type TDragStartCallback = (x: number, y: number) => void;
type TDragMoveCallback = (x: number, y: number) => void;
type TDragEndCallback = (x: number, y: number) => void;

/**
 * 拖拽参数
 */
interface IDraggableOptions {
  /** 用来触发拖拽的元素、句柄 */
  handle: HTMLElement;
  /** 真正移动的元素 */
  target: HTMLElement;
  /** 拖拽模式 */
  mode?: 'transform' | 'position';
  /** 拖拽的边界或容器元素 */
  boundary?: IBoundary | HTMLElement;
  /** 拖拽开始回调 */
  onStart?: TDragStartCallback;
  /** 拖拽移动中回调 */
  onMove?: TDragMoveCallback;
  /** 拖拽结束回调 */
  onEnd?: TDragEndCallback;
}

/** 拖拽的范围边界 */
interface IBoundary {
  /** 最小 X 坐标 */
  minX?: number;
  /** 最大 X 坐标 */
  maxX?: number;
  /** 最小 Y 坐标 */
  minY?: number;
  /** 最大 Y 坐标 */
  maxY?: number;
}

/**
 * 拖拽功能通用类
 */
export class Draggable {
  private handle: HTMLElement;
  private target: HTMLElement;
  private mode: 'transform' | 'position';
  private boundary?: IBoundary;
  private containerElement?: HTMLElement;
  private containerBounds?: IBoundary;

  private startX = 0;
  private startY = 0;
  private originX = 0;
  private originY = 0;
  private currentX = 0;
  private currentY = 0;
  private dragging = false;

  private onStart?: TDragStartCallback;
  private onMove?: TDragMoveCallback;
  private onEnd?: TDragEndCallback;

  private resizeObserver?: ResizeObserver;

  constructor(options: IDraggableOptions) {
    this.handle = options.handle;
    this.target = options.target;
    this.mode = options.mode ?? 'transform';
    this.onStart = options.onStart;
    this.onMove = options.onMove;
    this.onEnd = options.onEnd;

    // 判断 boundary 类型
    if (options.boundary instanceof HTMLElement) {
      this.containerElement = options.boundary;
      this.observeResize(); // 监听容器和目标变化
    } else {
      this.boundary = options.boundary;
    }

    if (this.mode === 'position') {
      const computed = window.getComputedStyle(this.target);
      if (computed.position === 'static') {
        this.target.style.position = 'absolute';
      }
    }

    this.handle.addEventListener('mousedown', this.onMouseDown);
  }

  /** 监听容器和目标大小变化 */
  private observeResize() {
    this.resizeObserver = new ResizeObserver(() => {
      this.updateContainerBounds();
    });

    if (this.containerElement) {
      this.resizeObserver.observe(this.containerElement);
    }

    // 监听目标大小变化
    this.resizeObserver.observe(this.target);

    this.updateContainerBounds();
  }

  /** 更新边界 */
  private updateContainerBounds() {
    if (!this.containerElement) return;

    const containerRect = this.containerElement.getBoundingClientRect();
    const targetRect = this.target.getBoundingClientRect();

    if (this.mode === 'transform') {
      this.containerBounds = {
        minX: containerRect.left + window.scrollX,
        maxX: containerRect.right + window.scrollX - targetRect.width,
        minY: containerRect.top + window.scrollY,
        maxY: containerRect.bottom + window.scrollY - targetRect.height,
      };
    } else {
      this.containerBounds = {
        minX: 0,
        minY: 0,
        maxX: containerRect.width - targetRect.width,
        maxY: containerRect.height - targetRect.height,
      };
    }
  }

  private onMouseDown = (e: MouseEvent) => {
    e.preventDefault();
    this.handle.style.cursor = 'move';
    this.dragging = true;

    const rect = this.target.getBoundingClientRect();
    this.originX = rect.left + window.scrollX;
    this.originY = rect.top + window.scrollY;

    if (this.mode === 'position') {
      const style = window.getComputedStyle(this.target);
      this.originX = parseFloat(style.left) || 0;
      this.originY = parseFloat(style.top) || 0;
    }

    this.startX = e.clientX;
    this.startY = e.clientY;

    this.currentX = this.originX;
    this.currentY = this.originY;

    this.onStart?.(this.currentX, this.currentY);

    document.addEventListener('mousemove', this.onMouseMove);
    document.addEventListener('mouseup', this.onMouseUp);
  };

  private onMouseMove = (e: MouseEvent) => {
    if (!this.dragging) return;

    let newX = this.originX + (e.clientX - this.startX);
    let newY = this.originY + (e.clientY - this.startY);

    const bounds = this.containerBounds || this.boundary;
    if (bounds) {
      if (bounds.minX !== undefined) newX = Math.max(newX, bounds.minX);
      if (bounds.maxX !== undefined) newX = Math.min(newX, bounds.maxX);
      if (bounds.minY !== undefined) newY = Math.max(newY, bounds.minY);
      if (bounds.maxY !== undefined) newY = Math.min(newY, bounds.maxY);
    }

    if (this.mode === 'transform') {
      this.target.style.transform = `translate(${newX}px, ${newY}px)`;
    } else {
      this.target.style.left = `${newX}px`;
      this.target.style.top = `${newY}px`;
    }

    this.currentX = newX;
    this.currentY = newY;

    this.onMove?.(this.currentX, this.currentY);
  };

  private onMouseUp = () => {
    this.dragging = false;
    this.handle.style.cursor = 'default';

    this.onEnd?.(this.currentX, this.currentY);

    document.removeEventListener('mousemove', this.onMouseMove);
    document.removeEventListener('mouseup', this.onMouseUp);
  };

  public destroy() {
    this.handle.removeEventListener('mousedown', this.onMouseDown);
    document.removeEventListener('mousemove', this.onMouseMove);
    document.removeEventListener('mouseup', this.onMouseUp);
    this.resizeObserver?.disconnect();
  }
}