/* t2.c
   synchronize threads through mutex and conditional variable
   To compile use: gcc -o t2 t2.c -lpthread
   SLMAAN ALBEADY
   3.2.2 Conditional Variable
*/
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#define RED   "\x1B[31m" //just color for a new word "again"
#define RESET "\x1B[0m"

void 	hello();    // define two routines called by threads
void 	world();
void    again();    //new*/ theard
/* global variable shared by threads */
pthread_mutex_t 	mutex;  		// mutex
pthread_cond_t 		done_hello , done_world ; 	// conditional variable //new*/ done for second word
int 			    done = 0;      	// testing variable

int main (int argc, char *argv[]){
    pthread_t 	tid_hello, // thread id
    		    tid_world,
                tid_again;    //new*/
    /*  initialization on mutex and cond variable  */
    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&done_hello, NULL);
    pthread_cond_init(&done_world, NULL);                   //new*/ to enter a new thread


    pthread_create(&tid_hello, NULL, (void*)&hello, NULL); //thread creation
    pthread_create(&tid_world, NULL, (void*)&world, NULL); //thread creation
    pthread_create(&tid_again, NULL, (void*)&again, NULL); //new*/ thread creation again

    /* main waits for the two threads to finish */
    pthread_join(tid_hello, NULL);
    pthread_join(tid_world, NULL);
    pthread_join(tid_again, NULL);     //new*/

    printf("\n");
    return 0;
}

void hello() {
    pthread_mutex_lock  (&mutex);
    printf              ("Hello ");
    fflush              (stdout); 	// flush buffer to allow instant print out
    done = 1;
    pthread_cond_signal (&done_hello);	// signal world() thread
    pthread_mutex_unlock(&mutex);	// unlocks mutex to allow world to print
    return ;
}


void world() {
    pthread_mutex_lock(&mutex);

    /* world thread waits until done == 1. */
    while(done == 0) {
    	pthread_cond_wait   (&done_hello, &mutex);
    }

    printf                  ("World");
    fflush                  (stdout);
    usleep(1);
    done=2;      //new*/  to wait a world finish
    pthread_cond_signal     (&done_world);       //new*/
    pthread_cond_broadcast  (&done_hello);       //new*/  unblock all threads currently blocked on the specified condition variable cond.

    pthread_mutex_unlock    (&mutex); // unlocks mutex

    return ;
}
//|  ALL NEW  : new thread for print therd word "Again" |*/
void again(){
    pthread_mutex_lock(&mutex);
    /* again thread waits until done == 2. */
    while(done == 0) {
    	pthread_cond_wait(&done_hello, &mutex);
    }
    while(done == 1) {
    	pthread_cond_wait(&done_world, &mutex);
        usleep(1);
    }

    printf              (RED" Again!"RESET);
    fflush              (stdout);
    pthread_mutex_unlock(&mutex); // unlocks mutex
    return ; //NULL
}
/*
salbeady@penguin:~/os$ gcc -o t2 t2.c -lpthread
salbeady@penguin:~/os$ ./t2
Hello World Again!
salbeady@penguin:~/os$ ./t2
Hello World Again!
*/