# Compose Utilities

## Purpose

The compose utilities provide functional combinators for working with validation results and schemas. `mergeResults` aggregates multiple `ParseResult<T>` values into a single `ParseResult<T[]>`, collecting all issues from failures. `pipe` composes a schema with one or more transform functions into a new pipeline schema, enabling clean left-to-right data transformation chains without manual wrapping.

## Features

- `mergeResults<T>(results)` — aggregate array of results, collecting all failures
- `pipe<T, U>(schema, ...transforms)` — compose schema with sequential transforms

## Usage: Basic Example

```typescript
import { pipe, string } from "@suaveplan/validation";

const trimmedLength = pipe(
  string(),
  (v: unknown) => (v as string).trim(),
  (v: unknown) => (v as string).length,
);
trimmedLength.parse("  hello  "); // 5
```

## Usage: Advanced Example

```typescript
import { mergeResults, number } from "@suaveplan/validation";

const n = number().min(0);
const results = [1, 2, -3, 4].map((v) => n.safeParse(v));
const merged = mergeResults(results);
// merged.success === false, merged.error.issues has one issue for -3
```

## API Reference

### `mergeResults<T>(results: ParseResult<T>[]): ParseResult<T[]>`

If all results are successes, returns `{ success: true, data: T[] }`.
If any result is a failure, returns `{ success: false, error: ValidationError }` with all issues aggregated from all failures.

### `pipe<T, U>(schema: BaseSchema<unknown, T>, ...transforms: TransformFn<unknown, unknown>[]): BaseSchema<unknown, U>`

Chains `schema` with each transform in order using `TransformSchema`. Each transform receives the previous stage's output as `unknown` (type-cast by the caller). Returns a new schema producing type `U`.

## Implementation Notes

- `mergeResults` with an empty array returns `{ success: true, data: [] }`.
- `pipe` with no transforms returns the original schema (zero iterations of the loop).
- Transform functions in `pipe` accept `unknown` to avoid TypeScript variance issues across the chain; callers must cast appropriately.