# Willyu1007 AI First Template Services And Repositories

> Services and Repositories

- Skill: `tomevault-io/willyu1007-ai-first-template-services-and-repositories` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/willyu1007-ai-first-template-services-and-repositories`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/willyu1007-ai-first-template-services-and-repositories/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/willyu1007-ai-first-template-services-and-repositories

---


# Services and Repositories

This skill describes how to structure business logic (services) and data access (repositories).

---

## 1. Service layer (business rules)

Services should:
- Enforce business rules
- Orchestrate multiple repositories
- Avoid HTTP-specific types and concerns

Example:

```ts
export class UserService {
  constructor(private readonly userRepo: UserRepository) {}

  async create(input: CreateUserInput): Promise<User> {
    const existing = await this.userRepo.findByEmail(input.email);
    if (existing) throw new ConflictError("Email already exists");
    return await this.userRepo.create(input);
  }
}
```

---

## 2. Repository layer (data access)

Repositories should:
- Encapsulate query construction
- Hide ORM details from services
- Provide transaction helpers where needed

```ts
export class UserRepository {
  constructor(private readonly db: PrismaClient) {}

  findByEmail(email: string) {
    return this.db.user.findUnique({ where: { email } });
  }

  create(input: CreateUserInput) {
    return this.db.user.create({ data: input });
  }
}
```

---

## 3. When to introduce repositories

Use repositories when:
- Queries are non-trivial (joins, pagination, filtering)
- Multiple call sites reuse the same query logic
- You need better test seams and isolation

If a service is a thin wrapper over a single simple query, a repository may be optional.

---

## Related Skills

- `database-patterns`
- `testing-guide`

---
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<!-- tomevault:4.0:skill_md:2026-04-15 -->