import 'package:equatable/equatable.dart';

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

enum Gender {
  male('Male'),
  female('Female'),
  other('Other'),
  unspecified('Prefer not to say');

  const Gender(this.label);

  final String label;
}

/// Loyalty tier, derived from lifetime spend.
enum MembershipTier {
  bronze('Bronze', 0, 0.0),
  silver('Silver', 10000, 0.02),
  gold('Gold', 50000, 0.05),
  platinum('Platinum', 150000, 0.08);

  const MembershipTier(this.label, this.threshold, this.discountRate);

  final String label;

  /// Lifetime spend in rupees required to reach this tier.
  final double threshold;

  /// Automatic bill discount granted to members of this tier.
  final double discountRate;

  static MembershipTier forSpend(double lifetimeSpend) {
    return MembershipTier.values.lastWhere(
      (t) => lifetimeSpend >= t.threshold,
      orElse: () => MembershipTier.bronze,
    );
  }

  MembershipTier? get next {
    final i = index;
    return i < MembershipTier.values.length - 1
        ? MembershipTier.values[i + 1]
        : null;
  }
}

/// A registered shopper. A `null` customer on a sale means walk-in.
class Customer extends Equatable {
  const Customer({
    required this.id,
    required this.name,
    required this.mobile,
    this.email,
    this.gender = Gender.unspecified,
    this.dateOfBirth,
    this.loyaltyPoints = 0,
    this.lifetimeSpend = 0,
    this.visitCount = 0,
    this.createdAt,
    this.lastVisitAt,
  });

  final String id;
  final String name;
  final String mobile;
  final String? email;
  final Gender gender;
  final DateTime? dateOfBirth;
  final int loyaltyPoints;
  final double lifetimeSpend;
  final int visitCount;
  final DateTime? createdAt;
  final DateTime? lastVisitAt;

  MembershipTier get tier => MembershipTier.forSpend(lifetimeSpend);

  /// Cash value of the points currently held.
  double get redeemableValue =>
      loyaltyPoints * AppConstants.loyaltyPointValue;

  /// Rupees of additional spend needed to reach the next tier.
  double? get spendToNextTier {
    final next = tier.next;
    if (next == null) return null;
    return (next.threshold - lifetimeSpend).clamp(0, double.infinity);
  }

  bool get isBirthdayToday {
    final dob = dateOfBirth;
    if (dob == null) return false;
    final now = DateTime.now();
    return dob.month == now.month && dob.day == now.day;
  }

  /// The shopper as they stand after a completed sale.
  ///
  /// Pure, so the caller can compute the new row and persist it in the same
  /// transaction as the bill rather than as a separate write that might fail
  /// on its own.
  Customer applySale({
    required double amount,
    required int pointsEarned,
    required int pointsRedeemed,
    DateTime? at,
  }) {
    return copyWith(
      loyaltyPoints:
          (loyaltyPoints - pointsRedeemed + pointsEarned).clamp(0, 1 << 31),
      lifetimeSpend: (lifetimeSpend + amount).asMoney,
      visitCount: visitCount + 1,
      lastVisitAt: at ?? DateTime.now(),
    );
  }

  Customer copyWith({
    String? name,
    String? email,
    Gender? gender,
    DateTime? dateOfBirth,
    int? loyaltyPoints,
    double? lifetimeSpend,
    int? visitCount,
    DateTime? lastVisitAt,
  }) {
    return Customer(
      id: id,
      name: name ?? this.name,
      mobile: mobile,
      email: email ?? this.email,
      gender: gender ?? this.gender,
      dateOfBirth: dateOfBirth ?? this.dateOfBirth,
      loyaltyPoints: loyaltyPoints ?? this.loyaltyPoints,
      lifetimeSpend: lifetimeSpend ?? this.lifetimeSpend,
      visitCount: visitCount ?? this.visitCount,
      createdAt: createdAt,
      lastVisitAt: lastVisitAt ?? this.lastVisitAt,
    );
  }

  @override
  List<Object?> get props => [id, name, mobile, loyaltyPoints, lifetimeSpend];
}