//Lab 8
//Condition Variables and Scheduling

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

pthread_mutex_t bank_mutex;

//Add output statements to the code and record your output.  Then modify the 
//code to remove the condition variable and record your output.  Finally, add
//the condition variable back to the code.
pthread_cond_t zero_balance_cv;

static double account_balance;

//What happens when you increase the number of deposits and withdrawls
//to 1000?
static const int NUM_DEPOSITS = 100;
static const int NUM_WITHDRAWLS = 100;


//What happens when you increase the number of threads to 10
//for deposit and withdrawl threads?
static const int NUM_DEPOSIT_THREADS = 1;
static const int NUM_WITHDRAWL_THREADS = 1;

//Deposit threads should always be able to add funds to the
//account
void * deposit(void * tid)
{
  int i = 0;
  for(i = 0; i < NUM_DEPOSITS; i++)
  {
    pthread_mutex_lock(&bank_mutex);

    //Add between 100 and 200 dollars to the account.
    //What happens if you change this to 1 to 100 dollars?
    account_balance += rand()%101 + 100;

    //Signal the condition variable to indicate that the account has a positive
    //balance.
    if(account_balance > 0)
      pthread_cond_signal(&zero_balance_cv);

    pthread_mutex_unlock(&bank_mutex);
  }

  pthread_exit(NULL);
}

void * withdraw(void * tid)
{
  int i = 0;
  for(i = 0; i < NUM_WITHDRAWLS; i++)
  {
    pthread_mutex_lock(&bank_mutex);

    //Withdraw between 1 and 100 dollars from the account.
    //Ensure that the account is never overdrawn
    int withdrawl_amount = rand()%100 + 1;
      
    while(withdrawl_amount > account_balance)
    {
      pthread_cond_wait(&zero_balance_cv, &bank_mutex);
    }

    //Withdraw funds from the bank.
    account_balance -= withdrawl_amount;

    pthread_mutex_unlock(&bank_mutex);
  }
  pthread_exit(NULL);

}

int main(int argc, char ** argv)
{
  account_balance = 0.0;

  printf("The starting balance is $%.2lf\n", account_balance);

  pthread_attr_t attr;

  pthread_attr_init(&attr);  //Initialize thread attributes.

  //What happens when you change the scheduling policy?  Try 
  //SCHED_FIFO and SCHED_OTHER.  Read the man pages and online and
  //explain what these do.
  pthread_attr_setschedpolicy(&attr, SCHED_RR);  //Set scheduling policy as 
                                                 //round robin.

  pthread_mutex_init(&bank_mutex, NULL);

  pthread_attr_init(&attr);

  pthread_t deposits[NUM_DEPOSIT_THREADS];
  pthread_t withdrawls[NUM_WITHDRAWL_THREADS];

  int i;
  for(i = 0; i <  NUM_DEPOSIT_THREADS; i++)
    pthread_create(&deposits[i], &attr, deposit, (void *) i);

  for(i = 0; i <  NUM_WITHDRAWL_THREADS; i++)
    pthread_create(&withdrawls[i], &attr, withdraw, 
      (void *) i+NUM_DEPOSIT_THREADS);

  for(i = 0; i <  NUM_DEPOSIT_THREADS; i++)
    pthread_join(deposits[i], NULL);

  for(i = 0; i <  NUM_WITHDRAWL_THREADS; i++)
    pthread_join(withdrawls[i], NULL);

  printf("The remaining balance is $%.2lf\n", account_balance);

  pthread_mutex_destroy(&bank_mutex);
  pthread_cond_destroy(&zero_balance_cv);
  pthread_attr_destroy(&attr);
  return 0;
}