euv-core 0.24.3

use super::*;

/// A `(subscription_id, callback)` pair stored in a signal's listener list.
pub(crate) type ListenerEntry = (usize, Box<dyn FnMut()>);

/// Inner state of a signal, holding the value and subscribed listeners.
///
/// This struct is not exposed directly; use `Signal` instead.
#[derive(CustomDebug, Data, New)]
pub(crate) struct SignalInner<T>
where
    T: Clone,
{
    /// The current value of the signal.
    #[debug(skip)]
    #[get(pub(crate))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) value: T,
    /// Callbacks to invoke when the value changes, each paired with its
    /// subscription id so [`Signal::unsubscribe`] can detach a single
    /// listener without disturbing the rest.
    #[debug(skip)]
    #[get(pub(crate))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) listeners: Vec<ListenerEntry>,
    /// Monotonic counter backing subscription ids for `listeners`.
    #[get(pub, type(copy))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    #[new(skip)]
    pub(crate) next_listener_id: usize,
    /// Ids detached via [`Signal::unsubscribe`] while `update` had the
    /// listener list swapped out. Drained by `update`'s merge-back pass so
    /// a listener detached mid-notification is not resurrected.
    #[debug(skip)]
    #[get(pub(crate))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    #[new(skip)]
    pub(crate) removed_listener_ids: Vec<usize>,
    /// `true` while `update` has the listener list swapped out for
    /// notification. `unsubscribe` consults this flag to decide between
    /// direct removal and deferred removal via `removed_listener_ids`.
    #[get(pub, type(copy))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    #[new(skip)]
    pub(crate) notifying: bool,
    /// Whether this signal is still active. Set to `false` by `deactivate()`
    /// (and `clear_signal_listeners`) to make subsequent `set()` calls
    /// complete no-ops (no value update, no listener invocation, no
    /// dispatch scheduling), ensuring stale closures like orphaned
    /// `setInterval` handlers or pending `spawn_local` futures become harmless.
    #[get(pub, type(copy))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) alive: bool,
    /// IDs of dynamic nodes that depend on this signal for precise dirty marking.
    /// When this signal changes, only these dynamic nodes are marked dirty
    /// instead of broadcasting to all registered dynamic nodes.
    #[debug(skip)]
    #[get_mut(pub(crate))]
    #[new(skip)]
    pub(crate) dependents: Vec<usize>,
}

/// A reactive signal handle.
///
/// Allows reading, writing, and subscribing to changes.
/// Implements `Clone` and `Copy` for ergonomic use; all copies share the same
/// underlying state. The inner state lives in the global append-only signal
/// slab and the handle carries its slot index as a `usize`. The `Copy`
/// semantics are safe because only the slot index is copied — the actual
/// slot is owned by the slab and is never freed or recycled.
#[derive(CustomDebug, Data, Eq, Hash, New, Ord, PartialEq, PartialOrd)]
pub struct Signal<T>
where
    T: Clone + PartialEq + 'static,
{
    /// Slot index of the inner state in the global signal slab.
    #[debug(skip)]
    #[get(pub, type(copy))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) inner: usize,
    /// Marker for the generic type parameter (uses fn pointer to be `Copy`
    /// regardless of `T`).
    #[debug(skip)]
    #[get(pub, type(copy))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) _marker: PhantomData<fn() -> T>,
}

/// A `Sync` wrapper for single-threaded global `Signal` access.
///
/// SAFETY: This type is only safe to use in single-threaded contexts
/// (e.g., WASM). It implements `Sync` to allow usage as a `static`
/// variable, but concurrent access from multiple threads would be
/// undefined behavior.
#[derive(CustomDebug, Data, New)]
pub struct SignalCell<T>
where
    T: Clone + PartialEq + 'static,
{
    /// Interior-mutable storage for an optional signal handle.
    #[debug(skip)]
    #[get(pub(crate))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) inner: UnsafeCell<Option<Signal<T>>>,
}

/// Typed slab allocator for `SignalInner<T>`.
///
/// The slab owns all `SignalInner<T>` allocations for the program's
/// lifetime. `Signal<T>` carries only a `usize` slot index, so signals are
/// trivially `Copy` and stay cheap to clone. Slots are append-only and
/// never recycled: a stale `Signal<T>` handle therefore always finds its
/// original slot (marked `alive == false` after `Signal::deactivate`), so
/// stale reads return the last stored value instead of hitting a reused
/// slot of a different type or — worse — a `mem::zeroed()` fallback for
/// a freed slot.
pub(crate) struct SignalSlab {
    /// Slot storage. Index 0..len.
    pub(crate) entries: Vec<Box<dyn AnySignalInner>>,
}

/// A handle to a leaked `FnMut()` closure, stored as the closure's heap address.
///
/// The closure is double-boxed (`Box<Box<dyn FnMut()>>`) and leaked, so its
/// memory outlives any `FireHandle` copy and can be safely invoked from any
/// context via the raw pointer. The handle is `Copy` because it only holds
/// the address — repeated invocations on captured copies all resolve to the
/// same underlying closure.
///
/// This type replaces the inline `Box::leak(... as *mut Box<dyn FnMut()> as usize)`
/// pattern that was used by `watch!`/`computed!` macros and the virtual list
/// component, encapsulating the unsized coercion, double-boxing, and raw
/// pointer arithmetic behind `From`/`Into` conversions and a dedicated
/// `fire` method.
#[derive(Clone, Copy, CustomDebug, Data, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct FireHandle {
    /// Address of the leaked `Box<dyn FnMut()>` allocation.
    #[get(pub, type(copy))]
    #[get_mut(pub(crate))]
    #[set(pub(crate))]
    pub(crate) inner: usize,
}