using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace MeowmentDebugTool
{
    /// <summary>
    /// 可拖动的悬浮按钮
    /// 点击打开调试工具，可以在屏幕上自由拖动
    /// </summary>
    public class DraggableFloatingButton : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
    {
        [Header("设置")]
        [Tooltip("是否限制在屏幕范围内")]
        public bool clampToScreen = true;

        [Tooltip("与屏幕边缘的最小距离")]
        public float edgePadding = 20f;

        [Header("自动吸附")]
        [Tooltip("是否自动吸附到屏幕边缘")]
        public bool snapToEdge = true;

        [Tooltip("吸附动画时间")]
        public float snapDuration = 0.3f;

        private RectTransform rectTransform;
        private Canvas canvas;
        private Vector2 dragOffset;
        private bool isDragging = false;
        private Vector2 targetPosition;
        private bool isSnapping = false;

        // 用于区分点击和拖动
        private Vector2 dragStartPosition;
        private const float clickThreshold = 5f; // 小于这个距离算点击
        private bool wasDragging = false; // 标记刚才是否拖动过

        private void Awake()
        {
            rectTransform = GetComponent<RectTransform>();
            canvas = GetComponentInParent<Canvas>();

            if (canvas == null)
            {
                Debug.LogError("DraggableFloatingButton 必须在Canvas下！");
            }

            targetPosition = rectTransform.anchoredPosition;
        }

        private void Update()
        {
            // 平滑移动到目标位置（吸附动画）
            if (isSnapping && !isDragging)
            {
                rectTransform.anchoredPosition = Vector2.Lerp(
                    rectTransform.anchoredPosition,
                    targetPosition,
                    Time.deltaTime / snapDuration
                );

                if (Vector2.Distance(rectTransform.anchoredPosition, targetPosition) < 0.5f)
                {
                    rectTransform.anchoredPosition = targetPosition;
                    isSnapping = false;
                }
            }
        }

        public void OnBeginDrag(PointerEventData eventData)
        {
            isDragging = true;
            isSnapping = false;

            // 记录起始位置，用于判断是点击还是拖动
            dragStartPosition = eventData.position;

            // 计算拖动偏移
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
                canvas.transform as RectTransform,
                eventData.position,
                eventData.pressEventCamera,
                out Vector2 localPoint
            );

            dragOffset = rectTransform.anchoredPosition - localPoint;
        }

        public void OnDrag(PointerEventData eventData)
        {
            if (!isDragging) return;

            // 转换屏幕坐标到Canvas局部坐标
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
                canvas.transform as RectTransform,
                eventData.position,
                eventData.pressEventCamera,
                out Vector2 localPoint
            );

            // 应用拖动偏移
            Vector2 newPosition = localPoint + dragOffset;

            // 限制在屏幕范围内
            if (clampToScreen)
            {
                newPosition = ClampToScreen(newPosition);
            }

            rectTransform.anchoredPosition = newPosition;
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            isDragging = false;

            // 计算拖动距离
            float dragDistance = Vector2.Distance(dragStartPosition, eventData.position);

            // 如果拖动距离超过阈值，说明是拖动而不是点击
            if (dragDistance > clickThreshold)
            {
                wasDragging = true;
                // 在下一帧重置标记
                StartCoroutine(ResetDragFlag());
            }

            // 自动吸附到最近的边缘
            if (snapToEdge)
            {
                SnapToNearestEdge();
            }
        }

        private System.Collections.IEnumerator ResetDragFlag()
        {
            yield return null; // 等待一帧
            wasDragging = false;
        }

        /// <summary>
        /// 检查是否刚拖动过（用于Button点击事件判断）
        /// </summary>
        public bool GetWasDragging()
        {
            return wasDragging;
        }

        private Vector2 ClampToScreen(Vector2 position)
        {
            RectTransform canvasRect = canvas.transform as RectTransform;
            Vector2 canvasSize = canvasRect.sizeDelta;
            Vector2 buttonSize = rectTransform.sizeDelta;

            // 计算可移动范围
            float minX = -canvasSize.x / 2 + buttonSize.x / 2 + edgePadding;
            float maxX = canvasSize.x / 2 - buttonSize.x / 2 - edgePadding;
            float minY = -canvasSize.y / 2 + buttonSize.y / 2 + edgePadding;
            float maxY = canvasSize.y / 2 - buttonSize.y / 2 - edgePadding;

            position.x = Mathf.Clamp(position.x, minX, maxX);
            position.y = Mathf.Clamp(position.y, minY, maxY);

            return position;
        }

        private void SnapToNearestEdge()
        {
            RectTransform canvasRect = canvas.transform as RectTransform;
            Vector2 canvasSize = canvasRect.sizeDelta;
            Vector2 currentPos = rectTransform.anchoredPosition;

            // 计算到各个边缘的距离
            float distToLeft = Mathf.Abs(currentPos.x + canvasSize.x / 2);
            float distToRight = Mathf.Abs(currentPos.x - canvasSize.x / 2);
            float distToTop = Mathf.Abs(currentPos.y - canvasSize.y / 2);
            float distToBottom = Mathf.Abs(currentPos.y + canvasSize.y / 2);

            // 找到最近的边
            float minDist = Mathf.Min(distToLeft, distToRight, distToTop, distToBottom);

            Vector2 snapPosition = currentPos;
            Vector2 buttonSize = rectTransform.sizeDelta;

            if (minDist == distToLeft)
            {
                // 吸附到左边
                snapPosition.x = -canvasSize.x / 2 + buttonSize.x / 2 + edgePadding;
            }
            else if (minDist == distToRight)
            {
                // 吸附到右边
                snapPosition.x = canvasSize.x / 2 - buttonSize.x / 2 - edgePadding;
            }
            else if (minDist == distToTop)
            {
                // 吸附到顶部
                snapPosition.y = canvasSize.y / 2 - buttonSize.y / 2 - edgePadding;
            }
            else if (minDist == distToBottom)
            {
                // 吸附到底部
                snapPosition.y = -canvasSize.y / 2 + buttonSize.y / 2 + edgePadding;
            }

            // 确保在屏幕范围内
            snapPosition = ClampToScreen(snapPosition);

            targetPosition = snapPosition;
            isSnapping = true;
        }

        /// <summary>
        /// 设置悬浮按钮位置
        /// </summary>
        public void SetPosition(Vector2 position)
        {
            if (clampToScreen)
            {
                position = ClampToScreen(position);
            }
            rectTransform.anchoredPosition = position;
            targetPosition = position;
        }

        /// <summary>
        /// 获取当前位置
        /// </summary>
        public Vector2 GetPosition()
        {
            return rectTransform.anchoredPosition;
        }
    }
}