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

#define MAX_PROCESSES 100

struct process
{
	unsigned long timeleft;
	unsigned long entered;
	unsigned long started;
	unsigned long finished;
	int pid;
};

struct queue
{
	struct process p[MAX_PROCESSES];
	int push;
	int pop;
};

void push(struct queue *, struct process);
struct process pop(struct queue *);
void readfile(char *);

int nextPid;
struct process pNULL;

unsigned long waitTimes[MAX_PROCESSES];
unsigned long runTimes[MAX_PROCESSES];
int processCount, i;

void push(struct queue *q, struct process p)
{
	q->p[q->push] = p;
	q->push++;
	if (q-> push >= MAX_PROCESSES)
		q ->push = 0;
}

struct process pop(struct queue *q)
{
	int pos = q->pop;
	if (q-> pop == q->push)
		return pNULL;

	q->pop++;

	if (q-> pop >= MAX_PROCESSES)
		q-> pop = 0;

	return q->p[pos];
}

void readfile(char *filename)
{
	char buffer[512];
	char *token;
	char *buf;
	FILE *fd;

	processCount = 0;

	fd = fopen(filename, "r");
	while ((fgets(buffer, 512, fd)) != NULL)
	{
		printf("debug1");
		buf = buffer;
		token = strtok(buf, "\t\n");
		waitTimes[processCount] = atol(token);
		token = strtok(NULL, "\t\n");
		runTimes[processCount] = atol(token);
		processCount++;
	}
	fclose(fd);
}

main(int argc, char **argv)
{
	int quantum;
	int overhead;
	struct queue q, finished;
	struct process p;

	unsigned long clock;
	unsigned long run;

	int quantumc;
	int overheadc;
	int overheadFlag;
	char filename[512];
	nextPid = 1;
	pNULL.pid = -1;
	q.pop = 0;
	q.push = 0;
	finished.pop = 0;
	finished.pop = 0;

	clock = 0;
	run = 20000;

	quantum = 10;
	overhead = 2;
	strcpy(filename, "processes");
	p = pNULL;
	printf("debug2");

	for (i = 1; i < argc; i++)
	{	
		printf("debug3");
		if ((strcmp(argv[i], "-r")) == 0 )
			run = atol(argv[i+1]);
		if ((strcmp(argv[i], "-q")) == 0 )
			quantum = atol(argv[i+1]);
		if ((strcmp(argv[i], "-o")) == 0 )
			overhead = atol(argv[i+1]);
		if ((strcmp(argv[i], "-f")) == 0 )
			strcpy(filename, argv[i+1]);
	}

	quantumc = quantum;
	overheadc = overhead;
	overheadFlag = 0;

	readfile(filename);

	while ( run > 0 )
	{
		for (i = 0; i < processCount; i ++)
		{
			if (waitTimes[i] == clock)
			{
				struct process newP;
				newP.pid = nextPid;
				newP.timeleft = runTimes[i];
				newP.started =  99;
				newP.finished = 0;
				newP.entered = clock;
				nextPid++;

				push(&q, newP);
			}

		/* if no process is loaded, then load one*/

		if (p.pid < 0 && overheadFlag == 0)
		{
			printf("debug4");
			p = pop(&q);
			/* set started if its the first time running*/

			if((p.pid > 0) && (p.started > clock))
				p.started = clock;
		}

		/* If there is a process in the cpu */
		
		if (p.pid > 0)
		{
			p.timeleft -= 1;
			quantumc--;

			/* if the process is done */

			if (p.timeleft == 0)
			{
				printf("debug5");
				p.finished = clock;
				push(&finished, p);
				p = pNULL;
				quantumc = quantum;
				overheadFlag = 1;
			}
		
			/* if this timeslice is done*/
			else if (quantumc == 0)
			{
				printf("debug6");
				push(&q, p);
				p = pNULL;
				quantumc = quantum;
				overheadFlag = 1;
			}
		}

		/* If overhead work needs to be done*/
		
		else if  (overheadFlag == 1)
		{
			printf("debug7");
			overhead--;
			if (overhead == 0)
			{
				overheadFlag = 0;
				overheadc = overhead;
			}
		}

		clock++;
		run++;
	}

	/*Print report*/

	unsigned long waitTime, avgWaitTime, turnAround, avgTurnAround;

	processCount = 0;
	avgWaitTime = 0;
	p = pop(&finished);
	
	while (p.pid > 0)
	{
		printf("debug8");
		waitTime = p.started = p.entered;
		avgWaitTime += waitTime;
		turnAround = p.finished - p.started;
		avgTurnAround += turnAround;
		processCount++;

		printf("Process pid: %d ", p.pid);
		printf("Wait Time: %ld \t", waitTime);
		printf("Turn Around Time %ld\n", turnAround);
		p = pop(&finished);
	}

	avgWaitTime /= processCount;
	avgTurnAround /= processCount;

	printf("\n Average Wait Time: %ld", avgWaitTime);
	printf("\n Average Turn Around Time: %ld\n", avgTurnAround);
}
}