using System;
using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEngine;

namespace XNodeEditor {
    /// <summary> Contains GUI methods </summary>
    public partial class NodeGraphWindow {
        private List<UnityEngine.Object> selectionCache;
        private List<XNode.Node> culledNodes;
        /// <summary> 19 if docked, 22 if not </summary>
        private int topPadding { get { return isDocked() ? 19 : 22; } }
        /// <summary> 0 if docked, 3 if not </summary>
        private int leftPadding { get { return isDocked() ? 2 : 0; } }
        /// <summary> Executed after all other window GUI. Useful if Zoom is ruining your day. Automatically resets after being run.</summary>
        public event Action onLateGUI;

        private Matrix4x4 prevGuiMatrix;

        private void OnGUI() {
            Event e = Event.current;
            Matrix4x4 m = GUI.matrix;
            if (graph == null) return;
            Controls();

            DrawGrid(position, zoom, panOffset);
            DrawConnections();
            DrawDraggedConnection();
            DrawNodes();
            DrawSelectionBox();
            DrawTooltip();
            DrawGraphOnGUI();

            // Run and reset onLateGUI
            if (onLateGUI != null) {
                onLateGUI();
                onLateGUI = null;
            }

            GUI.matrix = m;
        }

        public void BeginZoomed() {
            GUI.EndGroup();

            Rect position = new Rect(this.position);
            position.x = 0;
            position.y = topPadding;

            Vector2 topLeft = new Vector2(position.xMin, position.yMin - topPadding);
            Rect clippedArea = ScaleSizeBy(position, zoom, topLeft);
            GUI.BeginGroup(clippedArea);

            prevGuiMatrix = GUI.matrix;
            Matrix4x4 translation = Matrix4x4.TRS(Vector3.zero, Quaternion.identity, Vector3.one);
            Matrix4x4 scale = Matrix4x4.Scale(new Vector3(1.0f / zoom, 1.0f / zoom, 1.0f));
            GUI.matrix = translation * scale * translation.inverse * GUI.matrix;
        }

        public void EndZoomed() {
            GUI.matrix = prevGuiMatrix;
            GUI.EndGroup();
            GUI.BeginGroup(new Rect(0.0f, topPadding - (topPadding * zoom), Screen.width, Screen.height));
        }

        /// <summary> Ends the GUI Group temporarily to draw any additional elements in the NodeGraphEditor. </summary>
        private void DrawGraphOnGUI() {
            GUI.EndGroup();
            Rect rect = new Rect(new Vector2(leftPadding, topPadding), new Vector2(Screen.width, Screen.height));
            GUI.BeginGroup(rect);
            OnOverlayGUI();
            GUI.EndGroup();
            GUI.BeginGroup(new Rect(0.0f, topPadding - (topPadding * zoom), Screen.width, Screen.height));
        }

        public static Rect ScaleSizeBy(Rect rect, float scale, Vector2 pivotPoint) {
            Rect result = rect;
            result.x -= pivotPoint.x;
            result.y -= pivotPoint.y;
            result.xMin *= scale;
            result.xMax *= scale;
            result.yMin *= scale;
            result.yMax *= scale;
            result.x += pivotPoint.x;
            result.y += pivotPoint.y;
            return result;
        }

        public void DrawGrid(Rect rect, float zoom, Vector2 panOffset) {

            rect.position = Vector2.zero;

            Vector2 center = rect.size / 2f;
            Texture2D gridTex = GetGridTexture();
            Texture2D crossTex = GetSecondaryGridTexture();

            // Offset from origin in tile units
            float xOffset = -(center.x * zoom + panOffset.x) / gridTex.width;
            float yOffset = ((center.y - rect.size.y) * zoom + panOffset.y) / gridTex.height;

            Vector2 tileOffset = new Vector2(xOffset, yOffset);

            // Amount of tiles
            float tileAmountX = Mathf.Round(rect.size.x * zoom) / gridTex.width;
            float tileAmountY = Mathf.Round(rect.size.y * zoom) / gridTex.height;

            Vector2 tileAmount = new Vector2(tileAmountX, tileAmountY);

            // Draw tiled background
            GUI.DrawTextureWithTexCoords(rect, gridTex, new Rect(tileOffset, tileAmount));
            GUI.DrawTextureWithTexCoords(rect, crossTex, new Rect(tileOffset + new Vector2(0.5f, 0.5f), tileAmount));
        }

        public void DrawSelectionBox() {
            if (currentActivity == NodeActivity.DragGrid) {
                Vector2 curPos = WindowToGridPosition(Event.current.mousePosition);
                Vector2 size = curPos - dragBoxStart;
                Rect r = new Rect(dragBoxStart, size);
                r.position = GridToWindowPosition(r.position);
                r.size /= zoom;
                Handles.DrawSolidRectangleWithOutline(r, new Color(0, 0, 0, 0.1f), new Color(1, 1, 1, 0.6f));
            }
        }

        public static bool DropdownButton(string name, float width) {
            return GUILayout.Button(name, EditorStyles.toolbarDropDown, GUILayout.Width(width));
        }

        /// <summary> Show right-click context menu for hovered reroute </summary>
        void ShowRerouteContextMenu(RerouteReference reroute) {
            GenericMenu contextMenu = new GenericMenu();
            contextMenu.AddItem(new GUIContent("Remove"), false, () => reroute.RemovePoint());
            contextMenu.DropDown(new Rect(Event.current.mousePosition, Vector2.zero));
            if (NodeEditorPreferences.GetSettings().autoSave) AssetDatabase.SaveAssets();
        }

        /// <summary> Show right-click context menu for hovered port </summary>
        void ShowPortContextMenu(XNode.NodePort hoveredPort) {
            GenericMenu contextMenu = new GenericMenu();
            contextMenu.AddItem(new GUIContent("Clear Connections"), false, () => hoveredPort.ClearConnections());
            contextMenu.DropDown(new Rect(Event.current.mousePosition, Vector2.zero));
            if (NodeEditorPreferences.GetSettings().autoSave) AssetDatabase.SaveAssets();
        }

        /// <summary> Draw a bezier from output to input in grid coordinates </summary>
        public void DrawNoodle(Color col, List<Vector2> gridPoints) {
            Vector2[] windowPoints = gridPoints.Select(x => GridToWindowPosition(x)).ToArray();
            Handles.color = col;
            int length = gridPoints.Count;
            switch (NodeEditorPreferences.GetSettings().noodleType) {
                case NodeEditorPreferences.NoodleType.Curve:
                    Vector2 outputTangent = Vector2.right;
                    for (int i = 0; i < length - 1; i++) {
                        Vector2 inputTangent = Vector2.left;

                        if (i == 0) outputTangent = Vector2.right * Vector2.Distance(windowPoints[i], windowPoints[i + 1]) * 0.01f * zoom;
                        if (i < length - 2) {
                            Vector2 ab = (windowPoints[i + 1] - windowPoints[i]).normalized;
                            Vector2 cb = (windowPoints[i + 1] - windowPoints[i + 2]).normalized;
                            Vector2 ac = (windowPoints[i + 2] - windowPoints[i]).normalized;
                            Vector2 p = (ab + cb) * 0.5f;
                            float tangentLength = (Vector2.Distance(windowPoints[i], windowPoints[i + 1]) + Vector2.Distance(windowPoints[i + 1], windowPoints[i + 2])) * 0.005f * zoom;
                            float side = ((ac.x * (windowPoints[i + 1].y - windowPoints[i].y)) - (ac.y * (windowPoints[i + 1].x - windowPoints[i].x)));

                            p = new Vector2(-p.y, p.x) * Mathf.Sign(side) * tangentLength;
                            inputTangent = p;
                        } else {
                            inputTangent = Vector2.left * Vector2.Distance(windowPoints[i], windowPoints[i + 1]) * 0.01f * zoom;
                        }

                        Handles.DrawBezier(windowPoints[i], windowPoints[i + 1], windowPoints[i] + ((outputTangent * 50) / zoom), windowPoints[i + 1] + ((inputTangent * 50) / zoom), col, null, 4);
                        outputTangent = -inputTangent;
                    }
                    break;
                case NodeEditorPreferences.NoodleType.Line:
                    for (int i = 0; i < length - 1; i++) {
                        Handles.DrawAAPolyLine(5, windowPoints[i], windowPoints[i + 1]);
                    }
                    break;
                case NodeEditorPreferences.NoodleType.Angled:
                    for (int i = 0; i < length - 1; i++) {
                        if (i == length - 1) continue; // Skip last index
                        if (windowPoints[i].x <= windowPoints[i + 1].x - (50 / zoom)) {
                            float midpoint = (windowPoints[i].x + windowPoints[i + 1].x) * 0.5f;
                            Vector2 start_1 = windowPoints[i];
                            Vector2 end_1 = windowPoints[i + 1];
                            start_1.x = midpoint;
                            end_1.x = midpoint;
                            Handles.DrawAAPolyLine(5, windowPoints[i], start_1);
                            Handles.DrawAAPolyLine(5, start_1, end_1);
                            Handles.DrawAAPolyLine(5, end_1, windowPoints[i + 1]);
                        } else {
                            float midpoint = (windowPoints[i].y + windowPoints[i + 1].y) * 0.5f;
                            Vector2 start_1 = windowPoints[i];
                            Vector2 end_1 = windowPoints[i + 1];
                            start_1.x += 25 / zoom;
                            end_1.x -= 25 / zoom;
                            Vector2 start_2 = start_1;
                            Vector2 end_2 = end_1;
                            start_2.y = midpoint;
                            end_2.y = midpoint;
                            Handles.DrawAAPolyLine(5, windowPoints[i], start_1);
                            Handles.DrawAAPolyLine(5, start_1, start_2);
                            Handles.DrawAAPolyLine(5, start_2, end_2);
                            Handles.DrawAAPolyLine(5, end_2, end_1);
                            Handles.DrawAAPolyLine(5, end_1, windowPoints[i + 1]);
                        }
                    }
                    break;
            }
        }

        /// <summary> Draws all connections </summary>
        public void DrawConnections() {
            Vector2 mousePos = Event.current.mousePosition;
            List<RerouteReference> selection = preBoxSelectionReroute != null ? new List<RerouteReference>(preBoxSelectionReroute) : new List<RerouteReference>();
            hoveredReroute = new RerouteReference();

            Color col = GUI.color;
            foreach (XNode.Node node in graph.nodes) {
                //If a null node is found, return. This can happen if the nodes associated script is deleted. It is currently not possible in Unity to delete a null asset.
                if (node == null) continue;

                // Draw full connections and output > reroute
                foreach (XNode.NodePort output in node.Outputs) {
                    //Needs cleanup. Null checks are ugly
                    Rect fromRect;
                    if (!_portConnectionPoints.TryGetValue(output, out fromRect)) continue;

                    Color connectionColor = GetPortColor(output);

                    for (int k = 0; k < output.ConnectionCount; k++) {
                        XNode.NodePort input = output.GetConnection(k);

                        // Error handling
                        if (input == null) continue; //If a script has been updated and the port doesn't exist, it is removed and null is returned. If this happens, return.
                        if (!input.IsConnectedTo(output)) input.Connect(output);
                        Rect toRect;
                        if (!_portConnectionPoints.TryGetValue(input, out toRect)) continue;

                        List<Vector2> reroutePoints = output.GetReroutePoints(k);

                        List<Vector2> gridPoints = new List<Vector2>();
                        gridPoints.Add(fromRect.center);
                        gridPoints.AddRange(reroutePoints);
                        gridPoints.Add(toRect.center);
                        DrawNoodle(connectionColor, gridPoints);

                        // Loop through reroute points again and draw the points
                        for (int i = 0; i < reroutePoints.Count; i++) {
                            RerouteReference rerouteRef = new RerouteReference(output, k, i);
                            // Draw reroute point at position
                            Rect rect = new Rect(reroutePoints[i], new Vector2(12, 12));
                            rect.position = new Vector2(rect.position.x - 6, rect.position.y - 6);
                            rect = GridToWindowRect(rect);

                            // Draw selected reroute points with an outline
                            if (selectedReroutes.Contains(rerouteRef)) {
                                GUI.color = NodeEditorPreferences.GetSettings().highlightColor;
                                GUI.DrawTexture(rect, NodeEditorResources.dotOuter);
                            }

                            GUI.color = connectionColor;
                            GUI.DrawTexture(rect, NodeEditorResources.dot);
                            if (rect.Overlaps(selectionBox)) selection.Add(rerouteRef);
                            if (rect.Contains(mousePos)) hoveredReroute = rerouteRef;

                        }
                    }
                }
            }
            GUI.color = col;
            if (Event.current.type != EventType.Layout && currentActivity == NodeActivity.DragGrid) selectedReroutes = selection;
        }

        private void DrawNodes() {
            Event e = Event.current;
            if (e.type == EventType.Layout) {
                selectionCache = new List<UnityEngine.Object>(Selection.objects);
            }

            BeginZoomed();

            Vector2 mousePos = Event.current.mousePosition;

            if (e.type != EventType.Layout) {
                hoveredNode = null;
                hoveredPort = null;
            }

            List<UnityEngine.Object> preSelection = preBoxSelection != null ? new List<UnityEngine.Object>(preBoxSelection) : new List<UnityEngine.Object>();

            // Selection box stuff
            Vector2 boxStartPos = GridToWindowPositionNoClipped(dragBoxStart);
            Vector2 boxSize = mousePos - boxStartPos;
            if (boxSize.x < 0) { boxStartPos.x += boxSize.x; boxSize.x = Mathf.Abs(boxSize.x); }
            if (boxSize.y < 0) { boxStartPos.y += boxSize.y; boxSize.y = Mathf.Abs(boxSize.y); }
            Rect selectionBox = new Rect(boxStartPos, boxSize);

            //Save guiColor so we can revert it
            Color guiColor = GUI.color;

            if (e.type == EventType.Layout) culledNodes = new List<XNode.Node>();
            for (int n = 0; n < graph.nodes.Count; n++) {
                // Skip null nodes. The user could be in the process of renaming scripts, so removing them at this point is not advisable.
                if (graph.nodes[n] == null) continue;
                if (n >= graph.nodes.Count) return;
                XNode.Node node = graph.nodes[n];

                // Culling
                if (e.type == EventType.Layout) {
                    // Cull unselected nodes outside view
                    if (!Selection.Contains(node) && ShouldBeCulled(node)) {
                        culledNodes.Add(node);
                        continue;
                    }
                } else if (culledNodes.Contains(node)) continue;

                if (e.type == EventType.Repaint) {
                    _portConnectionPoints = _portConnectionPoints.Where(x => x.Key.node != node).ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
                }

                NodeEditor nodeEditor = NodeEditor.GetEditor(node, this);

                NodeEditor.portPositions.Clear();

                //Get node position
                Vector2 nodePos = GridToWindowPositionNoClipped(node.position);

                GUILayout.BeginArea(new Rect(nodePos, new Vector2(nodeEditor.GetWidth(), 4000)));

                bool selected = selectionCache.Contains(graph.nodes[n]);

                if (selected) {
                    GUIStyle style = new GUIStyle(nodeEditor.GetBodyStyle());
                    GUIStyle highlightStyle = new GUIStyle(NodeEditorResources.styles.nodeHighlight);
                    highlightStyle.padding = style.padding;
                    style.padding = new RectOffset();
                    GUI.color = nodeEditor.GetTint();
                    GUILayout.BeginVertical(style);
                    GUI.color = NodeEditorPreferences.GetSettings().highlightColor;
                    GUILayout.BeginVertical(new GUIStyle(highlightStyle));
                } else {
                    GUIStyle style = new GUIStyle(nodeEditor.GetBodyStyle());
                    GUI.color = nodeEditor.GetTint();
                    GUILayout.BeginVertical(style);
                }

                GUI.color = guiColor;
                EditorGUI.BeginChangeCheck();

                //Draw node contents
                nodeEditor.OnHeaderGUI();
                nodeEditor.OnBodyGUI();

                //If user changed a value, notify other scripts through onUpdateNode
                if (EditorGUI.EndChangeCheck()) {
                    if (NodeEditor.onUpdateNode != null) NodeEditor.onUpdateNode(node);
                    EditorUtility.SetDirty(node);
                    nodeEditor.serializedObject.ApplyModifiedProperties();
                }

                GUILayout.EndVertical();

                //Cache data about the node for next frame
                if (e.type == EventType.Repaint) {
                    Vector2 size = GUILayoutUtility.GetLastRect().size;
                    if (nodeSizes.ContainsKey(node)) nodeSizes[node] = size;
                    else nodeSizes.Add(node, size);

                    foreach (var kvp in NodeEditor.portPositions) {
                        Vector2 portHandlePos = kvp.Value;
                        portHandlePos += node.position;
                        Rect rect = new Rect(portHandlePos.x - 8, portHandlePos.y - 8, 16, 16);
                        portConnectionPoints[kvp.Key] = rect;
                    }
                }

                if (selected) GUILayout.EndVertical();

                if (e.type != EventType.Layout) {
                    //Check if we are hovering this node
                    Vector2 nodeSize = GUILayoutUtility.GetLastRect().size;
                    Rect windowRect = new Rect(nodePos, nodeSize);
                    if (windowRect.Contains(mousePos)) hoveredNode = node;

                    //If dragging a selection box, add nodes inside to selection
                    if (currentActivity == NodeActivity.DragGrid) {
                        if (windowRect.Overlaps(selectionBox)) preSelection.Add(node);
                    }

                    //Check if we are hovering any of this nodes ports
                    //Check input ports
                    foreach (XNode.NodePort input in node.Inputs) {
                        //Check if port rect is available
                        if (!portConnectionPoints.ContainsKey(input)) continue;
                        Rect r = GridToWindowRectNoClipped(portConnectionPoints[input]);
                        if (r.Contains(mousePos)) hoveredPort = input;
                    }
                    //Check all output ports
                    foreach (XNode.NodePort output in node.Outputs) {
                        //Check if port rect is available
                        if (!portConnectionPoints.ContainsKey(output)) continue;
                        Rect r = GridToWindowRectNoClipped(portConnectionPoints[output]);
                        if (r.Contains(mousePos)) hoveredPort = output;
                    }
                }

                GUILayout.EndArea();
            }

            if (e.type != EventType.Layout && currentActivity == NodeActivity.DragGrid) Selection.objects = preSelection.ToArray();
            EndZoomed();
        }

        private bool ShouldBeCulled(XNode.Node node) {

            Vector2 nodePos = GridToWindowPositionNoClipped(node.position);
            if (nodePos.x / _zoom > position.width) return true; // Right
            else if (nodePos.y / _zoom > position.height) return true; // Bottom
            else if (nodeSizes.ContainsKey(node)) {
                Vector2 size = nodeSizes[node];
                if (nodePos.x + size.x < 0) return true; // Left
                else if (nodePos.y + size.y < 0) return true; // Top
            }
            return false;
        }

        private void DrawTooltip() {
            if (hoveredPort != null && NodeEditorPreferences.GetSettings().portTooltips) {
                string tooltip = GetPortTooltip(hoveredPort);
                if (string.IsNullOrEmpty(tooltip)) return;
                GUIContent content = new GUIContent(tooltip);
                Vector2 size = NodeEditorResources.styles.tooltip.CalcSize(content);
                Rect rect = new Rect(Event.current.mousePosition - (size), size);
                EditorGUI.LabelField(rect, content, NodeEditorResources.styles.tooltip);
                Repaint();
            }
        }
    }
}