feagi-structures 0.0.10

use crate::{define_index, FeagiDataError};
use std::collections::HashMap;
use std::fmt::Debug;
use std::sync::{Arc, Mutex};

define_index!(
    FeagiSignalIndex,
    u32,
    "A unique identifier for a subscription to a FeagiSignal"
);

/// Event signal system similar to Godot signals.
///
/// Allows subscribing callbacks that will be invoked when events are emitted.
/// Uses `FnMut` to allow closures to capture and modify external state via `Arc<Mutex<T>>`.
///
/// # Example with Shared State
/// ```
/// use std::sync::{Arc, Mutex};
/// use feagi_structures::FeagiSignal;
///
/// struct MyHandler {
///     count: i32,
/// }
///
/// impl MyHandler {
///     fn handle_event(&mut self, data: &String) {
///         self.count += 1;
///         println!("Event {}: {}", self.count, data);
///     }
/// }
///
/// let handler = Arc::new(Mutex::new(MyHandler { count: 0 }));
/// let mut signal = FeagiSignal::new();
///
/// // Clone Arc for the closure
/// let handler_clone = Arc::clone(&handler);
/// signal.connect(move |data| {
///     handler_clone.lock().unwrap().handle_event(data);
/// });
///
/// signal.emit(&"Hello".to_string());
/// assert_eq!(handler.lock().unwrap().count, 1);
/// ```
type SignalListener<T> = Box<dyn FnMut(&T) + Send>;

pub struct FeagiSignal<T> {
    listeners: HashMap<FeagiSignalIndex, SignalListener<T>>,
    next_index: u32,
}

impl<T> FeagiSignal<T> {
    /// Creates a new empty signal.
    pub fn new() -> Self {
        Self {
            listeners: HashMap::new(),
            next_index: 0,
        }
    }

    /// Connects a callback to this signal.
    ///
    /// The callback will be invoked whenever `emit()` is called.
    /// Returns a handle that can be used to disconnect later.
    ///
    /// # Example
    /// ```
    /// use feagi_structures::FeagiSignal;
    ///
    /// let mut signal = FeagiSignal::new();
    /// let handle = signal.connect(|value: &i32| {
    ///     println!("Received: {}", value);
    /// });
    ///
    /// signal.emit(&42);
    /// signal.disconnect(handle).unwrap();
    /// ```
    pub fn connect<F>(&mut self, f: F) -> FeagiSignalIndex
    // Will overflow after 4 billion subscriptions. Too bad!
    where
        F: FnMut(&T) + Send + 'static,
    {
        self.listeners.insert(self.next_index.into(), Box::new(f));
        self.next_index += 1;
        (self.next_index - 1).into()
    }

    /// Disconnects a previously connected callback.
    ///
    /// Returns an error if no callback with the given index exists.
    pub fn disconnect(&mut self, index: FeagiSignalIndex) -> Result<(), FeagiDataError> {
        if self.listeners.remove(&index).is_some() {
            return Ok(());
        }
        Err(FeagiDataError::BadParameters(format!(
            "No subscription found with identifier {}!",
            index
        )))
    }

    /// Emits an event to all connected callbacks.
    ///
    /// Callbacks are invoked in arbitrary order.
    pub fn emit(&mut self, value: &T) {
        for f in self.listeners.values_mut() {
            f(value);
        }
    }

    /// Helper to connect a closure that captures an `Arc<Mutex<S>>`.
    ///
    /// This is a convenience method for the common pattern of calling methods
    /// on shared mutable state from within the callback.
    ///
    /// # Example
    /// ```
    /// use std::sync::{Arc, Mutex};
    /// use feagi_structures::FeagiSignal;
    ///
    /// struct Counter { value: i32 }
    /// impl Counter {
    ///     fn increment(&mut self) { self.value += 1; }
    /// }
    ///
    /// let counter = Arc::new(Mutex::new(Counter { value: 0 }));
    /// let mut signal = FeagiSignal::new();
    ///
    /// signal.connect_with_shared_state(
    ///     Arc::clone(&counter),
    ///     |state, _event| state.increment()
    /// );
    ///
    /// signal.emit(&"event");
    /// assert_eq!(counter.lock().unwrap().value, 1);
    /// ```
    pub fn connect_with_shared_state<S, F>(
        &mut self,
        state: Arc<Mutex<S>>,
        mut callback: F,
    ) -> FeagiSignalIndex
    where
        S: Send + 'static,
        F: FnMut(&mut S, &T) + Send + 'static,
    {
        self.connect(move |event| {
            if let Ok(mut guard) = state.lock() {
                callback(&mut *guard, event);
            }
        })
    }

    /// Returns the number of connected listeners.
    pub fn listener_count(&self) -> usize {
        self.listeners.len()
    }

    /// Removes all connected listeners.
    pub fn disconnect_all(&mut self) {
        self.listeners.clear();
    }
}

// Note: For PyO3 users, you can use this pattern:
//
// ```rust,ignore
// use pyo3::prelude::*;
// use pyo3::types::PyAny;
// use std::sync::Arc;
//
// #[pyclass]
// struct MyPythonHandler {
//     callback: Arc<Py<PyAny>>, // Python callable stored as Arc
// }
//
// impl MyPythonHandler {
//     fn handle_event(&self, py: Python, data: &MyEventType) -> PyResult<()> {
//         self.callback.call1(py, (data.clone(),))?;
//         Ok(())
//     }
// }
//
// // In your PyO3 setup:
// let handler = Arc::new(MyPythonHandler { callback: Arc::new(python_fn) });
// let handler_clone = Arc::clone(&handler);
//
// signal.connect(move |event| {
//     Python::with_gil(|py| {
//         let _ = handler_clone.handle_event(py, event);
//     });
// });
// ```

impl<T> Default for FeagiSignal<T> {
    fn default() -> Self {
        Self::new()
    }
}

impl<T> Debug for FeagiSignal<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("FeagiSignal")
            .field("listener_count", &self.listeners.len())
            .field("next_index", &self.next_index)
            .field(
                "listener_indices",
                &self.listeners.keys().collect::<Vec<_>>(),
            )
            .finish()
    }
}