Concurrence

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

// Basic thread creation
fn basic_threads() {
    let handle = thread::spawn(|| {
        for i in 1..10 {
            println!("hi number {} from the spawned thread!", i);
            thread::sleep(Duration::from_millis(1));
        }
    });

    handle.join().unwrap();

    for i in 1..5 {
        println!("hi number {} from the main thread!", i);
        thread::sleep(Duration::from_millis(1));
    }
}

// Moving data into threads
fn move_data() {
    let v = vec![1, 2, 3];

    let handle = thread::spawn(move || {
        println!("Here's a vector: {:?}", v);
    });

    handle.join().unwrap();
}

// Message passing with channels
fn message_passing() {
    let (tx, rx) = mpsc::channel();

    thread::spawn(move || {
        let val = String::from("hi");
        tx.send(val).unwrap();
        // println!("val is {}", val); // Error: val was moved
    });

    let received = rx.recv().unwrap();
    println!("Got: {}", received);
}

// Multiple producers
fn multiple_producers() {
    let (tx, rx) = mpsc::channel();
    let tx2 = tx.clone();

    thread::spawn(move || {
        let vals = vec![
            String::from("hi"),
            String::from("from"),
            String::from("the"),
            String::from("thread"),
        ];

        for val in vals {
            tx.send(val).unwrap();
            thread::sleep(Duration::from_millis(100));
        }
    });

    thread::spawn(move || {
        let vals = vec![
            String::from("more"),
            String::from("messages"),
            String::from("for"),
            String::from("you"),
        ];

        for val in vals {
            tx2.send(val).unwrap();
            thread::sleep(Duration::from_millis(100));
        }
    });

    for received in rx {
        println!("Got: {}", received);
    }
}

// Shared state with Mutex
fn shared_state() {
    let counter = Arc::new(Mutex::new(0));
    let mut handles = vec![];

    for _ in 0..10 {
        let counter = Arc::clone(&counter);
        let handle = thread::spawn(move || {
            let mut num = counter.lock().unwrap();
            *num += 1;
        });
        handles.push(handle);
    }

    for handle in handles {
        handle.join().unwrap();
    }

    println!("Result: {}", *counter.lock().unwrap());
}

// Read-write lock
use std::sync::RwLock;

fn read_write_lock() {
    let lock = Arc::new(RwLock::new(5));
    let lock_clone = Arc::clone(&lock);

    let handle = thread::spawn(move || {
        let read_guard = lock_clone.read().unwrap();
        println!("Read value: {}", *read_guard);
        // Multiple readers can hold the lock simultaneously
    });

    {
        let write_guard = lock.write().unwrap();
        *write_guard += 1;
        println!("Modified value to: {}", *write_guard);
    } // Write lock is released here

    handle.join().unwrap();
}

// Async programming (experimental in stable Rust)
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

// Simple async function
async fn hello_world() {
    println!("Hello, world!");
}

// Async function with await
async fn async_example() -> String {
    hello_world().await; // Wait for hello_world to complete
    String::from("Done!")
}

fn main() {
    // Basic threads
    println!("=== Basic Threads ===");
    basic_threads();

    // Move data
    println!("\n=== Move Data ===");
    move_data();

    // Message passing
    println!("\n=== Message Passing ===");
    message_passing();

    // Multiple producers
    println!("\n=== Multiple Producers ===");
    multiple_producers();

    // Shared state
    println!("\n=== Shared State ===");
    shared_state();

    // Read-write lock
    println!("\n=== Read-Write Lock ===");
    read_write_lock();

    // Note: Async example requires async runtime like tokio
    // println!("\n=== Async Example ===");
    // let future = async_example();
    // This would need an async runtime to execute
}