[Refactor] Phase 4: Service Topology DDD Layer Alignment

[josecelano]

Overview

Move port derivation and network computation logic from the infrastructure layer to the domain layer, ensuring proper DDD layer separation. This phase was identified during Phase 3 implementation when we discovered business rules incorrectly placed in infrastructure.

Problem Statement

The current architecture has domain logic (port derivation, network computation) incorrectly placed in the infrastructure layer:

infrastructure/context/port_derivation.rs  ← Business rules about port exposure
infrastructure/context/tracker.rs          ← compute_networks() method
infrastructure/context/grafana.rs          ← compute_networks() method
infrastructure/context/prometheus.rs       ← compute_networks() method

These are business rules that should be in the domain layer:

• "UDP ports are always exposed (no TLS for UDP)" - PORT-02
• "HTTP ports hidden when TLS enabled" - PORT-03, PORT-04
• "Tracker joins metrics_network when Prometheus is enabled"

Implementation Plan

P4.1: Add Trait and Implement in Domain

• Create src/domain/topology/traits.rs with PortDerivation trait
• Implement PortDerivation for TrackerConfig, GrafanaConfig, PrometheusConfig
• Create src/domain/topology/fixed_ports.rs for Caddy and MySQL
• Add unit tests for each implementation

P4.2: Create Domain Topology Builder

• Create src/domain/topology/builder.rs with DockerComposeTopologyBuilder
• Move network computation logic from infrastructure to domain builder
• Wire up port derivation via trait calls
• Add integration tests

P4.3: Refactor Infrastructure to Pure DTOs

• Remove compute_networks() from all service context types
• Rename types to *Context (e.g., TrackerServiceContext)
• Update DockerComposeContextBuilder to receive domain topology
• Update tests

P4.4: Cleanup

• Delete src/infrastructure/.../context/port_derivation.rs
• Remove any remaining business logic from infrastructure
• Update documentation
• Run full E2E test suite

Acceptance Criteria

• Pre-commit checks pass: ./scripts/pre-commit.sh
• PortDerivation trait defined in domain/topology/traits.rs
• All service configs implement PortDerivation
• DockerComposeTopologyBuilder computes networks in domain layer
• Infrastructure context types are pure DTOs with no compute_*() methods
• port_derivation.rs deleted from infrastructure
• All existing E2E tests pass

Related

• Parent Epic: [Epic] Docker Compose Topology Domain Model Refactoring #287 - Docker Compose Topology Domain Model Refactoring
• Predecessor: [Refactor] Phase 3: Port Topology Template Integration (P3.4) #300 - Phase 3 Port Topology Template Integration
• Spec: docs/issues/phase-4-service-topology-ddd-alignment.md