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

namespace BaseGames.World.Map
{
    /// <summary>
    /// 全屏地图输入处理器（架构 15_MapShopModule §1.3.1）。
    /// 挂在与 MapPanel 相同的 GameObject 上（MapPanel OnEnable/OnDisable 联动启停）。
    /// <list type="bullet">
    ///   <item>鼠标滚轮缩放（以鼠标位置为缩放中心）</item>
    ///   <item>键盘方向键 / WASD 平移</item>
    /// </list>
    /// </summary>
    [RequireComponent(typeof(MapPanel))]
    public class MapInputHandler : MonoBehaviour, IScrollHandler
    {
        [SerializeField] private ScrollRect     _scrollRect;
        [SerializeField] private RectTransform  _zoomTarget;   // 通常为 _roomContainer（格子根节点）

        [Header("缩放")]
        [SerializeField, Range(0.2f, 1f)]  private float _zoomMin   = 0.4f;
        [SerializeField, Range(1f, 5f)]    private float _zoomMax   = 3.0f;
        [SerializeField, Range(0.05f, 0.5f)] private float _zoomStep = 0.12f;

        [Header("键盘平移")]
        [SerializeField] private float _keyPanSpeed = 600f;    // px / 秒

        private float _zoom = 1f;

        private void OnEnable()
        {
            // 重新激活时还原缩放，避免上次关闭时的残留状态
            if (_zoomTarget != null)
                _zoom = _zoomTarget.localScale.x;
        }

        private void Update()
        {
            if (_scrollRect == null) return;

            float h = Input.GetAxisRaw("Horizontal");
            float v = Input.GetAxisRaw("Vertical");
            if (h == 0 && v == 0) return;

            var delta = new Vector2(h, v) * (_keyPanSpeed * Time.unscaledDeltaTime);
            _scrollRect.content.anchoredPosition += delta;
        }

        // ── 鼠标滚轮缩放 ─────────────────────────────────────────────────────

        public void OnScroll(PointerEventData eventData)
        {
            if (_zoomTarget == null) return;

            float newZoom = Mathf.Clamp(
                _zoom + eventData.scrollDelta.y * _zoomStep,
                _zoomMin, _zoomMax);

            if (Mathf.Approximately(newZoom, _zoom)) return;

            // 将鼠标屏幕坐标转为 zoomTarget 本地坐标（缩放前）
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
                _zoomTarget, eventData.position, eventData.pressEventCamera, out Vector2 pivotBefore);

            _zoom = newZoom;
            _zoomTarget.localScale = new Vector3(_zoom, _zoom, 1f);

            // 将同一屏幕点再次映射（缩放后），计算偏移量保持鼠标下方内容不动
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
                _zoomTarget, eventData.position, eventData.pressEventCamera, out Vector2 pivotAfter);

            // pivotAfter - pivotBefore 是 zoomTarget 本地空间的偏差，需转为父空间偏差
            Vector2 offset = pivotAfter - pivotBefore;
            _zoomTarget.anchoredPosition += offset * _zoom;
        }
    }
}