lazily 0.2.0

Lazy reactive signals with dependency tracking and cache invalidation
Documentation 
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use std::marker::PhantomData;

use crate::context::SlotId;
use crate::Context;

/// A typed handle to a mutable cell within a [`Context`].
///
/// Like [`SlotHandle`], this is a lightweight id. The actual value lives
/// inside the Context.
pub struct CellHandle<T> {
    pub(crate) id: SlotId,
    pub(crate) _marker: PhantomData<T>,
}

impl<T> CellHandle<T> {
    pub(crate) fn new(id: SlotId) -> Self {
        Self {
            id,
            _marker: PhantomData,
        }
    }

    /// Clear all dependent slots without changing the cell's value.
    ///
    /// Useful when you know derived caches are stale but the input hasn't
    /// changed (e.g., an external resource was mutated).
    pub fn clear_dependents(&self, ctx: &Context) {
        let dependents: Vec<SlotId> = {
            let nodes = ctx.nodes.borrow();
            match nodes.get(&self.id) {
                Some(crate::context::Node::Cell(c)) => c.dependents.iter().copied().collect(),
                _ => vec![],
            }
        };
        for dep_id in dependents {
            ctx.clear_slot(dep_id);
        }
    }
}

impl<T> Clone for CellHandle<T> {
    fn clone(&self) -> Self {
        *self
    }
}

impl<T> Copy for CellHandle<T> {}