loyalty_levels 0.1.0

A DDD-based loyalty, streak, and levels package modeling the relationship system between customers and business.

Loyalty Levels

A production-grade Dart package for modeling loyalty relationships using Domain-Driven Design (DDD) principles.

Overview

loyalty_levels models the relationship system between customers and business through three distinct concepts:

• Level = Lifetime trust (NEVER resets)
• Streak = Current momentum (CAN reset or pause)
• Rewards = Tied to STREAK count, not level

This is NOT a gamification system. This is a relationship system built on fairness.

Core Philosophy

1. Level ≠ Streak ≠ Reward

These are three independent but coordinated concepts:

• Level: Represents lifetime customer trust. Upgrades monotonically (identity → habit → legend). Can only downgrade by ONE zone at a time. Never resets completely.

• Streak: Tracks current momentum through consecutive successful cycles. Can be active, paused, or broken. Subject to fair pause rules.

• Rewards: Calculated from streak count, NOT from level. Level only determines WHICH reward policy applies.

2. Fairness Over Aggression

Loyal customers must never feel cheated:

• Pause ≤15 days: Streak frozen (count preserved)
• Pause 16-45 days: Streak reset to 0, level unchanged
• Pause >45 days: Streak reset to 0, level downgraded by ONE zone

No hard resets unless fraud. Punishment is soft, gradual, and explainable.

Installation

Add to your pubspec.yaml:

dependencies:
  loyalty_levels: ^0.1.0

Then run:

dart pub get

Usage

Creating a Loyalty Account

import 'package:loyalty_levels/loyalty_levels.dart';

final clock = SystemClock();
final account = LoyaltyAccount.create(
  accountId: 'customer-123',
  createdAt: clock.now(),
);

print(account.level.current); // LoyaltyLevel.identity
print(account.streak.count); // 0

Recording Activity (Extends Streak)

final service = LoyaltyEvaluationService(clock: clock);

var account = LoyaltyAccount.create(
  accountId: 'customer-123',
  createdAt: clock.now(),
);

// Customer completes an order
account = service.processActivity(account);
print(account.streak.count); // 1

// Another order next day
account = service.processActivity(account);
print(account.streak.count); // 2

Pause and Resume (Fair Rules)

// Customer pauses subscription
account = service.pauseAccount(account);

// ... 10 days pass ...

// Resume after short pause (≤15 days)
account = service.resumeAccount(account);
print(account.streak.count); // FROZEN - count preserved

// Resume after medium pause (16-45 days)
// Streak resets to 0, but level unchanged

// Resume after long pause (>45 days)
// Streak resets to 0, level downgrades by ONE zone

Calculating Rewards

// Rewards based on STREAK, not level
final rewards = service.calculateRewards(account);

// Level determines WHICH policy applies:
// - Identity: streak × baseReward
// - Habit: streak × baseReward × 1.5
// - Legend: (streak × baseReward × 2.0) + bonus

Upgrading Levels

account = service.upgradeAccountLevel(account);
print(account.level.current); // LoyaltyLevel.habit

// Can upgrade: identity → habit → legend
// Streak count is preserved during upgrade

Domain Rules

Level Rules

• Level NEVER resets completely
• Upgrades are monotonic (identity → habit → legend)
• Downgrade limited to ONE zone only
• All level changes emit LevelUpgraded event

Streak Rules

• Streak count is always ≥ 0
• Can be active, paused, or broken
• Pause ≤15 days → frozen
• Pause 16-45 days → reset
• Pause >45 days → reset + level downgrade
• All state changes emit appropriate events

Reward Rules

• Rewards tied to STREAK count, not LEVEL
• Level only influences WHICH policy applies
• Policies are interchangeable (Liskov Substitution)

Time Safety

• ABSOLUTE BAN on DateTime.now() in domain code
• All time comes from injected Clock
• Production: use SystemClock
• Tests: use FakeClock for determinism

Testing

This package includes FakeClock for deterministic testing:

import 'package:loyalty_levels/loyalty_levels.dart';
import 'package:test/test.dart';

void main() {
  test('deterministic time-based testing', () {
    final clock = FakeClock(DateTime(2026, 1, 1));
    final service = LoyaltyEvaluationService(clock: clock);

    var account = LoyaltyAccount.create(
      accountId: 'test-123',
      createdAt: clock.now(),
    );

    clock.advanceDays(1);
    account = service.processActivity(account);

    expect(account.streak.count, 1);
  });
}

Architecture

Built with strict DDD principles:

• Entities: LoyaltyAccount (aggregate root), Level, Streak
• Value Objects: LoyaltyLevel enum
• Events: StreakStarted, StreakBroken, LevelUpgraded
• Policies: RewardPolicy (interface), IdentityRewardPolicy, HabitRewardPolicy, LegendRewardPolicy
• Ports: Clock abstraction for time safety
• Services: LoyaltyEvaluationService for thin orchestration

Bounded Context

This package has ZERO dependencies on:

• Ordering
• Delivery
• Inventory
• Payments

It ONLY consumes:

• Signals (events/inputs)
• Time (via Clock)

License

MIT License - see LICENSE file for details.

Philosophy

If a rule feels unfair, redesign it.
If a rule can be abused, block it.
If logic is ambiguous, THROW.

Safety > Convenience.