#include<iostream>
#include<cctype>
#include<sstream>
#include<algorithm>
#include<string>
#include<cstring>
using namespace std;
class Create;
class Browser {
	friend ostream& operator<<(ostream& os, Browser& a) {
		os << "当前网址是: ";
		os << a.sa << endl;
		return os;
	}
	friend class Create;
private:
	string sa;
	Browser* next;
	Browser* pre;
public:
	Browser(){}
	~Browser(){}
};
class Create {
private:
	Browser* ptr;
	Browser* root;
	Browser* roar;
public:
	Create() {
		root = new Browser;
		ptr = new Browser;
		roar = new Browser;
		root->pre = nullptr;
		root->next = NULL;
		roar = root;
	}
	~Create(){}
	void insert(string s) {
		Browser* pp = root;
		Browser* middle=new Browser;
		middle->sa = s;
		cout << *middle;
		if (root->next == NULL) {
			root->next = middle;
			middle->next = NULL;
			middle->pre = roar;
			roar = middle;
		}
		else {
			roar->next = middle;
			middle->pre = roar;
			roar = middle;
			roar->next = NULL;
		}
		ptr = roar;
	}
	void back() {
		if (ptr->pre == NULL) {
			cout << "不可后退" << endl;
		}
		else {
			ptr = ptr->pre;
			cout << *ptr;
		}
	}
	void front() {
		if (ptr->next == NULL) {
			cout << "不可前进" << endl;
		}
		else {
			ptr = ptr->next;
			cout << *ptr;
		}
	}
};
int main()
{
	Create op;
	cout << "欢迎来到有趣小巧的模拟浏览器，现在有如下指令\n";
	cout << "v或V-访问新网址\n";
	cout << "b或B-后退\n";
	cout << "f或F-前进\n";
	cout << "x或X-退出\n";
	while (1 == 1) {
		char ch; cin >> ch;
		if (ch == 'F' || ch == 'f') {
			op.front();
		}
		else if (ch == 'x' || ch == 'X') {
			cout << "已退出模拟器\n";
			break;
		}
		else if (ch == 'v' || ch == 'V') {
			string s;
			cout << "请输入新网址: ";
			cin >> s;
			op.insert(s);
		}
		else if (ch == 'b' || ch == 'B') {
			op.back();
		}
	}
}