// scheduler.h 
//  Data structures for the thread dispatcher and scheduler.
//  Primarily, the list of threads that are ready to run.
//
// Copyright (c) 1992-1993 The Regents of the University of California.
// All rights reserved.  See copyright.h for copyright notice and limitation 
// of liability and disclaimer of warranty provisions.

// Modified 9/19/2005 by Jacob Lee and Soumi Sinha for CS423ug MP1.

#ifndef SCHEDULER_H
#define SCHEDULER_H

#include "copyright.h"
#include "list.h"
#include "thread.h"
#include "timer.h"
#include "stats.h"
#include "oneshot.h"

enum SchedPolicy { 
  SCHED_FCFS,
  SCHED_PRIO_P,
  SCHED_RR,
  SCHED_PRIO_RR
};


// The following class defines the scheduler/dispatcher abstraction -- 
// the data structures and operations needed to keep track of which 
// thread is running, and which threads are ready but not running.

class Scheduler {
  public:
    Scheduler();  // Initialize list of ready threads 
    ~Scheduler(); // De-allocate ready list

    void ReadyToRun(Thread* thread); // Thread can be dispatched.
    Thread* FindNextToRun();         // Dequeue first thread on the ready 
                                     // list, if any, and return thread.
    bool ShouldISwitch(Thread* oldThread, Thread* newThread);
    void Run(Thread* nextThread);    // Cause nextThread to start running
    void Print();                    // Print contents of ready list
    void Suspend(Thread *thread);
    void Resume(Thread *thread);
    void SetSchedPolicy(SchedPolicy pol); 
    void SetNumOfQueues(int level);  // set the number of queues for MLQ
    void InterruptHandler( int dummy );
    SchedPolicy getPolicy();

  private:
    SchedPolicy policy;            // scheduling policy to be used
    List<Thread *> *readyList;     // queue of threads that are ready to run,
                                   // but not running
    List<Thread *> *suspendedList; // List of suspended threads.
    //Timer * ptimer;                // A timer, if needed.
    // We use a one-shot timer instead of a recurring timer.
    OneShot *ptimer;
};

#endif // SCHEDULER_H