package ulid

import (
	"sync"
	"testing"
)

func TestNew_ReturnsValidULID(t *testing.T) {
	id := New()
	if len(id) != 26 {
		t.Errorf("expected 26 chars, got %d: %s", len(id), id)
	}
}

func TestNew_Unique(t *testing.T) {
	a := New()
	b := New()
	if a == b {
		t.Errorf("two calls returned same ULID: %s", a)
	}
}

func TestNew_Sortable(t *testing.T) {
	a := New()
	b := New()
	if b < a {
		t.Errorf("expected b >= a for sequential calls: a=%s b=%s", a, b)
	}
}

func TestNew_ConcurrentUnique(t *testing.T) {
	const n = 100
	ids := make([]string, n)
	var wg sync.WaitGroup
	wg.Add(n)
	for i := 0; i < n; i++ {
		go func(idx int) {
			defer wg.Done()
			ids[idx] = New()
		}(i)
	}
	wg.Wait()

	seen := make(map[string]struct{}, n)
	for _, id := range ids {
		if _, dup := seen[id]; dup {
			t.Fatalf("duplicate ULID under concurrency: %s", id)
		}
		seen[id] = struct{}{}
	}
}