// UIMotionTween.cs
// 控制 UI 的位移动画和透明度渐变动画。
// - 位移：在两个锚点之间按 AnimationCurve 插值（支持本地坐标偏移）
// - 渐变：另一条 AnimationCurve 驱动当前 GameObject 下所有 Graphic 的 alpha
// 两条动画可独立启用，共用同一个时长和播放控制。

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

namespace NLD.UI
{
    public class UIMotionTween : MonoBehaviour
    {
        // ── 通用设置 ──────────────────────────────────────────────────
        [Header("通用")]
        [Tooltip("动画总时长（秒）")]
        public float duration = 0.5f;

        [Tooltip("启动时自动播放")]
        public bool playOnEnable = true;

        [Tooltip("播放结束后是否循环")]
        public bool loop = false;

        // ── 位移设置 ──────────────────────────────────────────────────
        [Header("位移")]
        [Tooltip("是否启用位移动画")]
        public bool enableMove = true;

        [Tooltip("起点（本地坐标偏移，相对于 RectTransform 的初始 anchoredPosition）")]
        public Vector2 fromOffset = new Vector2(0f, -50f);

        [Tooltip("终点（本地坐标偏移，相对于 RectTransform 的初始 anchoredPosition）")]
        public Vector2 toOffset = Vector2.zero;

        [Tooltip("位移曲线：X 轴为归一化时间(0-1)，Y 轴为插值进度(0-1)。\n" +
                 "用曲线形态控制运动快慢/弹性等动态效果。")]
        public AnimationCurve moveCurve = AnimationCurve.EaseInOut(0f, 0f, 1f, 1f);

        // ── 渐变设置 ──────────────────────────────────────────────────
        [Header("渐变")]
        [Tooltip("是否启用透明度渐变")]
        public bool enableFade = true;

        [Tooltip("渐变曲线：X 轴为归一化时间(0-1)，Y 轴为 alpha 值(0-1)。\n" +
                 "影响此 GameObject 下所有 Graphic 组件的 color.a。")]
        public AnimationCurve fadeCurve = AnimationCurve.EaseInOut(0f, 0f, 1f, 1f);

        // ── 内部状态 ──────────────────────────────────────────────────
        public bool IsPlaying => _isPlaying;
        private RectTransform _rectTransform;
        private Vector2       _basePosition;
        private float         _elapsed;
        private bool          _isPlaying;

        // 缓存子级所有 Graphic，避免每帧 GetComponentsInChildren
        private readonly List<Graphic> _graphics      = new List<Graphic>();
        // 对应每个 Graphic 在 CacheGraphics 时记录的原始 alpha（渐变目标值）
        private readonly List<float>   _originalAlphas = new List<float>();

        // ── 生命周期 ──────────────────────────────────────────────────
        private void Awake()
        {
            _rectTransform = GetComponent<RectTransform>();
            if (_rectTransform == null)
            {
                Debug.LogWarning("[UIMotionTween] 未找到 RectTransform，位移功能将不生效。", this);
            }
            else
            {
                _basePosition = _rectTransform.anchoredPosition;
            }
        }

        private void Start()
        {
            CacheGraphics();
            SetAllTransparent();
        }

        private void OnEnable()
        {
            if (playOnEnable)
                Play();
        }

        private void OnDisable()
        {
            _isPlaying = false;
            SetAllTransparent();
        }

        private void Update()
        {
            if (!_isPlaying) return;

            _elapsed += Time.deltaTime;

            float t = duration > 0f ? Mathf.Clamp01(_elapsed / duration) : 1f;

            ApplyMove(t);
            ApplyFade(t);

            if (t >= 1f)
            {
                if (loop)
                    _elapsed = 0f;
                else
                    _isPlaying = false;
            }
        }

        // ── 公开接口 ──────────────────────────────────────────────────

        /// <summary>从头开始播放动画。</summary>
        public void Play()
        {
            _elapsed   = 0f;
            _isPlaying = true;
            enabled    = true;
        }

        /// <summary>从头开始反向播放（终点→起点）。</summary>
        public void PlayReverse()
        {
            _elapsed   = duration;
            _isPlaying = true;
            enabled    = true;
        }

        /// <summary>暂停动画，保持当前状态。</summary>
        public void Pause() => _isPlaying = false;

        /// <summary>继续播放（从暂停处恢复）。</summary>
        public void Resume() => _isPlaying = true;

        /// <summary>停止并重置到起始状态（t=0）。</summary>
        public void Stop()
        {
            _isPlaying = false;
            _elapsed   = 0f;
            ApplyMove(0f);
            ApplyFade(0f);
        }

        /// <summary>手动跳转到指定归一化时间（0-1）。</summary>
        public void SetProgress(float normalizedTime)
        {
            _elapsed = Mathf.Clamp01(normalizedTime) * duration;
            float t = Mathf.Clamp01(normalizedTime);
            ApplyMove(t);
            ApplyFade(t);
        }

        /// <summary>重新扫描子级 Graphic 列表（动态增删子节点后调用）。</summary>
        public void CacheGraphics()
        {
            _graphics.Clear();
            _originalAlphas.Clear();
            GetComponentsInChildren(true, _graphics);
            foreach (var g in _graphics)
                _originalAlphas.Add(g != null ? g.color.a : 1f);
        }

        // ── 内部实现 ──────────────────────────────────────────────────
        private void ApplyMove(float t)
        {
            if (!enableMove || _rectTransform == null) return;

            float curveValue = moveCurve.Evaluate(t);
            _rectTransform.anchoredPosition = _basePosition + Vector2.LerpUnclamped(fromOffset, toOffset, curveValue);
        }

        private void ApplyFade(float t)
        {
            if (!enableFade) return;

            float progress = fadeCurve.Evaluate(t);
            for (int i = 0; i < _graphics.Count; i++)
            {
                var graphic = _graphics[i];
                if (graphic == null) continue;
                Color c = graphic.color;
                c.a           = progress * _originalAlphas[i];
                graphic.color = c;
            }
        }

        /// <summary>将所有 Graphic 设置为完全透明。</summary>
        private void SetAllTransparent()
        {
            for (int i = 0; i < _graphics.Count; i++)
            {
                var graphic = _graphics[i];
                if (graphic == null) continue;
                Color c = graphic.color;
                c.a = 0f;
                graphic.color = c;
            }
        }

        // 判断该 Graphic 是否应跳过渐变：
        //   Image  - 未设置 Sprite，或使用了 Unity 内置默认 Sprite（GUID 全零）
        //   RawImage - 未设置 Texture
        private static bool ShouldSkipFade(Graphic graphic)
        {
            if (graphic is Image img)
            {
                if (img.sprite == null) return true;
                // Unity 内置 Sprite 的名称（来自 Resources/unity_builtin_extra）
                string n = img.sprite.name;
                return n == "UISprite"             ||
                       n == "Background"           ||
                       n == "InputFieldBackground" ||
                       n == "Knob"                 ||
                       n == "Checkmark"            ||
                       n == "DropdownArrow"        ||
                       n == "UIMask";
            }
            if (graphic is RawImage raw)
            {
                return raw.texture == null;
            }
            return false;
        }

#if UNITY_EDITOR
        private void OnValidate()
        {
            // Inspector 修改参数时实时预览（Edit Mode）
            if (!Application.isPlaying) return;
            if (_rectTransform == null) return;
            float t = duration > 0f ? Mathf.Clamp01(_elapsed / duration) : 1f;
            ApplyMove(t);
            ApplyFade(t);
        }
#endif
    }
}