package notlinq

func UniqueBy[T any, K comparable](items []T, keySelector func(T) K) []T {
	seen := make(map[K]struct{})
	result := make([]T, 0, len(items))
	for _, item := range items {
		key := keySelector(item)
		if _, exists := seen[key]; !exists {
			seen[key] = struct{}{}
			result = append(result, item)
		}
	}
	return result
}

func Where[T any](items []T, predicate func(T) bool) []T {
	result := make([]T, 0)
	for _, item := range items {
		if predicate(item) {
			result = append(result, item)
		}
	}
	return result
}