# Solid Generic

> Use when building CLI tools, libraries, scripts, hooks, or non-framework TypeScript code (Bun/Node.js -- SOLID, files < 100 lines, JSDoc mandatory).

- Skill: `fusengine/solid-generic` (Agent Skill, multi-file: 15 files)
- Install (CLI): `npx skillmds@latest add fusengine/solid-generic`
- Raw SKILL.md: https://api.skillmd.com/api/skills/fusengine/solid-generic/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: fusengine (https://skillmd.com/u/fusengine)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/fusengine/solid-generic

---


<objective>
SOLID Generic enforces a modular architecture for plain TypeScript/Bun/Node.js code with no framework (CLI tools, libraries, scripts, hooks): interfaces live in `modules/[feature]/src/interfaces/` or `modules/cores/interfaces/` for shared types, never in implementation files; files stay under 100 lines (modules <80, services <60, validators <40); every export carries JSDoc.

Before writing any new code it requires a DRY check across `modules/cores/lib`, `modules/cores/interfaces`, and `modules/cores/errors`, extracting anything repeated 3+ times into a shared helper. Each of the 5 SOLID principles has its own detailed reference (`single-responsibility.md` through `dependency-inversion.md`), plus copy-paste-ready templates for modules, services, interfaces, validators, factories, errors, and tests.
</objective>

# SOLID Generic - TypeScript / Bun / Node.js

## Agent Workflow (MANDATORY)

Before ANY implementation, spawn 3 agents in parallel, one `Agent` call each with a `name`:

1. **fuse-ai-pilot:explore-codebase** - Analyze project structure and existing patterns
2. **fuse-ai-pilot:research-expert** - Verify latest TypeScript/Bun docs via Context7
3. **mcp__context7__query-docs** - Check integration compatibility

After implementation, run **fuse-ai-pilot:sniper** for validation.

---

## DRY - Reuse Before Creating (MANDATORY)

**Before writing ANY new code:**
1. **Grep the codebase** for similar function names, patterns, or logic
2. Check shared locations: `modules/cores/lib/`, `modules/cores/interfaces/`, `modules/cores/errors/`
3. If similar code exists -> extend/reuse instead of duplicate
4. If code will be used by 2+ modules -> create in `modules/cores/`
5. Extract repeated logic (3+ occurrences) into shared helpers

---

## Absolute Rules (MANDATORY)

### 1. Files < 100 lines
- **Split at 90 lines** - Never exceed 100
- Modules < 80 lines
- Services < 60 lines
- Validators < 40 lines

### 2. Interfaces Separated (Modular MANDATORY)
```text
modules/[feature]/src/interfaces/   # Feature types
  |- user.interface.ts
  \- service.interface.ts
modules/cores/interfaces/            # Shared types
  \- shared.interface.ts
```
**NEVER put interfaces in implementation files.**
**NEVER use flat `src/` structure - always `modules/`.**

### 3. JSDoc Mandatory
```typescript
/**
 * Parse configuration from file path.
 *
 * @param filePath - Absolute path to config file
 * @returns Parsed configuration object
 * @throws ConfigError if file is invalid
 */
export function parseConfig(filePath: string): Config
```

---

## SOLID Principles (Detailed Guides)

| # | Principle | Reference | Key Rule |
|---|-----------|-----------|----------|
| S | Single Responsibility | [single-responsibility.md](references/single-responsibility.md) | One file = one reason to change |
| O | Open/Closed | [open-closed.md](references/open-closed.md) | Extend via composition, not modification |
| L | Liskov Substitution | [liskov-substitution.md](references/liskov-substitution.md) | Implementations honor interface contracts |
| I | Interface Segregation | [interface-segregation.md](references/interface-segregation.md) | Many focused interfaces > one fat interface |
| D | Dependency Inversion | [dependency-inversion.md](references/dependency-inversion.md) | Depend on abstractions, inject dependencies |

See [solid-principles.md](references/solid-principles.md) for overview and [architecture-patterns.md](references/architecture-patterns.md) for project structure.

---

## Code Templates

| Template | Usage | Max Lines |
|----------|-------|-----------|
| [module.md](references/templates/module.md) | TypeScript/Bun module | 80 |
| [service.md](references/templates/service.md) | Service with DI | 60 |
| [interface.md](references/templates/interface.md) | TypeScript interfaces | - |
| [validator.md](references/templates/validator.md) | Zod validation schemas | 40 |
| [factory.md](references/templates/factory.md) | Factory pattern | 60 |
| [error.md](references/templates/error.md) | Custom error classes | 40 |
| [test.md](references/templates/test.md) | Bun test / Vitest | - |

---

## Forbidden

- Files > 100 lines
- Interfaces in implementation files
- Business logic in entry points
- Missing JSDoc on exports
- `any` type
- Barrel exports (index.ts re-exports)
- Duplicating existing utility without Grep search first
- Copy-pasting logic blocks instead of extracting shared function
- Concrete dependencies without interface abstraction