// Parallel is a concurrent implementation of Executor
type Parallel struct{}

// Execute performs all provided actions in concurrently, failing closed on the
// first error or if ctx is cancelled.
func (p Parallel) Execute(ctx context.Context, actions []Action) error {
	grp, ctx := errgroup.WithContext(ctx)

	for _, a := range actions {
		grp.Go(p.execFn(ctx, a))
	}

	return grp.Wait()
}

// execFn binds the Context and Action to the proper function signature for the
// errgroup.Group.
func (p Parallel) execFn(ctx context.Context, a Action) func() error {
	return func() error { return a.Execute(ctx) }
}