/* Modified from 
   https://gist.github.com/nvnmo/c6719faf72c37be7e20020f31be8cec3
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>

/* use the pthread flag with gcc to compile this code
   ~$ gcc -pthread producer_consumer.c -o producer_consumer
*/


pthread_t *producers;
pthread_t *consumers;

sem_t buf_mutex,empty_count,fill_count;

int *buf,buf_pos=-1,prod_count,con_count,buf_len;


int produce(pthread_t self){
  int i = 0;
  int p = 1 + rand()%40;
  while(!pthread_equal(*(producers+i),self) && i < prod_count){
    i++;
  }
  printf("Producer %d produced %d \n",i+1,p);
  return p;
}


void consume(int p,pthread_t self){
  int i = 0;
  while(!pthread_equal(*(consumers+i),self) && i < con_count){
    i++;
  }

  printf("Buffer:");
  for(i=0;i<=buf_pos;++i)
    printf("%d ",*(buf+i));
  printf("\nConsumer %d consumed %d \nCurrent buffer len: %d\n",i+1,p,buf_pos);
    
}


void* producer(void *args){

  while(1){
    int p = produce(pthread_self());
    sem_wait(&empty_count);
    sem_wait(&buf_mutex);
    ++buf_pos;            // critical section
    *(buf + buf_pos) = p; 
    sem_post(&buf_mutex);
    sem_post(&fill_count);
    sleep(1 + rand()%3);
  }
    
  return NULL;
}


void* consumer(void *args){
  int c;
  while(1){
    sem_wait(&fill_count);
    sem_wait(&buf_mutex);
    c = *(buf+buf_pos);
    consume(c,pthread_self());
    --buf_pos;
    sem_post(&buf_mutex);
    sem_post(&empty_count);
    sleep(1+rand()%5);
  }

  return NULL;
}

int main(void){
    
  int i,err;

  srand(time(NULL));

  sem_init(&buf_mutex,0,1);
  sem_init(&fill_count,0,0);

  printf("Enter the number of Producers:");
  scanf("%d",&prod_count);
  producers = (pthread_t*) malloc(prod_count*sizeof(pthread_t));

  printf("Enter the number of Consumers:");
  scanf("%d",&con_count);
  consumers = (pthread_t*) malloc(con_count*sizeof(pthread_t));

  printf("Enter buffer capacity:");
  scanf("%d",&buf_len);
  buf = (int*) malloc(buf_len*sizeof(int));

  sem_init(&empty_count,0,buf_len);

  for(i=0;i<prod_count;i++){
    err = pthread_create(producers+i,NULL,&producer,NULL);
    if(err != 0){
      printf("Error creating producer %d: %s\n",i+1,strerror(err));
    }else{
      printf("Successfully created producer %d\n",i+1);
    }
  }

  for(i=0;i<con_count;i++){
    err = pthread_create(consumers+i,NULL,&consumer,NULL);
    if(err != 0){
      printf("Error creating consumer %d: %s\n",i+1,strerror(err));
    }else{
      printf("Successfully created consumer %d\n",i+1);
    }
  }

  for(i=0;i<prod_count;i++){
    pthread_join(*(producers+i),NULL);
  }
  for(i=0;i<con_count;i++){
    pthread_join(*(consumers+i),NULL);
  }


  return 0;
}