# Core Data Flow (Strict)

This document defines the **Core** data flow rules and boundaries.

Core scope:

- `core/**`

Core does not know:

- HTTP
- Next.js
- databases
- DTOs
- UI models

## 1) Layers inside Core

Core contains two inner layers:

- Domain
- Application

### 1.1 Domain

Domain is business truth.

Allowed:

- Entities
- Value Objects
- Domain Services

Forbidden:

- DTOs
- frameworks
- IO

See [`docs/architecture/core/DOMAIN_OBJECTS.md`](docs/architecture/core/DOMAIN_OBJECTS.md:1).

### 1.2 Application

Application coordinates business intents.

Allowed:

- Use Cases (commands and queries)
- Application-level ports (repository ports, gateways)

Forbidden:

- HTTP
- persistence implementations
- frontend models

## 2) Core I/O boundary

All communication across the Core boundary occurs through **ports**.

Rules:

- Port interfaces live in Core.
- Implementations live outside Core.

## 3) Core data types (strict)

- Use Case inputs are plain data and/or domain types.
- Use Case outputs are plain data and/or domain types.

Core MUST NOT define HTTP DTOs.

## 4) Canonical flow

```text
Delivery App (HTTP or Website)
  ↓
Core Application (Use Case)
  ↓
Core Domain (Entities, Value Objects)
  ↓
Ports (repository, gateway)
  ↓
Adapter implementation (outside Core)
```

## 5) Non-negotiable rules

1. Core is framework-agnostic.
2. DTOs do not enter Core.
3. Core defines ports; outer layers implement them.