add product stock preview

src/utils/productStock.ts

@@ -0,0 +1,86 @@
+import type { ProductStock } from "@/types/Product";
+import { addPackageQuantity, comparePackageQuantity } from "@/utils/package";
+
+export type ProductStockRequirement = {
+	skuId: string;
+	baseQuantity: string;
+	productName: string;
+	unitName: string;
+	stockEnabled: boolean;
+};
+
+export type ProductStockPreviewItem = ProductStockRequirement & {
+	availableQuantity: string;
+	shortageQuantity?: string;
+};
+
+/** 合并同一 SKU 的基础库存需求，避免多单位订单拆开校验造成误判。 */
+export function mergeProductStockRequirements(requirementList: ProductStockRequirement[]): ProductStockRequirement[] {
+	const requirementMap = new Map<string, ProductStockRequirement>();
+	for (const requirement of requirementList) {
+		const existing = requirementMap.get(requirement.skuId);
+		if (!existing) {
+			requirementMap.set(requirement.skuId, { ...requirement });
+			continue;
+		}
+		const baseQuantity = addPackageQuantity(existing.baseQuantity, requirement.baseQuantity);
+		if (baseQuantity) {
+			existing.baseQuantity = baseQuantity;
+		}
+	}
+	return [...requirementMap.values()];
+}
+
+/** 返回库存不足提示；库存单位统一为 SKU 基础单位。 */
+export function getProductStockShortageMessage(stockList: ProductStock[], requirementList: ProductStockRequirement[]): string | undefined {
+	const stockMap = new Map(stockList.map(stock => [stock.skuId, stock]));
+	const shortageList: string[] = [];
+	for (const requirement of requirementList) {
+		if (!requirement.stockEnabled) {
+			continue;
+		}
+		const availableQuantity = stockMap.get(requirement.skuId)?.availableQuantity ?? "0";
+		if (!(0 < comparePackageQuantity(requirement.baseQuantity, availableQuantity))) {
+			continue;
+		}
+		const shortageQuantity = subtractPackageQuantity(requirement.baseQuantity, availableQuantity);
+		shortageList.push(`${requirement.productName} 可用 ${availableQuantity} ${requirement.unitName}，缺少 ${shortageQuantity} ${requirement.unitName}`);
+	}
+	return shortageList.length ? `库存不足：${shortageList.join("；")}` : undefined;
+}
+
+/** 生成启用库存管理 SKU 的库存预检明细。 */
+export function buildProductStockPreview(stockList: ProductStock[], requirementList: ProductStockRequirement[]): ProductStockPreviewItem[] {
+	const stockMap = new Map(stockList.map(stock => [stock.skuId, stock]));
+	return requirementList.filter(requirement => requirement.stockEnabled).map(requirement => {
+		const availableQuantity = String(stockMap.get(requirement.skuId)?.availableQuantity ?? "0");
+		const shortageQuantity = 0 < comparePackageQuantity(requirement.baseQuantity, availableQuantity)
+			? subtractPackageQuantity(requirement.baseQuantity, availableQuantity)
+			: undefined;
+		return { ...requirement, availableQuantity, shortageQuantity };
+	});
+}
+
+function subtractPackageQuantity(left: string, right: number | string): string {
+	const leftParts = toQuantityParts(left);
+	const rightParts = toQuantityParts(right);
+	if (!leftParts || !rightParts) {
+		return left;
+	}
+	const scale = Math.max(leftParts.scale, rightParts.scale);
+	const result = leftParts.value * 10n ** BigInt(scale - leftParts.scale)
+		- rightParts.value * 10n ** BigInt(scale - rightParts.scale);
+	const text = result.toString().padStart(scale + 1, "0");
+	const integerText = scale ? text.slice(0, -scale) : text;
+	const fractionText = scale ? text.slice(-scale).replace(/0+$/, "") : "";
+	return fractionText ? `${integerText}.${fractionText}` : integerText;
+}
+
+function toQuantityParts(value: number | string): { value: bigint; scale: number } | undefined {
+	const text = String(value).trim();
+	if (!/^\d+(?:\.\d{1,3})?$/.test(text)) {
+		return undefined;
+	}
+	const [integerText, fractionText = ""] = text.split(".");
+	return { value: BigInt(`${integerText}${fractionText}`), scale: fractionText.length };
+}