dioxus/packages/core/src/scope.rs

use crate::innerlude::*;
use std::{
    any::{Any, TypeId},
    cell::{Cell, RefCell},
    collections::{HashMap, HashSet},
    future::Future,
    pin::Pin,
    rc::Rc,
};

/// 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
/// usecase they might have.
pub struct Scope {
    // Book-keeping about the arena
    pub(crate) parent_idx: Option<ScopeId>,
    pub(crate) descendents: RefCell<HashSet<ScopeId>>,
    pub(crate) our_arena_idx: ScopeId,
    pub(crate) height: u32,

    // Nodes
    // an internal, highly efficient storage of vnodes
    pub(crate) frames: ActiveFrame,
    pub(crate) child_nodes: &'static [VNode<'static>],
    pub(crate) caller: Rc<WrappedCaller>,

    // Listeners
    pub(crate) listeners: RefCell<Vec<(*mut Cell<RealDomNode>, *mut dyn FnMut(VirtualEvent))>>,
    pub(crate) listener_idx: Cell<usize>,

    // State
    pub(crate) hooks: HookList,
    pub(crate) shared_contexts: RefCell<HashMap<TypeId, Rc<dyn Any>>>,

    // Events
    pub(crate) event_channel: Rc<dyn Fn() + 'static>,

    // Tasks
    pub(crate) task_submitter: TaskSubmitter,

    // A reference to the list of components.
    // This lets us traverse the component list whenever we need to access our parent or children.
    pub(crate) arena_link: SharedArena,
}

// The type of the channel function
type EventChannel = Rc<dyn Fn()>;

// The type of closure that wraps calling components
pub type WrappedCaller = dyn for<'b> Fn(&'b Scope) -> DomTree<'b>;

// The type of task that gets sent to the task scheduler
pub type FiberTask = Pin<Box<dyn Future<Output = EventTrigger>>>;

impl Scope {
    // we are being created in the scope of an existing component (where the creator_node lifetime comes into play)
    // we are going to break this lifetime by force in order to save it on ourselves.
    // To make sure that the lifetime isn't truly broken, we receive a Weak RC so we can't keep it around after the parent dies.
    // This should never happen, but is a good check to keep around
    //
    // Scopes cannot be made anywhere else except for this file
    // Therefore, their lifetimes are connected exclusively to the virtual dom
    pub fn new<'creator_node>(
        caller: Rc<WrappedCaller>,
        arena_idx: ScopeId,
        parent: Option<ScopeId>,
        height: u32,
        event_channel: EventChannel,
        arena_link: SharedArena,
        child_nodes: &'creator_node [VNode<'creator_node>],
        task_submitter: TaskSubmitter,
    ) -> Self {
        let child_nodes = unsafe { std::mem::transmute(child_nodes) };
        Self {
            child_nodes,
            caller,
            parent_idx: parent,
            our_arena_idx: arena_idx,
            height,
            event_channel,
            arena_link,
            task_submitter,
            listener_idx: Default::default(),
            frames: ActiveFrame::new(),
            hooks: Default::default(),
            shared_contexts: Default::default(),
            listeners: Default::default(),
            descendents: Default::default(),
        }
    }

    pub(crate) fn update_caller<'creator_node>(&mut self, caller: Rc<WrappedCaller>) {
        self.caller = caller;
    }

    pub(crate) fn update_children<'creator_node>(
        &mut self,
        child_nodes: &'creator_node [VNode<'creator_node>],
    ) {
        let child_nodes = unsafe { std::mem::transmute(child_nodes) };
        self.child_nodes = child_nodes;
    }

    pub(crate) fn run_scope<'sel>(&'sel mut self) -> Result<()> {
        // 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

        // This is a very dangerous operation
        self.frames.next().bump.reset();

        self.listeners.borrow_mut().clear();

        unsafe { self.hooks.reset() };
        self.listener_idx.set(0);

        // Cast the caller ptr from static to one with our own reference
        let c3: &WrappedCaller = self.caller.as_ref();

        self.frames.cur_frame_mut().head_node = unsafe { self.call_user_component(c3) };

        Ok(())
    }

    // this is its own function so we can preciesly control how lifetimes flow
    unsafe fn call_user_component<'a>(&'a self, caller: &WrappedCaller) -> VNode<'static> {
        let new_head: Option<VNode<'a>> = caller(self);
        let new_head = new_head.unwrap_or(errored_fragment());
        std::mem::transmute(new_head)
    }

    // A safe wrapper around calling listeners
    // calling listeners will invalidate the list of listeners
    // The listener list will be completely drained because the next frame will write over previous listeners
    pub(crate) fn call_listener(&mut self, trigger: EventTrigger) -> Result<()> {
        let EventTrigger {
            real_node_id,
            event,
            ..
        } = trigger;

        if let &VirtualEvent::AsyncEvent { .. } = &event {
            log::info!("arrived a fiber event");
            return Ok(());
        }

        log::debug!(
            "There are  {:?} listeners associated with this scope {:#?}",
            self.listeners.borrow().len(),
            self.our_arena_idx
        );

        let listners = self.listeners.borrow_mut();

        let raw_listener = listners.iter().find(|(domptr, _)| {
            let search = unsafe { &**domptr };
            let search_id = search.get();
            log::info!("searching listener {:#?}", search_id);
            match real_node_id {
                Some(e) => search_id == e,
                None => false,
            }
        });

        match raw_listener {
            Some((_node, listener)) => unsafe {
                // TODO: Don'tdo a linear scan! Do a hashmap lookup! It'll be faster!
                let listener_fn = &mut **listener;
                listener_fn(event);
            },
            None => todo!(),
        }

        Ok(())
    }

    pub(crate) fn submit_task(&self, task: FiberTask) {
        log::debug!("Task submitted into scope");
        (self.task_submitter)(task);
    }

    #[inline]
    pub(crate) fn next_frame<'bump>(&'bump self) -> &'bump VNode<'bump> {
        self.frames.current_head_node()
    }

    #[inline]
    pub(crate) fn old_frame<'bump>(&'bump self) -> &'bump VNode<'bump> {
        self.frames.prev_head_node()
    }

    #[inline]
    pub(crate) fn cur_frame(&self) -> &BumpFrame {
        self.frames.cur_frame()
    }

    /// Get the root VNode of this component
    #[inline]
    pub fn root<'a>(&'a self) -> &'a VNode<'a> {
        &self.frames.cur_frame().head_node
    }
}

pub fn errored_fragment() -> VNode<'static> {
    VNode {
        dom_id: RealDomNode::empty_cell(),
        key: None,
        kind: VNodeKind::Fragment(VFragment {
            children: &[],
            is_static: false,
            is_error: true,
        }),
    }
}