customer_relation

A deterministic, domain-driven customer relationship and trust model for Dart.

This package helps you model customers, profiles, trust levels, and brand relationships with strict invariants, immutable identities, and fully controlled time.

If a rule can be violated, the API is considered broken.

Why this package exists

Most customer/loyalty systems fail because:

• Identity can be mutated accidentally
• Trust levels can be skipped or forged
• Business rules live in services instead of the domain
• Time (DateTime.now()) makes logic untestable and non-replayable

customer_relation fixes this by enforcing rules inside the domain, not in documentation or developer discipline.

Core principles

• Identity is sacred
  Customer identity fields are immutable and validated.

• Trust is monotonic
  Relationship levels can only move forward in a defined order.

• No hidden mutations
  All state changes go through explicit intent-revealing methods.

• Time is injected, not magical
  No DateTime.now() leaks into the domain.

• Deterministic by design
  Same input + same time = same output.

Features

• Immutable CustomerId
• Safe CustomerProfile mutation
• Brand relationship lifecycle
• Trust level progression
  Identity → Habit → Legend
• Relationship status management
• Clock / TimeProvider abstraction
• Fully testable & replayable domain logic

Installation

dart pub add customer_relation