package ds

import "testing"

func TestLinkedListPushDelete(t *testing.T) {
	l := NewLinkedList[int]()
	if !l.Empty() {
		t.Fatal("新建应为空")
	}
	l.PushBack(2)
	l.PushBack(3)
	l.PushFront(1)
	l.PushFront(0)
	// 期望 [0,1,2,3]
	got := l.ToSlice()
	want := []int{0, 1, 2, 3}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("ToSlice[%d] = %d, want %d", i, got[i], want[i])
		}
	}

	// 删中间
	if !l.Delete(2) {
		t.Fatal("Delete(2) 应成功")
	}
	if l.Delete(99) {
		t.Fatal("Delete(99) 不应成功")
	}
	// 删头部
	if !l.Delete(0) {
		t.Fatal("Delete(0) 应成功")
	}
	// 删尾部
	if !l.Delete(3) {
		t.Fatal("Delete(3) 应成功")
	}
	got = l.ToSlice()
	if len(got) != 1 || got[0] != 1 {
		t.Fatalf("删完后剩 %v, want [1]", got)
	}
	// 删到空,验证 tail 回到 head
	if !l.Delete(1) {
		t.Fatal("Delete(1) 应成功")
	}
	if !l.Empty() {
		t.Fatal("应为空")
	}
}

func TestLinkedListReverse(t *testing.T) {
	l := NewLinkedList[string]()
	for _, s := range []string{"a", "b", "c", "d"} {
		l.PushBack(s)
	}
	l.Reverse()
	got := l.ToSlice()
	want := []string{"d", "c", "b", "a"}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("Reverse[%d] = %q, want %q", i, got[i], want[i])
		}
	}
	// 反转空表不应 panic
	l2 := NewLinkedList[int]()
	l2.Reverse()
	if !l2.Empty() {
		t.Fatal("空表反转后应仍为空")
	}
}

func TestLinkedListSingleNode(t *testing.T) {
	l := NewLinkedList[int]()
	l.PushBack(42)
	if l.Len() != 1 {
		t.Fatalf("Len = %d, want 1", l.Len())
	}
	if !l.Delete(42) {
		t.Fatal("Delete 单节点应成功")
	}
	// 删空后再次 PushBack,验证 tail 指针正确
	l.PushBack(7)
	if got := l.ToSlice(); len(got) != 1 || got[0] != 7 {
		t.Fatalf("删空后再插 = %v, want [7]", got)
	}
}