utls 0.5.4

use std::{
    sync::{atomic::AtomicBool, Arc, Mutex},
    thread::{self, JoinHandle},
    time::Duration,
};

/// A thread-safe wrapper that watches for changes in a value.
///
/// The `Watcher<T>` maintains a value of type `T` and monitors it for changes
/// in a separate thread. It provides thread-safe access to the value and
/// tracks whether the value has changed since the last check.
///
/// # Type Parameters
///
/// * `T`: The type of value to watch. Must implement `PartialEq`, `Send`, and have a static lifetime.
///
/// # Examples
///
/// ```
/// use std::sync::{Arc, Mutex, atomic::AtomicBool};
/// 
/// let shutdown = Arc::new(Mutex::new(AtomicBool::new(false)));
/// let watcher = Watcher::new(42, 100, shutdown.clone()); // (cloning is optional)
/// 
/// watcher.set_value(43);
/// assert!(watcher.has_changed());
/// ```
pub struct Watcher<T: PartialEq + Send + 'static> {
    value: Arc<Mutex<T>>,
    changed: Arc<Mutex<bool>>,
    handle: Option<JoinHandle<()>>,
    shutdown: Arc<Mutex<AtomicBool>>,
}

impl<T: PartialEq + Send + Clone + 'static> Watcher<T> {
    /// Creates a new `Watcher` instance.
    ///
    /// # Parameters
    ///
    /// * `initial_value`: The initial value to watch
    /// * `poll_delay_ms`: The delay between checks for changes in milliseconds
    /// * `shutdown`: An atomic boolean wrapped in Arc<Mutex> to control the watcher thread's lifecycle
    ///
    /// # Returns
    ///
    /// A new `Watcher` instance initialized with the given value
    pub fn new(initial_value: T, poll_delay_ms: u64, shutdown: Arc<Mutex<AtomicBool>>) -> Self {
        let value = Arc::new(Mutex::new(initial_value));
        let changed = Arc::new(Mutex::new(false));
        
        let value_watch = value.clone();
        let changed_watch = changed.clone();
        
        let shutdown = Arc::clone(&shutdown);
        let shutdown2 = Arc::clone(&shutdown);

        let handle = thread::spawn(move || {
            let mut last_val = value_watch.lock().unwrap().clone();
            loop {
                {
                    let lock = shutdown.lock().unwrap();
                    if lock.load(std::sync::atomic::Ordering::Relaxed) {
                        break;
                    }
                }
                let current_val = value_watch.lock().unwrap().clone();
                if current_val != last_val {
                    *changed_watch.lock().unwrap() = true;
                    last_val = current_val;
                }
                thread::sleep(Duration::from_millis(poll_delay_ms));
            }
        });

        Self {
            value,
            changed,
            handle: Some(handle),
            shutdown: shutdown2,
        }
    }

    /// Sets a new value to watch.
    ///
    /// If the new value is different from the current value,
    /// the changed flag will be set to true.
    ///
    /// # Parameters
    ///
    /// * `new_value`: The new value to set
    pub fn set_value(&self, new_value: T) {
        let mut value = self.value.lock().unwrap();
        if *value != new_value {
            *value = new_value;
            *self.changed.lock().unwrap() = true;
        }
    }    

    /// Retrieves the current value.
    ///
    /// # Returns
    ///
    /// A clone of the current value
    ///
    /// # Type Constraints
    ///
    /// The type T must implement Clone
    pub fn get_value(&self) -> T 
    where T: Clone {
        self.value.lock().unwrap().clone()
    }

    /// Checks if the value has changed since the last check or reset.
    ///
    /// # Returns
    ///
    /// `true` if the value has changed, `false` otherwise
    pub fn has_changed(&self) -> bool {
        *self.changed.lock().unwrap()
    }

    /// Resets the changed flag to false.
    pub fn reset_changed(&self) {
        *self.changed.lock().unwrap() = false;
    }
}

impl<T: PartialEq + Send + 'static> Watcher<T> {
    /// Signals the watching thread to shut down.
    ///
    /// This method sets the shutdown flag to true, which will cause
    /// the watching thread to terminate on its next iteration.
    pub fn shutdown_thread(&mut self) {
        self.shutdown.lock().unwrap().store(true, std::sync::atomic::Ordering::Relaxed);
    }
}

impl<T: PartialEq + Send + 'static> Drop for Watcher<T> {
    /// Implements the drop behavior for Watcher.
    ///
    /// This ensures that the watching thread is properly shut down
    /// and joined when the Watcher is dropped.
    fn drop(&mut self) {
        self.shutdown_thread();
        if let Some(handle) = self.handle.take() {
            handle.join().ok();
        }
    }
}