#include <QCoreApplication>

#include <QString>

class Command {
private:
    bool _isSuccess { false };
public:
    virtual ~Command() { }
    virtual void execute() = 0;
    bool isSuccess() const { return _isSuccess; }
protected:
    void setSuccess(const bool value) {
        _isSuccess = value;
    }
}; // Command

template<class TInput>
class CommandWithInput : public Command {
private:
    TInput _input;
public:
    void setInput(TInput value) {
        _input = value;
    }
    TInput getInput() const {
        return _input;
    }
}; // CommandWithInput

template<class TInput, class TOutput>
class CommandWithInputOtput : public Command {
private:
    TInput _input;
    TOutput _output;
public:
    void setInput(TInput value) {
        _input = value;
    }
    TInput getInput() const {
        return _input;
    }
    TOutput getOutput() const {\
        return _output;
    }
protected:
    void setOutput(TOutput value) {
        _output = value;
    }
}; // CommandWithInput

template<class TInput, class TOutput>
struct Converter {
private:
    TInput _input;
    TOutput _output;
    bool _isSuccess { false };
public:
    virtual ~Converter() { }
    virtual void convert() = 0;
    virtual bool isSuccess() const { return _isSuccess; }
    virtual void setInput(TInput value) {
        _input = value;
    }
    virtual TOutput getOutput() const {
        return _output;
    }
protected:
    void setSuccess(const bool value) {
        _isSuccess = value;
    }
}; // Converter

#include <QFile>

class OpenFileCommand : public CommandWithInputOtput<QString, QFile*> {
public:
    typedef CommandWithInputOtput<QString, QFile*> base;
    void execute() override {
        QFile *file = getOutput();
        if (file == nullptr) {
            file = new QFile();
        }
        if (file->isOpen()) {
            file->close();
        }
        file->setFileName(getInput());
        if (file->open(QFile::ReadOnly)) {
            setOutput(file);
            setSuccess(true);
        } else {
            setSuccess(false);
        }
    }
}; // OpenFileCommand

class ReadAllCommand : public CommandWithInputOtput<QFile*, QString> {
public:
    typedef CommandWithInputOtput<QFile*, QString> base;
    void execute() override {
        QFile *file = getInput();
        if (file->isOpen()) {
            setOutput(file->readAll());
            setSuccess(true);
        } else {
            setSuccess(false);
        }
    }
}; // ReadAllCommand

class CloseFileCommand : public CommandWithInput<QFile*> {
public:
    typedef CommandWithInput<QFile*> base;
    void execute() override {
        QFile *file = getInput();
        if (file->isOpen()) {
            file->close();
            setSuccess(true);
        } else {
            setSuccess(false);
        }
    }
}; // CloseFileCommand

#include <QDir>
#include <QTextStream>
#include <QTextCodec>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    const QString filePath = QString::fromUtf8("%1%2%3")
            .arg(QCoreApplication::applicationDirPath())
            .arg(QDir::separator())
            .arg("test.txt");

    QFile file(filePath);
    file.open(QFile::ReadWrite);
    QTextStream stream(&file);
    stream.setCodec(QTextCodec::codecForName("UTF-8"));
    stream << QString::fromUtf8("Hello world!\nFuck you C++!!!!\nCommand pattern!");
    stream.flush();
    file.close();

    OpenFileCommand::base *open = new OpenFileCommand();
    open->setInput(filePath);
    ReadAllCommand::base *readAll = new ReadAllCommand();
    readAll->setInput(open->getOutput());
    CloseFileCommand::base *close = new CloseFileCommand();
    close->setInput(open->getOutput());

    QVector<Command*> commands {
        open, readAll, close
    };

    foreach (Command *command, commands) {
        if (command != nullptr) {
            command->execute();
            if (command->isSuccess()) {
                qDebug() << "Current command success!";
            } else {
                qDebug() << "Current command failed!";
            }
        }
    }

    qDebug() << "Commands result: ";
    qDebug() << readAll->getOutput();

    QFile::remove(filePath);

    return 0;
}