/* 
 * File:   main.c
 * Author: rshe005
 *
 * Simplistic Dining Philosophers program with a pseudo
 * simultaneous wait on the forks.
 *
 * Created on 12 August 2009, 3:41 PM
 * Revised 18 August 2015
 */

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

#define NUM_PHILOSOPHERS 5;

typedef struct philos {
    char *status;
    pthread_mutex_t *right, *left;
} Philosopher;

void philosopherSetup(Philosopher *philosopher, pthread_mutex_t *left, pthread_mutex_t *right) {
    philosopher->left = left;
    philosopher->right = right;
}

void *philosopherRun(void *phil) {
    Philosopher *philosopher = phil;
    while (true) {
        philosopher->status = "thinking";
        philosopher->status = "waiting";
        bool both = false;
        do {
            if (pthread_mutex_lock(philosopher->left) != 0)
                fprintf(stderr, "Left lock error.\n");
            int right_lock_result = pthread_mutex_trylock(philosopher->right);
            switch (right_lock_result) {
                case 0:
                    both = true;
                    break;
                case EBUSY:
                    pthread_mutex_unlock(philosopher->left); // try again
                    both = false;
                    break;
                default:
                    fprintf(stderr, "Right lock error\n.");
            }
        } while (!both);
        printf("."); // this won't appear if blocked
        philosopher->status = "eating";
        sleep(1);
        pthread_mutex_unlock(philosopher->left);
        pthread_mutex_unlock(philosopher->right);
    }
}

/*
 * Starts all of the philosopher threads and reports on their progress.
 */
int main(int argc, char** argv) {
    int number = NUM_PHILOSOPHERS;
    if (argc > 1) {
        number = atoi(argv[1]);
    }
    printf("Creating %d philosophers.\n", number);
    Philosopher philosophers[number];
    pthread_mutex_t forks[number];
    pthread_t threads[number];

    int i;
    for (i = 0; i < number; i++) { // create the locks
        if (pthread_mutex_init(&forks[i], NULL)) {
            fprintf(stderr, "Unable to create locks.\n");
            return (EXIT_FAILURE);
        }
    }
    for (i = 0; i < number; i++) { // setup the philosophers
        philosopherSetup(&philosophers[i], &forks[i], &forks[(i + 1) % number]);
    }

    for (i = 0; i < number; i++) { // create and start the threads
        pthread_create(&threads[number], NULL, philosopherRun, &philosophers[i]);
    }

    while (true) {
        sleep(1);
        for (i = 0; i < number; i++) {
            usleep(1000);
            printf("%d: %-8s ", i, philosophers[i].status);
        }
        printf("\n");
    }

    return (EXIT_SUCCESS);
}