//
// DiskStrategy
//
// An abstract class defining the interface that all disk strategies
// should implement.
class DiskStrategy {
public:
    // Returns the name of the strategy for display purposes.
    virtual char* getName() = 0;

    // Returns the process index among those available in !q! that
    // should be selected next for process by !arm!, according
    // to the represented strategy.
    virtual int selectProcess(DiskArm *arm, RequestQueue *q) = 0;
};

// defines the First In, First Out strategy
class FIFO : public DiskStrategy {
public:
    FIFO(Disk *disk);

    // Returns the name of the strategy for display purposes
    char* getName() { return "FIFO"; }

    // Returns the process index among those available in !q! that
    // should be selected next for process by !arm!, according to FIFO.
    int selectProcess(DiskArm *arm, RequestQueue *q);

private:
    // Tracks the process index from which we last made our request.
    int last_req;
};