#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h> 
int shared_data = 0; 
int reader_count = 0;
int waiting_reader_count = 0;
int writer_count = 0;
pthread_mutex_t mutex_lock; 
pthread_cond_t readers_cond; 
pthread_cond_t writers_cond; 

void *reader(void *not_used) {
    while (1) {
        // ACQUIRE
        pthread_mutex_lock(&mutex_lock);
        waiting_reader_count++;
        while (writer_count > 0) {
            pthread_cond_wait(&readers_cond, &mutex_lock);
        }
        waiting_reader_count--;
        reader_count++;
        assert(writer_count == 0);
        pthread_mutex_unlock(&mutex_lock);
        // USE (DO_TASK)
        usleep(100000); 
        printf("I read\n"); 
        // RELEASE
        pthread_mutex_lock(&mutex_lock);
        reader_count--;
        assert(writer_count == 0);
        if (reader_count == 0) {
            pthread_cond_signal(&writers_cond); 
        }
        pthread_mutex_unlock(&mutex_lock);
        usleep(1000000); 
    }
    return NULL;
}
void *writer(void *not_used) {
    while (1) {
        // ACQUIRE
        pthread_mutex_lock(&mutex_lock);
        while (reader_count > 0 || waiting_reader_count > 0 ||
               writer_count > 0) {
            pthread_cond_wait(&writers_cond, &mutex_lock);
        }
        assert(reader_count == 0 && waiting_reader_count == 0 &&
               writer_count == 0);
        writer_count++;
        pthread_mutex_unlock(&mutex_lock);
        // USE (DO_TASK)
        shared_data++;
        usleep(200000); 
        printf("I wrote\n"); 
        // RELEASE
        pthread_mutex_lock(&mutex_lock);
        writer_count--;
        assert(reader_count == 0 && writer_count == 0);
        if (waiting_reader_count > 0) {
            pthread_cond_broadcast(&readers_cond); 
        } else {
            pthread_cond_signal(&writers_cond); 
        }
        pthread_mutex_unlock(&mutex_lock);
        usleep(100000); 
    }
    return NULL;
}
#define NUM_READERS 5
#define NUM_WRITERS 2
int main() {
    pthread_t readers[NUM_READERS];
    pthread_t writers[NUM_WRITERS];
    int reader_ids[NUM_READERS];
    int writer_ids[NUM_WRITERS];
    pthread_mutex_init(&mutex_lock, NULL);
    pthread_cond_init(&readers_cond, NULL);
    pthread_cond_init(&writers_cond, NULL);
    for (int i = 0; i < NUM_READERS; i++) {
        reader_ids[i] = i + 1;
        if (pthread_create(&readers[i], NULL, reader, &reader_ids[i]) != 0) {
            return 1;
        }
    }
    for (int i = 0; i < NUM_WRITERS; i++) {
        writer_ids[i] = i + 1;
        if (pthread_create(&writers[i], NULL, writer, &writer_ids[i]) != 0) {
            return 1;
        }
    }
    for (int i = 0; i < NUM_READERS; i++) {
        pthread_join(readers[i], NULL);
    }
    for (int i = 0; i < NUM_WRITERS; i++) {
        pthread_join(writers[i], NULL);
    }
    pthread_mutex_destroy(&mutex_lock);
    pthread_cond_destroy(&readers_cond);
    pthread_cond_destroy(&writers_cond);
    return 0;
}