package ds

import "testing"

func TestDequeBothEnds(t *testing.T) {
	var d Deque[int]
	d.PushBack(2)
	d.PushBack(3)
	d.PushFront(1)
	d.PushFront(0)
	// 队列内容应为 [0,1,2,3]
	if got, _ := d.Front(); got != 0 {
		t.Fatalf("Front = %d, want 0", got)
	}
	if got, _ := d.Back(); got != 3 {
		t.Fatalf("Back = %d, want 3", got)
	}
	if d.Len() != 4 {
		t.Fatalf("Len = %d, want 4", d.Len())
	}

	// 交替弹出,验证两端 O(1)
	if v, _ := d.PopFront(); v != 0 {
		t.Fatalf("PopFront = %d, want 0", v)
	}
	if v, _ := d.PopBack(); v != 3 {
		t.Fatalf("PopBack = %d, want 3", v)
	}
	if v, _ := d.PopFront(); v != 1 {
		t.Fatalf("PopFront = %d, want 1", v)
	}
	if v, _ := d.PopBack(); v != 2 {
		t.Fatalf("PopBack = %d, want 2", v)
	}
	if !d.Empty() {
		t.Fatal("应为空")
	}
}

func TestDequeGrowAcrossBoundary(t *testing.T) {
	// 跨越 head 边界触发扩容,验证数据顺序不乱。
	var d Deque[int]
	for i := 0; i < 20; i++ {
		d.PushBack(i)
	}
	// 先弹出几个,让 head 前移,再继续插入触发扩容。
	for i := 0; i < 5; i++ {
		_, _ = d.PopFront()
	}
	for i := 20; i < 40; i++ {
		d.PushBack(i)
	}
	// 期望顺序 5..39
	for want := 5; want < 40; want++ {
		got, ok := d.PopFront()
		if !ok || got != want {
			t.Fatalf("PopFront = %d,%v, want %d", got, ok, want)
		}
	}
}

func TestDequeString(t *testing.T) {
	var d Deque[string]
	d.PushFront("b")
	d.PushFront("a")
	d.PushBack("c")
	var got []string
	for !d.Empty() {
		v, _ := d.PopFront()
		got = append(got, v)
	}
	want := []string{"a", "b", "c"}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("结果[%d] = %q, want %q", i, got[i], want[i])
		}
	}
}