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

use crate::innerlude::*;

use futures_channel::mpsc::UnboundedSender;
use fxhash::FxHashMap;
use std::{
    any::{Any, TypeId},
    cell::{Cell, RefCell},
    collections::HashMap,
    future::Future,
    rc::Rc,
};

use bumpalo::{boxed::Box as BumpBox, Bump};

/// Components in Dioxus use the "Context" object to interact with their lifecycle.
///
/// This lets components access props, schedule updates, integrate hooks, and expose shared state.
///
/// For the most part, the only method you should be using regularly is `render`.
///
/// ## Example
///
/// ```ignore
/// #[derive(Props)]
/// struct ExampleProps {
///     name: String
/// }
///
/// fn Example((cx, props): Scope<Props>) -> Element {
///     cx.render(rsx!{ div {"Hello, {props.name}"} })
/// }
/// ```
pub type Context<'a> = &'a ScopeInner;

/// Every component in Dioxus is represented by a `Scope`.
///
/// Scopes contain the state for hooks, the component's props, and other lifecycle information.
///
/// Scopes are allocated in a generational arena. As components are mounted/unmounted, they will replace slots of dead components.
/// The actual contents of the hooks, though, will be allocated with the standard allocator. These should not allocate as frequently.
///
/// We expose the `Scope` type so downstream users can traverse the Dioxus VirtualDOM for whatever
/// use case they might have.
pub struct ScopeInner {
    // Book-keeping about our spot in the arena
    // yes, a raw pointer
    // it's bump allocated so it's stable
    // the safety of parent pointers is guaranteed by the logic in this crate
    pub(crate) parent_scope: Option<*mut ScopeInner>,
    pub(crate) our_arena_idx: ScopeId,
    pub(crate) height: u32,

    pub(crate) subtree: Cell<u32>,
    pub(crate) is_subtree_root: Cell<bool>,

    // Nodes
    pub(crate) frames: ActiveFrame,

    pub(crate) vcomp: *const VComponent<'static>,

    /*
    we care about:
    - listeners (and how to call them when an event is triggered)
    - borrowed props (and how to drop them when the parent is dropped)
    - suspended nodes (and how to call their callback when their associated tasks are complete)
    */
    pub(crate) items: RefCell<SelfReferentialItems<'static>>,

    // State
    pub(crate) hooks: HookList,

    // todo: move this into a centralized place - is more memory efficient
    pub(crate) shared_contexts: RefCell<HashMap<TypeId, Rc<dyn Any>>>,

    pub(crate) sender: UnboundedSender<SchedulerMsg>,
}

pub struct SelfReferentialItems<'a> {
    pub(crate) listeners: Vec<*const Listener<'a>>,
    pub(crate) borrowed_props: Vec<*const VComponent<'a>>,
    pub(crate) suspended_nodes: FxHashMap<u64, *const VSuspended<'a>>,
    pub(crate) tasks: Vec<BumpBox<'a, dyn Future<Output = ()>>>,
    pub(crate) pending_effects: Vec<BumpBox<'a, dyn FnMut()>>,
}

pub struct ScopeVcomp {
    // important things
}

impl ScopeInner {
    /// This method cleans up any references to data held within our hook list. This prevents mutable aliasing from
    /// causing UB in our tree.
    ///
    /// This works by cleaning up our references from the bottom of the tree to the top. The directed graph of components
    /// essentially forms a dependency tree that we can traverse from the bottom to the top. As we traverse, we remove
    /// any possible references to the data in the hook list.
    ///
    /// References to hook data can only be stored in listeners and component props. During diffing, we make sure to log
    /// all listeners and borrowed props so we can clear them here.
    ///
    /// This also makes sure that drop order is consistent and predictable. All resources that rely on being dropped will
    /// be dropped.
    pub(crate) fn ensure_drop_safety(&mut self) {
        // make sure we drop all borrowed props manually to guarantee that their drop implementation is called before we
        // run the hooks (which hold an &mut Reference)
        // right now, we don't drop
        self.items
            .get_mut()
            .borrowed_props
            .drain(..)
            .map(|li| unsafe { &*li })
            .for_each(|comp| {
                // First drop the component's undropped references
                let scope_id = comp
                    .associated_scope
                    .get()
                    .expect("VComponents should be associated with a valid Scope");

                let scope = unsafe { &mut *scope_id };

                scope.ensure_drop_safety();

                todo!("drop the component's props");
                // let mut drop_props = comp.drop_props.borrow_mut().take().unwrap();
                // drop_props();
            });

        // Now that all the references are gone, we can safely drop our own references in our listeners.
        self.items
            .get_mut()
            .listeners
            .drain(..)
            .map(|li| unsafe { &*li })
            .for_each(|listener| drop(listener.callback.borrow_mut().take()));
    }

    /// A safe wrapper around calling listeners
    pub(crate) fn call_listener(&mut self, event: UserEvent, element: ElementId) {
        let listners = &mut self.items.get_mut().listeners;

        let raw_listener = listners.iter().find(|lis| {
            let search = unsafe { &***lis };
            if search.event == event.name {
                let search_id = search.mounted_node.get();
                search_id.map(|f| f == element).unwrap_or(false)
            } else {
                false
            }
        });

        if let Some(raw_listener) = raw_listener {
            let listener = unsafe { &**raw_listener };
            let mut cb = listener.callback.borrow_mut();
            if let Some(cb) = cb.as_mut() {
                (cb)(event.event);
            }
        } else {
            log::warn!("An event was triggered but there was no listener to handle it");
        }
    }

    // General strategy here is to load up the appropriate suspended task and then run it.
    // Suspended nodes cannot be called repeatedly.
    pub(crate) fn call_suspended_node<'a>(&'a mut self, task_id: u64) {
        let mut nodes = &mut self.items.get_mut().suspended_nodes;

        if let Some(suspended) = nodes.remove(&task_id) {
            let sus: &'a VSuspended<'static> = unsafe { &*suspended };
            let sus: &'a VSuspended<'a> = unsafe { std::mem::transmute(sus) };
            let mut boxed = sus.callback.borrow_mut().take().unwrap();
            let new_node: Element<'a> = boxed();
        }
    }

    // run the list of effects
    pub(crate) fn run_effects(&mut self) {
        // pub(crate) fn run_effects(&mut self, pool: &ResourcePool) {
        for mut effect in self.items.get_mut().pending_effects.drain(..) {
            effect();
        }
    }

    /// Render this component.
    ///
    /// Returns true if the scope completed successfully and false if running failed (IE a None error was propagated).
    pub(crate) fn run_scope<'sel>(&'sel mut self) -> bool {
        // Cycle to the next frame and then reset it
        // This breaks any latent references, invalidating every pointer referencing into it.
        // Remove all the outdated listeners
        self.ensure_drop_safety();

        // Safety:
        // - We dropped the listeners, so no more &mut T can be used while these are held
        // - All children nodes that rely on &mut T are replaced with a new reference
        unsafe { self.hooks.reset() };

        // Safety:
        // - We've dropped all references to the wip bump frame
        unsafe { self.frames.reset_wip_frame() };

        let items = self.items.get_mut();

        // just forget about our suspended nodes while we're at it
        items.suspended_nodes.clear();

        // guarantee that we haven't screwed up - there should be no latent references anywhere
        debug_assert!(items.listeners.is_empty());
        debug_assert!(items.suspended_nodes.is_empty());
        debug_assert!(items.borrowed_props.is_empty());

        log::debug!("Borrowed stuff is successfully cleared");

        // temporarily cast the vcomponent to the right lifetime
        let vcomp = self.load_vcomp();

        let render: &dyn for<'b> Fn(&'b ScopeInner) -> Element<'b> = todo!();

        // Todo: see if we can add stronger guarantees around internal bookkeeping and failed component renders.
        if let Some(builder) = render(self) {
            let new_head = builder.into_vnode(NodeFactory {
                bump: &self.frames.wip_frame().bump,
            });
            log::debug!("Render is successful");

            // the user's component succeeded. We can safely cycle to the next frame
            self.frames.wip_frame_mut().head_node = unsafe { std::mem::transmute(new_head) };
            self.frames.cycle_frame();

            true
        } else {
            false
        }
    }

    pub(crate) fn new_subtree(&self) -> Option<u32> {
        todo!()
        // if self.is_subtree_root.get() {
        //     None
        // } else {
        //     let cur = self.shared.cur_subtree.get();
        //     self.shared.cur_subtree.set(cur + 1);
        //     Some(cur)
        // }
    }

    pub(crate) fn update_vcomp(&mut self, vcomp: &VComponent) {
        let f: *const _ = vcomp;
        self.vcomp = unsafe { std::mem::transmute(f) };
    }

    pub(crate) fn load_vcomp<'a>(&'a mut self) -> &'a VComponent<'a> {
        unsafe { std::mem::transmute(&*self.vcomp) }
    }

    /// Get the root VNode for this Scope.
    ///
    /// This VNode is the "entrypoint" VNode. If the component renders multiple nodes, then this VNode will be a fragment.
    ///
    /// # Example
    /// ```rust
    /// let mut dom = VirtualDom::new(|(cx, props)|cx.render(rsx!{ div {} }));
    /// dom.rebuild();
    ///
    /// let base = dom.base_scope();
    ///
    /// if let VNode::VElement(node) = base.root_node() {
    ///     assert_eq!(node.tag_name, "div");
    /// }
    /// ```
    pub fn root_node(&self) -> &VNode {
        self.frames.fin_head()
    }

    /// Get the subtree ID that this scope belongs to.
    ///
    /// Each component has its own subtree ID - the root subtree has an ID of 0. This ID is used by the renderer to route
    /// the mutations to the correct window/portal/subtree.
    ///
    ///
    /// # Example
    ///
    /// ```rust
    /// let mut dom = VirtualDom::new(|(cx, props)|cx.render(rsx!{ div {} }));
    /// dom.rebuild();
    ///
    /// let base = dom.base_scope();
    ///
    /// assert_eq!(base.subtree(), 0);
    /// ```
    pub fn subtree(&self) -> u32 {
        self.subtree.get()
    }

    /// Get the height of this Scope - IE the number of scopes above it.
    ///
    /// A Scope with a height of `0` is the root scope - there are no other scopes above it.
    ///
    /// # Example
    ///
    /// ```rust
    /// let mut dom = VirtualDom::new(|(cx, props)|cx.render(rsx!{ div {} }));
    /// dom.rebuild();
    ///
    /// let base = dom.base_scope();
    ///
    /// assert_eq!(base.height(), 0);
    /// ```
    pub fn height(&self) -> u32 {
        self.height
    }

    /// Get the Parent of this Scope within this Dioxus VirtualDOM.
    ///
    /// This ID is not unique across Dioxus VirtualDOMs or across time. IDs will be reused when components are unmounted.
    ///
    /// The base component will not have a parent, and will return `None`.
    ///
    /// # Example
    ///
    /// ```rust
    /// let mut dom = VirtualDom::new(|(cx, props)|cx.render(rsx!{ div {} }));
    /// dom.rebuild();
    ///
    /// let base = dom.base_scope();
    ///
    /// assert_eq!(base.parent(), None);
    /// ```
    pub fn parent(&self) -> Option<ScopeId> {
        match self.parent_scope {
            Some(p) => Some(unsafe { &*p }.our_arena_idx),
            None => None,
        }
    }

    /// Get the ID of this Scope within this Dioxus VirtualDOM.
    ///
    /// This ID is not unique across Dioxus VirtualDOMs or across time. IDs will be reused when components are unmounted.
    ///
    /// # Example
    ///
    /// ```rust
    /// let mut dom = VirtualDom::new(|(cx, props)|cx.render(rsx!{ div {} }));
    /// dom.rebuild();
    /// let base = dom.base_scope();
    ///
    /// assert_eq!(base.scope_id(), 0);
    /// ```
    pub fn scope_id(&self) -> ScopeId {
        self.our_arena_idx
    }

    /// Create a subscription that schedules a future render for the reference component
    ///
    /// ## Notice: you should prefer using prepare_update and get_scope_id
    pub fn schedule_update(&self) -> Rc<dyn Fn() + 'static> {
        // pub fn schedule_update(&self) -> Rc<dyn Fn() + 'static> {
        let chan = self.sender.clone();
        let id = self.scope_id();
        Rc::new(move || {
            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 [`Context::scope_id`] method.
    ///
    /// This method should be used when you want to schedule an update for a component
    pub fn schedule_update_any(&self) -> Rc<dyn Fn(ScopeId)> {
        let chan = self.sender.clone();
        Rc::new(move |id| {
            chan.unbounded_send(SchedulerMsg::Immediate(id));
        })
    }

    /// Get the [`ScopeId`] of a mounted component.
    ///
    /// `ScopeId` is not unique for the lifetime of the VirtualDom - a ScopeId will be reused if a component is unmounted.
    pub fn needs_update(&self) {
        self.needs_update_any(self.scope_id())
    }

    /// Get the [`ScopeId`] of a mounted component.
    ///
    /// `ScopeId` is not unique for the lifetime of the VirtualDom - a ScopeId will be reused if a component is unmounted.
    pub fn needs_update_any(&self, id: ScopeId) {
        self.sender
            .unbounded_send(SchedulerMsg::Immediate(id))
            .unwrap();
    }

    /// Get the [`ScopeId`] of a mounted component.
    ///
    /// `ScopeId` is not unique for the lifetime of the VirtualDom - a ScopeId will be reused if a component is unmounted.
    pub fn bump(&self) -> &Bump {
        let bump = &self.frames.wip_frame().bump;
        bump
    }

    /// Take a lazy VNode structure and actually build it with the context of the VDom's efficient VNode allocator.
    ///
    /// This function consumes the context and absorb the lifetime, so these VNodes *must* be returned.
    ///
    /// ## Example
    ///
    /// ```ignore
    /// fn Component(cx: Context<()>) -> VNode {
    ///     // Lazy assemble the VNode tree
    ///     let lazy_tree = html! {<div> "Hello World" </div>};
    ///
    ///     // Actually build the tree and allocate it
    ///     cx.render(lazy_tree)
    /// }
    ///```
    pub fn render<'src>(
        &'src self,
        lazy_nodes: Option<LazyNodes<'src, '_>>,
    ) -> Option<VNode<'src>> {
        let bump = &self.frames.wip_frame().bump;
        let factory = NodeFactory { bump };
        lazy_nodes.map(|f| f.call(factory))
    }

    /// Push an effect to be ran after the component has been successfully mounted to the dom
    /// Returns the effect's position in the stack
    pub fn push_effect<'src>(&'src self, effect: impl FnOnce() + 'src) -> usize {
        // this is some tricker to get around not being able to actually call fnonces
        let mut slot = Some(effect);
        let fut: &mut dyn FnMut() = self.bump().alloc(move || slot.take().unwrap()());

        // wrap it in a type that will actually drop the contents
        let boxed_fut = unsafe { BumpBox::from_raw(fut) };

        // erase the 'src lifetime for self-referential storage
        let self_ref_fut = unsafe { std::mem::transmute(boxed_fut) };

        let mut items = self.items.borrow_mut();
        items.pending_effects.push(self_ref_fut);
        items.pending_effects.len() - 1
    }

    /// Pushes the future onto the poll queue to be polled
    /// The future is forcibly dropped if the component is not ready by the next render
    pub fn push_task<'src>(&'src self, fut: impl Future<Output = ()> + 'src) -> usize {
        // allocate the future
        let fut: &mut dyn Future<Output = ()> = self.bump().alloc(fut);

        // wrap it in a type that will actually drop the contents
        let boxed_fut: BumpBox<dyn Future<Output = ()>> = unsafe { BumpBox::from_raw(fut) };

        // erase the 'src lifetime for self-referential storage
        let self_ref_fut = unsafe { std::mem::transmute(boxed_fut) };

        let mut items = self.items.borrow_mut();
        items.tasks.push(self_ref_fut);
        items.tasks.len() - 1
    }

    /// This method enables the ability to expose state to children further down the VirtualDOM 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_state` and `use_consume_state` instead.
    ///
    /// When the component is dropped, so is the context. Be aware of this behavior when consuming
    /// the context via Rc/Weak.
    ///
    /// # Example
    ///
    /// ```
    /// struct SharedState(&'static str);
    ///
    /// static App: FC<()> = |(cx, props)|{
    ///     cx.use_hook(|_| cx.provide_state(SharedState("world")), |_| {}, |_| {});
    ///     rsx!(cx, Child {})
    /// }
    ///
    /// static Child: FC<()> = |(cx, props)|{
    ///     let state = cx.consume_state::<SharedState>();
    ///     rsx!(cx, div { "hello {state.0}" })
    /// }
    /// ```
    pub fn provide_state<T>(&self, value: T)
    where
        T: 'static,
    {
        self.shared_contexts
            .borrow_mut()
            .insert(TypeId::of::<T>(), Rc::new(value))
            .map(|f| f.downcast::<T>().ok())
            .flatten();
    }

    /// Try to retrieve a SharedState with type T from the any parent Scope.
    pub fn consume_state<T: 'static>(&self) -> Option<Rc<T>> {
        if let Some(shared) = self.shared_contexts.borrow().get(&TypeId::of::<T>()) {
            Some(shared.clone().downcast::<T>().unwrap())
        } else {
            let mut search_parent = self.parent_scope;

            while let Some(parent_ptr) = search_parent {
                let parent = unsafe { &*parent_ptr };
                if let Some(shared) = parent.shared_contexts.borrow().get(&TypeId::of::<T>()) {
                    return Some(shared.clone().downcast::<T>().unwrap());
                }
                search_parent = parent.parent_scope;
            }
            None
        }
    }

    /// Create a new subtree with this scope as the root of the subtree.
    ///
    /// Each component has its own subtree ID - the root subtree has an ID of 0. This ID is used by the renderer to route
    /// the mutations to the correct window/portal/subtree.
    ///
    /// This method
    ///
    /// # Example
    ///
    /// ```rust
    /// static App: FC<()> = |(cx, props)| {
    ///     todo!();
    ///     rsx!(cx, div { "Subtree {id}"})
    /// };
    /// ```
    pub fn create_subtree(&self) -> Option<u32> {
        self.new_subtree()
    }

    /// Get the subtree ID that this scope belongs to.
    ///
    /// Each component has its own subtree ID - the root subtree has an ID of 0. This ID is used by the renderer to route
    /// the mutations to the correct window/portal/subtree.
    ///
    /// # Example
    ///
    /// ```rust
    /// static App: FC<()> = |(cx, props)| {
    ///     let id = cx.get_current_subtree();
    ///     rsx!(cx, div { "Subtree {id}"})
    /// };
    /// ```
    pub fn get_current_subtree(&self) -> u32 {
        self.subtree()
    }

    /// Store a value between renders
    ///
    /// This is *the* foundational hook for all other hooks.
    ///
    /// - Initializer: closure used to create the initial hook state
    /// - Runner: closure used to output a value every time the hook is used
    ///
    /// To "cleanup" the hook, implement `Drop` on the stored hook value. Whenever the component is dropped, the hook
    /// will be dropped as well.
    ///
    /// # Example
    ///
    /// ```ignore
    /// // use_ref is the simplest way of storing a value between renders
    /// fn use_ref<T: 'static>(initial_value: impl FnOnce() -> T) -> &RefCell<T> {
    ///     use_hook(
    ///         || Rc::new(RefCell::new(initial_value())),
    ///         |state| state,
    ///     )
    /// }
    /// ```
    pub fn use_hook<'src, State: 'static, Output: 'src>(
        &'src self,
        initializer: impl FnOnce(usize) -> State,
        runner: impl FnOnce(&'src mut State) -> Output,
    ) -> Output {
        if self.hooks.at_end() {
            self.hooks.push_hook(initializer(self.hooks.len()));
        }

        runner(self.hooks.next::<State>().expect(HOOK_ERR_MSG))
    }
}

const HOOK_ERR_MSG: &str = 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.
"###;