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

/*
 * Default values for parameterized variables.
 */
static int num_accts = 1024;   // number of bank accounts
static int num_trans = 10000;  // number of transactions
static int think_time = 50;    // amount of "thinking time"
static int num_threads = 1;
/*
 * Struct representing a single bank account
 */
struct acct_t {
    int bal;
};
void *transact(void *dummy);
/*
 * Pointer to accounts
 */
struct acct_t *accts;

/*
 * Method to perform a number of transactions.
 * Parameter "dummy" is not used.
 */
void *transact(void *dummy)
{
    int i;
    for (i = 0; i < num_trans; i++) {
        // pick two random accounts
        int acct_id_from = rand() % num_accts;
        int acct_id_to = rand() % num_accts;
        // pick a random amount
        int amt = rand() % 100;

        // try to transfer the money
        if (accts[acct_id_from].bal > amt) {
            accts[acct_id_from].bal -= amt;
            accts[acct_id_to].bal += amt;


            amt *= think_time; while (amt--) ;
        }


    }
}

int main(int argc, char **argv)
{

    // make sure the number of arguments is odd (including the program name)
    if (!(argc == 1 || argc == 3 || argc == 5 || argc == 7 || argc == 9)) {
        fprintf(stderr, "usage: %s [-a <accts>] [-i <transactions>] [-t <think-time>][-n <thread-numbers>]\n", argv[0]);
        exit(-1);
    }

    // look at each runtime argument and see which value it's attempting to set
    int i;
    for (i = 1; i < argc; i++) {
        if (!strcmp(argv[i], "-a")) {
            num_accts = atoi(argv[i+1]);
            i++;
        } else if (!strcmp(argv[i], "-i")) {
            num_trans = atoi(argv[i+1]);
            i++;
        } else if (!strcmp(argv[i], "-t")) {
            think_time = atoi(argv[i+1]);
            i++;
        } else if (!strcmp(argv[i], "-n")) {
            num_threads = atoi(argv[i+1]);
            i++;
        }else {
            fprintf(stderr, "usage: %s [-a <accts>] [-i <transactions>] [-t <think-time>] [-n <thread-numbers>]\n", argv[0]);
            exit(-1);
        }
    }

    // display the parameters that will be used for this test run
    fprintf(stderr, "%s: -a %d -i %d -t %d -n %d\n", argv[0], num_accts, num_trans, think_time, num_threads);

    // initialize the random number generator
    srand(1);

    // create the bank accounts
    accts = (struct acct_t *)malloc(num_accts * sizeof(struct acct_t));

    // initialize the bank accounts' values and keep track of the total sum in all accounts
    int original_sum = 0;
    for (i = 0; i < num_accts; i++) {
        accts[i].bal = rand() % 1000;
        original_sum += accts[i].bal;
    }
    pthread_t mythreads[num_threads];
    for (i = 0; i < num_threads; i++)
    {
        pthread_create(&mythreads[i], NULL, transact, NULL);
    }

    for (i = 0; i < num_threads; i++)
    {
        pthread_join(mythreads[i], NULL);
    }
    // call the transact function to do the transfers
    //transact(NULL);

    // find the total sum of all accounts after the transfers are done
    int sum = 0;
    for (i = 0; i < num_accts; i++) {
        sum += accts[i].bal;
    }

    // if the sum is not equal to the original sum, then we had a race condition!!
    if (sum != original_sum) {
        fprintf(stderr, "ERROR! original_sum = %d, sum = %d\n", original_sum, sum);
    }
    else {
        fprintf(stderr, "Values are still consistent\n");
    }
    pthread_exit(NULL);
    return 0;
}