using System;
using System.Collections.Generic;
using Ichni.RhythmGame.Beatmap;
using UnityEngine;

namespace Ichni.RhythmGame
{
    /// <summary>
    /// Synchronizes this element's position to another element's world position.
    /// </summary>
    public partial class PositionSync : AnimationBase
    {
        #region [暴露属性字段与关联] Exposed Fields & References
        public TransformSubmodule targetTransformSubmodule;
        public GameElement syncTargetObject;
        public FlexibleBool enabling;
        #endregion

        #region [生命周期与工厂] Lifecycle & Factory
        public static PositionSync GenerateElement(string elementName, Guid id,
            List<string> tags, bool isFirstGenerated, GameElement animatedObject,
            GameElement syncTargetObject, FlexibleBool enabling)
        {
            PositionSync sync = Instantiate(GameManager.Instance.basePrefabs.emptyObject).AddComponent<PositionSync>();

            sync.Initialize(elementName, id, tags, isFirstGenerated, animatedObject);

            sync.animatedObject = animatedObject;
            sync.syncTargetObject = syncTargetObject;
            sync.enabling = enabling ?? new FlexibleBool();
            sync.animationReturnType = FlexibleReturnType.Before;
            sync.targetTransformSubmodule = (animatedObject as IHaveTransformSubmodule)?.transformSubmodule;

            return sync;
        }

        public override void SetDefaultSubmodules()
        {
            timeDurationSubmodule = new TimeDurationSubmodule(this);
        }

        public override void OnDelete()
        {
            base.OnDelete();
            targetTransformSubmodule?.MarkPositionDirty();
        }
        #endregion

        #region [核心动画逻辑] Core Animation Logic
        public override void ScheduledUpdate(UpdatePhase phase, float songTime)
        {
            base.ScheduledUpdate(phase, songTime);

            // 与 CreatorStudio 保持一致：这里在 Animation 阶段读取 target world position。
            // 如果 target 是 TrackPercentPoint，当前帧 TrackFollower 尚未执行，因此读到的可能是上一帧位置。
            // 这个一帧延后是有意保留的兼容行为；好处是随后 Apply 阶段能刷新被同步的 PathNode/Track，
            // 让本帧后续 TrackFollower/Note 使用更新后的轨道数据。
            if (phase == UpdatePhase.Animation && enabling != null && enabling.value)
            {
                ApplyPositionSync();
            }
        }

        protected override void UpdateAnimation(float songTime, bool forceUpdate)
        {
            if (enabling == null)
            {
                animationReturnType = FlexibleReturnType.None;
                return;
            }

            enabling.UpdateFlexibleBool(songTime);

            if (enabling.value)
            {
                animationReturnType = FlexibleReturnType.MiddleExecuting;
                targetTransformSubmodule?.MarkPositionDirty();
            }
            else if (animationReturnType != FlexibleReturnType.MiddleInterval)
            {
                animationReturnType = FlexibleReturnType.MiddleInterval;
                targetTransformSubmodule?.MarkPositionDirty();
            }
        }

        private void ApplyPositionSync()
        {
            if (targetTransformSubmodule == null || syncTargetObject == null)
            {
                return;
            }

            Transform self = targetTransformSubmodule.attachedGameElement.transform;
            Transform parent = self.parent;
            Vector3 targetWorldPosition = syncTargetObject.transform.position;
            Vector3 desiredLocalPosition = parent != null
                ? parent.InverseTransformPoint(targetWorldPosition)
                : targetWorldPosition;
            Vector3 syncOffset = desiredLocalPosition - targetTransformSubmodule.originalPosition;

            targetTransformSubmodule.positionOffset += syncOffset;
            targetTransformSubmodule.MarkPositionDirty();
        }

        public override void ApplyTimeOffset(float offset)
        {
            base.ApplyTimeOffset(offset);
            enabling?.animations.ForEach(anim => anim.ApplyTimeOffset(offset));
        }
        #endregion
    }
}