// programa thread5.cpp
// Programa que sincroniza threads utilizando-se mutexes 
// Para compilá-lo utilise: g++ -o thread5 thread5.cpp -lpthread


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

void *thread_function(void *arg);
pthread_mutex_t work_mutex; /* proteção para:work_area e time_to_exit */

#define WORK_SIZE 1024
char work_area[WORK_SIZE];
int time_to_exit = 0;

int main() {
    int res;
    pthread_t a_thread;
    void *thread_result;
    res = pthread_mutex_init(&work_mutex, NULL);
    if (res != 0) {
        perror("Iniciação do Mutex falhou");
        exit(EXIT_FAILURE);
    }
    res = pthread_create(&a_thread, NULL, thread_function, NULL);
    if (res != 0) {
        perror("Criação da Thread falhou");
        exit(EXIT_FAILURE);
    }
    pthread_mutex_lock(&work_mutex);
  
    while(!time_to_exit) {
        printf("MAIN() --> Entre com algum texto. Entre com 'fim' para terminar\n");
        fgets(work_area, WORK_SIZE, stdin);
        pthread_mutex_unlock(&work_mutex);
        while(1) {
            pthread_mutex_lock(&work_mutex);
            if (work_area[0] != '\0') {
                pthread_mutex_unlock(&work_mutex);
                sleep(1);
            }
            else {
                break;
            }
        }
    }
    pthread_mutex_unlock(&work_mutex);
    printf("\nMAIN() --> Esperando a thread terminar...\n");
    res = pthread_join(a_thread, &thread_result);
    if (res != 0) {
        perror("Junção da Thread falhou");
        exit(EXIT_FAILURE);
    }
    printf("MAIN() --> Thread foi juntada com sucesso\n");
    pthread_mutex_destroy(&work_mutex);
    exit(EXIT_SUCCESS);
}

void *thread_function(void *arg) {
    sleep(1);
    pthread_mutex_lock(&work_mutex);
    while(strncmp("fim", work_area, 3) != 0) {
        printf("THREAD() --> Seu texto tem %d caracteres\n", strlen(work_area) -1);
        work_area[0] = '\0';
        pthread_mutex_unlock(&work_mutex);
        sleep(1);
        pthread_mutex_lock(&work_mutex);
        while (work_area[0] == '\0' ) {
            pthread_mutex_unlock(&work_mutex);
            sleep(1);
            pthread_mutex_lock(&work_mutex);
        }
    }
    time_to_exit = 1;
    work_area[0] = '\0';
    pthread_mutex_unlock(&work_mutex);
    pthread_exit(0);
}