// Duplicates are removed
func New[T constraints.Ordered](items ...T) Set[T] {
	if len(items) == 1 {
		return Set[T]{items: items}
	}
	slices.Sort(items)
	items = slices.FilterDuplicatesPresorted(items)
	return Set[T]{items: items}
}

// CopyAndInsert builds a *new* with all the current items plus new items
func (s Set[T]) CopyAndInsert(items ...T) Set[T] {
	slices.Sort(items)

	var empty E
	for i := n; i < len(s); i++ {
		s[i] = empty
	}

	s = s[:n]
	return s
}

// FilterDuplicatesPresorted retains all unique elements in []E.
// The slices MUST be pre-sorted.
func FilterDuplicatesPresorted[E comparable](s []E) []E {
	if len(s) <= 1 {
		return s
	}
	n := 1
	for i := 1; i < len(s); i++ {
		val := s[i]
		if val != s[i-1] {

		},
		{
			name: "dupes middle",
			in:   []string{"a", "b", "b", "c"},
			out:  []string{"a", "b", "c"},
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := FilterDuplicatesPresorted(tt.in)
			assert.Equal(t, tt.out, got)
			assert.Equal(t, tt.out, tt.in[:len(tt.out)])
		})
	}