#include <iostream>
#include <vector>
#include <memory>

/*
在这个例子中，当股票价格发生变化时，所有的投资者都会收到通知并更新他们的状态。观察者模式使得我们可以轻松地添加或删除投资者，而不需要修改股票类的代码，从而实现了解耦和灵活性。
*/

// 抽象观察者类：投资者
class Investor {
public:
    virtual ~Investor() {}
    virtual void update(double price) = 0;
};


// 具体观察者类：具体投资者
class ConcreteInvestor : public Investor {
private:
    std::string name;
public:
    ConcreteInvestor(const std::string& name) : name(name) {}
    void update(double price) override {
        std::cout << "Investor " << name << " is notified. New stock price: " << price << std::endl;
    }
};


// 抽象主题类：股票
class Stock {
public:
    virtual ~Stock() {}
    virtual void addObserver(std::shared_ptr<Investor> investor) = 0;
    virtual void removeObserver(std::shared_ptr<Investor> investor) = 0;
    virtual void notifyObservers() = 0;
};


// 具体主题类：具体股票
class ConcreteStock : public Stock {
private:
    std::vector<std::shared_ptr<Investor>> investors;
    double price;
public:
    void addObserver(std::shared_ptr<Investor> investor) override {
        investors.push_back(investor);
    }
    void removeObserver(std::shared_ptr<Investor> investor) override {
        investors.erase(std::remove(investors.begin(), investors.end(), investor), investors.end());
    }
    void notifyObservers() override {
        for (const auto& investor : investors) {
            investor->update(price);
        }
    }
    void setPrice(double newPrice) {
        price = newPrice;
        notifyObservers();
    }
};


int main() {
    // 创建具体股票
    std::shared_ptr<ConcreteStock> stock = std::make_shared<ConcreteStock>();


    // 创建具体投资者
    std::shared_ptr<Investor> investor1 = std::make_shared<ConcreteInvestor>("Alice");
    std::shared_ptr<Investor> investor2 = std::make_shared<ConcreteInvestor>("Bob");


    // 添加投资者到股票的观察者列表中
    stock->addObserver(investor1);
    stock->addObserver(investor2);


    // 修改股票价格
    stock->setPrice(100.0);
    stock->setPrice(105.0);


    return 0;
}