import React, { useCallback, useRef, useEffect } from 'react';
import JsBarcode from 'jsbarcode';
import { QRCodeSVG } from 'qrcode.react';
import type { LabelTemplate, LabelElement, ElementType } from '../../../types/labelTemplate';
import { PRESET_LABEL_SIZES } from '../../../types/labelTemplate';
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from '../../ui/select';
import { cn } from '../../ui/utils';

/** 真实条形码渲染（JsBarcode），支持水平/竖排 */
function BarcodeBlock({
  data,
  width,
  height,
  showText,
  orientation = 'horizontal',
}: {
  data: string;
  width: number;
  height: number;
  showText?: boolean;
  orientation?: 'horizontal' | 'vertical';
}) {
  const svgRef = useRef<SVGSVGElement>(null);
  const isVertical = orientation === 'vertical';
  const barHeight = Math.max(20, (isVertical ? width : height) - (showText ? 14 : 4));
  useEffect(() => {
    if (svgRef.current && data) {
      try {
        JsBarcode(svgRef.current, data, {
          format: 'CODE128',
          width: 1,
          height: barHeight,
          displayValue: showText !== false,
          margin: 2,
          fontOptions: '',
          fontSize: 10,
        });
      } catch {
        // invalid data, ignore
      }
    }
  }, [data, barHeight, showText]);
  const svg = <svg ref={svgRef} className="w-full h-full min-h-0" style={{ maxHeight: isVertical ? width : height }} />;
  if (isVertical) {
    return (
      <div className="w-full h-full flex items-center justify-center">
        <div
          style={{
            transform: 'rotate(-90deg)',
            transformOrigin: 'center center',
            width: height,
            height: width,
            display: 'flex',
            alignItems: 'center',
            justifyContent: 'center',
          }}
        >
          {svg}
        </div>
      </div>
    );
  }
  return svg;
}

/** 画布网格步长（px），控件吸附到该步长 */
const GRID_SIZE = 8;

/** 将数值对齐到网格 */
function snapToGrid(value: number): number {
  return Math.round(value / GRID_SIZE) * GRID_SIZE;
}

/** 1cm ≈ 37.8px (96 DPI); 1 inch = 96px */
function unitToPx(value: number, unit: 'cm' | 'inch'): number {
  return unit === 'cm' ? value * 37.8 : value * 96;
}

/** px 转单位 */
function pxToUnit(px: number, unit: 'cm' | 'inch'): number {
  return unit === 'cm' ? px / 37.8 : px / 96;
}

const RULER_H = 20;
const RULER_W = 20;

/** Ruler at scroll container level - uses container dimensions for tick placement */
function RulerTop({ unit, width }: { unit: 'cm' | 'inch'; width: number }) {
  const minorStep = unit === 'cm' ? 0.5 : 0.5;
  const majorStep = unit === 'cm' ? 1 : 1;
  const widthInUnit = unit === 'cm' ? width / 37.8 : width / 96;
  const ticks: { value: number; px: number; isMajor: boolean }[] = [];
  for (let v = 0; v <= widthInUnit + 0.01; v += minorStep) {
    const px = unitToPx(v, unit);
    if (px <= width + 1) ticks.push({ value: v, px, isMajor: Math.abs(v % majorStep) < 0.01 });
  }
  return (
    <div className="bg-gray-100 border-b border-gray-200 pointer-events-none select-none relative overflow-hidden">
      {ticks.map((t) => (
        <div key={`t-${t.value}`} className="absolute bottom-0 border-l border-gray-400" style={{ left: t.px, height: t.isMajor ? 8 : 4 }} />
      ))}
      {ticks.filter((t) => t.isMajor).map((t) => (
        <span key={`tl-${t.value}`} className="absolute text-[8px] text-gray-600" style={{ left: t.px + 1, top: 0 }}>{t.value}</span>
      ))}
    </div>
  );
}

function RulerLeft({ unit, height }: { unit: 'cm' | 'inch'; height: number }) {
  const minorStep = unit === 'cm' ? 0.5 : 0.5;
  const majorStep = unit === 'cm' ? 1 : 1;
  const heightInUnit = unit === 'cm' ? height / 37.8 : height / 96;
  const ticks: { value: number; px: number; isMajor: boolean }[] = [];
  for (let v = 0; v <= heightInUnit + 0.01; v += minorStep) {
    const px = unitToPx(v, unit);
    if (px <= height + 1) ticks.push({ value: v, px, isMajor: Math.abs(v % majorStep) < 0.01 });
  }
  return (
    <div className="bg-gray-100 border-r border-gray-200 pointer-events-none select-none relative overflow-hidden">
      {ticks.map((t) => (
        <div key={`l-${t.value}`} className="absolute left-0 border-t border-gray-400" style={{ top: t.px, width: t.isMajor ? 8 : 4 }} />
      ))}
      {ticks.filter((t) => t.isMajor).map((t) => (
        <span key={`ll-${t.value}`} className="absolute text-[8px] text-gray-600" style={{ left: 1, top: t.px }}>{t.value}</span>
      ))}
    </div>
  );
}

/** Ruler OUTSIDE canvas frame - variant: top (corner+top) or left. Unit = display unit for ruler. */
function CanvasRulers({
  unit,
  baseW,
  baseH,
  variant = 'top',
}: {
  unit: 'cm' | 'inch';
  baseW: number;
  baseH: number;
  variant?: 'top' | 'left';
}) {
  const minorStep = unit === 'cm' ? 0.5 : 0.5;
  const majorStep = unit === 'cm' ? 1 : 1;
  // Convert canvas size to display unit for tick range (baseW/baseH are in px)
  const widthInUnit = unit === 'cm' ? baseW / 37.8 : baseW / 96;
  const heightInUnit = unit === 'cm' ? baseH / 37.8 : baseH / 96;

  const topTicks: { value: number; px: number; isMajor: boolean }[] = [];
  for (let v = 0; v <= widthInUnit + 0.01; v += minorStep) {
    const px = unitToPx(v, unit);
    if (px <= baseW + 1) {
      topTicks.push({ value: v, px, isMajor: Math.abs(v % majorStep) < 0.01 });
    }
  }

  const leftTicks: { value: number; px: number; isMajor: boolean }[] = [];
  for (let v = 0; v <= heightInUnit + 0.01; v += minorStep) {
    const px = unitToPx(v, unit);
    if (px <= baseH + 1) {
      leftTicks.push({ value: v, px, isMajor: Math.abs(v % majorStep) < 0.01 });
    }
  }

  const unitLabel = unit === 'cm' ? 'cm' : 'in';

  if (variant === 'left') {
    return (
      <div
        className="bg-gray-100 border-r border-gray-200 pointer-events-none select-none relative shrink-0"
        style={{ width: RULER_W, height: baseH }}
      >
        {leftTicks.map((t) => (
          <div
            key={`l-${t.value}-${t.px}`}
            className="absolute left-0 border-t border-gray-400"
            style={{ top: t.px, width: t.isMajor ? 8 : 4 }}
          />
        ))}
        {leftTicks.filter((t) => t.isMajor).map((t) => (
          <span
            key={`ll-${t.value}`}
            className="absolute text-[8px] text-gray-600"
            style={{ left: 1, top: t.px }}
          >
            {t.value}
          </span>
        ))}
      </div>
    );
  }

  return (
    <>
      <div
        className="bg-gray-100 border-b border-r border-gray-200 pointer-events-none select-none flex items-end justify-end pr-0.5 pb-0.5 shrink-0"
        style={{ width: RULER_W, height: RULER_H }}
      >
        <span className="text-[8px] text-gray-500">{unitLabel}</span>
      </div>
      <div
        className="bg-gray-100 border-b border-gray-200 pointer-events-none select-none relative shrink-0"
        style={{ width: baseW, height: RULER_H }}
      >
        {topTicks.map((t) => (
          <div
            key={`t-${t.value}-${t.px}`}
            className="absolute bottom-0 border-l border-gray-400"
            style={{ left: t.px, height: t.isMajor ? 8 : 4 }}
          />
        ))}
        {topTicks.filter((t) => t.isMajor).map((t) => (
          <span
            key={`tl-${t.value}`}
            className="absolute text-[8px] text-gray-600"
            style={{ left: t.px + 1, top: 0 }}
          >
            {t.value}
          </span>
        ))}
      </div>
    </>
  );
}

/** 根据元素类型与 config 渲染画布上的默认内容 */
function ElementContent({ el }: { el: LabelElement }) {
  const cfg = el.config as Record<string, unknown>;
  const type = el.type as ElementType;

  // Common styles
  const commonStyle: React.CSSProperties = {
    fontSize: (cfg?.fontSize as number) ?? 14,
    fontFamily: (cfg?.fontFamily as string) ?? 'Arial',
    fontWeight: (cfg?.fontWeight as string) ?? 'normal',
    textAlign: (cfg?.textAlign as any) ?? 'left',
    color: (cfg?.color as string) ?? '#000',
  };

  // 文本类
  const inputType = cfg?.inputType as string | undefined;
  if (type === 'TEXT_STATIC') {
    const text = (cfg?.text as string) ?? '文本';
    if (inputType === 'number') {
      return (
        <input
          type="number"
          readOnly
          value={(cfg?.text as string) ?? '0'}
          className="w-full h-full min-w-0 border border-gray-200 bg-white rounded px-1 pointer-events-none"
          style={{ ...commonStyle, textAlign: 'right' }}
        />
      );
    }
    if (inputType === 'options') {
      return (
        <div className="w-full h-full min-w-0 border border-gray-200 bg-white rounded px-1 flex items-center pointer-events-none text-gray-600" style={commonStyle}>
          <span className="truncate flex-1">{text || 'Select...'}</span>
          <span className="ml-auto text-gray-600/70">▼</span>
        </div>
      );
    }
    if (inputType === 'text') {
      return (
        <input
          type="text"
          readOnly
          value={text}
          className="w-full h-full min-w-0 border border-gray-200 bg-white rounded px-1 pointer-events-none"
          style={commonStyle}
        />
      );
    }
    return (
      <div className="w-full h-full px-1 overflow-hidden whitespace-pre-wrap break-all leading-tight" style={commonStyle}>
        {text}
      </div>
    );
  }
  if (type === 'TEXT_PRODUCT') {
    const text = (cfg?.text as string) ?? '商品名';
    return (
      <div className="w-full h-full px-1 overflow-hidden whitespace-pre-wrap break-all leading-tight" style={commonStyle}>
        {text}
      </div>
    );
  }
  if (type === 'TEXT_PRICE') {
    const prefix = (cfg?.prefix as string) ?? '￥';
    const text = (cfg?.text as string) ?? '0.00';
    return (
      <div className="w-full h-full px-1 overflow-hidden flex items-center" style={{ ...commonStyle, justifyContent: commonStyle.textAlign === 'center' ? 'center' : commonStyle.textAlign === 'right' ? 'flex-end' : 'flex-start' }}>
        <span>{prefix}</span>
        <span>{text}</span>
      </div>
    );
  }

  // 条码（支持水平/竖排）
  if (type === 'BARCODE') {
    const data = (cfg?.data as string) ?? '123456789';
    const showText = (cfg?.showText as boolean) !== false;
    const orientation = ((cfg?.orientation as string) === 'vertical' ? 'vertical' : 'horizontal') as 'horizontal' | 'vertical';
    return (
      <div className="flex flex-col items-center justify-center w-full h-full overflow-hidden p-0.5">
        <div className="flex-1 w-full min-h-0 flex items-center justify-center">
          <BarcodeBlock
            data={data}
            width={el.width}
            height={el.height}
            showText={showText}
            orientation={orientation}
          />
        </div>
      </div>
    );
  }

  // 二维码
  if (type === 'QRCODE') {
    const data = (cfg?.data as string) ?? 'https://example.com';
    const size = Math.min(el.width, el.height) - 4;
    return (
      <div className="w-full h-full flex items-center justify-center p-0.5">
        <QRCodeSVG value={data} size={Math.max(20, size)} level="M" includeMargin={false} />
      </div>
    );
  }

  // 图片/Logo
  if (type === 'IMAGE') {
    const src = cfg?.src as string | undefined;
    if (src) {
      return (
        <img
          src={src}
          alt=""
          className="w-full h-full object-contain"
        />
      );
    }
    return (
      <div className="w-full h-full flex flex-col items-center justify-center bg-gray-50 text-gray-500 text-[10px] border border-dashed border-gray-200">
        <span className="font-medium">Logo</span>
      </div>
    );
  }

  // 日期/时间
  if (type === 'DATE') {
    const format = (cfg?.format as string) ?? 'YYYY-MM-DD';
    const example = format.replace('YYYY', '2025').replace('MM', '02').replace('DD', '01');
    const isInput = cfg?.inputType === 'datetime' || cfg?.inputType === 'date';
    if (isInput) {
      return (
        <input
          type="date"
          readOnly
          value="2025-02-01"
          className="w-full h-full min-w-0 border border-gray-200 bg-white rounded px-1 pointer-events-none text-[10px]"
          style={commonStyle}
        />
      );
    }
    return <div className="w-full h-full px-1 overflow-hidden whitespace-nowrap" style={commonStyle}>{example}</div>;
  }

  // (Simplified other types similarly for brevity, ensuring style prop is passed)
  if (type === 'TIME') {
    const format = (cfg?.format as string) ?? 'HH:mm';
    const example = format.replace('HH', '12').replace('mm', '30');
    return <div className="w-full h-full px-1 overflow-hidden whitespace-nowrap" style={commonStyle}>{example}</div>;
  }

  if (type === 'DURATION') {
    return <div className="w-full h-full px-1 overflow-hidden whitespace-nowrap" style={commonStyle}>保质期 2025-02-04</div>;
  }

  if (type === 'WEIGHT') {
    const value = (cfg?.value as number) ?? 500;
    const unit = (cfg?.unit as string) ?? 'g';
    return <div className="w-full h-full px-1 overflow-hidden whitespace-nowrap" style={commonStyle}>{value}{unit}</div>;
  }

  if (type === 'WEIGHT_PRICE') {
    const unitPrice = (cfg?.unitPrice as number) ?? 10;
    const weight = (cfg?.weight as number) ?? 0.5;
    const currency = (cfg?.currency as string) ?? '￥';
    return <div className="w-full h-full px-1 overflow-hidden whitespace-nowrap" style={commonStyle}>{currency}{(unitPrice * weight).toFixed(2)}</div>;
  }

  // 营养成分表
  if (type === 'NUTRITION') {
    const calories = (cfg?.calories as number) ?? 120;
    return (
      <div className="text-[8px] p-0.5 w-full h-full overflow-hidden flex flex-col">
        <div className="font-semibold border-b border-black">Nutrition Facts</div>
        <div>Calories {calories}</div>
      </div>
    );
  }

  // 空白占位
  if (type === 'BLANK') {
    return <div className="w-full h-full border border-dashed border-gray-200" />;
  }

  return (
    <div className="text-gray-500 text-[10px] px-1 truncate w-full flex items-center justify-center">
      {el.type.replace(/_/g, ' ')}
    </div>
  );
}

interface LabelCanvasProps {
  template: LabelTemplate;
  selectedId: string | null;
  onSelect: (id: string | null) => void;
  onUpdateElement: (id: string, patch: Partial<LabelElement>) => void;
  onDeleteElement: (id: string) => void;
  onTemplateChange?: (patch: Partial<LabelTemplate>) => void;
  scale?: number;
  onZoomIn?: () => void;
  onZoomOut?: () => void;
  onPreview?: () => void;
}

export function LabelCanvas({
  template,
  selectedId,
  onSelect,
  onUpdateElement,
  onDeleteElement,
  onTemplateChange,
  scale = 1,
  onZoomIn,
  onZoomOut,
  onPreview,
}: LabelCanvasProps) {
  const scrollContainerRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLDivElement>(null);
  const dragRef = useRef<{ id: string; startX: number; startY: number; elX: number; elY: number } | null>(null);
  const resizeRef = useRef<{ id: string; corner: string; startX: number; startY: number; w: number; h: number; elX: number; elY: number } | null>(null);
  const lastUpdateRef = useRef<{ id: string; x?: number; y?: number; width?: number; height?: number } | null>(null);

  const nextFrameRef = useRef<number | null>(null);
  const [isSpacePressed, setIsSpacePressed] = React.useState(false);
  const [isPanning, setIsPanning] = React.useState(false);
  const [rulerUnit, setRulerUnit] = React.useState<'cm' | 'inch'>(template.unit);
  const [containerSize, setContainerSize] = React.useState({ w: 400, h: 430 });
  const panStartRef = useRef<{ x: number; y: number; scrollLeft: number; scrollTop: number } | null>(null);
  const [panOffset, setPanOffset] = React.useState({ x: 0, y: 0 });
  const panOffsetStartRef = useRef<{ x: number; y: number; startX: number; startY: number } | null>(null);

  const baseW = unitToPx(template.width, template.unit);
  const baseH = unitToPx(template.height, template.unit);
  const widthPx = baseW * scale;
  const heightPx = baseH * scale;
  const showGrid = template.showGrid !== false;

  // Sync ruler unit when template unit changes (e.g. preset applied)
  React.useEffect(() => {
    setRulerUnit(template.unit);
  }, [template.unit]);

  // Measure scroll container for ruler dimensions
  const measureContainer = React.useCallback(() => {
    const el = scrollContainerRef.current;
    if (el) setContainerSize({ w: el.clientWidth, h: el.clientHeight });
  }, []);
  React.useEffect(() => {
    measureContainer();
    const el = scrollContainerRef.current;
    if (!el) return;
    const ro = new ResizeObserver(measureContainer);
    ro.observe(el);
    return () => ro.disconnect();
  }, [measureContainer, template.showRuler]);

  const handlePointerDown = useCallback(
    (e: React.PointerEvent, id: string) => {
      // 如果按住了空格，直接返回，交给外层 panning 处理
      // 允许中键 (button 1) 拖动
      if (isSpacePressed || e.button === 1) return;

      e.stopPropagation();
      onSelect(id);

      // Focus canvas for keyboard events
      canvasRef.current?.focus();

      const el = template.elements.find((x) => x.id === id);
      if (!el) return;

      const domEl = document.getElementById(`element-${id}`);
      if (domEl) {
        domEl.classList.add('z-50', 'opacity-90', 'shadow-xl', 'ring-2', 'ring-blue-400', 'ring-offset-2');
        domEl.style.cursor = 'grabbing';
      }

      dragRef.current = { id, startX: e.clientX, startY: e.clientY, elX: el.x, elY: el.y };
      lastUpdateRef.current = { id, x: el.x, y: el.y }; // 初始化
      (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
    },
    [template.elements, onSelect, isSpacePressed]
  );

  const requestUpdate = useCallback((updateFn: () => void) => {
    if (nextFrameRef.current !== null) {
      cancelAnimationFrame(nextFrameRef.current);
    }
    nextFrameRef.current = requestAnimationFrame(() => {
      updateFn();
      nextFrameRef.current = null;
    });
  }, []);

  const handlePointerMove = useCallback(
    (e: React.PointerEvent) => {
      // 画布平移：优先处理（translate 方式，不依赖滚动）
      if (isPanning && panOffsetStartRef.current) {
        const dx = e.clientX - panOffsetStartRef.current.startX;
        const dy = e.clientY - panOffsetStartRef.current.startY;
        setPanOffset({
          x: panOffsetStartRef.current.x + dx,
          y: panOffsetStartRef.current.y + dy,
        });
        return;
      }
      if (isPanning && panStartRef.current && scrollContainerRef.current) {
        const dx = e.clientX - panStartRef.current.x;
        const dy = e.clientY - panStartRef.current.y;
        scrollContainerRef.current.scrollLeft = panStartRef.current.scrollLeft - dx;
        scrollContainerRef.current.scrollTop = panStartRef.current.scrollTop - dy;
        return;
      }
      // Drag Element
      if (dragRef.current) {
        // e.persist(); // React 17+ doesn't strictly need this for properties access in rAF closure if we read them now
        const { id, startX, startY, elX, elY } = dragRef.current;
        const clientX = e.clientX;
        const clientY = e.clientY;

        requestUpdate(() => {
          const dx = (clientX - startX) / scale;
          const dy = (clientY - startY) / scale;
          const rawX = Math.max(0, elX + dx);
          const rawY = Math.max(0, elY + dy);
          const snappedX = snapToGrid(rawX);
          const snappedY = snapToGrid(rawY);

          // 直接操作 DOM 避免频繁重渲染
          const domEl = document.getElementById(`element-${id}`);
          if (domEl) {
            domEl.style.left = `${snappedX}px`;
            domEl.style.top = `${snappedY}px`;
          }
          lastUpdateRef.current = { id, x: snappedX, y: snappedY };
          // 注意：这里不再更新 dragRef.current，因为我们在闭包里计算 dx, dy 也是 Ok 的。
          // 只要我们始终基于 startX/elX 计算，就不会有精度积累误差。
        });
      }

      // Resize Element
      if (resizeRef.current) {
        const { id, corner, startX, startY, w, h, elX, elY } = resizeRef.current;
        const clientX = e.clientX;
        const clientY = e.clientY;

        requestUpdate(() => {
          const dx = (clientX - startX) / scale;
          const dy = (clientY - startY) / scale;
          let nw = w;
          let nh = h;
          let nx = elX;
          let ny = elY;
          if (corner.includes('e')) nw = Math.max(20, w + dx);
          if (corner.includes('w')) {
            nw = Math.max(20, w - dx);
            nx = elX + dx;
          }
          if (corner.includes('s')) nh = Math.max(12, h + dy);
          if (corner.includes('n')) {
            nh = Math.max(12, h - dy);
            ny = elY + dy;
          }
          const snappedW = snapToGrid(nw);
          const snappedH = snapToGrid(nh);
          const snappedX = snapToGrid(nx);
          const snappedY = snapToGrid(ny);

          // 直接操作 DOM
          const domEl = document.getElementById(`element-${id}`);
          if (domEl) {
            domEl.style.width = `${snappedW}px`;
            domEl.style.height = `${snappedH}px`;
            domEl.style.left = `${snappedX}px`;
            domEl.style.top = `${snappedY}px`;
          }

          lastUpdateRef.current = { id, width: snappedW, height: snappedH, x: snappedX, y: snappedY };
        });
      }

    },
    [isPanning, onTemplateChange, scale, template.unit, requestUpdate]
  );

  const handlePointerUp = useCallback(() => {
    // 结束画布平移
    if (isPanning) {
      setIsPanning(false);
      panStartRef.current = null;
      panOffsetStartRef.current = null;
    }
    // Cancel pending animation frame
    if (nextFrameRef.current !== null) {
      cancelAnimationFrame(nextFrameRef.current);
      nextFrameRef.current = null;
    }

    const activeId = dragRef.current?.id || resizeRef.current?.id;
    if (activeId) {
      const domEl = document.getElementById(`element-${activeId}`);
      if (domEl) {
        domEl.classList.remove('z-50', 'opacity-90', 'shadow-xl', 'ring-2', 'ring-blue-400', 'ring-offset-2');
        domEl.style.cursor = '';
      }
    }

    if (lastUpdateRef.current) {
      const { id, ...patch } = lastUpdateRef.current;
      onUpdateElement(id, patch);
      lastUpdateRef.current = null;
    }
    dragRef.current = null;
    resizeRef.current = null;
  }, [onUpdateElement]);

  useEffect(() => {
    const onKeyDown = (e: KeyboardEvent) => {
      if (e.code === 'Space' && !e.repeat) {
        setIsSpacePressed(true);
      }
    };
    const onKeyUp = (e: KeyboardEvent) => {
      if (e.code === 'Space') {
        setIsSpacePressed(false);
        setIsPanning(false);
        panStartRef.current = null;
        panOffsetStartRef.current = null;
      }
    };
    window.addEventListener('keydown', onKeyDown);
    window.addEventListener('keyup', onKeyUp);
    return () => {
      window.removeEventListener('keydown', onKeyDown);
      window.removeEventListener('keyup', onKeyUp);
    };
  }, []);

  // 画布初始居中：挂载或尺寸/缩放变化后让内容居中
  useEffect(() => {
    const el = scrollContainerRef.current;
    if (!el) return;
    const center = () => {
      el.scrollLeft = Math.max(0, (el.scrollWidth - el.clientWidth) / 2);
      el.scrollTop = Math.max(0, (el.scrollHeight - el.clientHeight) / 2);
    };
    const raf = requestAnimationFrame(center);
    const t = setTimeout(center, 100);
    return () => {
      cancelAnimationFrame(raf);
      clearTimeout(t);
    };
  }, [scale, baseW, baseH]);

  // Keyboard navigation for elements
  const handleKeyDown = useCallback((e: React.KeyboardEvent) => {
    if (!selectedId) return;
    if (e.key === 'Delete' || e.key === 'Backspace') {
      // ... existing delete logic
      e.preventDefault();
      const idx = template.elements.findIndex((x) => x.id === selectedId);
      if (idx >= 0) {
        const next = template.elements.filter((x) => x.id !== selectedId);
        onDeleteElement(selectedId);
        onSelect(next[idx]?.id ?? next[idx - 1]?.id ?? null);
      }
      return;
    }

    const el = template.elements.find(x => x.id === selectedId);
    if (!el) return;

    // allow typing in inputs without triggering move? 
    // Actually our elements are not inputs (unless we implement inline edit).
    // But preventDefault is good.

    const step = e.shiftKey ? 1 : GRID_SIZE;
    let dx = 0;
    let dy = 0;

    switch (e.key) {
      case 'ArrowLeft': dx = -step; break;
      case 'ArrowRight': dx = step; break;
      case 'ArrowUp': dy = -step; break;
      case 'ArrowDown': dy = -step; break; // Wait, ArrowDown should be +step (y increases downwards)
      default: return;
    }

    // Fix: ArrowDown +step
    if (e.key === 'ArrowDown') dy = step;

    e.preventDefault();
    onUpdateElement(el.id, {
      x: Math.max(0, el.x + dx),
      y: Math.max(0, el.y + dy)
    });

  }, [selectedId, template.elements, onUpdateElement, onDeleteElement, onSelect]);

  const canvasClick = () => onSelect(null);

  // 容器的 Pan 处理
  // 容器的 Pan 处理
  const handleContainerPointerDown = (e: React.PointerEvent) => {
    if (isSpacePressed || e.button === 1) {
      e.preventDefault();
      setIsPanning(true);
      panStartRef.current = {
        x: e.clientX,
        y: e.clientY,
        scrollLeft: scrollContainerRef.current?.scrollLeft || 0,
        scrollTop: scrollContainerRef.current?.scrollTop || 0
      };
      (e.currentTarget as HTMLElement).setPointerCapture(e.pointerId);
    }
  };

  const handleContainerPointerMove = (e: React.PointerEvent) => {
    if (isPanning && panStartRef.current && scrollContainerRef.current) {
      const dx = e.clientX - panStartRef.current.x;
      const dy = e.clientY - panStartRef.current.y;
      scrollContainerRef.current.scrollLeft = panStartRef.current.scrollLeft - dx;
      scrollContainerRef.current.scrollTop = panStartRef.current.scrollTop - dy;
    }
  };

  const handleContainerPointerUp = (e: React.PointerEvent) => {
    if (isPanning) {
      setIsPanning(false);
      panStartRef.current = null;
    }
  };

  return (
    <div className="flex-1 flex flex-col min-h-0 overflow-hidden bg-gray-100/50 h-full">
      {/* Label Preview header */}
      <div className="shrink-0 px-4 py-2 border-b border-gray-200 bg-white flex items-center justify-between gap-2 flex-wrap z-10 border-l-[3px] border-l-[#1e3a8a]">
        <span className="text-sm font-medium text-gray-800">Label Preview</span>
        <div className="flex items-center gap-2 flex-wrap">
          {onPreview && (
            <button
              type="button"
              onClick={onPreview}
              className="h-8 px-3 rounded border border-gray-200 bg-white hover:bg-gray-50 text-xs font-medium transition-all active:scale-95"
            >
              Preview
            </button>
          )}
          {onTemplateChange && (
            <>
              <Select
                value={(() => {
                  const i = PRESET_LABEL_SIZES.findIndex(
                    (p) => p.width === template.width && p.height === template.height && p.unit === template.unit
                  );
                  return i >= 0 ? String(i) : 'custom';
                })()}
                onValueChange={(v: string) => {
                  if (v === 'custom') return;
                  const p = PRESET_LABEL_SIZES[Number(v)];
                  if (p) onTemplateChange({ width: p.width, height: p.height, unit: p.unit });
                }}
              >
                <SelectTrigger className="h-8 w-[130px] text-xs">
                  <SelectValue placeholder="Canvas size" />
                </SelectTrigger>
                <SelectContent>
                  {PRESET_LABEL_SIZES.map((p, i) => (
                    <SelectItem key={i} value={String(i)} className="text-xs">
                      {p.name}
                    </SelectItem>
                  ))}
                  <SelectItem value="custom" className="text-xs text-gray-600">
                    Custom
                  </SelectItem>
                </SelectContent>
              </Select>
              <Select value={rulerUnit} onValueChange={(v: 'cm' | 'inch') => setRulerUnit(v)}>
                <SelectTrigger className="h-8 w-[90px] text-xs">
                  <SelectValue placeholder="Unit" />
                </SelectTrigger>
                <SelectContent>
                  <SelectItem value="cm">cm</SelectItem>
                  <SelectItem value="inch">inch</SelectItem>
                </SelectContent>
              </Select>
              <button
                type="button"
                onClick={() => onTemplateChange({ showGrid: !showGrid })}
                className={cn(
                  'h-8 px-3 rounded border text-xs font-medium transition-colors',
                  showGrid ? 'border-gray-200 bg-white hover:bg-gray-50' : 'border-gray-200 bg-gray-100 text-gray-500'
                )}
              >
                {showGrid ? 'Hide grid' : 'Show grid'}
              </button>
            </>
          )}
          <div className="flex items-center gap-1 bg-white rounded border border-gray-200 p-0.5 h-8">
            <button
              type="button"
              onClick={onZoomOut}
              disabled={!onZoomOut}
              className="h-6 w-6 rounded hover:bg-gray-100 text-gray-600 disabled:opacity-50 disabled:pointer-events-none flex items-center justify-center text-sm font-medium active:scale-90 transition-transform"
              title="缩小"
            >
              −
            </button>
            <span className="min-w-[3rem] text-center text-xs text-gray-600 font-medium">
              {Math.round(scale * 100)}%
            </span>
            <button
              type="button"
              onClick={onZoomIn}
              disabled={!onZoomIn}
              className="h-6 w-6 rounded hover:bg-gray-100 text-gray-600 disabled:opacity-50 disabled:pointer-events-none flex items-center justify-center text-sm font-medium active:scale-90 transition-transform"
              title="放大"
            >
              +
            </button>
          </div>
        </div>
      </div>

      {/* Canvas area: ruler at this level + scroll container, fills remaining space */}
      <div className="flex-1 min-h-0 flex flex-col">
        {template.showRuler ? (
          <div
            className="flex-1 min-h-0 bg-gray-100"
            style={{
              display: 'grid',
              gridTemplateColumns: `${RULER_W}px 1fr`,
              gridTemplateRows: `${RULER_H}px 1fr`,
            }}
          >
            {/* Corner */}
            <div className="bg-gray-100 border-r border-b border-gray-200 flex items-end justify-end pr-0.5 pb-0.5">
              <span className="text-[8px] text-gray-500">{rulerUnit === 'cm' ? 'cm' : 'in'}</span>
            </div>
            {/* Top ruler - spans scroll area width */}
            <RulerTop unit={rulerUnit} width={containerSize.w} />
            {/* Left ruler - spans scroll area height */}
            <RulerLeft unit={rulerUnit} height={containerSize.h} />
            {/* Scroll container - canvas content inside */}
            <div
              ref={scrollContainerRef}
              className={cn(
                "overflow-auto bg-gray-100 relative",
                isSpacePressed ? "cursor-grab active:cursor-grabbing" : ""
              )}
              onClick={canvasClick}
              onPointerDown={handleContainerPointerDown}
              onPointerMove={handleContainerPointerMove}
              onPointerUp={handleContainerPointerUp}
              onPointerLeave={handleContainerPointerUp}
            >
              <div
                style={{
                  minWidth: '100%',
                  minHeight: '100%',
                  width: 'fit-content',
                  height: 'fit-content',
                  display: 'flex',
                  padding: 50,
                  boxSizing: 'border-box',
                  transform: `translate(${panOffset.x}px, ${panOffset.y}px) scale(${scale})`,
                  transformOrigin: '0 0',
                }}
              >
                <div
                  ref={canvasRef}
                  tabIndex={0}
                  className={cn(
                    'relative bg-white shadow-md border border-dashed border-gray-300 origin-top-left outline-none shrink-0 m-auto',
                    isPanning ? 'cursor-grabbing' : 'cursor-grab'
                  )}
                  style={{
                    width: baseW,
                    height: baseH,
                    backgroundImage: showGrid
                      ? `linear-gradient(to right, rgba(0,0,0,0.06) 1px, transparent 1px),
                         linear-gradient(to bottom, rgba(0,0,0,0.06) 1px, transparent 1px)`
                      : undefined,
                    backgroundSize: showGrid ? `${GRID_SIZE}px ${GRID_SIZE}px` : undefined,
                    pointerEvents: isSpacePressed ? 'none' : 'auto'
                  }}
                  onPointerDown={(e) => {
                    const target = e.target as HTMLElement;
                    const isOnElement = target.closest('[id^="element-"]');
                    const isOnCanvasArea = canvasRef.current?.contains(target);
                    if (isOnCanvasArea && !isOnElement && !dragRef.current && !resizeRef.current) {
                      e.preventDefault();
                      e.stopPropagation();
                      setIsPanning(true);
                      panOffsetStartRef.current = {
                        x: panOffset.x,
                        y: panOffset.y,
                        startX: e.clientX,
                        startY: e.clientY,
                      };
                      panStartRef.current = {
                        x: e.clientX,
                        y: e.clientY,
                        scrollLeft: scrollContainerRef.current?.scrollLeft ?? 0,
                        scrollTop: scrollContainerRef.current?.scrollTop ?? 0,
                      };
                      (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
                    }
                  }}
                  onPointerMove={handlePointerMove}
                  onPointerUp={handlePointerUp}
                  onKeyDown={handleKeyDown}
                >
                  {template.elements.map((el) => (
              <div
                key={el.id}
                id={`element-${el.id}`}
                className={cn(
                  'absolute box-border cursor-move overflow-hidden transition-shadow',
                  el.border === 'line' && 'border border-gray-400',
                  el.border === 'dotted' && 'border border-dotted border-gray-400',
                  selectedId === el.id && 'ring-2 ring-[#1e3a8a] ring-offset-1 z-10'
                )}
                style={{
                  left: el.x,
                  top: el.y,
                  width: el.width,
                  height: el.height,
                }}
                onClick={(e) => {
                  e.stopPropagation();
                  onSelect(el.id);
                }}
                onPointerDown={(e) => handlePointerDown(e, el.id)}
              >
                <ElementContent el={el} />
                {selectedId === el.id && (
                  <>
                    {/* 4 Corners */}
                    {(['nw', 'ne', 'sw', 'se'] as const).map((corner) => (
                      <div
                        key={corner}
                        className="absolute w-4 h-4 bg-white border-2 border-[#1e3a8a] rounded-full z-20 shadow-md hover:scale-110 transition-transform"
                        style={{
                          cursor: 'nwse-resize',
                          top: corner.startsWith('n') ? -6 : undefined,
                          bottom: corner.startsWith('s') ? -6 : undefined,
                          left: corner.endsWith('w') ? -6 : undefined,
                          right: corner.endsWith('e') ? -6 : undefined,
                        }}
                        onPointerDown={(e) => {
                          e.stopPropagation();
                          const el0 = template.elements.find((x) => x.id === el.id)!;
                          resizeRef.current = {
                            id: el.id,
                            corner,
                            startX: e.clientX,
                            startY: e.clientY,
                            w: el0.width,
                            h: el0.height,
                            elX: el0.x,
                            elY: el0.y,
                          };
                          (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
                        }}
                      />
                    ))}
                    {/* 4 Edges */}
                    {(['n', 's', 'w', 'e'] as const).map((edge) => (
                      <div
                        key={edge}
                        className="absolute bg-[#1e3a8a]/50 border border-white/50 rounded-sm z-10 shadow-sm hover:bg-[#1e3a8a]/70"
                        style={{
                          cursor: edge === 'n' || edge === 's' ? 'ns-resize' : 'ew-resize',
                          width: edge === 'n' || edge === 's' ? '20px' : '6px',
                          height: edge === 'n' || edge === 's' ? '6px' : '20px',
                          top: edge === 'n' ? -3 : edge === 's' ? undefined : '50%',
                          bottom: edge === 's' ? -3 : undefined,
                          left: edge === 'w' ? -3 : edge === 'e' ? undefined : '50%',
                          right: edge === 'e' ? -3 : undefined,
                          transform: edge === 'n' || edge === 's' ? 'translateX(-50%)' : 'translateY(-50%)',
                        }}
                        onPointerDown={(e) => {
                          e.stopPropagation();
                          const el0 = template.elements.find((x) => x.id === el.id)!;

                          const domEl = document.getElementById(`element-${el.id}`);
                          if (domEl) {
                            domEl.classList.add('z-50', 'opacity-90');
                          }

                          resizeRef.current = {
                            id: el.id,
                            corner: edge,
                            startX: e.clientX,
                            startY: e.clientY,
                            w: el0.width,
                            h: el0.height,
                            elX: el0.x,
                            elY: el0.y,
                          };
                          (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
                        }}
                      />
                    ))}
                  </>
                )}
              </div>
            ))}
                </div>
              </div>
            </div>
          </div>
        ) : (
            <div
              ref={scrollContainerRef}
              className={cn(
                "overflow-auto bg-gray-100 relative h-full",
                isSpacePressed ? "cursor-grab active:cursor-grabbing" : ""
              )}
              onClick={canvasClick}
              onPointerDown={handleContainerPointerDown}
              onPointerMove={handleContainerPointerMove}
              onPointerUp={handleContainerPointerUp}
              onPointerLeave={handleContainerPointerUp}
            >
              <div
                style={{
                  minWidth: '100%',
                  minHeight: '100%',
                  width: 'fit-content',
                  height: 'fit-content',
                  display: 'flex',
                  padding: 50,
                  boxSizing: 'border-box',
                  transform: `translate(${panOffset.x}px, ${panOffset.y}px) scale(${scale})`,
                  transformOrigin: '0 0',
                }}
              >
                <div
                  ref={canvasRef}
                  tabIndex={0}
                  className={cn(
                    'relative bg-white shadow-md border border-dashed border-gray-300 origin-top-left outline-none shrink-0 m-auto',
                    isPanning ? 'cursor-grabbing' : 'cursor-grab'
                  )}
                style={{
                  width: baseW,
                  height: baseH,
                  backgroundImage: showGrid
                    ? `linear-gradient(to right, rgba(0,0,0,0.06) 1px, transparent 1px),
                       linear-gradient(to bottom, rgba(0,0,0,0.06) 1px, transparent 1px)`
                    : undefined,
                  backgroundSize: showGrid ? `${GRID_SIZE}px ${GRID_SIZE}px` : undefined,
                  pointerEvents: isSpacePressed ? 'none' : 'auto'
                }}
                onPointerDown={(e) => {
                  const target = e.target as HTMLElement;
                  const isOnElement = target.closest('[id^="element-"]');
                  const isOnCanvasArea = canvasRef.current?.contains(target);
                  if (isOnCanvasArea && !isOnElement && !dragRef.current && !resizeRef.current) {
                    e.preventDefault();
                    e.stopPropagation();
                    setIsPanning(true);
                    panOffsetStartRef.current = { x: panOffset.x, y: panOffset.y, startX: e.clientX, startY: e.clientY };
                    panStartRef.current = {
                      x: e.clientX,
                      y: e.clientY,
                      scrollLeft: scrollContainerRef.current?.scrollLeft ?? 0,
                      scrollTop: scrollContainerRef.current?.scrollTop ?? 0,
                    };
                    (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
                  }
                }}
                onPointerMove={handlePointerMove}
                onPointerUp={handlePointerUp}
                onKeyDown={handleKeyDown}
              >
                {template.elements.map((el) => (
                  <div
                    key={el.id}
                    id={`element-${el.id}`}
                    className={cn(
                      'absolute box-border cursor-move overflow-hidden transition-shadow',
                      el.border === 'line' && 'border border-gray-400',
                      el.border === 'dotted' && 'border border-dotted border-gray-400',
                      selectedId === el.id && 'ring-2 ring-[#1e3a8a] ring-offset-1 z-10'
                    )}
                    style={{ left: el.x, top: el.y, width: el.width, height: el.height }}
                    onClick={(e) => { e.stopPropagation(); onSelect(el.id); }}
                    onPointerDown={(e) => handlePointerDown(e, el.id)}
                  >
                    <ElementContent el={el} />
                    {selectedId === el.id && (
                      <>
                        {(['nw', 'ne', 'sw', 'se'] as const).map((corner) => (
                          <div
                            key={corner}
                            className="absolute w-4 h-4 bg-white border-2 border-[#1e3a8a] rounded-full z-20 shadow-md"
                            style={{
                              cursor: 'nwse-resize',
                              top: corner.startsWith('n') ? -6 : undefined,
                              bottom: corner.startsWith('s') ? -6 : undefined,
                              left: corner.endsWith('w') ? -6 : undefined,
                              right: corner.endsWith('e') ? -6 : undefined,
                            }}
                            onPointerDown={(e) => {
                              e.stopPropagation();
                              const el0 = template.elements.find((x) => x.id === el.id)!;
                              resizeRef.current = {
                                id: el.id,
                                corner,
                                startX: e.clientX,
                                startY: e.clientY,
                                w: el0.width,
                                h: el0.height,
                                elX: el0.x,
                                elY: el0.y,
                              };
                              (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
                            }}
                          />
                        ))}
                        {(['n', 's', 'w', 'e'] as const).map((edge) => (
                          <div
                            key={edge}
                            className="absolute bg-[#1e3a8a]/50 border border-white/50 rounded-sm z-10"
                            style={{
                              cursor: edge === 'n' || edge === 's' ? 'ns-resize' : 'ew-resize',
                              width: edge === 'n' || edge === 's' ? '20px' : '6px',
                              height: edge === 'n' || edge === 's' ? '6px' : '20px',
                              top: edge === 'n' ? -3 : edge === 's' ? undefined : '50%',
                              bottom: edge === 's' ? -3 : undefined,
                              left: edge === 'w' ? -3 : edge === 'e' ? undefined : '50%',
                              right: edge === 'e' ? -3 : undefined,
                              transform: edge === 'n' || edge === 's' ? 'translateX(-50%)' : 'translateY(-50%)',
                            }}
                            onPointerDown={(e) => {
                              e.stopPropagation();
                              const el0 = template.elements.find((x) => x.id === el.id)!;
                              const domEl = document.getElementById(`element-${el.id}`);
                              if (domEl) domEl.classList.add('z-50', 'opacity-90');
                              resizeRef.current = {
                                id: el.id,
                                corner: edge,
                                startX: e.clientX,
                                startY: e.clientY,
                                w: el0.width,
                                h: el0.height,
                                elX: el0.x,
                                elY: el0.y,
                              };
                              (e.currentTarget as HTMLElement).setPointerCapture?.(e.pointerId);
                            }}
                          />
                        ))}
                      </>
                    )}
                  </div>
                ))}
              </div>
            </div>
          </div>
        )}
      </div>
    </div>
  );
}

/** 仅用于预览：无网格、无标尺、无拖拽，按比例缩放 */
export function LabelPreviewOnly({
  template,
  maxWidth = 480,
}: {
  template: LabelTemplate;
  maxWidth?: number;
}) {
  const baseW = unitToPx(template.width, template.unit);
  const baseH = unitToPx(template.height, template.unit);
  const scaleToFit = maxWidth ? Math.min(maxWidth / baseW, maxWidth / baseH, 2) : 1;
  const displayW = baseW * scaleToFit;
  const displayH = baseH * scaleToFit;
  // 与编辑区一致：内层 baseW×baseH，transformOrigin 0 0 缩放，保证位置/样式一致
  return (
    <div className="flex items-center justify-center p-4 bg-gray-100 rounded">
      <div style={{ width: displayW, height: displayH }} className="relative bg-white shadow-md overflow-hidden">
        <div
          className="origin-top-left"
          style={{
            position: 'absolute',
            left: 0,
            top: 0,
            width: baseW,
            height: baseH,
            transform: `scale(${scaleToFit})`,
            transformOrigin: '0 0',
          }}
        >
          {template.elements.map((el) => (
            <div
              key={el.id}
              className="absolute box-border overflow-hidden pointer-events-none flex items-center justify-center text-xs"
              style={{
                left: el.x,
                top: el.y,
                width: el.width,
                height: el.height,
                border: el.border === 'line' ? '1px solid #999' : el.border === 'dotted' ? '1px dotted #999' : undefined,
              }}
            >
              <ElementContent el={el} />
            </div>
          ))}
        </div>
      </div>
    </div>
  );
}