/**
 * A simple consumer-producer problem without synchronization.
 * This program will generate incorrect results.
 * This is to demonstrate the potential issues with multiple threads/processes.
 */

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

#define false 0
#define true 1

#include "buffer.h"
#define BFSIZE 5

void * producer();
void * consumer();

int count;    // number of items in the buffer
int in;       // index to the next free position
int out;      // index to the next full position
int order = 0;// total number of products so far

struct product_t  * buffer[BFSIZE];

int main(int argc, char *argv[])   {

  pthread_t tid[2]; /* the thread identifier */
  pthread_attr_t attr; /* set of attributes for the thread */

  // buffer is initially empty
  count = 0;
  in = 0;
  out = 0;

  /* create the producer thread */
  pthread_create(&tid[0], NULL, producer, NULL);
  /* create the consumer thread */
  pthread_create(&tid[1], NULL, consumer, NULL);

  /* now wait for the thread to exit */
  pthread_join(tid[0],NULL);
  pthread_join(tid[1],NULL);

  return 0;
}

void * producer() {
  struct product_t * item;
  int i = 0;
  while (i < 100) {  // repeat
    item = make_item();
    insert_item(item);
    i ++;
  }
}

void insert_item(struct product_t * item) { 

  while (count >= BFSIZE); // do nothing -- no free buffers

  printf("producer: count in p %d\n", count);
  fflush(stdout);

  // now we have a free slot, add an item to the buffer
  ++count;
  buffer[in] = item;
  in = (in + 1) % BFSIZE;
}

void * consumer() {
  struct product_t * item;
  int i = 0;
  while (i < 100) {  // repeat
    item = remove_item();
    consume_item(item);
    i ++;
  }
}

struct product_t * remove_item() { 
  struct  product_t * item;
  while (count == 0); // do nothing -- nothing to consume

  printf("   -- consumer: count in c %d\n", count);
  fflush(stdout);

  // remove an item from the buffer
  --count;
  item = buffer[out];
  out = (out + 1) % BFSIZE;
  return item;
}

void consume_item(struct product_t *item) {

  printf("   -- consumer: product name %s\n", item->name);
  printf("   -- consumer: product value %10.2f\n", item->value);
  fflush(stdout);
}

struct product_t * make_item() {
  
  struct product_t * an_item = (struct product_t *)malloc(sizeof(struct product_t));
  char number[32];

  strcpy(an_item->name, "Name ");
  sprintf(number, "%d", order);
  strcat(an_item->name, number);
  order ++;
  an_item->value = 100;

  return an_item;
}