---
description: TypeScript and React Native coding style conventions — enforced for all project types
globs: "**/*.{ts,tsx,js,jsx}"
alwaysApply: false
---

# Coding Style

## TypeScript
- Enable `strict` mode in tsconfig.json
- No `any` types — use `unknown` + type guards or proper generics
- Use type inference where possible; annotate function signatures explicitly
- Prefer `interface` for object shapes, `type` for unions/intersections
- Use `as const` for literal types instead of enums

## Components
- Functional components only — no class components
- Named exports only — no default exports
- One component per file (colocated helpers are fine)
- Props interface named `[Component]Props` (e.g., `ButtonProps`)
- Destructure props in function signature

```tsx
// GOOD
export function UserCard({ name, avatar }: UserCardProps) { ... }

// BAD
export default class UserCard extends Component { ... }
```

## File Naming
- Components: `PascalCase.tsx` (e.g., `UserCard.tsx`)
- Hooks: `camelCase.ts` prefixed with `use` (e.g., `useAuth.ts`)
- Utils/helpers: `camelCase.ts` (e.g., `formatDate.ts`)
- Types: `camelCase.ts` or colocated in component file
- Tests: `[name].test.ts(x)` adjacent to source
- Platform-specific: `[name].ios.tsx` / `[name].android.tsx`

## Imports
- Use path aliases (`@/` maps to `src/`)
- No barrel files (`index.ts` re-exports) — import directly
- Group imports: react → react-native → expo → third-party → local
- Use `import type` for type-only imports

## General
- Max line length: 100 characters (Prettier enforced)
- Trailing commas in multiline structures
- Single quotes for strings
- Semicolons required
- No `var` — use `const` by default, `let` when reassignment needed