# Type System Reference

This reference details the TypeScript utility types exported by Locality IDB for type-safe database integration.

## Inference Utilities

### `InferSelectType<T>`

Extracts the full row type returned from select queries.

```typescript
type User = InferSelectType<typeof schema.users>;
```

### `InferInsertType<T>`

Extracts the required insertion payload. Auto-generated and default columns are optional.

```typescript
type InsertUser = InferInsertType<typeof schema.users>;
```

### `InferUpdateType<T>`

Extracts the payload for update calls. Primary keys are excluded, and all other fields are optional.

```typescript
type UpdateUser = InferUpdateType<typeof schema.users>;
```

### `$InferRow<T>`

Low-level inference helper to extract row types directly from column definition records.

```typescript
type UserRow = $InferRow<typeof schema.users.columns>;
```

## Branded Types

### `UUID<Version>`

Represents a branded string for UUID values, checking the version parameter.

```typescript
import type { UUID } from 'locality-idb';

type UserId = UUID<'v4'>; // Branded UUID v4
```

## Helper Types

### `GenericObject`

Alias for `Record<string, any>`.

### `Prettify<T>`

Flattens complex intersecting types to make IDE hover labels human-readable.

### `NestedPrimitiveKey<T>`

Extracts nested primitive keys into dot-separated paths (e.g. `"profile.address.zip"`).

```typescript
type Keys = NestedPrimitiveKey<{ user: { profile: { age: number } } }>; 
// "user.profile.age"
```

### `SelectFields<T, Selection>`

Applies a select/exclude projection mask to a target object type.

## Transaction & Pagination Types

### `TransactionContext<Schema, TableName, TargetTables>`

The database transaction context API provided inside the transaction callback.

### `TransactionCallback<Schema, TableName, TargetTables>`

The transaction callback signature.

```typescript
type TxCallback = TransactionCallback<Schema, TableName, ['users']>;
```

### `ExportOptions<Tables>`

Configuration payload passed to `$export()` or `exportToObject()`.

### `ExportData`

The backup payload format containing `metadata` and `data`.

### `ImportOptions`

Options defining the import `mode` (`merge`, `replace`, `upsert`).

### `PageOptions`

Arguments for cursor-based pagination.

```typescript
interface PageOptions {
  cursor?: IDBValidKey;
  limit?: number;
}
```

### `PageResult<T, Cursor>`

Response structure returned by `page()`.

```typescript
interface PageResult<T, Cursor> {
  items: T[];
  nextCursor: Cursor | undefined;
}
```