String? _parseDate(String? s) {
  if (s == null || s.isEmpty) return null;
  return s.length >= 10 ? s.substring(0, 10) : s;
}

class Inventory {
  final int id;
  final int? warehouseId;
  final int? productId;
  final int? stockInItemId;
  final double quantity;
  final String productCode;
  final String productName;
  final String series;
  final String spec;
  final String unit;
  final String warehouseName;
  final double? unitPrice; // 成本价（入库进价）
  final double? salePrice; // 单价（product 售价）
  final String? productionDate;
  final String batchNo;
  final String supplierName;
  final String remark;
  final int? minStock;
  final String brand;
  final String? createdAt;

  const Inventory({
    required this.id,
    this.warehouseId,
    this.productId,
    this.stockInItemId,
    required this.quantity,
    this.productCode = '',
    this.productName = '',
    this.series = '',
    this.spec = '',
    this.unit = '',
    this.warehouseName = '',
    this.unitPrice,
    this.salePrice,
    this.productionDate,
    this.batchNo = '',
    this.supplierName = '',
    this.remark = '',
    this.minStock,
    this.brand = '',
    this.createdAt,
  });

  factory Inventory.fromJson(Map<String, dynamic> json) => Inventory(
        id: (json['id'] as num).toInt(),
        warehouseId: (json['warehouse_id'] as num?)?.toInt(),
        productId: (json['product_id'] as num?)?.toInt(),
        stockInItemId: (json['stock_in_item_id'] as num?)?.toInt(),
        quantity: (json['quantity'] as num).toDouble(),
        productCode: json['product_code'] as String? ?? '',
        productName: json['product_name'] as String? ?? '',
        series: json['series'] as String? ?? '',
        spec: json['spec'] as String? ?? '',
        unit: json['unit'] as String? ?? '',
        warehouseName: json['warehouse_name'] as String? ?? '',
        unitPrice: (json['unit_price'] as num?)?.toDouble(),
        salePrice: (json['sale_price'] as num?)?.toDouble(),
        productionDate: _parseDate(json['production_date'] as String?),
        batchNo: json['batch_no'] as String? ?? '',
        supplierName: json['supplier_name'] as String? ?? '',
        remark: json['remark'] as String? ?? '',
        minStock: (json['min_stock'] as num?)?.toInt(),
        brand: json['brand'] as String? ?? '',
        createdAt: json['created_at'] as String?,
      );
}

/// 全店库存 KPI 汇总（GET /inventory/summary，不随分页）。
class InventorySummary {
  final int skuCount;
  final double stockValue;
  final double inStockQty;
  final int shortageCount;
  final int warningCount;
  // 月初快照（KPI 环比）：由 inventory_logs 反推
  final int lastMonthSku;
  final double lastMonthQty;
  final double lastMonthValue;
  const InventorySummary({
    this.skuCount = 0,
    this.stockValue = 0,
    this.inStockQty = 0,
    this.shortageCount = 0,
    this.warningCount = 0,
    this.lastMonthSku = 0,
    this.lastMonthQty = 0,
    this.lastMonthValue = 0,
  });
  factory InventorySummary.fromJson(Map<String, dynamic> j) => InventorySummary(
        skuCount: (j['sku_count'] as num?)?.toInt() ?? 0,
        stockValue: (j['stock_value'] as num?)?.toDouble() ?? 0,
        inStockQty: (j['in_stock_qty'] as num?)?.toDouble() ?? 0,
        shortageCount: (j['shortage_count'] as num?)?.toInt() ?? 0,
        warningCount: (j['warning_count'] as num?)?.toInt() ?? 0,
        lastMonthSku: (j['last_month_sku'] as num?)?.toInt() ?? 0,
        lastMonthQty: (j['last_month_qty'] as num?)?.toDouble() ?? 0,
        lastMonthValue: (j['last_month_value'] as num?)?.toDouble() ?? 0,
      );
}

class InventoryLog {
  final int warehouseId;
  final String? warehouseName;
  final int productId;
  final String? productName;
  final String direction; // in | out
  final double quantity;
  final double? qtyBefore;
  final double? qtyAfter;
  final String? refType;
  final int? refId;
  final String? createdAt;

  const InventoryLog({
    required this.warehouseId,
    this.warehouseName,
    required this.productId,
    this.productName,
    required this.direction,
    required this.quantity,
    this.qtyBefore,
    this.qtyAfter,
    this.refType,
    this.refId,
    this.createdAt,
  });

  factory InventoryLog.fromJson(Map<String, dynamic> json) => InventoryLog(
        warehouseId: (json['warehouse_id'] as num).toInt(),
        warehouseName:
            (json['warehouse'] as Map<String, dynamic>?)?['name'] as String?,
        productId: (json['product_id'] as num).toInt(),
        productName:
            (json['product'] as Map<String, dynamic>?)?['name'] as String?,
        direction: json['direction'] as String,
        quantity: (json['quantity'] as num).toDouble(),
        qtyBefore: json['qty_before'] != null
            ? (json['qty_before'] as num).toDouble()
            : null,
        qtyAfter: json['qty_after'] != null
            ? (json['qty_after'] as num).toDouble()
            : null,
        refType: json['ref_type'] as String?,
        refId: json['ref_id'] != null ? (json['ref_id'] as num).toInt() : null,
        createdAt: json['created_at'] as String?,
      );
}