euv_core/reactive/

impl.rs

use crate::*;

/// Implementation of SignalInner construction.
impl<T> SignalInner<T>
where
    T: Clone,
{
    /// Creates a new signal inner with the given initial value and no listeners.
    pub fn new(value: T) -> Self {
        let inner: SignalInner<T> = SignalInner {
            value,
            listeners: Vec::new(),
            alive: true,
        };
        inner
    }
}

/// Implementation of reactive signal operations.
impl<T> Signal<T>
where
    T: Clone + PartialEq,
{
    /// Creates a new `Signal` with the given initial value.
    ///
    /// The inner state is allocated via `Box::leak` and lives for the
    /// remainder of the program. This is safe in single-threaded WASM
    /// contexts where no concurrent access can occur.
    ///
    /// # Arguments
    ///
    /// - `T` - The initial value of the signal.
    ///
    /// # Returns
    ///
    /// - `Signal<T>` - A handle to the newly created reactive signal.
    pub fn new(value: T) -> Self {
        let boxed: Box<SignalInner<T>> = Box::new(SignalInner::new(value));
        Signal {
            inner: Box::leak(boxed) as *mut SignalInner<T>,
        }
    }

    /// Creates a new `Signal` from an existing raw pointer.
    ///
    /// # Safety
    ///
    /// The caller must ensure the pointer was allocated via `Box::leak`
    /// and remains valid for the entire program lifetime.
    pub(crate) fn from_inner(inner: *mut SignalInner<T>) -> Self {
        Signal { inner }
    }

    /// Returns a mutable reference to the inner signal state.
    ///
    /// # Safety
    ///
    /// The caller must ensure no other references to the inner state exist.
    /// In single-threaded WASM this is always safe.
    #[allow(clippy::mut_from_ref)]
    fn get_inner_mut(&self) -> &mut SignalInner<T> {
        unsafe { &mut *self.inner }
    }

    /// Returns the current value of the signal.
    ///
    /// # Returns
    ///
    /// - `T` - The current value of the signal.
    pub fn get(&self) -> T {
        self.get_inner_mut().get_value().clone()
    }

    /// Attempts to return the current value of the signal without panicking.
    ///
    /// # Returns
    ///
    /// - `Some(T)` - The current value if the borrow succeeds.
    /// - `None` - If the inner value is already mutably borrowed.
    pub fn try_get(&self) -> Option<T> {
        Some(self.get_inner_mut().get_value().clone())
    }

    /// Subscribes a callback to be invoked when the signal changes.
    ///
    /// # Arguments
    ///
    /// - `FnMut() + 'static` - The callback to invoke when the signal changes.
    pub fn subscribe<F>(&self, callback: F)
    where
        F: FnMut() + 'static,
    {
        self.get_inner_mut()
            .get_mut_listeners()
            .push(Rc::new(RefCell::new(callback)));
    }

    /// Replaces all listeners with a single new callback.
    ///
    /// Unlike `subscribe`, which appends a listener, this method clears any
    /// existing listeners first and then adds the new one. This prevents
    /// listener accumulation across re-renders: each signal is guaranteed
    /// to have at most one active listener at any time, eliminating
    /// cascading `set()` calls that would otherwise grow exponentially.
    ///
    /// # Arguments
    ///
    /// - `FnMut() + 'static` - The callback to invoke when the signal changes.
    pub fn replace_subscribe<F>(&self, callback: F)
    where
        F: FnMut() + 'static,
    {
        let listeners: &mut Vec<Rc<RefCell<dyn FnMut()>>> =
            self.get_inner_mut().get_mut_listeners();
        listeners.clear();
        listeners.push(Rc::new(RefCell::new(callback)));
    }

    /// Removes all subscribed listeners from this signal and marks it as
    /// inactive. After calling this method, subsequent `set()` and
    /// `try_set()` calls become complete no-ops: the value is not updated,
    /// no listeners are invoked, and `schedule_signal_update()` is not
    /// called. This is used during hook context cleanup when a `match`
    /// arm switch discards old signals, ensuring that stale `setInterval`
    /// closures referencing these signals become entirely harmless.
    pub fn clear_listeners(&self) {
        let inner: &mut SignalInner<T> = self.get_inner_mut();
        inner.set_alive(false);
        inner.get_mut_listeners().clear();
    }

    /// Sets the value of the signal and notifies listeners.
    ///
    /// If the signal has been marked as inactive (via `clear_listeners()`),
    /// this method is a complete no-op: the value is not updated, no
    /// listeners are invoked, and no global update is scheduled.
    ///
    /// If the new value is equal to the current value, no update is performed
    /// and no listeners are notified. This prevents unnecessary re-renders and
    /// avoids cascading no-op updates through intermediate signal chains.
    ///
    /// # Arguments
    ///
    /// - `T` - The new value to assign to the signal.
    pub fn set(&self, value: T) {
        let inner: &mut SignalInner<T> = self.get_inner_mut();
        if !inner.get_alive() {
            return;
        }
        if inner.get_value() == &value {
            return;
        }
        let listeners: ListenerList = {
            inner.set_value(value);
            inner.get_listeners().iter().map(Rc::clone).collect()
        };
        for listener in &listeners {
            let mut borrowed: RefMut<dyn FnMut()> = listener.borrow_mut();
            borrowed();
        }
        schedule_signal_update();
    }

    /// Sets the value of the signal and notifies listeners without scheduling
    /// a global DOM update dispatch.
    ///
    /// This is identical to `set` except it does not call
    /// `schedule_signal_update()`, meaning no `__euv_signal_update__` event
    /// will be dispatched. Use this for internal bookkeeping signals whose
    /// changes should not trigger DynamicNode re-renders.
    ///
    /// # When to use
    ///
    /// Prefer `set` in almost all cases. Only use `set_silent` when the
    /// signal change is guaranteed not to affect any DynamicNode output
    /// (e.g., internal guard flags, derived-value caches already at the
    /// correct value, or within a `with_suppressed_updates` block where
    /// the caller takes responsibility for batching the update).
    ///
    /// If the new value is equal to the current value, no update is performed
    /// and no listeners are notified.
    ///
    /// If the signal has been marked as inactive (via `clear_listeners()`),
    /// this method is a complete no-op.
    pub fn set_silent(&self, value: T) {
        let inner: &mut SignalInner<T> = self.get_inner_mut();
        if !inner.get_alive() {
            return;
        }
        if inner.get_value() == &value {
            return;
        }
        let listeners: ListenerList = {
            inner.set_value(value);
            inner.get_listeners().iter().map(Rc::clone).collect()
        };
        for listener in &listeners {
            let mut borrowed: RefMut<dyn FnMut()> = listener.borrow_mut();
            borrowed();
        }
    }

    /// Attempts to set the value of the signal and notify listeners without panicking.
    ///
    /// If the new value is equal to the current value, no update is performed.
    ///
    /// # Arguments
    ///
    /// - `T` - The new value to assign to the signal.
    ///
    /// # Returns
    ///
    /// - `bool` - `true` if the value was successfully updated and listeners were notified, `false` if unchanged or inactive.
    pub fn try_set(&self, value: T) -> bool {
        let inner: &mut SignalInner<T> = self.get_inner_mut();
        if !inner.get_alive() {
            return false;
        }
        if inner.get_value() == &value {
            return false;
        }
        let listeners: ListenerList = {
            inner.set_value(value);
            inner.get_listeners().iter().map(Rc::clone).collect()
        };
        for listener in &listeners {
            listener.borrow_mut()();
        }
        schedule_signal_update();
        true
    }
}

/// Prevents direct dereference of a signal to enforce explicit API usage.
impl<T> Deref for Signal<T>
where
    T: Clone + PartialEq,
{
    type Target = T;

    fn deref(&self) -> &Self::Target {
        panic!("Signal does not support direct dereference; use .get() instead");
    }
}

/// Prevents direct mutable dereference of a signal to enforce explicit API usage.
impl<T> DerefMut for Signal<T>
where
    T: Clone + PartialEq,
{
    fn deref_mut(&mut self) -> &mut Self::Target {
        panic!("Signal does not support direct dereference; use .set() instead");
    }
}

/// Clones the signal, sharing the same inner state.
impl<T> Clone for Signal<T>
where
    T: Clone + PartialEq,
{
    fn clone(&self) -> Self {
        *self
    }
}

/// Copies the signal, sharing the same inner state.
///
/// A `Signal` is just a raw pointer; copying it is a trivial bitwise copy.
impl<T> Copy for Signal<T> where T: Clone + PartialEq {}

/// Converts a static `String` into a text attribute value.
impl IntoReactiveValue for String {
    fn into_reactive_value(self) -> AttributeValue {
        AttributeValue::Text(self)
    }
}

/// Converts a string slice into a text attribute value.
impl IntoReactiveValue for &str {
    fn into_reactive_value(self) -> AttributeValue {
        AttributeValue::Text(self.to_string())
    }
}

/// Converts a string signal into a reactive attribute value.
impl IntoReactiveValue for Signal<String> {
    fn into_reactive_value(self) -> AttributeValue {
        AttributeValue::Signal(self)
    }
}

/// Converts a mutable bool signal into a reactive attribute value.
///
/// The signal is mapped to a `Signal<String>` that yields `"true"` or `"false"`,
/// enabling boolean attributes like `checked` to reactively update the DOM.
impl IntoReactiveValue for Signal<bool> {
    fn into_reactive_value(self) -> AttributeValue {
        bool_signal_to_string_attribute_value(self)
    }
}

/// Converts a CSS class reference into an attribute value.
impl IntoReactiveValue for CssClass {
    fn into_reactive_value(self) -> AttributeValue {
        AttributeValue::Css(self)
    }
}

/// Converts a reference to a CSS class into an attribute value by cloning.
impl IntoReactiveValue for &'static CssClass {
    fn into_reactive_value(self) -> AttributeValue {
        AttributeValue::Css(self.clone())
    }
}

/// Converts a `String` into its own value for reactive string storage.
impl IntoReactiveString for String {
    fn into_reactive_string(self) -> String {
        self
    }
}

/// Converts a string slice into an owned string for reactive string storage.
impl IntoReactiveString for &str {
    fn into_reactive_string(self) -> String {
        self.to_string()
    }
}

/// Converts a `CssClass` into its class name for reactive string storage.
impl IntoReactiveString for CssClass {
    fn into_reactive_string(self) -> String {
        self.get_name().to_string()
    }
}

/// Converts a reference to a `CssClass` into its class name for reactive string storage.
impl IntoReactiveString for &'static CssClass {
    fn into_reactive_string(self) -> String {
        self.get_name().to_string()
    }
}

/// Converts a `bool` into `"true"` or `"false"` for reactive string storage.
impl IntoReactiveString for bool {
    fn into_reactive_string(self) -> String {
        self.to_string()
    }
}

/// Converts an `i32` into a string for reactive string storage.
impl IntoReactiveString for i32 {
    fn into_reactive_string(self) -> String {
        self.to_string()
    }
}

/// Converts a `u32` into a string for reactive string storage.
impl IntoReactiveString for u32 {
    fn into_reactive_string(self) -> String {
        self.to_string()
    }
}

/// Converts a `f64` into a string for reactive string storage.
impl IntoReactiveString for f64 {
    fn into_reactive_string(self) -> String {
        self.to_string()
    }
}

/// Converts a string signal into a reactive string by resolving its current value.
impl IntoReactiveString for Signal<String> {
    fn into_reactive_string(self) -> String {
        self.get()
    }
}

/// Converts a bool signal into a reactive string by resolving its current value.
impl IntoReactiveString for Signal<bool> {
    fn into_reactive_string(self) -> String {
        self.get().to_string()
    }
}

/// Converts a closure into a callback attribute value.
impl<F> IntoCallbackAttribute for F
where
    F: FnMut(NativeEvent) + 'static,
{
    fn into_callback_attribute(self) -> AttributeValue {
        AttributeValue::Event(NativeEventHandler::new(
            NativeEventName::Other("callback".to_string()),
            self,
        ))
    }
}

/// Converts an owned event handler into a callback attribute value.
impl IntoCallbackAttribute for NativeEventHandler {
    fn into_callback_attribute(self) -> AttributeValue {
        AttributeValue::Event(self)
    }
}

/// Converts an optional event handler into a callback attribute value.
impl IntoCallbackAttribute for Option<NativeEventHandler> {
    fn into_callback_attribute(self) -> AttributeValue {
        match self {
            Some(handler) => AttributeValue::Event(handler),
            None => AttributeValue::Text(String::new()),
        }
    }
}

/// Implementation of hook context lifecycle and hook index management.
impl HookContext {
    /// Creates a new `HookContext` from an existing raw pointer.
    ///
    /// # Safety
    ///
    /// The caller must ensure the pointer was allocated via `Box::leak`
    /// and remains valid for the entire program lifetime.
    pub fn from_inner(inner: *mut HookContextInner) -> Self {
        HookContext { inner }
    }

    /// Returns a mutable reference to the inner hook context state.
    ///
    /// # Safety
    ///
    /// The caller must ensure no other references to the inner state exist.
    /// In single-threaded WASM this is always safe.
    #[allow(clippy::mut_from_ref)]
    fn get_inner_mut(&self) -> &mut HookContextInner {
        unsafe { &mut *self.inner }
    }

    /// Returns the current hook index.
    pub fn get_hook_index(&self) -> usize {
        self.get_inner_mut().get_hook_index()
    }

    /// Sets the hook index.
    ///
    /// # Arguments
    ///
    /// - `usize` - The new hook index value.
    pub fn set_hook_index(&mut self, index: usize) {
        self.get_inner_mut().set_hook_index(index);
    }

    /// Returns a reference to the hooks storage.
    pub fn get_hooks(&self) -> &Vec<Box<dyn Any>> {
        self.get_inner_mut().get_hooks()
    }

    /// Returns a mutable reference to the hooks storage.
    pub fn get_mut_hooks(&mut self) -> &mut Vec<Box<dyn Any>> {
        self.get_inner_mut().get_mut_hooks()
    }

    /// Returns a mutable reference to the cleanup closures storage.
    pub fn get_mut_cleanups(&mut self) -> &mut Vec<Box<dyn FnOnce()>> {
        self.get_inner_mut().get_mut_cleanups()
    }

    /// Resets the hook index for a new render cycle.
    pub fn reset_hook_index(&mut self) {
        self.set_hook_index(0_usize);
    }

    /// Notifies the hook context that a match arm is being entered.
    /// Toggles the `arm_changed` flag; if it differs from the previous value,
    /// the hooks array is cleared to prevent signal leakage between arms.
    pub fn set_arm_changed(&mut self, changed: bool) {
        let inner: &mut HookContextInner = self.get_inner_mut();
        if inner.get_arm_changed() != changed {
            let cleanups: Vec<Box<dyn FnOnce()>> = std::mem::take(inner.get_mut_cleanups());
            for cleanup in cleanups {
                cleanup();
            }
            inner.get_mut_hooks().clear();
            inner.set_arm_changed(changed);
        }
        self.reset_hook_index();
    }
}

/// Clones the hook context, sharing the same inner state.
impl Clone for HookContext {
    fn clone(&self) -> Self {
        *self
    }
}

/// Copies the hook context, sharing the same inner state.
///
/// A `HookContext` is just a raw pointer; copying it is a trivial bitwise copy.
impl Copy for HookContext {}

/// Provides a default empty hook context.
impl Default for HookContext {
    fn default() -> Self {
        let boxed: Box<HookContextInner> = Box::default();
        HookContext::from_inner(Box::leak(boxed) as *mut HookContextInner)
    }
}

/// Implementation of HookContextInner construction.
impl HookContextInner {
    /// Creates a new empty hook context inner.
    pub const fn new() -> Self {
        HookContextInner {
            hooks: Vec::new(),
            arm_changed: false,
            hook_index: 0_usize,
            cleanups: Vec::new(),
        }
    }
}

/// Provides a default empty hook context inner.
impl Default for HookContextInner {
    fn default() -> Self {
        Self::new()
    }
}

/// SAFETY: `HookContextCell` is only used in single-threaded WASM contexts.
/// Concurrent access from multiple threads would be undefined behavior.
unsafe impl Sync for HookContextCell {}

/// Implementation of SignalCell construction and access.
impl<T> SignalCell<T>
where
    T: Clone + PartialEq,
{
    /// Creates a new empty `SignalCell` with no signal stored.
    ///
    /// # Returns
    ///
    /// - `SignalCell<T>` - An empty cell ready to hold a signal.
    pub const fn new() -> Self {
        SignalCell {
            inner: UnsafeCell::new(None),
        }
    }

    /// Stores a signal into the cell.
    ///
    /// # Arguments
    ///
    /// - `Signal<T>` - The signal to store.
    ///
    /// # Panics
    ///
    /// Panics if a signal has already been stored.
    pub fn set(&self, signal: Signal<T>) {
        unsafe {
            let ptr: &mut Option<Signal<T>> = &mut *self.inner.get();
            if ptr.is_some() {
                panic!("SignalCell::set called on an already-initialized cell");
            }
            *ptr = Some(signal);
        }
    }

    /// Returns the signal stored in the cell.
    ///
    /// # Returns
    ///
    /// - `Signal<T>` - The stored signal.
    ///
    /// # Panics
    ///
    /// Panics if no signal has been stored via `set`.
    pub fn get(&self) -> Signal<T> {
        unsafe {
            let ptr: &Option<Signal<T>> = &*self.inner.get();
            match ptr {
                Some(signal) => *signal,
                None => panic!("SignalCell::get called on an uninitialized cell"),
            }
        }
    }
}

/// SAFETY: `SignalCell` is only used in single-threaded WASM contexts.
/// Concurrent access from multiple threads would be undefined behavior.
unsafe impl<T> Sync for SignalCell<T> where T: Clone + PartialEq {}

/// Provides a default empty `SignalCell`.
impl<T> Default for SignalCell<T>
where
    T: Clone + PartialEq,
{
    fn default() -> Self {
        Self::new()
    }
}