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

#define NUM_THREADS 4
#define OPS_PER_THREAD 5

int balance = 1000;                      // shared resource
pthread_mutex_t balance_mutex;

void *bank_worker(void *arg) {
    int id = *(int *)arg;

    for (int i = 0; i < OPS_PER_THREAD; i++) {
        int amount = (rand() % 400) + 100; // 100–499
        int is_deposit = rand() % 2;

        pthread_mutex_lock(&balance_mutex);

        if (is_deposit) {
            balance += amount;
            printf("[Thread %d] Deposit %d | Balance = %d\n",
                   id, amount, balance);
        } else {
            if (balance >= amount) {
                balance -= amount;
                printf("[Thread %d] Withdraw %d | Balance = %d\n",
                       id, amount, balance);
            } else {
                printf("[Thread %d] Withdraw %d FAILED (insufficient funds) | Balance = %d\n",
                       id, amount, balance);
            }
        }

        pthread_mutex_unlock(&balance_mutex);

        usleep(100000);
    }
    return NULL;
}

int main() {
    pthread_t threads[NUM_THREADS];
    int ids[NUM_THREADS];

    srand((unsigned int)time(NULL));
    pthread_mutex_init(&balance_mutex, NULL);

    printf("Initial balance = %d\n\n", balance);

    for (int i = 0; i < NUM_THREADS; i++) {
        ids[i] = i;
        pthread_create(&threads[i], NULL, bank_worker, &ids[i]);
    }

    for (int i = 0; i < NUM_THREADS; i++)
        pthread_join(threads[i], NULL);

    printf("\nFinal balance = %d\n", balance);

    pthread_mutex_destroy(&balance_mutex);
    return 0;
}