using System;
using RosettaUI.Builder;
using UnityEngine;
using UnityEngine.UIElements;

namespace RosettaUI.UIToolkit.AnimationCurveEditor
{
    /// <summary>
    /// Control point of the animation curve editor.
    /// 
    /// ControlPointはAnimationCurveのKeyframeと1対1対応するが、直接Keyframeを編集はしない
    /// Keyframeの値を変えると隣り合ったKeyframeの値も変更する必要があることがある（インデックスが変わったり、TangentモードがLinearだとTangentが変わるなど）ので、
    /// ControlPoint単体でKeyframeを編集せずにAnimationCurve全体での整合性を取るようControlPointHolderなどに変更を依頼する
    /// </summary>
    public class ControlPoint : VisualElement
    {
        private const string ContainerClassName = "rosettaui-animation-curve-editor__control-point-container";
        private const string ControlPointClassName = "rosettaui-animation-curve-editor__control-point";
        private const string ActiveControlPointClassName = "rosettaui-animation-curve-editor__control-point--active";

        // Weightの固定値は1/3の模様
        // https://github.com/Unity-Technologies/UnityCsReference/blob/4b463aa72c78ec7490b7f03176bd012399881768/Editor/Mono/Animation/AnimationWindow/CurveMenuManager.cs#L193
        // Ferguson/Coons曲線をベジエ曲線にするときの係数
        // https://olj611.hatenablog.com/entry/2023/12/01/150842
        private const float WeightDefaultValue = 1 / 3f;

        private readonly CurveController _curveController;
        private readonly PreviewTransform _previewTransform;
        private readonly VisualElement _controlPointCore;
        private readonly ControlPointHandle _leftHandle;
        private readonly ControlPointHandle _rightHandle;
        private readonly WrapModeButton _wrapModeButton;

        private readonly Action<Vector2, ControlPoint> _showPopupMenu;

        private Vector2 _pointerDownPositionToElementOffset;
        private Vector2 _keyframePositionOnPointerDown;


        /// Needs to call CurveController.OnCurveChanged() after this to reflect the change in the view
        public bool IsKeyBroken { get; set; }

        /// Needs to call CurveController.OnCurveChanged() after this to reflect the change in the view
        public TangentMode InTangentMode { get; set; } = TangentMode.Free;

        /// Needs to call CurveController.OnCurveChanged() after this to reflect the change in the view
        public TangentMode OutTangentMode { get; set; } = TangentMode.Free;


        public bool IsActive
        {
            get => _controlPointCore.ClassListContains(ActiveControlPointClassName);
            set
            {
                _controlPointCore.EnableInClassList(ActiveControlPointClassName, value);
                UpdateHandleView();
            }
        }

        public Keyframe Keyframe => _curveController.GetKeyframe(this);

        public Vector2 KeyframePosition => Keyframe.GetPosition();

        /// <summary>
        /// UIToolkitのLocalPosition
        /// get時、resolveStyleに反映されるのはレイアウト計算後なのでstyle.left/topを直接参照する
        /// </summary>
        public Vector2 LocalPosition
        {
            get => new(style.left.value.value, style.top.value.value);
            private set
            {
                style.left = value.x;
                style.top = value.y;
            }
        }

        private ControlPoint Left => _curveController.GetControlPointLeft(this);
        private ControlPoint Right => _curveController.GetControlPointRight(this);


        public ControlPoint(CurveController curveController, PreviewTransform previewTransform,
            Action<Vector2, ControlPoint> showPopupMenu)
        {
            _curveController = curveController;
            _previewTransform = previewTransform;
            _showPopupMenu = showPopupMenu;

            // Control point container
            AddToClassList(ContainerClassName);
            RegisterCallback<PointerDownEvent>(OnPointerDown);

            // Handles
            _leftHandle = new ControlPointHandle(InOrOut.In,
                _previewTransform,
                (tangent, weight) => OnTangentAndWeightChanged(InOrOut.In, tangent, weight)
            );
            Add(_leftHandle);

            _rightHandle = new ControlPointHandle(InOrOut.Out,
                _previewTransform,
                (tangent, weight) => OnTangentAndWeightChanged(InOrOut.Out, tangent, weight)
            );
            Add(_rightHandle);


            // Control point
            _controlPointCore = new VisualElement { name = "AnimationCurveEditorControlPoint" };
            _controlPointCore.AddToClassList(ControlPointClassName);
            Add(_controlPointCore);


            // Clamp mode button
            _wrapModeButton = new WrapModeButton();
            _wrapModeButton.RegisterCallback<PointerDownEvent>(_ => OnWrapModeButtonClicked());
            Add(_wrapModeButton);
            
            
            // hide handles
            UpdateHandleView();
            
            return;


            void OnTangentAndWeightChanged(InOrOut inOrOut, float tangent, float weight)
            {
                var keyframe = Keyframe;

                keyframe.SetTangent(inOrOut, tangent);

                if (!IsKeyBroken)
                {
                    var oppositeTangent = float.IsInfinity(tangent) ? -tangent : tangent;
                    keyframe.SetTangent(inOrOut.Opposite(), oppositeTangent);
                }

                keyframe.SetWeight(inOrOut, keyframe.IsWeighted(inOrOut) ? weight : WeightDefaultValue);

                
                _curveController.Command.SetControlPointKeyframe(this, keyframe);
            }

            void OnWrapModeButtonClicked()
            {
                Action<WrapMode> setWrapMode;
                WrapMode currentMode;

                switch (_wrapModeButton.CurrentPreOrPost)
                {
                    case WrapModeButton.PreOrPost.Pre:
                        setWrapMode = _curveController.Command.SetPreWrapMode;
                        currentMode = _curveController.Curve.preWrapMode;
                        break;
                    case WrapModeButton.PreOrPost.Post:
                        setWrapMode = _curveController.Command.SetPostWrapMode;
                        currentMode = _curveController.Curve.postWrapMode;
                        break;

                    default:
                        throw new ArgumentOutOfRangeException();
                }

                var position = _wrapModeButton.worldBound.position;
                position.y += 10f;

                PopupMenuUtility.Show(new[]
                    {
                        CreateItem("Loop", WrapMode.Loop),
                        CreateItem("Ping Pong", WrapMode.PingPong),
                        CreateItem("Clamp", WrapMode.ClampForever),
                    },
                    position,
                    _wrapModeButton
                );

                return;

                MenuItem CreateItem(string itemName, WrapMode mode)
                {
                    return new MenuItem(itemName, () => setWrapMode(mode)) { isChecked = mode == currentMode };
                }
            }
        }

        public void UpdateView()
        {
            LocalPosition = _previewTransform.GetScreenPosFromCurvePos(KeyframePosition);

            UpdateWrapModeButton();

            if (IsActive)
            {
                UpdateHandleView();
            }
        }

        private void UpdateWrapModeButton()
        {
            var hasLeft = Left != null;
            var hasRight = Right != null;

            // ReSharper disable once ConvertIfStatementToSwitchStatement
            if (!hasLeft && hasRight)
            {
                _wrapModeButton.Show(WrapModeButton.PreOrPost.Pre);
            }
            else if (hasLeft && !hasRight)
            {
                _wrapModeButton.Show(WrapModeButton.PreOrPost.Post);
            }
            else
            {
                _wrapModeButton.Hide();
            }
        }

        private void UpdateHandleView()
        {
            var keyframe = Keyframe;

            var leftHandleEnable = IsActive && (Left != null) && (InTangentMode == TangentMode.Free);
            var rightHandleEnable = IsActive && (Right != null) && (OutTangentMode == TangentMode.Free);

            Update(leftHandleEnable, _leftHandle, keyframe, GetXDistInScreen(Left, this));
            Update(rightHandleEnable, _rightHandle, keyframe, GetXDistInScreen(this, Right));

            return;


            static void Update(bool enable, ControlPointHandle handle, Keyframe keyframe, float xDistToNeighborInScreen)
            {
                if (!enable)
                {
                    handle.style.visibility = Visibility.Hidden;
                    return;
                }

                handle.style.visibility = Visibility.Visible;
                handle.UpdateView(keyframe, xDistToNeighborInScreen);
            }


            float GetXDistInScreen(ControlPoint left, ControlPoint right)
            {
                if (left == null || right == null) return 0f;
                var screesPosLeft = _previewTransform.GetScreenPosFromCurvePos(left.KeyframePosition);
                var screesPosRight = _previewTransform.GetScreenPosFromCurvePos(right.KeyframePosition);
                return screesPosRight.x - screesPosLeft.x;
            }
        }


        private void OnPointerDown(PointerDownEvent evt)
        {
            switch (evt.button)
            {
                // Left click
                // - subKey: select/unselect
                // - !subKey: select only this. and expect start drag.
                case 0:
                    var subKey = evt.shiftKey || evt.ctrlKey || evt.commandKey;

                    if (subKey)
                    {
                        if (IsActive)
                        {
                            _curveController.UnselectControlPoint(this);
                        }
                        else
                        {
                            _curveController.SelectControlPoint(this, keepOtherSelection: true);
                        }

                        evt.StopPropagation();
                        return;
                    }

                    // 未選択のコントロールポイントの場合はそれのみ選択する
                    // すでに選択済みの場合は複数選択のケースもあるのでそのまま
                    if (!IsActive)
                    {
                        _curveController.SelectControlPoint(this);
                    }

                    // ここでStopPropagationしない
                    // 別のマニュピレーターでDragされるのを期待する
                    // evt.StopPropagation();
                    break;


                // Right click
                //  Show popup menu
                case 1:
                    // IsActive(=選択中）の場合はそのまま（複数選択のとき複数選択状態をキープ）
                    // IsActiveでない場合は他の選択を外して自身のみ選択してからメニュー表示
                    if (!IsActive)
                    {
                        _curveController.SelectControlPoint(this, keepOtherSelection: false);
                    }

                    // Show menu
                    // SelectedControlPointsRectのときでも出して良い気がするが、
                    // - UnityのAnimationCurveEditorの挙動では出ない
                    // - DropdownMenuが、画面下部にスペースがなく上部にある場合targetエレメントの上にメニューが表示される
                    //   SelectedControlPointsRectの上部に出てしまいカーソルから離れすぎて不自然なので一旦なし
                    // ControlPointsPopupMenu.Show(evt.position, SelectedControlPointsEditor, _editPositionPopup, this);
                    _showPopupMenu(evt.position, this);

                    evt.StopPropagation();


                    break;
            }
        }
    }
}