/**
 * 标签模板设计坐标系（与 APP renderLabelPreviewCanvas.toCanvasPx、原生 DESIGN_DPI=96 一致）
 * 1 cm = 37.8 px，1 inch = 96 px
 */
export const PX_PER_CM = 37.8;
export const PX_PER_INCH = 96;

export type LabelTemplateUnit = "cm" | "inch" | "mm" | "px";

export function unitToPx(value: number, unit: LabelTemplateUnit | string): number {
  const v = Number(value) || 0;
  const u = String(unit || "inch").toLowerCase();
  if (u === "mm") return (v / 25.4) * PX_PER_INCH;
  if (u === "cm") return v * PX_PER_CM;
  if (u === "px") return v;
  return v * PX_PER_INCH;
}

export function pxToUnit(px: number, unit: LabelTemplateUnit | string): number {
  const u = String(unit || "inch").toLowerCase();
  if (u === "mm") return (px * 25.4) / PX_PER_INCH;
  if (u === "cm") return px / PX_PER_CM;
  if (u === "px") return px;
  return px / PX_PER_INCH;
}

/** 模板纸张在设计像素下的宽高（如 5cm → 189×189） */
export function templatePaperPx(
  width: number,
  height: number,
  unit: LabelTemplateUnit | string,
): { widthPx: number; heightPx: number } {
  return {
    widthPx: Math.max(1, Math.round(unitToPx(width, unit))),
    heightPx: Math.max(1, Math.round(unitToPx(height, unit))),
  };
}