#include <stdio.h>
#include "thread.h"			/* thread interface */
#include "semaphore.h"		/* semaphore interface */
#include "queue.h"			/* queue interface */

/* the thread functions */
int task1(void);
int task2(void);
int task3(void);
int task4(void);

/* the semaphore */
sema4 a_semaphore;

int main(int argc, char **argv)
{
	int i;
	/* init the semaphore */
	a_semaphore = (sema4) sema4_new(1);

	/* create threads, check for errors */
	if(thread_init() < 0) {
		fprintf(stderr,"Error initializing threads.\n");
		exit(1);
	}
	if(thread_create(task1, 1) < 0) {
		fprintf(stderr,"Error starting task 1.\n");
		exit(1);
	}
	if(thread_create(task2, 2) < 0) {
		fprintf(stderr,"Error starting task 2.\n");
		exit(1);
	}
	if(thread_create(task3, 3) < 0) {
		fprintf(stderr,"Error starting task 3.\n");
		exit(1);
	}
	if(thread_create(task4, 4) < 0) {
		fprintf(stderr,"Error starting task 4.\n");
		exit(1);
	}
	while(1) {
		printf("MAIN THREAD\n");
		for(i=0; i<9000000; i++) ;
	}
	thread_exit();
	return 0;
}

//task implementations
int task1(void)
{
	int i,j,k,x;
	while(1){
		printf("\tTHREAD 1 - start of loop\n", i);
		//delay loop
		for(j=0; j<1000; j++);
		printf("\tTHREAD 1 - calling P\n");
		sema4_p(a_semaphore);
		printf("\tTHREAD 1 - inside critical section\n");
		//delay loop
		for(x=0; x<100000000; x++); 
		printf("\tTHREAD 1 - leaving the critical section\n");
		sema4_v(a_semaphore);			
	}
	thread_exit();
}

int task2(void)
{
	int i,j,k,x;
	while(1) {
		printf("\t\tTHREAD 2 - start of loop\n", i);
		//delay loop
		for(j=0; j<1000; j++);
		printf("\t\tTHREAD 2 - calling P\n");
		sema4_p(a_semaphore);
		printf("\t\tTHREAD 2 - inside critical section\n");
		//delay loop
		for(x=0; x<100000000; x++);
		printf("\t\tTHREAD 2 - leaving the critical section\n");
		sema4_v(a_semaphore);
	}
	thread_exit();
}

int task3(void)
{
	int i,j,k,x;
	while(1) {
		printf("\t\t\tTHREAD 3 - start of loop\n");
		//delay loop
		for(j=0; j<1000; j++) ;
		printf("\t\t\tTHREAD 3 - calling P\n");
		sema4_p(a_semaphore);
		printf("\t\t\tTHREAD 3 - inside critical section\n");
		//delay loop
		for(x=0; x<100000000; x++);
		printf("\t\t\tTHREAD 3 - leaving the critical section\n");
		sema4_v(a_semaphore);
	}
	thread_exit();
}

int task4(void)
{
	int i,j,k,x;
	while(1) {
		printf("\t\t\t\tTHREAD 4 - start of loop\n", i);
		//delay loop
		for(j=0; j<1000; j++);
		printf("\t\t\t\tTHREAD 4 - calling P\n");
		sema4_p(a_semaphore);
		printf("\t\t\t\tTHREAD 4 - inside critical section\n");
		//delay loop
		for(x=0; x<100000000; x++);
		printf("\t\t\t\tTHREAD 4 - leaving the critical section\n");
		sema4_v(a_semaphore);	
	}
	thread_exit();
}