dioxus-mirror/packages/core/src/scope_context.rs

use crate::{innerlude::SchedulerMsg, Element, Runtime, ScopeId, Task};
use rustc_hash::FxHashSet;
use std::{
    any::Any,
    cell::{Cell, RefCell},
    future::Future,
    sync::Arc,
};

/// A component's state separate from its props.
///
/// This struct exists to provide a common interface for all scopes without relying on generics.
pub(crate) struct Scope {
    pub(crate) name: &'static str,
    pub(crate) id: ScopeId,
    pub(crate) parent_id: Option<ScopeId>,
    pub(crate) height: u32,
    pub(crate) render_count: Cell<usize>,
    pub(crate) suspended: Cell<bool>,

    // Note: the order of the hook and context fields is important. The hooks field must be dropped before the contexts field in case a hook drop implementation tries to access a context.
    pub(crate) hooks: RefCell<Vec<Box<dyn Any>>>,
    pub(crate) hook_index: Cell<usize>,
    pub(crate) shared_contexts: RefCell<Vec<Box<dyn Any>>>,
    pub(crate) spawned_tasks: RefCell<FxHashSet<Task>>,
    pub(crate) before_render: RefCell<Vec<Box<dyn FnMut()>>>,
}

impl Scope {
    pub(crate) fn new(
        name: &'static str,
        id: ScopeId,
        parent_id: Option<ScopeId>,
        height: u32,
    ) -> Self {
        Self {
            name,
            id,
            parent_id,
            height,
            render_count: Cell::new(0),
            suspended: Cell::new(false),
            shared_contexts: RefCell::new(vec![]),
            spawned_tasks: RefCell::new(FxHashSet::default()),
            hooks: RefCell::new(vec![]),
            hook_index: Cell::new(0),
            before_render: RefCell::new(vec![]),
        }
    }

    pub fn parent_id(&self) -> Option<ScopeId> {
        self.parent_id
    }

    fn sender(&self) -> futures_channel::mpsc::UnboundedSender<SchedulerMsg> {
        Runtime::with(|rt| rt.sender.clone()).unwrap()
    }

    /// Mark this scope as dirty, and schedule a render for it.
    pub fn needs_update(&self) {
        self.sender()
            .unbounded_send(SchedulerMsg::Immediate(self.id))
            .expect("Scheduler to exist if scope exists");
    }

    /// Create a subscription that schedules a future render for the reference component
    ///
    /// ## Notice: you should prefer using [`Self::schedule_update_any`] and [`Self::scope_id`]
    pub fn schedule_update(&self) -> Arc<dyn Fn() + Send + Sync + 'static> {
        let (chan, id) = (self.sender(), self.id);
        Arc::new(move || drop(chan.unbounded_send(SchedulerMsg::Immediate(id))))
    }

    /// Schedule an update for any component given its [`ScopeId`].
    ///
    /// A component's [`ScopeId`] can be obtained from `use_hook` or the [`current_scope_id`] method.
    ///
    /// This method should be used when you want to schedule an update for a component
    pub fn schedule_update_any(&self) -> Arc<dyn Fn(ScopeId) + Send + Sync> {
        let chan = self.sender();
        Arc::new(move |id| {
            chan.unbounded_send(SchedulerMsg::Immediate(id)).unwrap();
        })
    }

    /// Return any context of type T if it exists on this scope
    pub fn has_context<T: 'static + Clone>(&self) -> Option<T> {
        self.shared_contexts
            .borrow()
            .iter()
            .find_map(|any| any.downcast_ref::<T>())
            .cloned()
    }

    /// Try to retrieve a shared state with type `T` from any parent scope.
    ///
    /// Clones the state if it exists.
    pub fn consume_context<T: 'static + Clone>(&self) -> Option<T> {
        tracing::trace!(
            "looking for context {} ({:?}) in {}",
            std::any::type_name::<T>(),
            std::any::TypeId::of::<T>(),
            self.name
        );
        if let Some(this_ctx) = self.has_context() {
            return Some(this_ctx);
        }

        let mut search_parent = self.parent_id;
        let cur_runtime = Runtime::with(|runtime| {
            while let Some(parent_id) = search_parent {
                let parent = runtime.get_state(parent_id).unwrap();
                tracing::trace!(
                    "looking for context {} ({:?}) in {}",
                    std::any::type_name::<T>(),
                    std::any::TypeId::of::<T>(),
                    parent.name
                );
                if let Some(shared) = parent.shared_contexts.borrow().iter().find_map(|any| {
                    tracing::trace!("found context {:?}", (**any).type_id());
                    any.downcast_ref::<T>()
                }) {
                    return Some(shared.clone());
                }
                search_parent = parent.parent_id;
            }
            None
        });

        match cur_runtime.flatten() {
            Some(ctx) => Some(ctx),
            None => {
                tracing::trace!(
                    "context {} ({:?}) not found",
                    std::any::type_name::<T>(),
                    std::any::TypeId::of::<T>()
                );
                None
            }
        }
    }

    /// Inject a Box<dyn Any> into the context of this scope
    pub(crate) fn provide_any_context(&self, mut value: Box<dyn Any>) {
        let mut contexts = self.shared_contexts.borrow_mut();

        // If the context exists, swap it out for the new value
        for ctx in contexts.iter_mut() {
            // Swap the ptr directly
            if ctx.as_ref().type_id() == value.as_ref().type_id() {
                std::mem::swap(ctx, &mut value);
                return;
            }
        }

        // Else, just push it
        contexts.push(value);
    }

    /// Expose state to children further down the [`crate::VirtualDom`] Tree. Requires `Clone` on the context to allow getting values down the tree.
    ///
    /// This is a "fundamental" operation and should only be called during initialization of a hook.
    ///
    /// For a hook that provides the same functionality, use `use_provide_context` and `use_context` instead.
    ///
    /// # Example
    ///
    /// ```rust, ignore
    /// struct SharedState(&'static str);
    ///
    /// static app: Component = |cx| {
    ///     cx.use_hook(|| cx.provide_context(SharedState("world")));
    ///     rsx!(Child {})
    /// }
    ///
    /// static Child: Component = |cx| {
    ///     let state = cx.consume_state::<SharedState>();
    ///     rsx!(div { "hello {state.0}" })
    /// }
    /// ```
    pub fn provide_context<T: 'static + Clone>(&self, value: T) -> T {
        tracing::trace!(
            "providing context {} ({:?}) in {}",
            std::any::type_name::<T>(),
            std::any::TypeId::of::<T>(),
            self.name
        );
        let mut contexts = self.shared_contexts.borrow_mut();

        // If the context exists, swap it out for the new value
        for ctx in contexts.iter_mut() {
            // Swap the ptr directly
            if let Some(ctx) = ctx.downcast_mut::<T>() {
                std::mem::swap(ctx, &mut value.clone());
                return value;
            }
        }

        // Else, just push it
        contexts.push(Box::new(value.clone()));

        value
    }

    /// Provide a context to the root and then consume it
    ///
    /// This is intended for "global" state management solutions that would rather be implicit for the entire app.
    /// Things like signal runtimes and routers are examples of "singletons" that would benefit from lazy initialization.
    ///
    /// Note that you should be checking if the context existed before trying to provide a new one. Providing a context
    /// when a context already exists will swap the context out for the new one, which may not be what you want.
    pub fn provide_root_context<T: 'static + Clone>(&self, context: T) -> T {
        Runtime::with(|runtime| {
            runtime
                .get_state(ScopeId::ROOT)
                .unwrap()
                .provide_context(context)
        })
        .expect("Runtime to exist")
    }

    /// Spawns the future but does not return the [`TaskId`]
    pub fn spawn(&self, fut: impl Future<Output = ()> + 'static) -> Task {
        let id = Runtime::with(|rt| rt.spawn(self.id, fut)).expect("Runtime to exist");
        self.spawned_tasks.borrow_mut().insert(id);
        id
    }

    /// Spawn a future that Dioxus won't clean up when this component is unmounted
    ///
    /// This is good for tasks that need to be run after the component has been dropped.
    pub fn spawn_forever(&self, fut: impl Future<Output = ()> + 'static) -> Task {
        // The root scope will never be unmounted so we can just add the task at the top of the app
        Runtime::with(|rt| rt.spawn(self.id, fut)).expect("Runtime to exist")
    }

    /// Mark this component as suspended and then return None
    pub fn suspend(&self) -> Option<Element> {
        self.suspended.set(true);
        None
    }

    /// Store a value between renders. The foundational hook for all other hooks.
    ///
    /// Accepts an `initializer` closure, which is run on the first use of the hook (typically the initial render). The return value of this closure is stored for the lifetime of the component, and a mutable reference to it is provided on every render as the return value of `use_hook`.
    ///
    /// When the component is unmounted (removed from the UI), the value is dropped. This means you can return a custom type and provide cleanup code by implementing the [`Drop`] trait
    ///
    /// # Example
    ///
    /// ```
    /// # use dioxus::prelude::*;
    /// // prints a greeting on the initial render
    /// pub fn use_hello_world() {
    ///     use_hook(|| println!("Hello, world!"));
    /// }
    /// ```
    pub fn use_hook<State: Clone + 'static>(&self, initializer: impl FnOnce() -> State) -> State {
        let cur_hook = self.hook_index.get();
        let mut hooks = self.hooks.try_borrow_mut().expect("The hook list is already borrowed: This error is likely caused by trying to use a hook inside a hook which violates the rules of hooks.");

        if cur_hook >= hooks.len() {
            hooks.push(Box::new(initializer()));
        }

        hooks
            .get(cur_hook)
            .and_then(|inn| {
                self.hook_index.set(cur_hook + 1);
                let raw_ref: &dyn Any = inn.as_ref();
                raw_ref.downcast_ref::<State>().cloned()
            })
            .expect(
                r#"
                Unable to retrieve the hook that was initialized at this index.
                Consult the `rules of hooks` to understand how to use hooks properly.

                You likely used the hook in a conditional. Hooks rely on consistent ordering between renders.
                Functions prefixed with "use" should never be called conditionally.
                "#,
            )
    }

    pub fn push_before_render(&self, f: impl FnMut() + 'static) {
        self.before_render.borrow_mut().push(Box::new(f));
    }

    /// Get the current render since the inception of this component
    ///
    /// This can be used as a helpful diagnostic when debugging hooks/renders, etc
    pub fn generation(&self) -> usize {
        self.render_count.get()
    }

    /// Get the height of this scope
    pub fn height(&self) -> u32 {
        self.height
    }
}

impl ScopeId {
    /// Get the current scope id
    pub fn current_scope_id(self) -> Option<ScopeId> {
        Runtime::with(|rt| rt.current_scope_id()).flatten()
    }

    #[doc(hidden)]
    /// Check if the virtual dom is currently inside of the body of a component
    pub fn vdom_is_rendering(self) -> bool {
        Runtime::with(|rt| rt.rendering.get()).unwrap_or_default()
    }

    /// Consume context from the current scope
    pub fn consume_context<T: 'static + Clone>(self) -> Option<T> {
        Runtime::with_scope(self, |cx| cx.consume_context::<T>()).flatten()
    }

    /// Consume context from the current scope
    pub fn consume_context_from_scope<T: 'static + Clone>(self, scope_id: ScopeId) -> Option<T> {
        Runtime::with(|rt| {
            rt.get_state(scope_id)
                .and_then(|cx| cx.consume_context::<T>())
        })
        .flatten()
    }

    /// Check if the current scope has a context
    pub fn has_context<T: 'static + Clone>(self) -> Option<T> {
        Runtime::with_scope(self, |cx| cx.has_context::<T>()).flatten()
    }

    /// Provide context to the current scope
    pub fn provide_context<T: 'static + Clone>(self, value: T) -> T {
        Runtime::with_scope(self, |cx| cx.provide_context(value))
            .expect("to be in a dioxus runtime")
    }

    /// Suspends the current component
    pub fn suspend(self) -> Option<Element> {
        Runtime::with_scope(self, |cx| {
            cx.suspend();
        });
        None
    }

    /// Pushes the future onto the poll queue to be polled after the component renders.
    pub fn push_future(self, fut: impl Future<Output = ()> + 'static) -> Option<Task> {
        Runtime::with_scope(self, |cx| cx.spawn(fut))
    }

    /// Spawns the future but does not return the [`TaskId`]
    pub fn spawn(self, fut: impl Future<Output = ()> + 'static) {
        Runtime::with_scope(self, |cx| cx.spawn(fut));
    }

    /// Get the current render since the inception of this component
    ///
    /// This can be used as a helpful diagnostic when debugging hooks/renders, etc
    pub fn generation(self) -> Option<usize> {
        Runtime::with_scope(self, |cx| Some(cx.generation())).expect("to be in a dioxus runtime")
    }

    /// Get the parent of the current scope if it exists
    pub fn parent_scope(self) -> Option<ScopeId> {
        Runtime::with_scope(self, |cx| cx.parent_id()).flatten()
    }

    /// Mark the current scope as dirty, causing it to re-render
    pub fn needs_update(self) {
        Runtime::with_scope(self, |cx| cx.needs_update());
    }

    /// Create a subscription that schedules a future render for the reference component. Unlike [`Self::needs_update`], this function will work outside of the dioxus runtime.
    ///
    /// ## Notice: you should prefer using [`dioxus_core::schedule_update_any`] and [`Self::scope_id`]
    pub fn schedule_update(&self) -> Arc<dyn Fn() + Send + Sync + 'static> {
        Runtime::with_scope(*self, |cx| cx.schedule_update()).expect("to be in a dioxus runtime")
    }

    /// Get the height of the current scope
    pub fn height(self) -> u32 {
        Runtime::with_scope(self, |cx| cx.height()).expect("to be in a dioxus runtime")
    }

    /// Run a closure inside of scope's runtime
    pub fn in_runtime<T>(self, f: impl FnOnce() -> T) -> T {
        Runtime::current()
            .expect("to be in a dioxus runtime")
            .on_scope(self, f)
    }
}