domain

gopilot:domain — Add a Business Domain

You are adding a new domain to the Go backend. Domains are isolated business areas with their own types, repository (DB access), and service (business logic).

Before Starting

1. Read skills/_shared/go-patterns.md for conventions
2. Read references/architecture.md for the architecture overview
3. Read backend/internal/api/router.go to see existing domains

Arguments

Parse $ARGUMENTS as: [domain-name]

• Must be singular, lowercase (e.g., item, booking, user)
• If not provided: ask the user what domain to add

Phase 1: Create Domain Package

Create the domain package at backend/internal/domain/[name]/:

[name].go — Domain Types

package [name]

import "time"

type [Name] struct {
    ID          string    `json:"id"`
    // Add fields based on user's description
    CreatedAt   time.Time `json:"created_at"`
    UpdatedAt   time.Time `json:"updated_at"`
}

repository.go — Database Access

package [name]

import (
    "context"
    "github.com/jackc/pgx/v5/pgxpool"
)

type Repository struct {
    pool *pgxpool.Pool
}

func NewRepository(pool *pgxpool.Pool) *Repository {
    return &Repository{pool: pool}
}

// Add methods: List, GetByID, Create, Update, Delete
// Use pgx directly — no ORM
// Always accept context.Context as first parameter
// Return (result, error) tuples

service.go — Business Logic

package [name]

type Service struct {
    repo *Repository
}

func NewService(repo *Repository) *Service {
    return &Service{repo: repo}
}

// Business logic methods that call repository
// Validation, authorization checks, side effects go here
// Services know nothing about HTTP

Phase 2: Add Database Table

Add the table to backend/schema.sql:

CREATE TABLE IF NOT EXISTS [name]s (
    id          TEXT PRIMARY KEY DEFAULT gen_random_uuid()::text,
    -- fields based on domain types
    created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT now()
);

• Use TEXT for IDs (UUIDs stored as text)
• Use TIMESTAMPTZ for all timestamps
• Add indexes for frequently queried columns
• Add foreign keys where needed

Phase 3: Wire into Router

Update backend/internal/api/router.go:

1. Instantiate the repository: [name]Repo := [name].NewRepository(pool)
2. Instantiate the service: [name]Svc := [name].NewService([name]Repo)
3. Comment placeholder for handler registration (handlers come via /gopilot:api)

Phase 4: Verify

1. Run go vet ./... in backend
2. Run go build ./... to check compilation
3. Tell user: "Domain [name] created. Add API endpoints with /gopilot:api [name] list|get|create|update|delete."

Conventions

• Domains know NOTHING about HTTP — no http.Request, no status codes
• Repository methods are pure DB operations
• Service methods contain business rules
• One domain per package, no cross-domain imports (use interfaces if needed)
• All errors are returned, never panicked