export const formatNum = (n: number) =>
  Number.isFinite(n) ? n.toLocaleString(undefined, { maximumFractionDigits: 4 }) : "—";

/** Packaging / compound stock unit (e.g. 1包X25千克) — not a simple unit like 斤 or kg. */
export const isPackagingUom = (uom?: string | null): boolean => {
  const unit = uom?.trim();
  if (!unit) return false;
  if (/^\d/.test(unit)) return true;
  if (/[xX×]/.test(unit) && /\d/.test(unit)) return true;
  return false;
};

/** Join qty with UOM; packaging units use parentheses to avoid "6 1包…" ambiguity. */
export const joinQtyUom = (num: string, unit: string): string =>
  isPackagingUom(unit) ? `${num}(${unit})` : `${num} ${unit}`;

/** Format a quantity with its unit when available. */
export const formatQty = (qty: number | null | undefined, uom?: string | null): string => {
  if (qty == null || !Number.isFinite(Number(qty))) return "—";
  const num = formatNum(Number(qty));
  const unit = uom?.trim();
  return unit ? joinQtyUom(num, unit) : num;
};

/** Signed variance for stock adjustments: IN → +qty, OUT → −qty. */
export const formatSignedQty = (
  qty: number | null | undefined,
  direction: string | null | undefined,
  uom?: string | null,
): string => {
  if (qty == null || !Number.isFinite(Number(qty))) return "—";
  const abs = Math.abs(Number(qty));
  const sign = (direction ?? "").trim().toUpperCase() === "OUT" ? "-" : "+";
  const num = formatNum(abs);
  const unit = uom?.trim();
  const signed = `${sign}${num}`;
  return unit ? joinQtyUom(signed, unit) : signed;
};