import { useRef, type PointerEvent as ReactPointerEvent } from "react";
import { useSchedulesStore } from "../state/schedulesStore";
import type { ScheduleNode } from "../../../services/api";

type DragState = {
  nodeId: string;
  pointerId: number;
  startClientX: number;
  startClientY: number;
  originX: number;
  originY: number;
  currentX: number;
  currentY: number;
  moved: boolean;
  nodeEl: HTMLDivElement;
};

/**
 * 画布节点拖拽编排。内部持有瞬时 dragRef + 节点 DOM 引用，避免每次拖拽都触发 store
 * 重渲染：pointermove 期间直接改节点的 inline left/top（只动 DOM，不动 store）；
 * 松手时把 rounded 后的位置一次性写入 store 的 setPositionDraft 模块级 Map（草稿
 * 持久化）+ setSchedule（让 React 知道最终位置），刷新不丢。
 */
export function useCanvasNodeDrag({
  busy,
  linkSourceId,
}: {
  busy: string | null | undefined;
  linkSourceId: string | null;
}): {
  startDrag: (event: ReactPointerEvent<HTMLDivElement>, node: ScheduleNode) => void;
  moveDrag: (event: ReactPointerEvent<HTMLDivElement>) => void;
  finishDrag: (event: ReactPointerEvent<HTMLDivElement>) => void;
} {
  const dragRef = useRef<DragState | null>(null);
  const setSchedule = useSchedulesStore((s) => s.setSchedule);
  const setSelectedNodeId = useSchedulesStore((s) => s.setSelectedNodeId);
  const setSelectedEdgeId = useSchedulesStore((s) => s.setSelectedEdgeId);

  const startDrag = (
    event: ReactPointerEvent<HTMLDivElement>,
    node: ScheduleNode,
  ): void => {
    if (event.button !== 0 || busy || linkSourceId) return;
    const target = event.target as HTMLElement;
    if (target.closest("button")) return;
    event.currentTarget.setPointerCapture(event.pointerId);
    dragRef.current = {
      nodeId: node.node_id,
      pointerId: event.pointerId,
      startClientX: event.clientX,
      startClientY: event.clientY,
      originX: node.position_x,
      originY: node.position_y,
      currentX: node.position_x,
      currentY: node.position_y,
      moved: false,
      nodeEl: event.currentTarget,
    };
    setSelectedNodeId(node.node_id);
    setSelectedEdgeId(null);
  };

  const moveDrag = (event: ReactPointerEvent<HTMLDivElement>): void => {
    const drag = dragRef.current;
    if (!drag || drag.pointerId !== event.pointerId) return;
    const deltaX = event.clientX - drag.startClientX;
    const deltaY = event.clientY - drag.startClientY;
    if (Math.abs(deltaX) + Math.abs(deltaY) > 3) drag.moved = true;
    const x = Math.max(10, drag.originX + deltaX);
    const y = Math.max(10, drag.originY + deltaY);
    drag.currentX = x;
    drag.currentY = y;
    // 只写 DOM，不动 store；拖拽期间 SchedulePage 不会因此重渲染。
    drag.nodeEl.style.left = `${x}px`;
    drag.nodeEl.style.top = `${y}px`;
  };

  const finishDrag = (event: ReactPointerEvent<HTMLDivElement>): void => {
    const drag = dragRef.current;
    if (!drag || drag.pointerId !== event.pointerId) return;
    dragRef.current = null;
    if (!drag.moved) return;
    const position = {
      position_x: Math.round(drag.currentX),
      position_y: Math.round(drag.currentY),
    };
    // 先记草稿（持久化），再把最终位置同步进 store 让节点 div 的 inline style 与
    // schedule.nodes 一致（下次重渲染/保存时不会出现位置回弹）。
    useSchedulesStore.getState().setPositionDraft(drag.nodeId, position);
    setSchedule((value) => {
      if (!value) return value;
      return {
        ...value,
        nodes: value.nodes.map((item) =>
          item.node_id === drag.nodeId ? { ...item, ...position } : item,
        ),
      };
    });
  };

  return { startDrag, moveDrag, finishDrag };
}