/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   semaphore_basics.c                                 :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: ruiferna <ruiferna@student.42porto.com>    +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2025/10/14 18:59:45 by ruiferna          #+#    #+#             */
/*   Updated: 2025/10/14 20:34:46 by ruiferna         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <semaphore.h>
#include <fcntl.h>

#define NUM_CHILDREN 5
#define NUM_RESOURCES 3
#define SEM_NAME "/philo_sem"

int main(int argc, char *argv[]) {
    sem_t *sem;
    pid_t pids[NUM_CHILDREN];
    int i;

	(void) argc;
	(void) argv;
    // Remove semaphore if it exists from previous run
    sem_unlink(SEM_NAME);

    // Create semaphore with 3 resources
    sem = sem_open(SEM_NAME, O_CREAT | O_EXCL, 0644, NUM_RESOURCES);
    if (sem == SEM_FAILED) {
        printf("Error creating semaphore\n");
        return 1;
    }
	
	i = 0;
    while (i < NUM_CHILDREN)
	{
        pids[i] = fork();
        if (pids[i] == -1) {
            printf("Error creating process\n");
            return 1;
        }
        if (pids[i] == 0) {
            // Child process
            int child_id = i + 1;
            sem_t *child_sem;

            // Open semaphore in child process
            child_sem = sem_open(SEM_NAME, 0);
            if (child_sem == SEM_FAILED) {
                printf("Child %d: Error opening semaphore\n", child_id);
                exit(1);
            }

            printf("Child %d (PID: %d): Waiting for resource...\n", child_id, getpid());
            
            // Acquire resource
            sem_wait(child_sem);
            printf("Child %d (PID: %d): Acquired resource\n", child_id, getpid());
            
            // Use resource for 500ms
            printf("Child %d (PID: %d): Using resource...\n", child_id, getpid());
            usleep(500000);
            
            // Release resource
            printf("Child %d (PID: %d): Released resource\n", child_id, getpid());
            sem_post(child_sem);

            sem_close(child_sem);
            exit(0);
        }
		i++;
    }

    // Use waitpid() to wait for all children to finish
	i = 0;
    while (i < NUM_CHILDREN)
	{
        waitpid(pids[i], NULL, 0);
		i++;
    }

    // Clean semaphone
    sem_close(sem);
    sem_unlink(SEM_NAME);

    return (0);
}