import { useRef, useCallback, useEffect } from "react";
import { useScale } from "@/contexts/ScaleContext";

type Point = { x: number; y: number };

export interface UseZoomAndDragOptions {
  /** 最小缩放比例，默认 0.8 */
  minScale?: number;
  /** 最大缩放比例，默认 3 */
  maxScale?: number;
  /** 是否可见，用于重置状态 */
  visible?: boolean;
}

export interface UseZoomAndDragReturn {
  /** 容器 ref */
  containerRef: React.RefObject<HTMLDivElement>;
  /** 视图元素 ref */
  viewElRef: React.RefObject<HTMLDivElement>;
  /** 重置变换 */
  resetTransform: () => void;
  /** 滚轮事件处理 */
  handleWheel: (e: React.WheelEvent<HTMLDivElement>) => void;
  /** 指针按下事件处理 */
  handlePointerDown: (e: React.PointerEvent<HTMLDivElement>) => void;
  /** 指针移动事件处理 */
  handlePointerMove: (e: React.PointerEvent<HTMLDivElement>) => void;
  /** 指针抬起事件处理 */
  handlePointerUp: (e: React.PointerEvent<HTMLDivElement>) => void;
  /** 双击事件处理 */
  handleDoubleClick: () => void;
}

/**
 * 缩放和拖拽 Hook
 * 提供图片/内容的缩放、拖拽、双击重置功能
 */
export const useZoomAndDrag = (
  options: UseZoomAndDragOptions = {}
): UseZoomAndDragReturn => {
  const { minScale = 0.8, maxScale = 3, visible = true } = options;
  const { scale } = useScale();

  const containerRef = useRef<HTMLDivElement | null>(null);
  const viewElRef = useRef<HTMLDivElement | null>(null);
  const frameRef = useRef<number | null>(null);
  const pointers = useRef<Map<number, Point>>(new Map());
  const lastDistance = useRef<number | null>(null);
  const dragStartRef = useRef<{
    pointerId: number;
    startX: number;
    startY: number;
    startTransform: { scale: number; x: number; y: number };
  } | null>(null);
  const transformRef = useRef({ scale: 1, x: 0, y: 0 });

  // 针对当前 scale 预计算 clamp
  const clampScale = useCallback(
    (next: number) => Math.min(maxScale, Math.max(minScale, next)),
    [minScale, maxScale]
  );

  const applyTransformStyle = useCallback(() => {
    const el = viewElRef.current;
    if (!el) return;
    const { scale, x, y } = transformRef.current;
    // 使用 translate3d 触发 GPU 加速
    el.style.transform = `translate3d(${x}px, ${y}px, 0) scale(${scale})`;
    el.style.transformOrigin = "0 0";
    el.style.touchAction = "none";
  }, []);

  const scheduleUpdate = useCallback(() => {
    if (frameRef.current) return;
    frameRef.current = requestAnimationFrame(() => {
      applyTransformStyle();
      frameRef.current = null;
    });
  }, [applyTransformStyle]);

  const resetTransform = useCallback(() => {
    transformRef.current = { scale: 1, x: 0, y: 0 };
    pointers.current.clear();
    lastDistance.current = null;
    dragStartRef.current = null;
    // 释放所有指针捕获
    if (containerRef.current) {
      pointers.current.forEach((_, pointerId) => {
        try {
          containerRef.current?.releasePointerCapture(pointerId);
        } catch {
          // 忽略捕获释放错误
        }
      });
    }
    applyTransformStyle();
  }, [applyTransformStyle]);

  // 关闭或切换时重置
  useEffect(() => {
    if (visible) {
      resetTransform();
    } else {
      // 不可见时清理所有状态和指针捕获
      transformRef.current = { scale: 1, x: 0, y: 0 };
      pointers.current.clear();
      lastDistance.current = null;
      dragStartRef.current = null;
      if (containerRef.current) {
        pointers.current.forEach((_, pointerId) => {
          try {
            containerRef.current?.releasePointerCapture(pointerId);
          } catch {
            // 忽略捕获释放错误
          }
        });
      }
      // 取消待处理的动画帧
      if (frameRef.current) {
        cancelAnimationFrame(frameRef.current);
        frameRef.current = null;
      }
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [visible]);

  // 组件卸载时清理资源
  useEffect(() => {
    const containerEl = containerRef.current;
    const pointersMap = pointers.current;
    const frameId = frameRef.current;

    return () => {
      // 清理所有指针捕获
      if (containerEl) {
        pointersMap.forEach((_, pointerId) => {
          try {
            containerEl.releasePointerCapture(pointerId);
          } catch {
            // 忽略捕获释放错误
          }
        });
      }
      // 取消待处理的动画帧
      if (frameId) {
        cancelAnimationFrame(frameId);
      }
    };
  }, []);

  // 缩放函数：origin 是屏幕坐标，需要转换为相对于 viewElRef 的坐标
  const applyZoom = useCallback(
    (factor: number, origin: Point) => {
      if (!viewElRef.current || !containerRef.current) return;

      const prev = transformRef.current;
      const nextScale = clampScale(prev.scale * factor);
      // 边界检查：避免除零
      if (prev.scale === 0) return;

      // 获取 viewElRef 相对于视口的位置
      const viewRect = viewElRef.current.getBoundingClientRect();
      // 将屏幕坐标转换为相对于 viewElRef 的坐标
      const relativeOrigin = {
        x: origin.x - viewRect.left,
        y: origin.y - viewRect.top,
      };

      const scaleChange = nextScale / prev.scale;
      // 以相对坐标 origin 为基准，保持该点视觉位置不动
      const nextX =
        (prev.x - relativeOrigin.x) * scaleChange + relativeOrigin.x;
      const nextY =
        (prev.y - relativeOrigin.y) * scaleChange + relativeOrigin.y;
      transformRef.current = { scale: nextScale, x: nextX, y: nextY };
      scheduleUpdate();
    },
    [clampScale, scheduleUpdate]
  );

  // 滚轮缩放：直接使用屏幕坐标
  const handleWheel = useCallback(
    (e: React.WheelEvent<HTMLDivElement>) => {
      const delta = e.deltaY;
      const factor = delta < 0 ? 1.05 : 0.95;
      // 直接使用屏幕坐标作为缩放中心
      applyZoom(factor, { x: e.clientX, y: e.clientY });
    },
    [applyZoom]
  );

  // 计算两点距离
  const getDistance = useCallback((p1: Point, p2: Point) => {
    const dx = p1.x - p2.x;
    const dy = p1.y - p2.y;
    return Math.hypot(dx, dy);
  }, []);

  // 指针按下：记录初始状态
  const handlePointerDown = useCallback(
    (e: React.PointerEvent<HTMLDivElement>) => {
      if (!containerRef.current || !viewElRef.current) return;
      try {
        containerRef.current.setPointerCapture(e.pointerId);
      } catch (err) {
        console.warn("Failed to capture pointer:", err);
      }

      // 记录屏幕坐标
      const point = {
        x: e.clientX,
        y: e.clientY,
      };
      pointers.current.set(e.pointerId, point);

      // 单指拖拽：记录初始状态
      if (pointers.current.size === 1) {
        dragStartRef.current = {
          pointerId: e.pointerId,
          startX: e.clientX,
          startY: e.clientY,
          startTransform: { ...transformRef.current },
        };
      } else if (pointers.current.size === 2) {
        // 双指缩放：记录初始距离
        const values = Array.from(pointers.current.values());
        if (values.length === 2) {
          const [p1, p2] = values;
          if (p1 && p2) {
            lastDistance.current = getDistance(p1, p2);
            dragStartRef.current = null;
          }
        }
      }
    },
    [getDistance]
  );

  /**
   * 单指拖拽处理
   * - 只关心当前 pointer 相对于按下时的位移
   * - 在这里统一做全局 scale 补偿，保持「手指移动 = 屏幕上移动」
   */
  const handleSingleDrag = useCallback(
    (e: React.PointerEvent<HTMLDivElement>) => {
      const dragStart = dragStartRef.current;
      if (!dragStart) return;

      // 1. 计算屏幕坐标系下的位移
      const dxScreen = e.clientX - dragStart.startX;
      const dyScreen = e.clientY - dragStart.startY;

      // 2. 映射到设计稿坐标系（补偿全局 scale）
      const dx = dxScreen / scale;
      const dy = dyScreen / scale;

      // 3. 应用到 transform（设计稿坐标）
      const nextX = dragStart.startTransform.x + dx;
      const nextY = dragStart.startTransform.y + dy;

      transformRef.current.x = nextX;
      transformRef.current.y = nextY;

      // 统一交给 rAF 的 scheduleUpdate，减少直接 DOM 操作次数
      scheduleUpdate();
    },
    [scale, scheduleUpdate]
  );

  /**
   * 双指缩放处理
   * - 使用两指间距离变化计算缩放因子
   * - 使用两指中点作为缩放中心
   */
  const handlePinchZoom = useCallback(() => {
    if (pointers.current.size !== 2) return;
    const values = Array.from(pointers.current.values());
    const [p1, p2] = values;
    if (!p1 || !p2) return;

    const distance = getDistance(p1, p2);
    if (!lastDistance.current || lastDistance.current <= 0) {
      lastDistance.current = distance;
      return;
    }

    const factor = distance / lastDistance.current;
    const center = {
      x: (p1.x + p2.x) * 0.5,
      y: (p1.y + p2.y) * 0.5,
    };

    applyZoom(factor, center);
    lastDistance.current = distance;
  }, [getDistance, applyZoom]);

  // 指针移动：更新指针位置，然后按当前手势类型分发给拖拽 / 缩放处理
  const handlePointerMove = useCallback(
    (e: React.PointerEvent<HTMLDivElement>) => {
      if (!pointers.current.has(e.pointerId)) return;

      // 更新当前 pointer 的屏幕坐标
      pointers.current.set(e.pointerId, {
        x: e.clientX,
        y: e.clientY,
      });

      // 优先处理双指缩放
      if (pointers.current.size === 2) {
        handlePinchZoom();
        return;
      }

      // 单指拖拽
      if (pointers.current.size === 1) {
        handleSingleDrag(e);
      }
    },
    [handlePinchZoom, handleSingleDrag]
  );

  // 指针抬起
  const handlePointerUp = useCallback(
    (e: React.PointerEvent<HTMLDivElement>) => {
      // 释放指针捕获
      if (containerRef.current) {
        try {
          containerRef.current.releasePointerCapture(e.pointerId);
        } catch {
          // 忽略捕获释放错误
        }
      }

      pointers.current.delete(e.pointerId);

      if (pointers.current.size < 2) {
        lastDistance.current = null;
      }

      // 如果剩余单指，重新记录拖拽初始状态
      if (pointers.current.size === 1) {
        const remaining = Array.from(pointers.current.values())[0];
        const remainingId = Array.from(pointers.current.keys())[0];
        if (remaining && remainingId !== undefined) {
          dragStartRef.current = {
            pointerId: remainingId,
            startX: remaining.x,
            startY: remaining.y,
            startTransform: { ...transformRef.current },
          };
        }
      } else {
        dragStartRef.current = null;
      }
    },
    []
  );

  // 双击重置
  const handleDoubleClick = useCallback(() => {
    resetTransform();
  }, [resetTransform]);

  return {
    containerRef: containerRef as React.RefObject<HTMLDivElement>,
    viewElRef: viewElRef as React.RefObject<HTMLDivElement>,
    resetTransform,
    handleWheel,
    handlePointerDown,
    handlePointerMove,
    handlePointerUp,
    handleDoubleClick,
  };
};