using System;
using UnityEditor;
using UnityEngine;
using System.Collections.Generic;
using UnityEditorInternal;
using Cinemachine.Utility;
using System.Linq;

namespace Cinemachine.Editor
{
    [CustomEditor(typeof(CinemachinePath))]
    sealed class CinemachinePathEditor : BaseEditor<CinemachinePath>
    {
        public static string kPreferTangentSelectionKey = "CinemachinePathEditor.PreferTangentSelection";
        public static bool PreferTangentSelection
        {
            get { return EditorPrefs.GetBool(kPreferTangentSelectionKey, false); }
            set
            {
                if (value != PreferTangentSelection)
                    EditorPrefs.SetBool(kPreferTangentSelectionKey, value);
            }
        }
        private ReorderableList mWaypointList;
        static bool mWaypointsExpanded;
        bool mPreferTangentSelection;

        /// <summary>Get the property names to exclude in the inspector.</summary>
        /// <param name="excluded">Add the names to this list</param>
        protected override void GetExcludedPropertiesInInspector(List<string> excluded)
        {
            base.GetExcludedPropertiesInInspector(excluded);
            excluded.Add(FieldPath(x => x.m_Waypoints));
        }

        void OnEnable()
        {
            mWaypointList = null;
            mPreferTangentSelection = PreferTangentSelection;
        }

        // ReSharper disable once UnusedMember.Global - magic method called when doing Frame Selected
        public bool HasFrameBounds()
        {
            return Target.m_Waypoints != null && Target.m_Waypoints.Length > 0;
        }

        // ReSharper disable once UnusedMember.Global - magic method called when doing Frame Selected
        public Bounds OnGetFrameBounds()
        {
            Vector3[] wp;
            int selected = mWaypointList == null ? -1 : mWaypointList.index;
            if (selected >= 0 && selected < Target.m_Waypoints.Length)
                wp = new Vector3[1] { Target.m_Waypoints[selected].position };
            else
                wp = Target.m_Waypoints.Select(p => p.position).ToArray();
            return GeometryUtility.CalculateBounds(wp, Target.transform.localToWorldMatrix);
        }

        public override void OnInspectorGUI()
        {
            BeginInspector();
            if (mWaypointList == null)
                SetupWaypointList();
            if (mWaypointList.index >= mWaypointList.count)
                mWaypointList.index = mWaypointList.count - 1;

            // Ordinary properties
            DrawRemainingPropertiesInInspector();

            // Path length
            EditorGUILayout.LabelField("Path Length", Target.PathLength.ToString());

            GUILayout.Label(new GUIContent("Selected Waypoint:"));
            EditorGUILayout.BeginVertical(GUI.skin.box);
            Rect rect = EditorGUILayout.GetControlRect(true, EditorGUIUtility.singleLineHeight * 3 + 10);
            if (mWaypointList.index >= 0)
            {
                DrawWaypointEditor(rect, mWaypointList.index);
                serializedObject.ApplyModifiedProperties();
            }
            else
            {
                if (Target.m_Waypoints.Length > 0)
                {
                    EditorGUI.HelpBox(rect,
                        "Click on a waypoint in the scene view\nor in the Path Details list",
                        MessageType.Info);
                }
                else if (GUI.Button(rect, new GUIContent("Add a waypoint to the path")))
                {
                    InsertWaypointAtIndex(mWaypointList.index);
                    mWaypointList.index = 0;
                }
            }
            EditorGUILayout.EndVertical();

            if (mPreferTangentSelection != EditorGUILayout.Toggle(
                    new GUIContent("Prefer Tangent Drag",
                        "When editing the path, if waypoint position and tangent coincide, dragging will apply preferentially to the tangent"),
                    mPreferTangentSelection))
            {
                PreferTangentSelection = mPreferTangentSelection = !mPreferTangentSelection;
            }

            mWaypointsExpanded = EditorGUILayout.Foldout(mWaypointsExpanded, "Path Details", true);
            if (mWaypointsExpanded)
            {
                EditorGUI.BeginChangeCheck();
                mWaypointList.DoLayoutList();
                if (EditorGUI.EndChangeCheck())
                    serializedObject.ApplyModifiedProperties();
            }
        }

        void SetupWaypointList()
        {
            mWaypointList = new ReorderableList(
                    serializedObject, FindProperty(x => x.m_Waypoints),
                    true, true, true, true);
            mWaypointList.elementHeight *= 3;

            mWaypointList.drawHeaderCallback = (Rect rect) =>
                {
                    EditorGUI.LabelField(rect, "Waypoints");
                };

            mWaypointList.drawElementCallback
                = (Rect rect, int index, bool isActive, bool isFocused) =>
                {
                    DrawWaypointEditor(rect, index);
                };

            mWaypointList.onAddCallback = (ReorderableList l) =>
                {
                    InsertWaypointAtIndex(l.index);
                };
        }

        void DrawWaypointEditor(Rect rect, int index)
        {
            // Needed for accessing string names of fields
            CinemachinePath.Waypoint def = new CinemachinePath.Waypoint();

            Vector2 numberDimension = GUI.skin.button.CalcSize(new GUIContent("999"));
            Vector2 labelDimension = GUI.skin.label.CalcSize(new GUIContent("Position"));
            Vector2 addButtonDimension = new Vector2(labelDimension.y + 5, labelDimension.y + 1);
            float vSpace = 2;
            float hSpace = 3;

            SerializedProperty element = mWaypointList.serializedProperty.GetArrayElementAtIndex(index);
            rect.y += vSpace / 2;

            Rect r = new Rect(rect.position, numberDimension);
            Color color = GUI.color;
            // GUI.color = Target.m_Appearance.pathColor;
            if (GUI.Button(r, new GUIContent(index.ToString(), "Go to the waypoint in the scene view")))
            {
                if (SceneView.lastActiveSceneView != null)
                {
                    mWaypointList.index = index;
                    SceneView.lastActiveSceneView.pivot = Target.EvaluatePosition(index);
                    SceneView.lastActiveSceneView.size = 3;
                    SceneView.lastActiveSceneView.Repaint();
                }
            }
            GUI.color = color;

            r = new Rect(rect.position, labelDimension);
            r.x += hSpace + numberDimension.x;
            EditorGUI.LabelField(r, "Position");
            r.x += hSpace + r.width;
            r.width = rect.width - (numberDimension.x + hSpace + r.width + hSpace + addButtonDimension.x + hSpace);
            EditorGUI.PropertyField(r, element.FindPropertyRelative(() => def.position), GUIContent.none);
            r.x += r.width + hSpace;
            r.size = addButtonDimension;
            GUIContent buttonContent = EditorGUIUtility.IconContent("d_RectTransform Icon");
            buttonContent.tooltip = "Set to scene-view camera position";
            GUIStyle style = new GUIStyle(GUI.skin.label);
            style.alignment = TextAnchor.MiddleCenter;
            if (GUI.Button(r, buttonContent, style) && SceneView.lastActiveSceneView != null)
            {
                Undo.RecordObject(Target, "Set waypoint");
                CinemachinePath.Waypoint wp = Target.m_Waypoints[index];
                Vector3 pos = SceneView.lastActiveSceneView.camera.transform.position;
                wp.position = Target.transform.InverseTransformPoint(pos);
                Target.m_Waypoints[index] = wp;
            }

            r = new Rect(rect.position, labelDimension);
            r.y += numberDimension.y + vSpace;
            r.x += hSpace + numberDimension.x; r.width = labelDimension.x;
            EditorGUI.LabelField(r, "Tangent");
            r.x += hSpace + r.width;
            r.width = rect.width - (numberDimension.x + hSpace + r.width + hSpace + addButtonDimension.x + hSpace);
            EditorGUI.PropertyField(r, element.FindPropertyRelative(() => def.tangent), GUIContent.none);
            r.x += r.width + hSpace;
            r.size = addButtonDimension;
            buttonContent = EditorGUIUtility.IconContent("ol minus@2x");
            buttonContent.tooltip = "Remove this waypoint";
            if (GUI.Button(r, buttonContent, style))
            {
                Undo.RecordObject(Target, "Delete waypoint");
                var list = new List<CinemachinePath.Waypoint>(Target.m_Waypoints);
                list.RemoveAt(index);
                Target.m_Waypoints = list.ToArray();
                if (index == Target.m_Waypoints.Length)
                    mWaypointList.index = index - 1;
            }

            r = new Rect(rect.position, labelDimension);
            r.y += 2 * (numberDimension.y + vSpace);
            r.x += hSpace + numberDimension.x; r.width = labelDimension.x;
            EditorGUI.LabelField(r, "Roll");
            r.x += hSpace + labelDimension.x;
            r.width = rect.width
                - (numberDimension.x + hSpace)
                - (labelDimension.x + hSpace)
                - (addButtonDimension.x + hSpace);
            r.width /= 3;
            EditorGUI.MultiPropertyField(r, new GUIContent[] { new GUIContent(" ") },
                element.FindPropertyRelative(() => def.roll));

            r.x = rect.x + rect.width - addButtonDimension.x;
            r.size = addButtonDimension;
            buttonContent = EditorGUIUtility.IconContent("ol plus@2x");
            buttonContent.tooltip = "Add a new waypoint after this one";
            if (GUI.Button(r, buttonContent, style))
            {
                mWaypointList.index = index;
                InsertWaypointAtIndex(index);
            }
        }

        void InsertWaypointAtIndex(int indexA)
        {
            Vector3 pos = Vector3.forward;
            Vector3 tangent = Vector3.right;
            float roll = 0;

            // Get new values from the current indexA (if any)
            int numWaypoints = Target.m_Waypoints.Length;
            if (indexA < 0)
                indexA = numWaypoints - 1;
            if (indexA >= 0)
            {
                int indexB = indexA + 1;
                if (Target.m_Looped && indexB >= numWaypoints)
                    indexB = 0;
                if (indexB >= numWaypoints)
                {
                    // Extrapolate the end
                    if (!Target.m_Waypoints[indexA].tangent.AlmostZero())
                        tangent = Target.m_Waypoints[indexA].tangent;
                    pos = Target.m_Waypoints[indexA].position + tangent;
                    roll = Target.m_Waypoints[indexA].roll;
                }
                else
                {
                    // Interpolate
                    pos = Target.transform.InverseTransformPoint(
                            Target.EvaluatePosition(0.5f + indexA));
                    tangent = Target.transform.InverseTransformDirection(
                            Target.EvaluateTangent(0.5f + indexA).normalized);
                    roll = Mathf.Lerp(
                            Target.m_Waypoints[indexA].roll, Target.m_Waypoints[indexB].roll, 0.5f);
                }
            }
            Undo.RecordObject(Target, "Add waypoint");
            var wp = new CinemachinePath.Waypoint();
            wp.position = pos;
            wp.tangent = tangent;
            wp.roll = roll;
            var list = new List<CinemachinePath.Waypoint>(Target.m_Waypoints);
            list.Insert(indexA + 1, wp);
            Target.m_Waypoints = list.ToArray();
            Target.InvalidateDistanceCache();
            mWaypointList.index = indexA + 1; // select it
        }

        void OnSceneGUI()
        {
            if (mWaypointList == null)
                SetupWaypointList();

            if (Tools.current == Tool.Move)
            {
                Color colorOld = Handles.color;
                var localToWorld = Target.transform.localToWorldMatrix;
                var localRotation = Target.transform.rotation;
                for (int i = 0; i < Target.m_Waypoints.Length; ++i)
                {
                    DrawSelectionHandle(i, localToWorld);
                    if (mWaypointList.index == i)
                    {
                        // Waypoint is selected
                        if (PreferTangentSelection)
                        {
                            DrawPositionControl(i, localToWorld, localRotation);
                            DrawTangentControl(i, localToWorld, localRotation);
                        }
                        else
                        {
                            DrawTangentControl(i, localToWorld, localRotation);
                            DrawPositionControl(i, localToWorld, localRotation);
                        }
                    }
                }
                Handles.color = colorOld;
            }
        }

        void DrawSelectionHandle(int i, Matrix4x4 localToWorld)
        {
            if (Event.current.button != 1)
            {
                Vector3 pos = localToWorld.MultiplyPoint(Target.m_Waypoints[i].position);
                float size = HandleUtility.GetHandleSize(pos) * 0.2f;
                Handles.color = Color.white;
                if (Handles.Button(pos, Quaternion.identity, size, size, Handles.SphereHandleCap)
                    && mWaypointList.index != i)
                {
                    mWaypointList.index = i;
                    InspectorUtility.RepaintGameView();
                }
                // Label it
                Handles.BeginGUI();
                Vector2 labelSize = new Vector2(
                        EditorGUIUtility.singleLineHeight * 2, EditorGUIUtility.singleLineHeight);
                Vector2 labelPos = HandleUtility.WorldToGUIPoint(pos);
                labelPos.y -= labelSize.y / 2;
                labelPos.x -= labelSize.x / 2;
                GUILayout.BeginArea(new Rect(labelPos, labelSize));
                GUIStyle style = new GUIStyle();
                style.normal.textColor = Color.black;
                style.alignment = TextAnchor.MiddleCenter;
                GUILayout.Label(new GUIContent(i.ToString(), "Waypoint " + i), style);
                GUILayout.EndArea();
                Handles.EndGUI();
            }
        }

        void DrawTangentControl(int i, Matrix4x4 localToWorld, Quaternion localRotation)
        {
            CinemachinePath.Waypoint wp = Target.m_Waypoints[i];
            Vector3 hPos = localToWorld.MultiplyPoint(wp.position + wp.tangent);

            Handles.color = Color.yellow;
            Handles.DrawLine(localToWorld.MultiplyPoint(wp.position), hPos);

            EditorGUI.BeginChangeCheck();
            Quaternion rotation = (Tools.pivotRotation == PivotRotation.Local)
                ? localRotation : Quaternion.identity;
            float size = HandleUtility.GetHandleSize(hPos) * 0.1f;
            Handles.SphereHandleCap(0, hPos, rotation, size, EventType.Repaint);
            Vector3 newPos = Handles.PositionHandle(hPos, rotation);
            if (EditorGUI.EndChangeCheck())
            {
                Undo.RecordObject(target, "Change Waypoint Tangent");
                newPos = Matrix4x4.Inverse(localToWorld).MultiplyPoint(newPos);
                wp.tangent = newPos - wp.position;
                Target.m_Waypoints[i] = wp;
                Target.InvalidateDistanceCache();
                InspectorUtility.RepaintGameView();
            }
        }

        void DrawPositionControl(int i, Matrix4x4 localToWorld, Quaternion localRotation)
        {
            CinemachinePath.Waypoint wp = Target.m_Waypoints[i];
            Vector3 pos = localToWorld.MultiplyPoint(wp.position);
            EditorGUI.BeginChangeCheck();
            Handles.color = Target.m_Appearance.pathColor;
            Quaternion rotation = (Tools.pivotRotation == PivotRotation.Local)
                ? localRotation : Quaternion.identity;
            float size = HandleUtility.GetHandleSize(pos) * 0.1f;
            Handles.SphereHandleCap(0, pos, rotation, size, EventType.Repaint);
            pos = Handles.PositionHandle(pos, rotation);
            if (EditorGUI.EndChangeCheck())
            {
                Undo.RecordObject(target, "Move Waypoint");
                wp.position = Matrix4x4.Inverse(localToWorld).MultiplyPoint(pos);;
                Target.m_Waypoints[i] = wp;
                Target.InvalidateDistanceCache();
                InspectorUtility.RepaintGameView();
            }
        }

        [DrawGizmo(GizmoType.Active | GizmoType.NotInSelectionHierarchy
             | GizmoType.InSelectionHierarchy | GizmoType.Pickable, typeof(CinemachinePath))]
        static void DrawGizmos(CinemachinePath path, GizmoType selectionType)
        {
            var isActive = Selection.activeGameObject == path.gameObject; 
            DrawPathGizmo(
                path, isActive ? path.m_Appearance.pathColor : path.m_Appearance.inactivePathColor, 
                isActive, LocalSpaceSamplePath);
        }

        // same as Quaternion.AngleAxis(roll, Vector3.forward), just simplified
        static Quaternion RollAroundForward(float angle)
        {
            var halfAngle = angle * 0.5F * Mathf.Deg2Rad;
            return new Quaternion(0, 0, Mathf.Sin(halfAngle), Mathf.Cos(halfAngle));
        }
        
        static Vector4[] s_BezierWeightsCache;

        // Optimizer for gizmo drawing
        static int LocalSpaceSamplePath(CinemachinePathBase pathBase, int samplesPerSegment, Vector3[] positions, Quaternion[] rotations)
        {
            var path = pathBase as CinemachinePath;

            int numSegments = path.m_Waypoints.Length - (path.Looped ? 0 : 1);
            if (numSegments == 0)
                return 0;

            // Compute the bezier weights only once - this is shared by all segments
            if (s_BezierWeightsCache == null || s_BezierWeightsCache.Length < samplesPerSegment)
                s_BezierWeightsCache = new Vector4[samplesPerSegment];
            for (int i = 0; i < samplesPerSegment; ++i)
            {
                float t = ((float)i) / samplesPerSegment;
                float d = 1.0f - t;
                s_BezierWeightsCache[i] = new Vector4(d * d * d, 3f * d * d * t, 3f * d * t * t, t * t * t);
            }

            // Process the positions
            int numSamples = 0;
            for (int wp = 0; wp < numSegments && numSamples < positions.Length; ++wp)
            {
                int nextWp = (wp + 1) % path.m_Waypoints.Length;
                for (int i = 0; i < samplesPerSegment; ++i)
                {
                    if (numSamples >= positions.Length)
                        break;
                    positions[numSamples++]
                        = (s_BezierWeightsCache[i].x * path.m_Waypoints[wp].position)
                        + (s_BezierWeightsCache[i].y * (path.m_Waypoints[wp].position + path.m_Waypoints[wp].tangent))
                        + (s_BezierWeightsCache[i].z * (path.m_Waypoints[nextWp].position - path.m_Waypoints[nextWp].tangent))
                        + (s_BezierWeightsCache[i].w * path.m_Waypoints[nextWp].position);
                }
            }
            if (numSamples < positions.Length)
                positions[numSamples++] = path.Looped ? positions[0] : path.m_Waypoints[path.m_Waypoints.Length - 1].position;

            // Process rotations
            if (rotations != null && rotations.Length >= numSamples)
            {
                int numRotSamples = 0;
                for (int wp = 0; wp < numSegments && numRotSamples < numSamples; ++wp)
                {
                    int nextWp = (wp + 1) % path.m_Waypoints.Length;
                    SplineHelpers.BezierTangentWeights3(
                        path.m_Waypoints[wp].position, path.m_Waypoints[wp].position + path.m_Waypoints[wp].tangent,
                        path.m_Waypoints[nextWp].position - path.m_Waypoints[nextWp].tangent, path.m_Waypoints[nextWp].position,
                        out var w0, out var w1, out var w2);

                    for (int i = 0; i < samplesPerSegment; ++i)
                    {
                        if (numRotSamples >= numSamples)
                            break;
                        float t = ((float)i) / samplesPerSegment;
                        var fwd = (w0 * (t * t)) + (w1 * t) + w2; // from SplineHelpers.BezierTangent3()
                        if (fwd.sqrMagnitude < 0.001f)
                            fwd = Vector3.forward;
                        rotations[numRotSamples++] = Quaternion.LookRotation(fwd) * RollAroundForward(path.GetRoll(wp, nextWp, t + wp));
                    }
                }
                if (numRotSamples < numSamples)
                    rotations[numRotSamples++] = path.Looped ? rotations[0] : path.EvaluateLocalOrientation(path.MaxPos);
            }

            return numSamples;
        }


        //===========================================
        // Generic service for drawing path gizmo

        static Vector3[] s_PositionsCache;
        static Quaternion[] s_RotationsCache;
#if UNITY_2023_1_OR_NEWER
        static Vector3[] s_RightRailCache;
        static Vector3[] s_SleepersCache;
#endif

        static ElementType[] EnsureArraySize<ElementType>(ElementType[] array, int requiredSize)
        {
            return ((array == null) || (array.Length < requiredSize)) ? new ElementType[requiredSize] : array;
        }

        /// <summary>
        /// Sample a path with a fixed number of samples per segment, in path-local space.  
        /// Used for efficient gizmo drawing.
        /// </summary>
        /// <param name="samplesPerSegment">How many samples to take in each segment</param>
        /// <param name="positions">Output buffer for position samples</param>
        /// <param name="rotations">Output buffer for rotation samples.  May be null if rotations are not needed.</param>
        /// <returns>Number of samples actually taken</returns>
        public delegate int BatchSamplerDelegate(CinemachinePathBase path, int samplesPerSegment, Vector3[] positions, Quaternion[] rotations);
        
        public static void DrawPathGizmo(CinemachinePathBase path, Color pathColor, bool isActive, BatchSamplerDelegate batchSampler = null)
        {
            var oldColor = Gizmos.color;
            Gizmos.color = pathColor;
            var oldMatrix = Gizmos.matrix;
            Gizmos.matrix = path.transform.localToWorldMatrix;

            if (batchSampler == null)
                batchSampler = DefaultBatchSampler;
            int numSegments = Mathf.CeilToInt(path.MaxPos - path.MinPos) + 1;
            int numSamples = numSegments * path.m_Resolution + 1;
            s_PositionsCache = EnsureArraySize(s_PositionsCache, numSamples);
            if (!isActive || path.m_Appearance.width < 0.01f)
            {
                numSamples = batchSampler(path, path.m_Resolution, s_PositionsCache, null);
#if UNITY_2023_1_OR_NEWER
                Gizmos.DrawLineStrip(new Span<Vector3>(s_PositionsCache, 0, numSamples), false);
#else
                for (int i = 1; i < numSamples; ++i)
                    Gizmos.DrawLine(s_PositionsCache[i], s_PositionsCache[i-1]);
#endif
            }
            else
            {
                s_RotationsCache = EnsureArraySize(s_RotationsCache, numSamples);
                numSamples = batchSampler(path, path.m_Resolution, s_PositionsCache, s_RotationsCache);

                // Draw the path
                var halfWidth = path.m_Appearance.width * 0.5f;
#if UNITY_2023_1_OR_NEWER
                s_RightRailCache = EnsureArraySize(s_RightRailCache, numSamples);
                s_SleepersCache = EnsureArraySize(s_SleepersCache, numSamples * 2);
                for (int i = 0; i < numSamples; ++i)
                {
                    var p = s_PositionsCache[i];
                    var q = s_RotationsCache[i];
                    var s = q * Vector3.right * halfWidth;
                    s_RightRailCache[i] = p + s;
                    s_PositionsCache[i] = p - s;
                    s *= 1.2f;
                    s_SleepersCache[i << 1] = p + s;
                    s_SleepersCache[(i << 1) + 1] = p - s;
                }
                Gizmos.DrawLineStrip(new Span<Vector3>(s_PositionsCache, 0, numSamples), false);
                Gizmos.DrawLineStrip(new Span<Vector3>(s_RightRailCache, 0, numSamples), false);
                Gizmos.DrawLineList(new Span<Vector3>(s_SleepersCache, 0, numSamples * 2));
#else
                var lastW = (s_RotationsCache[0] * Vector3.right) * halfWidth;
                for (int i = 1; i < numSamples; ++i)
                {
                    var lastPos = s_PositionsCache[i-1];
                    var p = s_PositionsCache[i];
                    var q = s_RotationsCache[i];
                    var w = (q * Vector3.right) * halfWidth;
                    var w2 = w * 1.2f;
                    var p0 = p - w2;
                    var p1 = p + w2;
                    Gizmos.DrawLine(p0, p1);
                    Gizmos.DrawLine(lastPos - lastW, p - w);
                    Gizmos.DrawLine(lastPos + lastW, p + w);
                    lastW = w;
                }
#endif
            }
            Gizmos.matrix = oldMatrix;
            Gizmos.color = oldColor;
        }

        // Fallback, used if a custom batch sampler is not provided to DrawPathGizmo()
        static int DefaultBatchSampler(CinemachinePathBase path, int samplesPerSegment, Vector3[] positions, Quaternion[] rotations)
        {
            int numSamples = 0;
            float step = 1f / samplesPerSegment;
            float tEnd = path.MaxPos + step / 2;
            for (float t = path.MinPos + step; t <= tEnd; t += step)
            {
                if (numSamples >= positions.Length || (rotations != null && numSamples >= rotations.Length))
                    break;
                positions[numSamples] = path.EvaluateLocalPosition(t);
                if (rotations != null)
                    rotations[numSamples] = path.EvaluateLocalOrientation(t);
                ++numSamples;
            }
            return numSamples;
        }
    }
}