use std::sync::{Arc, Mutex};
use std::thread;
use std::time::Duration;

fn main() {
    // A shared bank account starting with $100
    let account_balance = Arc::new(Mutex::new(100));

    // Thread A: Attempts to withdraw $80
    let balance_clone1 = Arc::clone(&account_balance);
    let handle1 = thread::spawn(move || {
        // 1. CHECK: Lock the account just to check the balance
        let current_balance = *balance_clone1.lock().unwrap();
        
        if current_balance >= 80 {
            println!("Thread A: Balance is ${}. Approval granted!", current_balance);
            
            // Simulate a tiny delay (e.g., network latency or CPU context switch)
            // This gives Thread B time to sneak in and check the balance
            thread::sleep(Duration::from_millis(5));
            
            // 2. ACT: Lock again to deduct the money
            let mut balance_guard = balance_clone1.lock().unwrap();
            *balance_guard -= 80;
            println!("Thread A: Successfully withdrew $80.");
        } else {
            println!("Thread A: Declined. Insufficient funds.");
        }
    });

    // Thread B: Simultaneously attempts to withdraw $80
    let balance_clone2 = Arc::clone(&account_balance);
    let handle2 = thread::spawn(move || {
        // 1. CHECK: Lock the account just to check the balance
        let current_balance = *balance_clone2.lock().unwrap();
        
        if current_balance >= 80 {
            println!("Thread B: Balance is ${}. Approval granted!", current_balance);
            
            // Simulate a tiny delay (e.g., network latency or CPU context switch)
            // This gives Thread B time to sneak in and check the balance
            thread::sleep(Duration::from_millis(5));
            
            // 2. ACT: Lock again to deduct the money
            let mut balance_guard = balance_clone2.lock().unwrap();
            *balance_guard -= 80;
            println!("Thread B: Successfully withdrew $80.");
        } else {
            println!("Thread B: Declined. Insufficient funds.");
        }
    });

    handle1.join().unwrap();
    handle2.join().unwrap();

    // Final result
    println!("Final Bank Balance: ${}", *account_balance.lock().unwrap());
}