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

#define BUFFER_SIZE 5
#define NUM_TASKS   20

int buffer[BUFFER_SIZE];
int in = 0, out = 0, count = 0;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t not_empty = PTHREAD_COND_INITIALIZER;
pthread_cond_t not_full  = PTHREAD_COND_INITIALIZER;

void *producer(void *arg) {
    for (int task = 1; task <= NUM_TASKS; task++) {
        pthread_mutex_lock(&mutex);

        while (count == BUFFER_SIZE)      // buffer full
            pthread_cond_wait(&not_full, &mutex);

        // produce
        buffer[in] = task;
        printf("[Producer] Produced task %d at index %d\n", task, in);
        in = (in + 1) % BUFFER_SIZE;
        count++;

        pthread_cond_signal(&not_empty);
        pthread_mutex_unlock(&mutex);

        usleep(100000); // just to see interleaving
    }

    // send a special task = -1 to indicate completion
    pthread_mutex_lock(&mutex);
    while (count == BUFFER_SIZE)
        pthread_cond_wait(&not_full, &mutex);
    buffer[in] = -1;
    in = (in + 1) % BUFFER_SIZE;
    count++;
    pthread_cond_signal(&not_empty);
    pthread_mutex_unlock(&mutex);

    return NULL;
}

void *consumer(void *arg) {
    while (1) {
        pthread_mutex_lock(&mutex);

        while (count == 0)       // buffer empty
            pthread_cond_wait(&not_empty, &mutex);

        int task = buffer[out];
        out = (out + 1) % BUFFER_SIZE;
        count--;

        pthread_cond_signal(&not_full);
        pthread_mutex_unlock(&mutex);

        if (task == -1) {
            printf("[Consumer] Received termination signal. Exiting.\n");
            break;
        }

        printf("[Consumer] Processing task %d\n", task);
        usleep(150000);
    }
    return NULL;
}

int main() {
    pthread_t prod_thread, cons_thread;

    pthread_create(&prod_thread, NULL, producer, NULL);
    pthread_create(&cons_thread, NULL, consumer, NULL);

    pthread_join(prod_thread, NULL);
    pthread_join(cons_thread, NULL);

    pthread_mutex_destroy(&mutex);
    pthread_cond_destroy(&not_empty);
    pthread_cond_destroy(&not_full);

    return 0;
}