Runtime Logging Abstraction

#include <iostream>
using namespace std;

/*
DESIGN REQUIREMENTS:

- Logging must use a runtime-selected stream abstraction
- Application code must not depend on transport type
- Transport-specific logic must be hidden
*/

// Abstract output stream
class OutputStream {
public:
    virtual void write(const char* msg) = 0;
    virtual ~OutputStream() = default;
};

class UART:public OutputStream{
    public:

    void write(const char* msg) override{
        cout<<"UART:"<<msg<<endl;
    }
};
class SPI: public OutputStream{
    public:

    void write(const char* msg) override{
        cout<<"SPI:"<<msg<<endl;
    }
};
/*
TASK FOR LEARNER:

- Implement two concrete OutputStream classes:
    - UART stream
    - SPI stream

- Implement the factory function below to:
    - Select the correct stream at runtime
    - Return nullptr for invalid transport values

DO NOT:
- Modify main()
- Add transport logic to logging code
*/

// Factory function (to be implemented)
OutputStream* selectStream(int type){
    static UART uart;
    static SPI spi;
    if(type == 1)
        return &uart;
    else if(type == 2)
        return &spi;
    else
        return nullptr;
}

// Transport-independent logging logic
void logMessage(OutputStream* stream, const char* msg) {
    if (stream) {
        stream->write(msg);
    }
}

int main() {
    int transport;
    cin >> transport;

    int n;
    cin >> n;

    OutputStream* stream = selectStream(transport);

    for (int i = 0; i < n; ++i) {
        char msg[33];
        cin >> msg;
        logMessage(stream, msg);
    }

    return 0;
}