support split unit for product order

src/utils/package.ts

@@ -59,6 +59,44 @@ export function comparePackageQuantity(left: number | string, right: number | st
 	return leftValue < rightValue ? -1 : rightValue < leftValue ? 1 : 0;
 }
 
+/** 将当前单位数量精确换算为最多三位小数的基础单位数量。 */
+export function toPackageBaseQuantity(quantity: number | string, baseQuantityPerUnit: number | string): string | undefined {
+	const quantityParts = toDecimalParts(quantity, 3);
+	const unitParts = toDecimalParts(baseQuantityPerUnit, 6);
+	if (!quantityParts || !unitParts) {
+		return undefined;
+	}
+	return formatDecimal(quantityParts.value * unitParts.value, quantityParts.scale + unitParts.scale, 3);
+}
+
+/** 将数量从一个单位精确换算到另一个单位，结果最多保留三位小数。 */
+export function convertPackageQuantity(quantity: number | string, fromBaseQuantityPerUnit: number | string, toBaseQuantityPerUnit: number | string): string | undefined {
+	const quantityParts = toDecimalParts(quantity, 3);
+	const fromParts = toDecimalParts(fromBaseQuantityPerUnit, 6);
+	const toParts = toDecimalParts(toBaseQuantityPerUnit, 6);
+	if (!quantityParts || !fromParts || !toParts || toParts.value === 0n) {
+		return undefined;
+	}
+	const numerator = quantityParts.value * fromParts.value * 10n ** BigInt(toParts.scale + 3);
+	const denominator = 10n ** BigInt(quantityParts.scale + fromParts.scale) * toParts.value;
+	if (numerator % denominator !== 0n) {
+		return undefined;
+	}
+	return formatDecimal(numerator / denominator, 3, 3);
+}
+
+/** 精确相加两个最多三位小数的数量。 */
+export function addPackageQuantity(left: number | string, right: number | string): string | undefined {
+	const leftParts = toQuantityParts(left);
+	const rightParts = toQuantityParts(right);
+	if (!leftParts || !rightParts) {
+		return undefined;
+	}
+	const scale = Math.max(leftParts.scale, rightParts.scale);
+	const value = leftParts.value * 10n ** BigInt(scale - leftParts.scale) + rightParts.value * 10n ** BigInt(scale - rightParts.scale);
+	return formatDecimal(value, scale, 3);
+}
+
 export function getPackageQuantityText(value?: number | string | null): string {
 	if (value === undefined || value === null || value === "") {
 		return "0";
@@ -79,13 +117,29 @@ export function getFundStatusText(status?: FundRecordStatus): string {
 }
 
 function toQuantityParts(value: number | string): { value: bigint; scale: number } | undefined {
-	const normalized = normalizePackageQuantity(value);
-	if (!normalized) {
+	return toDecimalParts(value, 3);
+}
+
+function toDecimalParts(value: number | string, maxScale: number): { value: bigint; scale: number } | undefined {
+	const text = String(value).trim();
+	if (!new RegExp(`^\\d+(?:\\.\\d{1,${maxScale}})?$`).test(text)) {
 		return undefined;
 	}
-	const [integerText, fractionText = ""] = normalized.split(".");
+	const [integerText, fractionText = ""] = text.split(".");
 	return {
 		value: BigInt(`${integerText}${fractionText}`),
 		scale: fractionText.length
 	};
 }
+
+function formatDecimal(value: bigint, scale: number, maxScale: number): string | undefined {
+	while (maxScale < scale && value % 10n === 0n) {
+		value /= 10n;
+		scale--;
+	}
+	if (maxScale < scale) {
+		return undefined;
+	}
+	const text = value.toString().padStart(scale + 1, "0");
+	return normalizePackageQuantity(scale ? `${text.slice(0, -scale)}.${text.slice(-scale)}` : text);
+}