import { unitToPx } from "./labelTemplateUnits";

/** 预览区标尺显示单位（与模板 `template.unit` 独立，仅影响刻度与读数） */
export type PreviewRulerDisplayUnit = "cm" | "mm" | "inch";

/** 将长度从模板单位换算到预览标尺显示单位 */
export function convertTemplateLengthToDisplay(
  value: number,
  templateUnit: "cm" | "inch",
  displayUnit: PreviewRulerDisplayUnit,
): number {
  if (!Number.isFinite(value)) return 0;
  const cm = templateUnit === "cm" ? value : value * 2.54;
  if (displayUnit === "cm") return cm;
  if (displayUnit === "mm") return cm * 10;
  return cm / 2.54;
}

/** 预览标尺显示单位 → 模板单位 */
export function convertDisplayLengthToTemplate(
  displayValue: number,
  templateUnit: "cm" | "inch",
  displayUnit: PreviewRulerDisplayUnit,
): number {
  if (!Number.isFinite(displayValue)) return 0;
  let cm: number;
  if (displayUnit === "cm") cm = displayValue;
  else if (displayUnit === "mm") cm = displayValue / 10;
  else cm = displayValue * 2.54;
  if (templateUnit === "cm") return cm;
  return cm / 2.54;
}

export function elementPxToDisplayLength(
  lengthPx: number,
  basePaperPx: number,
  paperSizeTemplate: number,
  templateUnit: "cm" | "inch",
  displayUnit: PreviewRulerDisplayUnit,
): number {
  if (!Number.isFinite(lengthPx) || !Number.isFinite(basePaperPx) || basePaperPx <= 0) return 0;
  const inTemplate = (lengthPx / basePaperPx) * paperSizeTemplate;
  return convertTemplateLengthToDisplay(inTemplate, templateUnit, displayUnit);
}

export function displayLengthToElementPx(
  displayValue: number,
  basePaperPx: number,
  paperSizeTemplate: number,
  templateUnit: "cm" | "inch",
  displayUnit: PreviewRulerDisplayUnit,
): number {
  if (!Number.isFinite(basePaperPx) || basePaperPx <= 0 || !Number.isFinite(paperSizeTemplate) || paperSizeTemplate <= 0) {
    return 0;
  }
  const inTemplate = convertDisplayLengthToTemplate(displayValue, templateUnit, displayUnit);
  return (inTemplate / paperSizeTemplate) * basePaperPx;
}

export function formatPreviewRulerDisplayValue(
  value: number,
  displayUnit: PreviewRulerDisplayUnit,
): string {
  if (!Number.isFinite(value)) return "";
  if (displayUnit === "mm") return String(Math.round(value * 10) / 10);
  if (displayUnit === "inch") return value.toFixed(4);
  return (Math.round(value * 1000) / 1000).toFixed(3);
}

export function previewRulerUnitLabel(displayUnit: PreviewRulerDisplayUnit): string {
  return displayUnit;
}

export function templatePaperBasePx(
  width: number,
  height: number,
  unit: "cm" | "inch",
): { baseW: number; baseH: number } {
  return {
    baseW: unitToPx(Number(width) || 0, unit),
    baseH: unitToPx(Number(height) || 0, unit),
  };
}