#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#define NUM_ACCOUNTS 8
#define NUM_TELLERS 128
#define TRANSACTIONS_PER_TELLER 100

// Monetary value in cents
typedef long currency;

void printf_currency(currency c) {
  if (c < 0) {
    c = -c;
    printf("-");
  }
  printf("$%ld.%.2ld", c / 100, c % 100);
}

// Accounts (shared resource)
typedef struct account {
  int account_id;
  currency balance;
  int transaction_count;
} account;

// Global account array
account accounts[NUM_ACCOUNTS];

// Teller threads

pthread_t tellers[NUM_TELLERS];

typedef struct teller_args {
  int teller_id;
  currency total;
} teller_args;

void *teller_thread(void *arg) {
  teller_args *args = (teller_args *)arg;
  int id = args->teller_id;
  currency total = 0;

  unsigned int seed = time(NULL) + pthread_self();
  for (int i = 0; i < TRANSACTIONS_PER_TELLER; i++) {
    printf("Thread %u: ", id);
    // Deposit or withdraw random currency amount from $0 to $1000
    currency random_amount = ((long)rand_r(&seed)) % 100000;
    if (rand_r(&seed) % 2) {
      printf("Withdrawing ");
      printf_currency(random_amount);
      random_amount = -random_amount;
    } else {
      printf("Depositing ");
      printf_currency(random_amount);
    }

    int random_acc = rand_r(&seed) % NUM_ACCOUNTS;
    accounts[random_acc].balance += random_amount;
    accounts[random_acc].transaction_count++;

    printf(" into account %u\n", random_acc);

    total += random_amount;
  }

  args->total = total;
  return NULL;
}

int main() {
  // Initialize all accounts with 0 balance
  for (int i = 0; i < NUM_ACCOUNTS; i++) {
    accounts[i] = (account){.account_id = i, .balance = 0};
  }

  // Initialize tellers
  teller_args args[NUM_TELLERS];
  for (int i = 0; i < NUM_TELLERS; i++) {
    args[i] = (teller_args){.teller_id = i};
    pthread_create(&tellers[i], NULL, teller_thread, &args[i]);
  }

  // Wait for all threads to finish
  currency expected_total = 0;
  for (int i = 0; i < NUM_TELLERS; i++) {
    pthread_join(tellers[i], NULL);
    expected_total += args[i].total;
  }

  currency actual_total = 0;
  for (int i = 0; i < NUM_ACCOUNTS; i++) {
    actual_total += accounts[i].balance;
  }

  printf("Total balance: ");
  printf_currency(actual_total);
  printf("\nExpected total: ");
  printf_currency(expected_total);
  printf("\n");

  return 0;
}