package ds

import "testing"

func TestQueueFIFO(t *testing.T) {
	var q Queue[int]
	if !q.Empty() {
		t.Fatal("新建队列应为空")
	}
	if _, ok := q.Dequeue(); ok {
		t.Fatal("空队列 Dequeue 应返回 false")
	}

	q.Enqueue(1)
	q.Enqueue(2)
	q.Enqueue(3)
	if q.Len() != 3 {
		t.Fatalf("Len = %d, want 3", q.Len())
	}

	// FIFO 顺序
	for _, want := range []int{1, 2, 3} {
		got, ok := q.Dequeue()
		if !ok {
			t.Fatalf("Dequeue 失败,期望 %d", want)
		}
		if got != want {
			t.Fatalf("Dequeue = %d, want %d", got, want)
		}
	}
	if !q.Empty() {
		t.Fatal("全部出队后应为空")
	}
}

func TestQueueFront(t *testing.T) {
	var q Queue[string]
	q.Enqueue("x")
	q.Enqueue("y")
	f, ok := q.Front()
	if !ok || f != "x" {
		t.Fatalf("Front = %q,%v, want \"x\",true", f, ok)
	}
	_, _ = q.Dequeue()
	f, _ = q.Front()
	if f != "y" {
		t.Fatalf("第二次 Front = %q, want \"y\"", f)
	}
}

func TestQueueCompactNoGrowth(t *testing.T) {
	// 大量入队/出队后,逻辑长度正确且不泄漏内存。
	var q Queue[int]
	for i := 0; i < 1000; i++ {
		q.Enqueue(i)
		_, _ = q.Dequeue()
	}
	if !q.Empty() {
		t.Fatal("1000 次入队+出队后应为空")
	}
}