using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using BaseGames.Input;

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>方向键 / 摇杆平移（经由 InputReaderSO.NavigateEvent 派发）</item>
    /// </list>
    /// </summary>
    [RequireComponent(typeof(MapPanel))]
    public class MapInputHandler : MonoBehaviour, IScrollHandler
    {
        [SerializeField] private InputReaderSO  _inputReader;
        [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("平移")]
        [SerializeField] private float _keyPanSpeed = 600f;    // px / 秒

        private Vector2  _navInput;
        private MapPanel _panel;

        private void Awake()
        {
            _panel = GetComponent<MapPanel>();
#if UNITY_EDITOR || DEVELOPMENT_BUILD
            // R25-N2 _zoomTarget 须配置为 MapPanel 的格子根节点（与 _roomContainer 相同），
            // 否则 OnScroll 写入的 scale 与 MapPanel.CurrentZoom 读取的 scale 将来自不同节点，导致静默状态分裂。
            if (_zoomTarget == null)
                Debug.LogWarning("[MapInputHandler] _zoomTarget 未配置，缩放功能将失效。请在 Inspector 中指定 MapPanel 的格子根节点（_roomContainer）。", this);
#endif
        }

        private void OnEnable()
        {
            if (_inputReader != null)
            {
                _inputReader.NavigateEvent      += OnNavigate;
                // R13-N4 居中到玩家快捷键
                _inputReader.MapCenterEvent     += OnMapCenter;
            }
        }

        private void OnDisable()
        {
            _navInput = Vector2.zero;

            if (_inputReader != null)
            {
                _inputReader.NavigateEvent      -= OnNavigate;
                _inputReader.MapCenterEvent     -= OnMapCenter;
            }
        }

        private void OnNavigate(Vector2 dir) => _navInput = dir;

        // R13-N4 将视图居中到玩家所在房间
        private void OnMapCenter() => _panel?.CenterOnCurrentRoom();

        private void Update()
        {
            if (_scrollRect == null || _navInput == Vector2.zero) return;

            // R18-N1 contentSize 需乘以当前缩放系数，否则缩放后平移速度感知偏差。
            // R19-N1 / R24-N2 统一读 _panel.CurrentZoom（_zoomTarget.localScale.x），
            // 消除独立 _zoom 字段与 CurrentZoom 的双份状态——OnScroll 直接写 localScale，
            // CurrentZoom 即时反映最新值，不再需要额外同步。
            var content  = _scrollRect.content;
            var viewport = _scrollRect.viewport != null
                             ? _scrollRect.viewport
                             : (RectTransform)_scrollRect.transform;
            Vector2 contentSize  = content.rect.size;
            Vector2 viewportSize = viewport.rect.size;
            float   currentZoom  = _panel != null ? _panel.CurrentZoom
                                   : (_zoomTarget != null ? _zoomTarget.localScale.x : 1f);
            float   rangeX = contentSize.x * currentZoom - viewportSize.x;
            float   rangeY = contentSize.y * currentZoom - viewportSize.y;

            if (rangeX <= 0f && rangeY <= 0f) return;  // 内容比视口小，无需平移

            Vector2 delta = _navInput * (_keyPanSpeed * Time.unscaledDeltaTime);
            Vector2 norm  = _scrollRect.normalizedPosition;
            if (rangeX > 0f) norm.x = Mathf.Clamp01(norm.x + delta.x / rangeX);
            if (rangeY > 0f) norm.y = Mathf.Clamp01(norm.y + delta.y / rangeY);
            _scrollRect.normalizedPosition = norm;
        }

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

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

            // R24-N2 直接读 _zoomTarget.localScale.x 作为当前缩放，消除独立 _zoom 字段
            float currentZoom = _zoomTarget.localScale.x;
            float newZoom = Mathf.Clamp(
                currentZoom + eventData.scrollDelta.y * _zoomStep,
                _zoomMin, _zoomMax);

            if (Mathf.Approximately(newZoom, currentZoom)) 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);

            _zoomTarget.localScale = new Vector3(newZoom, newZoom, 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);

            Vector2 offset = pivotAfter - pivotBefore;
            _zoomTarget.anchoredPosition += offset * newZoom;
        }
    }
}