string title = "New Note";
            string content = "Write something here";
            var stickyNoteData  = new StickyNoteData(title, content, new Rect(position.x, position.y, 200, 160));
            graph.owner.RegisterCompleteObjectUndo("Create Sticky Note");
            graph.AddStickyNote(stickyNoteData);
        }


        void RemoveFromGroupNode(DropdownMenuAction action)
        {
            graph.owner.RegisterCompleteObjectUndo("Ungroup Node(s)");
            foreach (ISelectable selectable in selection)
            {
                var node = selectable as Node;
                if(node == null)
                    continue;

                Group group = node.GetContainingScope() as Group;
                if (group != null)
                {
                    group.RemoveElement(node);
                }
            }
        }

        public void SetNodeExpandedOnSelection(bool state)
        {
            graph.owner.RegisterCompleteObjectUndo("Toggle Expansion");
            foreach (MaterialNodeView selectedNode in selection.Where(x => x is MaterialNodeView).Select(x => x as MaterialNodeView))
            {
                if(selectedNode.CanToggleExpanded())
                    selectedNode.expanded = state;
            }
        }

        public void SetPreviewExpandedOnSelection(bool state)
        {
            graph.owner.RegisterCompleteObjectUndo("Toggle Preview Visibility");
            foreach (MaterialNodeView selectedNode in selection.Where(x => x is MaterialNodeView).Select(x => x as MaterialNodeView))
            {
                selectedNode.node.previewExpanded = state;
            }
        }

        void CollapsePreviews(DropdownMenuAction action)
        {
            graph.owner.RegisterCompleteObjectUndo("Collapse Previews");
            foreach (AbstractMaterialNode node in graph.GetNodes<AbstractMaterialNode>())
            {
                node.previewExpanded = false;
            }
        }

        void ExpandPreviews(DropdownMenuAction action)
        {
            graph.owner.RegisterCompleteObjectUndo("Expand Previews");
            foreach (AbstractMaterialNode node in graph.GetNodes<AbstractMaterialNode>())
            {
                node.previewExpanded = true;
            }
        }

        void SeeDocumentation(DropdownMenuAction action)
        {
            var node = selection.OfType<IShaderNodeView>().First().node;
            if (node.documentationURL != null)
                System.Diagnostics.Process.Start(node.documentationURL);
        }

        void OpenSubGraph(DropdownMenuAction action)
        {
            SubGraphNode subgraphNode = selection.OfType<IShaderNodeView>().First().node as SubGraphNode;

            var path = AssetDatabase.GetAssetPath(subgraphNode.asset);
            ShaderGraphImporterEditor.ShowGraphEditWindow(path);
        }

        DropdownMenuAction.Status SeeDocumentationStatus(DropdownMenuAction action)
        {
            if (selection.OfType<IShaderNodeView>().First().node.documentationURL == null)
                return DropdownMenuAction.Status.Disabled;
            return DropdownMenuAction.Status.Normal;
        }

        DropdownMenuAction.Status ConvertToPropertyStatus(DropdownMenuAction action)
        {
            if (selection.OfType<IShaderNodeView>().Any(v => v.node != null))
            {
                if (selection.OfType<IShaderNodeView>().Any(v => v.node is IPropertyFromNode))
                    return DropdownMenuAction.Status.Normal;
                return DropdownMenuAction.Status.Disabled;
            }
            return DropdownMenuAction.Status.Hidden;
        }

        void ConvertToProperty(DropdownMenuAction action)
        {
            graph.owner.RegisterCompleteObjectUndo("Convert to Property");
            var selectedNodeViews = selection.OfType<IShaderNodeView>().Select(x => x.node).ToList();
            foreach (var node in selectedNodeViews)
            {
                if (!(node is IPropertyFromNode))
                    continue;

                var converter = node as IPropertyFromNode;
                var prop = converter.AsShaderProperty();
                graph.SanitizeGraphInputName(prop);
                graph.AddGraphInput(prop);

                var propNode = new PropertyNode();
                propNode.drawState = node.drawState;
                propNode.groupGuid = node.groupGuid;
                graph.AddNode(propNode);
                propNode.propertyGuid = prop.guid;

                var oldSlot = node.FindSlot<MaterialSlot>(converter.outputSlotId);
                var newSlot = propNode.FindSlot<MaterialSlot>(PropertyNode.OutputSlotId);

                foreach (var edge in graph.GetEdges(oldSlot.slotReference))
                    graph.Connect(newSlot.slotReference, edge.inputSlot);

                graph.RemoveNode(node);
            }
        }

        DropdownMenuAction.Status ConvertToInlineNodeStatus(DropdownMenuAction action)
        {
            if (selection.OfType<IShaderNodeView>().Any(v => v.node != null))
            {
                if (selection.OfType<IShaderNodeView>().Any(v => v.node is PropertyNode))
                    return DropdownMenuAction.Status.Normal;
                return DropdownMenuAction.Status.Disabled;
            }
            return DropdownMenuAction.Status.Hidden;
        }

        void ConvertToInlineNode(DropdownMenuAction action)
        {
            graph.owner.RegisterCompleteObjectUndo("Convert to Inline Node");
            var selectedNodeViews = selection.OfType<IShaderNodeView>()
                .Select(x => x.node)
                .OfType<PropertyNode>();

            foreach (var propNode in selectedNodeViews)
                ((GraphData)propNode.owner).ReplacePropertyNodeWithConcreteNode(propNode);
        }

        DropdownMenuAction.Status ConvertToSubgraphStatus(DropdownMenuAction action)
        {
            if (onConvertToSubgraphClick == null) return DropdownMenuAction.Status.Hidden;
            return selection.OfType<IShaderNodeView>().Any(v => v.node != null && v.node.allowedInSubGraph && !(v.node is SubGraphOutputNode) ) ? DropdownMenuAction.Status.Normal : DropdownMenuAction.Status.Hidden;
        }

        void ConvertToSubgraph(DropdownMenuAction action)
        {
            onConvertToSubgraphClick();
        }

        string SerializeGraphElementsImplementation(IEnumerable<GraphElement> elements)
        {
            var groups = elements.OfType<ShaderGroup>().Select(x => x.userData);
            var nodes = elements.OfType<IShaderNodeView>().Select(x => x.node).Where(x => x.canCopyNode);
            var edges = elements.OfType<Edge>().Select(x => x.userData).OfType<IEdge>();
            var inputs = selection.OfType<BlackboardField>().Select(x => x.userData as ShaderInput);
            var notes = elements.OfType<StickyNote>().Select(x => x.userData);

            // Collect the property nodes and get the corresponding properties
            var propertyNodeGuids = nodes.OfType<PropertyNode>().Select(x => x.propertyGuid);
            var metaProperties = this.graph.properties.Where(x => propertyNodeGuids.Contains(x.guid));

            // Collect the keyword nodes and get the corresponding keywords
            var keywordNodeGuids = nodes.OfType<KeywordNode>().Select(x => x.keywordGuid);
            var metaKeywords = this.graph.keywords.Where(x => keywordNodeGuids.Contains(x.guid));

            var graph = new CopyPasteGraph(this.graph.assetGuid, groups, nodes, edges, inputs, metaProperties, metaKeywords, notes);
            return JsonUtility.ToJson(graph, true);
        }

        bool CanPasteSerializedDataImplementation(string serializedData)
        {
            return CopyPasteGraph.FromJson(serializedData) != null;
        }

        void UnserializeAndPasteImplementation(string operationName, string serializedData)
        {
            graph.owner.RegisterCompleteObjectUndo(operationName);
            var pastedGraph = CopyPasteGraph.FromJson(serializedData);
            this.InsertCopyPasteGraph(pastedGraph);
        }

        void DeleteSelectionImplementation(string operationName, GraphView.AskUser askUser)
        {
            bool containsProperty = false;

            // Keywords need to be tested against variant limit based on multiple factors
            bool keywordsDirty = false;

            // Track dependent keyword nodes to remove them
            List<KeywordNode> keywordNodes = new List<KeywordNode>();

            foreach (var selectable in selection)
            {
                var field = selectable as BlackboardField;
                if (field != null && field.userData != null)
                {
                    switch(field.userData)
                    {
                        case AbstractShaderProperty property:
                            containsProperty = true;
                            break;
                        case ShaderKeyword keyword:
                            keywordNodes.AddRange(graph.GetNodes<KeywordNode>().Where(x => x.keywordGuid == keyword.guid));
                            break;
                        default:
                            throw new ArgumentOutOfRangeException();
                    }
                }
            }

            if(containsProperty)
            {
                if (graph.isSubGraph)
                {
                    if (!EditorUtility.DisplayDialog("Sub Graph Will Change", "If you remove a property and save the sub graph, you might change other graphs that are using this sub graph.\n\nDo you want to continue?", "Yes", "No"))
                        return;
                }
            }

            // Filter nodes that cannot be deleted
            var nodesToDelete = selection.OfType<IShaderNodeView>().Where(v => !(v.node is SubGraphOutputNode) && v.node.canDeleteNode).Select(x => x.node);
            
            // Add keyword nodes dependent on deleted keywords
            nodesToDelete = nodesToDelete.Union(keywordNodes);

            // If deleting a Sub Graph node whose asset contains Keywords test variant limit
            foreach(SubGraphNode subGraphNode in nodesToDelete.OfType<SubGraphNode>())
            {
                if(subGraphNode.asset.keywords.Count > 0)
                {
                    keywordsDirty = true;
                }
            }
            
            graph.owner.RegisterCompleteObjectUndo(operationName);
            graph.RemoveElements(nodesToDelete.ToArray(),
                selection.OfType<Edge>().Select(x => x.userData).OfType<IEdge>().ToArray(),
                selection.OfType<ShaderGroup>().Select(x => x.userData).ToArray(),
                selection.OfType<StickyNote>().Select(x => x.userData).ToArray());
            
            foreach (var selectable in selection)
            {
                var field = selectable as BlackboardField;
                if (field != null && field.userData != null)
                {
                    var input = (ShaderInput)field.userData;
                    graph.RemoveGraphInput(input);

                    // If deleting a Keyword test variant limit
                    if(input is ShaderKeyword keyword)
                    {
                        keywordsDirty = true;
                    }
                }
            }

            // Test Keywords against variant limit
            if(keywordsDirty)
            {
                graph.OnKeywordChangedNoValidate();
            }

            selection.Clear();
        }

        #region Drag and drop

        bool ValidateObjectForDrop(Object obj)
        {
            return EditorUtility.IsPersistent(obj) && (
                obj is Texture2D ||
                obj is Cubemap ||
                obj is SubGraphAsset asset && !asset.descendents.Contains(graph.assetGuid) ||
                obj is Texture2DArray ||
                obj is Texture3D);
        }

        void OnDragUpdatedEvent(DragUpdatedEvent e)
        {
            var selection = DragAndDrop.GetGenericData("DragSelection") as List<ISelectable>;
            bool dragging = false;
            if (selection != null)
            {
                // Blackboard
                if (selection.OfType<BlackboardField>().Any())
                    dragging = true;
            }
            else
            {
                // Handle unity objects
                var objects = DragAndDrop.objectReferences;
                foreach (Object obj in objects)
                {
                    if (ValidateObjectForDrop(obj))
                    {
                        dragging = true;
                        break;
                    }
                }
            }

            if (dragging)
            {
                DragAndDrop.visualMode = DragAndDropVisualMode.Generic;
            }
        }

        void OnDragPerformEvent(DragPerformEvent e)
        {
            Vector2 localPos = (e.currentTarget as VisualElement).ChangeCoordinatesTo(contentViewContainer, e.localMousePosition);

            var selection = DragAndDrop.GetGenericData("DragSelection") as List<ISelectable>;
            if (selection != null)
            {
                // Blackboard
                if (selection.OfType<BlackboardField>().Any())
                {
                    IEnumerable<BlackboardField> fields = selection.OfType<BlackboardField>();
                    foreach (BlackboardField field in fields)
                    {
                        CreateNode(field, localPos);
                    }
                }
            }
            else
            {
                // Handle unity objects
                var objects = DragAndDrop.objectReferences;
                foreach (Object obj in objects)
                {
                    if (ValidateObjectForDrop(obj))
                    {
                        CreateNode(obj, localPos);
                    }
                }
            }
        }

        void CreateNode(object obj, Vector2 nodePosition)
        {
            var texture2D = obj as Texture2D;
            if (texture2D != null)
            {
                graph.owner.RegisterCompleteObjectUndo("Drag Texture");

                bool isNormalMap = false;
                if (EditorUtility.IsPersistent(texture2D) && !string.IsNullOrEmpty(AssetDatabase.GetAssetPath(texture2D)))
                {
                    var importer = AssetImporter.GetAtPath(AssetDatabase.GetAssetPath(texture2D)) as TextureImporter;
                    if (importer != null)
                        isNormalMap = importer.textureType == TextureImporterType.NormalMap;
                }

                var node = new SampleTexture2DNode();
                var drawState = node.drawState;
                drawState.position = new Rect(nodePosition, drawState.position.size);
                node.drawState = drawState;
                graph.AddNode(node);

                if (isNormalMap)
                    node.textureType = TextureType.Normal;

                var inputslot = node.FindInputSlot<Texture2DInputMaterialSlot>(SampleTexture2DNode.TextureInputId);
                if (inputslot != null)
                    inputslot.texture = texture2D;
            }

            var textureArray = obj as Texture2DArray;
            if (textureArray != null)
            {
                graph.owner.RegisterCompleteObjectUndo("Drag Texture Array");
                
                var node = new SampleTexture2DArrayNode();
                var drawState = node.drawState;
                drawState.position = new Rect(nodePosition, drawState.position.size);
                node.drawState = drawState;
                graph.AddNode(node);

                var inputslot = node.FindSlot<Texture2DArrayInputMaterialSlot>(SampleTexture2DArrayNode.TextureInputId);
                if (inputslot != null)
                    inputslot.textureArray = textureArray;
            }

            var texture3D = obj as Texture3D;
            if (texture3D != null)
            {
                graph.owner.RegisterCompleteObjectUndo("Drag Texture 3D");

                var node = new SampleTexture3DNode();
                var drawState = node.drawState;
                drawState.position = new Rect(nodePosition, drawState.position.size);
                node.drawState = drawState;
                graph.AddNode(node);

                var inputslot = node.FindSlot<Texture3DInputMaterialSlot>(SampleTexture3DNode.TextureInputId);
                if (inputslot != null)
                    inputslot.texture = texture3D;
            }

            var cubemap = obj as Cubemap;
            if (cubemap != null)
            {
                graph.owner.RegisterCompleteObjectUndo("Drag Cubemap");
                
                var node = new SampleCubemapNode();
                var drawState = node.drawState;
                drawState.position = new Rect(nodePosition, drawState.position.size);
                node.drawState = drawState;
                graph.AddNode(node);

                var inputslot = node.FindInputSlot<CubemapInputMaterialSlot>(SampleCubemapNode.CubemapInputId);
                if (inputslot != null)
                    inputslot.cubemap = cubemap;
            }

            var subGraphAsset = obj as SubGraphAsset;
            if (subGraphAsset != null)
            {
                graph.owner.RegisterCompleteObjectUndo("Drag Sub-Graph");
                var node = new SubGraphNode();

                var drawState = node.drawState;
                drawState.position = new Rect(nodePosition, drawState.position.size);
                node.drawState = drawState;
                node.asset = subGraphAsset;
                graph.AddNode(node);
            }

            var blackboardField = obj as BlackboardField;
            if (blackboardField != null)
            {   
                graph.owner.RegisterCompleteObjectUndo("Drag Graph Input");

                switch(blackboardField.userData)
                {
                    case AbstractShaderProperty property:
                    {
                        var node = new PropertyNode();
                        var drawState = node.drawState;
                        drawState.position =  new Rect(nodePosition, drawState.position.size);
                        node.drawState = drawState;
                        graph.AddNode(node);

                        // Setting the guid requires the graph to be set first.
                        node.propertyGuid = property.guid;
                        break;
                    }
                    case ShaderKeyword keyword:
                    {
                        var node = new KeywordNode();
                        var drawState = node.drawState;
                        drawState.position =  new Rect(nodePosition, drawState.position.size);
                        node.drawState = drawState;
                        graph.AddNode(node);

                        // Setting the guid requires the graph to be set first.
                        node.keywordGuid = keyword.guid;
                        break;
                    }
                    default:
                        throw new ArgumentOutOfRangeException();
                }
            }
        }

        #endregion
    }

    static class GraphViewExtensions
    {
        internal static void InsertCopyPasteGraph(this MaterialGraphView graphView, CopyPasteGraph copyGraph)
        {
            if (copyGraph == null)
                return;

            // Keywords need to be tested against variant limit based on multiple factors
            bool keywordsDirty = false;

            // Make new inputs from the copied graph
            foreach (ShaderInput input in copyGraph.inputs)
            {
                ShaderInput copiedInput = input.Copy();
                graphView.graph.SanitizeGraphInputName(copiedInput);
                graphView.graph.SanitizeGraphInputReferenceName(copiedInput, input.overrideReferenceName);
                graphView.graph.AddGraphInput(copiedInput);

                switch(input)
                {
                    case AbstractShaderProperty property:
                        // Update the property nodes that depends on the copied node
                        var dependentPropertyNodes = copyGraph.GetNodes<PropertyNode>().Where(x => x.propertyGuid == input.guid);
                        foreach (var node in dependentPropertyNodes)
                        {
                            node.owner = graphView.graph;
                            node.propertyGuid = copiedInput.guid;
                        }
                        break;
                    case ShaderKeyword shaderKeyword:
                        // Update the keyword nodes that depends on the copied node
                        var dependentKeywordNodes = copyGraph.GetNodes<KeywordNode>().Where(x => x.keywordGuid == input.guid);
                        foreach (var node in dependentKeywordNodes)
                        {
                            node.owner = graphView.graph;
                            node.keywordGuid = copiedInput.guid;
                        }

                        // Pasting a new Keyword so need to test against variant limit
                        keywordsDirty = true;
                        break;
                    default:
                        throw new ArgumentOutOfRangeException();
                }
            }

            // Pasting a Sub Graph node that contains Keywords so need to test against variant limit
            foreach(SubGraphNode subGraphNode in copyGraph.GetNodes<SubGraphNode>())
            {
                if(subGraphNode.asset.keywords.Count > 0)
                {
                    keywordsDirty = true;
                }
            }

            // Test Keywords against variant limit
            if(keywordsDirty)
            {
                graphView.graph.OnKeywordChangedNoValidate();
            }

            using (var remappedNodesDisposable = ListPool<AbstractMaterialNode>.GetDisposable())
            {
                using (var remappedEdgesDisposable = ListPool<IEdge>.GetDisposable())
                {
                    var remappedNodes = remappedNodesDisposable.value;
                    var remappedEdges = remappedEdgesDisposable.value;
                    graphView.graph.PasteGraph(copyGraph, remappedNodes, remappedEdges);

                    if (graphView.graph.assetGuid != copyGraph.sourceGraphGuid)
                    {
                        // Compute the mean of the copied nodes.
                        Vector2 centroid = Vector2.zero;
                        var count = 1;
                        foreach (var node in remappedNodes)
                        {
                            var position = node.drawState.position.position;
                            centroid = centroid + (position - centroid) / count;
                            ++count;
                        }

                        // Get the center of the current view
                        var viewCenter = graphView.contentViewContainer.WorldToLocal(graphView.layout.center);

                        foreach (var node in remappedNodes)
                        {
                            var drawState = node.drawState;
                            var positionRect = drawState.position;
                            var position = positionRect.position;
                            position += viewCenter - centroid;
                            positionRect.position = position;
                            drawState.position = positionRect;
                            node.drawState = drawState;
                        }
                    }

                    // Add new elements to selection
                    graphView.ClearSelection();
                    graphView.graphElements.ForEach(element =>
                        {
                            if (element is Edge edge && remappedEdges.Contains(edge.userData as IEdge))
                                graphView.AddToSelection(edge);

                            if (element is IShaderNodeView nodeView && remappedNodes.Contains(nodeView.node))
                                graphView.AddToSelection((Node)nodeView);
                        });
                }
            }
        }
    }
}