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

using namespace std;

// The interface for communication between back and front
class Command {
public:
    virtual bool execute() = 0;
    virtual void undo() = 0;
};

// Reciever, which is a backend
class Light {
    int status;
public:
    Light() : status(0) {}
    bool on() {
        if (status == 0) {
            status = 1;
            cout << "Light on" << endl;
            return true;
        } else {
            cout << "Light is already on" << endl;
            return false;
        }
    }

    bool off() {
        if (status == 1) {
            status = 0;
            cout << "Light off" << endl;
            return true;
        } else {
            cout << "Light is already off" << endl;
            return false;
        }
    }

    int get_status() {
        return status;
    }
};


class OffCommand : public Command {
    shared_ptr<Light> l;
public:
    OffCommand(shared_ptr<Light> l) : l(l) {}
    bool execute() override {
        return l->off();
    }

    void undo() override {
        l->on();
    }
};

class OnCommand : public Command {
    shared_ptr<Light> l;
public:
    OnCommand(shared_ptr<Light> l) : l(l) {}
    bool execute() override {
        return l->on();
    }

    void undo() override {
        l->off();
    }
};

// The Invoker: manages and executes all commands.
// Any class that wants to operate the light can do so by simply
// executing a command, without needing to know the internal details
// of how the light works.
class RemoteControl {
    vector<shared_ptr<Command>> cmds;
public:
    RemoteControl() {}
    void exec_command(shared_ptr<Command> cmd) {
        if (cmd->execute()) {
            cmds.push_back(cmd);
        }
    }

    void undo() {
        if (cmds.size() != 0) {
            cmds[cmds.size() - 1]->undo();
            cmds.pop_back();
        }
    }
};


int main() {
    auto l = make_shared<Light>();
    auto c1 = make_shared<OnCommand>(l);
    auto c2 = make_shared<OffCommand>(l);

    RemoteControl rc;
    rc.exec_command(c1);
    rc.exec_command(c1);
    rc.exec_command(c2);
    rc.undo();
}