import 'package:equatable/equatable.dart';

import '../../core/constants/app_constants.dart';

/// Merchandise categories shown as filter chips on the POS dashboard.
enum ProductCategory {
  dairy('Dairy', '🥛'),
  grocery('Grocery', '🛒'),
  fruits('Fruits', '🍎'),
  vegetables('Vegetables', '🥦'),
  beverages('Beverages', '🥤'),
  snacks('Snacks', '🍪'),
  personalCare('Personal Care', '🧴'),
  household('Household', '🏠');

  const ProductCategory(this.label, this.emoji);

  final String label;
  final String emoji;
}

/// Unit of measure — drives whether fractional quantities are permitted.
enum UnitOfMeasure {
  piece('pc'),
  kilogram('kg'),
  gram('g'),
  litre('L'),
  millilitre('ml'),
  pack('pack');

  const UnitOfMeasure(this.symbol);

  final String symbol;

  bool get allowsFractional =>
      this == UnitOfMeasure.kilogram || this == UnitOfMeasure.litre;
}

/// A sellable item in the catalogue.
class Product extends Equatable {
  const Product({
    required this.id,
    required this.name,
    required this.barcode,
    required this.sku,
    required this.category,
    required this.price,
    required this.stock,
    this.mrp,
    this.emoji = '📦',
    this.imageUrl,
    this.unit = UnitOfMeasure.piece,
    this.gstRate = AppConstants.defaultGstRate,
    this.hsnCode,
    this.brand,
    this.isActive = true,
  });

  final String id;
  final String name;
  final String barcode;
  final String sku;
  final ProductCategory category;

  /// Selling price per [unit], inclusive of GST (Indian retail convention).
  final double price;

  /// Printed maximum retail price, used to display savings.
  final double? mrp;

  final double stock;
  final String emoji;
  final String? imageUrl;
  final UnitOfMeasure unit;
  final double gstRate;

  /// HSN/SAC code. Printed on the tax invoice — legally required on a GST
  /// invoice above the turnover threshold. Blank when the catalogue omits it.
  final String? hsnCode;

  final String? brand;
  final bool isActive;

  bool get isOutOfStock => stock <= 0;
  bool get isLowStock =>
      stock > 0 && stock <= AppConstants.lowStockThreshold;

  bool get hasDiscount => mrp != null && mrp! > price;

  double get savings => hasDiscount ? (mrp! - price) : 0;

  double get discountPercent =>
      hasDiscount ? ((mrp! - price) / mrp!) * 100 : 0;

  /// Price stripped of embedded GST — the taxable value.
  double get netPrice => price / (1 + gstRate);

  /// GST rupees embedded inside [price].
  double get taxPerUnit => price - netPrice;

  /// Fuzzy match used by the search bar across name, barcode, SKU and brand.
  bool matches(String query) {
    final q = query.trim().toLowerCase();
    if (q.isEmpty) return true;
    return name.toLowerCase().contains(q) ||
        barcode.toLowerCase().contains(q) ||
        sku.toLowerCase().contains(q) ||
        (brand?.toLowerCase().contains(q) ?? false) ||
        category.label.toLowerCase().contains(q);
  }

  Product copyWith({
    String? name,
    double? price,
    double? mrp,
    double? stock,
    ProductCategory? category,
    bool? isActive,
  }) {
    return Product(
      id: id,
      name: name ?? this.name,
      barcode: barcode,
      sku: sku,
      category: category ?? this.category,
      price: price ?? this.price,
      mrp: mrp ?? this.mrp,
      stock: stock ?? this.stock,
      emoji: emoji,
      imageUrl: imageUrl,
      unit: unit,
      gstRate: gstRate,
      hsnCode: hsnCode,
      brand: brand,
      isActive: isActive ?? this.isActive,
    );
  }

  @override
  List<Object?> get props => [id, name, barcode, sku, price, stock, isActive];
}